摘要:

1 Introduction By F. J. BERRY Department of Chemistry The Open University Milton Keynes MK7 6AA UK and N. G. CONNELLY School of Chemistry University of Bristol Cantock’s Close Bristol BS8 1TS UK In Volume 93 we have achieved our aim of covering progress in inorganic chemistry both by Group and by subjects of special interest. Note that Chapter 20 includes highlights from the literature for both 1995 and 1996 rectifying the omission of a chapter on The Coordination Chemistry of Macrocyclic Ligands in Volume 92 of Annual Reports Section A. With considerable e§ort on the part of our authors and editorial/production sta§ we have also achieved much earlier publication this year; the highlights of inorganic chemistry in 1996 are now uniquely surveyed and presented well within one year of first publication.Volume 93 again demonstrates the vibrancy of inorganic chemistry in all areas. In main group chemistry we have seen the synthesis of the first air-stable neutral metal-free odd-electron boron cluster MeCHB 11 Me 11 and the closo-monosilaborane [NEt 4 ][MeSiB 11 H 11 ] the amazing cyclogallene [MGa(C 6 H 3 Mes 2 )N3 ]2~ and the Zintl phase Na 8 K 23 Cd 12 In 48 with its fullerene structure. The well known ability of metal centres to stabilise ligands of the type [Sn]2~ has been taken a stage further by the discovery of the first example of a k-S 9 ligand in [MIr(k-SPr*)Cp*N2 (k-S 9 )] while the isolation of a number of new cyclic imides of the type SxNH underlines our ability to create new sulfur-based rings by rational synthesis. The first reports of the preparation of salts of [HSSH 2 ]` of main group adducts of Se 2 N 2 and of a bidentate complex of dmso serve to highlight the kind of conceptually straightforward (though synthetically challenging) bonding modes that remain to be found for simple Group 16-based molecules.We also note the cyclic polyhalide array in which a metal–thiomacrocyclic cation acts as a template and the oxygenation of organo–noble gas cations using XeF 2 –H 2 O–HF leading to reaction at the organic ligand without Xe–C bond cleavage. Also noteworthy in transition-metal chemistry is the synthesis of [Ir(CO) 6 ]3` the first homoleptic carbonyl of a tripositive metal the self assembly of ladder structures in CuI oligobipyridine complexes and the simple oxidation of metallic gold the most noble of metals by Me 3 EI 2 (E\P or As).In solid-state chemistry we have seen the synthesis and characterisation of UTD-1 the first 14-membered ring silica zeolite having one-dimensional channels of crosssection 7.5]10 Å in which the key ingredient of the synthesis was an organometallic template. Also of note is the characterisation of a new high-pressure silicate CaSi 2 O 5 having the very unusual feature of five-co-ordinate silicon. Perhaps most remarkable is Royal Society of Chemistry–Annual Reports–Book A 1 ZrW 2 O 8 a material which exhibits isotropic and uniform contraction on heating throughout the range 0.3 to 1050 K. Also notable is the discovery of superconductivity in materials which do not appear to have stoichiometric long-range CuO 2 layers for example the spin-ladder compound SrxCa 14~xCu 24 O 41 the high-pressure synthesised phase Sr 2 CuO 3`d and the isostructural ambient pressure phase Sr 0.8 Ba 1.2 CaO 3`d which raises fundamental questions concerning superconductivity in cuprates.The spin-ladder compound is particularly noteworthy since it was first predicted theoretically and has now been prepared. In the area of fast ion conductors and intercalation compounds we note the synthesis of LiMnO 2 isostructural with LiCoO 2 but cheaper and less toxic. The chemical synthesis of fullerenes (and their derivatives) from cheap commercially available compounds becomes an ever closer proposition with the preparation of the largest fullerene fragment to date C 36 H 12 . Also noteworthy are the first g5- and g6-fullerene complexes which mark major breakthroughs in the development of fullerene chemistry. The large-scale synthesis of aligned carbon nanotubes is another of the many highlights in this field. Finally we record the idea of using transmutation as a way of dealing with highly radioactive long-lived nuclear waste. If actinides (including plutonium) are subject to neutron (or other) irradiation they could be converted mostly by fission into much shorter lived isotopes. By extension the same approach could be used to deal with other long-lived species such as iodine-129 and chlorine-36. Whilst this would not make the problem of nuclear waste disappear it converts it from one which is unmanageable (for who can tell what will happen in 50,000 or 500,000 years) into one which can be dealt with in a time span of decades. It must be better (and safer) than launching nuclear waste into outer space. 2 F. J. Berry and N.G. Connelly

ISSN:0260-1818    

DOI:10.1039/ic093001

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

2 Alkali and alkaline-earth metals By I. B. GORRELL School of Chemistry Physics and Environmental Science University of Sussex Falmer Brighton BN1 9QJ UK 1 Introduction This chapter reviews literature published in 1996 with the emphasis on organometallic and coordination chemistry but excluding compounds containing macrocyclic ligands. Reviews have appeared on dissolved alkali metals in zeolites,1 the structural chemistry2 and thermal decomposition reactions3 of Group 2 metal diketonates and the use of Group 2 organometallic compounds as precursors for chemical vapour deposition.4 Computations of the exchange reaction of alkali-metal hydrides with hydrogen showed that the transition states approximate to ion pairs of alkali-metal cations with theH 3 ~ anion.5 A series of about 70 adducts of Group 2 halides and perchlorates with nitrogen and mixed nitrogen/oxygen bases including MeCN py en dien tmen dmf phen bipy terpy substituted pyridines water and ROH (R\Me Pr Bu) have been crystallographically characterized.6 The bonding of the cyanide anion to the Group 2 metals has been shown by ab initio calculations to exhibit remarkable structural variations including N-bonding C-bonding and bridged arrangements.7 2 Lithium Structure and bonding in hyperlithiated molecules,8 lithium derivatives of silylhydrazines9 and arene-catalysed lithiations of a range of substrates including alkyl sulfates and phosphates sulfides sulfoxides sulfones and nitriles have been reviewed.10 Carbon-donor ligands The crystal structure of [Li 2 (dibenzo[a,e]cyclooctatetraene)(tmen) 2 ] revealed g8- coordination to the metal centres.11 The preparations and X-ray structures of [PPh 2 Me 2 ][Li(g5-C 5 H 4 Bu`) 2 ]12 and the triple decker Li 2 [g5-C 5 (CH 2 Ph) 5 ] 2 (g2- C 6 H 6 )13 have been reported; reaction of the latter with Alcp* gave [LiMg5- C 5 (CH 2 Ph) 5N2 ][Alcp* 2 ] and Al[g5-C 5 (CH 2 Ph) 5 ].Detailed crystal structures of Li[g5-isodicp](tmeda) and [Li(12-crown-4) 2 ][Li(g5-isodicp) 2 ] have also appeared.14 A lithocenophane derivative of a tris(germole) anion [Li(thf)(tmen)][2,3,4,5-Et 4 -Ge Ge-MLi(2,3,4,5-Et 4 C 4 Ge) 2NC 4 Ge] has been prepared and structurally characterized. Royal Society of Chemistry–Annual Reports–Book A 3 One ring was g5-bonded and the other containing sp3 germanium p-bonded to the solvated lithium centre g4-bonded.15 The diethyl ether derivative of 9-[2- (dimethylamino)ethyl]fluorenyllithium contained a g5-coordinated fluorenyl group the thf analogue of which was g2-coordinated.16 The lithium cations associated with sulfur-stabilized allylic carbanions derived from (E)-1-(tert-butylthio)but-2-ene and (E)-1-(phenylthio)but-2-ene were found to be unsymmetrically g2-bonded to C(1) and C(2) [or g1-bonded to C(1)].Addition of tmen to a solution of the butyl compound had no e§ect but the solid state structure of the adduct revealed a g3 arrangement.17 Significant changes in isomer ratio of silyl-substituted allenyl/propargyllithium reagents in solution were ascribed to details of the solvated lithium cation–carbanion interaction.18 A partially delocalized allylic lithium centre has been observed and the dynamics of the associated 1,3-lithium sigmatropic shift investigated.19 The crystal structure of LiCH 2 Ph complexed with Bu5OMe revealed infinite chains of five-coordinate lithium cations and g2-benzyl anions;20 the latter were also observed in [Li(OEt 2 ) 2 (CHPh)PPh 2 ].21 The complexes M[(g5-C 5 HMe 4 ) 2 Ti(g1-C–– –CSiMe 3 ) 2 ] (M\Li Na K Cs) have been prepared.The structure of the potassium compound revealed the alkali metal situated between the acetylide arms and also bound to a C 5 HMe 4 ligand of the adjacent molecule to form a polymer chain.22 The structures of [Li(C 6 H 3 dipp 2 -2,6)] 2 [Li(C 6 H 6 )(C 6 H 3 trip 2 -2,6)] and [Li(OEt 2 )(C 6 H 3 trip 2 -2,6)] containing two-coordinate lithium have been reported.23 The X-ray structure of LiCHCl 2 ·3py was consistent with earlier NMR spectroscopic results and calculations suggesting that the C–Li bond in carbenoids should have higher s character and all other bonds higher p character.24 High yield preparations of non n-stabilized bis(lithiomethyl)silanes by reductive cleavage of C–S bonds in bis[(phenylthio)methyl]silanes have been reported.25 Double lithiation of tetramethylmethylenediamine gave [LiCH 2 N(Me)CH 2 N(Me)CH 2 Li].26 The preparation of [LiC(2-MeC 6 H 4 Me 2 Si) 3 ] and its reaction with MeI have been reported27 and the chelated species [Li(tmen) 2 ][CH 2 SiMe 2 C(SiMe 3 ) 2 LiC(SiMe 3 ) 2 SiMe 2 CH 2 ] has been prepared and structurally characterized; reaction with HgBr 2 gave the neutral mercury derivative.28 Isobutyllithium 2-ethylhexyllithium and 2-ethylhexylsodium have been prepared from the metals and the corresponding alkyl halides and characterized using NMR spectroscopy.29 The activation of aromatic hydrocarbons with atomic lithium in the presence of thf has been suggested to occur via small lithium clusters which complex the hydrocarbon.A double electron transfer breaks the C–H bond to form an LiH–LiPh adduct which then dissociates.30 The results of a- deuterium kinetic isotope e§ects in reactions of LiMe and MgMeI suggested a preequilibrium between an aggregate and the reactive monomer.31 The structure of [Li(C 5 H 5 S)(OEt 2 )] 4 revealed a tetrahedral array of lithium atoms with the 2-methylthiophene carbanions linked to each face.32 Reactions of Me 3 SiNPR 3 (R\Me Pr*) with LiBu/ yielded [LiCH 2 PMe 2 NSiMe 3 ] 4 also containing a lithium tetrahedron and [LiCMe 2 P(Pr*) 2 NSiMe 3 ] 2 with three-coordinate (2C]N) lithium.33 Although calculations indicated that dimeric unsolvated cyclopropenyllithium would have two planar tetracoordinate a-carbon centres a tetrahedral arrangement was observed in the structure of dimeric [3,3-dimethyl-2-(trimethylsilyl)cyclopropenyl] lithium(tmen).This was ascribed to the solvation of the lithium and the bulk of the ligands. The rehybridization at lithium did not result in carbenoid character.34 The anticipated arrangement has been realized experimentally in derivatives with 4 I.B. Gorrell additional coordinating ligands.35 The mixed aggregates RM/LiOH (M\Li–Cs; R\H Me NH 2 OH F) models for ‘superbasic’ reagents were found to be more stable than other possible combinations using ab initio methods.The main driving force was the formation of strong Li–O bonds and the reduction of electrostatic metal–metal repulsions.36 A theoretical study of C 3 Li 4 confirmed that the closed-shell singlet ground state was of C 2v symmetry but also that two other structures with triple lithium bridges and naked carbon atoms were close in energy to the ground state.37 Density-functional and conventional ab initio methods have been applied to [LiMe]n (n\1 2 4) and showed that the degree of ionic bonding decreased as n increased.38 The preferred site of lithiation (ortho to the X group or benzylic at the side-chain) of the ortho-substituted toluenes o-MeC 6 H 4 X (X\OH NH 2 F) has been shown by ab initio methods not to correlate with the acidity of the exchanged hydrogen. Stabilizing interactions in the transition state rather than initial complexation determine the metallation products.39 NMR studies and MNDO calculations of (1S 2S 9R 10R)- tetracyclo[8.2.1.02,9.03,7]trideca-3,6-dienyllithium have been reported.40 Nitrogen-donor ligands A slightly distorted trigonal planar environment was observed for lithium in [Li(OEt 2 )(py)N(SiMe 3 )(C 6 H 3 -2,6-Pr* 2 )].41 A stable methyl phosphane oxide-lithium amide complex has been prepared and structurally characterized as [LiN(Me 3 Si) 2 ·OP(Me)Ph 2 ] 2 ; the relevance of the structure to the mechanism of proton abstraction by alkali-metal reagents together with associated ab initio calculations was discussed.42 Reaction of [AlMe 3 ·HNBz 2 ] with [LiNBz 2 ] yielded [AlMe 3 ·LiNBz 2 ·NHBz 2 ] the structure of which contained an AlCLiN core with a monomeric lithium dibenzylamide fragment.43 X-Ray analysis of unsolvated benzyl- (trimethylsilyl)amidolithium revealed a trimeric structure with a shield-shaped Li 3 N 3 core; solvation with hmpa gave a dimer.The structures especially the Li · · · benzyl interactions were discussed in the light of ab initio calculations.44 The crystal structure of [MLiN(H)Bu5N8 ] revealed a cyclic octameric ladder based on a double crown arrangement,45 and the structures of [LiN(H)Ph(thf) 2 ] 2 and [LiN(H)C 6 F 5 (thf) 2 ] 2 were best rationalized in terms of sp2 hybridization at nitrogen.46 The u-cyanoeneamidolithium compound [LiMN(H)C(Me)––C(H)CNN]n formed a dimeric adduct with py the structure of which was based on a 12-membered ring.47 The crystal structures of [LiN(H)SiMeBu5 2 ] 4 based on an Li 4 N 4 cube and [Li(thf) 2 (k-F)(k- NSiMe)Si(F)N(SiMe 3 )(SiMeBu5 2 )] have been reported.48 Reaction of wet cyclopentylamine with LiBu/ under argon a§orded [M(c-C 5 H 9 )N(H)N12 (O)Li 14 ] the structure of which was based on a distorted face-centred cube of lithium cations with those occupying face positions octahedrally surrounding the central oxo anion.The amido ligands all bridged three (2 corner]1 face) lithium centres.49 The first trimetallic Li–Na–K complex [M(PhNMHN) 2 (Bu5O)LiNaK(tmen) 2N2 ] has been prepared; the structure contained a 12-vertex Li 2 Na 2 K 2 N 4 O 2 cage.50 Reaction of the g3-allyllithium or the potassium compounds [LiMg3-CH(CHSiMe 2 Bu5)(CHSiMe 2 R)N] (R\Me Bu5) and KMg3-CH(CHSiMe 2 Bu5) 2N with Bu5CN a§orded the 1-azapentadienyllithium or the potassium compounds [LiMg1-N(SiMe 2 R)C(Bu5)(CH) 3 - SiMe 2 Bu5NL] (L\tmen or absent; R\Me Bu5) or [KMg4- N(SiMe 2 Bu5)C(Bu5)(CH) 3 SiMe 2 Bu5N] = .Structures and reactivity were discussed.51 The crystallographically characterized dilithium amides [MLi(thf)N2MC 20 H 12 (NR) 2N] 5 Alkali and alkaline-earth metals (R\SiMe 3 CH 2 Bu5) have been prepared from (RS)-2,2@-diamino-1,1@-binaphthyl C 20 H 12 (NH 2 ) 2 via C 20 H 12 [N(H)SiMe 3 ] 2 or C 20 H 12 [NHC(O)Bu5] 2 and C 20 H 12 [N(H)CH 2 Bu5] 2 respectively and were transformed into SiCl 2 [C 20 H 12 (NR) 2 ] with SiCl 4 . The R and S enantiomers were also prepared.52 The lithiation of N,N@-di-tert-butylethylenediamine has been shown to proceed via cis-[MLi(k-N(Bu5)CH 2 CH 2 N(H)Bu5)N2 ] and [MLi(N(Bu5)CH 2 CH 2 N(H)Bu5)N2 LiMN- (Bu5)CH 2 CH 2 NBu5NLi] prior to formation of the dilithiated species [LiMN(Bu5)CH 2 CH 2 NBu5NLi].Structural data were presented along with ab initio calculations and the mechanism was discussed.53 The lithiation of N,N@-bis(trimethylsilyl) ethylenediamine in ether yielded [MLi(N(SiMe 3 )CH 2 CH 2 NSi-Me 3 )Li·OEt 2N2 ] and recrystallization from benzene gave the unsolvated trimer. Crystal structures and solution dynamics were discussed.54 The X-ray structure of [LiN(PPh 2 ) 2 ·3thf] revealed a trigonal bipyramidal coordination for lithium and ab initio calculations on model compounds showed strong stabilization of the anions by the phosphorus substituents due to negative hyperconjugation and phosphorus polarization. Much of the stabilization was negated by the metal.55 A bis(pyridine)dihydropyridyllithium dimer has been isolated from the reaction of py with LiBu/ (7 1) and a mechanism proposed which involved the product [Li(py) 2 (2-Bu/C 5 H 5 N)] obtained earlier from the 3 1 reaction.56 Lithiation of 3,3@- dimethyl-2,2@-bipyridine and its derivatives (2-RCH 2 C 5 H 3 N) 2 (R\H SiMe 3 ) with the appropriate amount of LiBu/(tmen) yielded the corresponding mono- and dilithiated compounds with deprotonation occurring at the a-methyl carbon atom.The crystal structure of [MLi(tmen)N2M2-CH(SiMe 3 )C 5 H 3 NN2 ] showed lithium to be C,N-chelated by the a-carbon and the nitrogen of the other pyridine ring.57 X-Ray di§raction of Li 2 [Bi 2 (NBu5) 4 ]·2thf revealed a Bi 2 Li 2 N 4 cube; solution dynamics were studied and compared with data for Li 4 [Sb 2 (Ncy) 4 ] 2 .58 Lithium reduction of oxalic amidines yielded the dilithium diimides via monolithium radical anions.The solid state structure of Li 2 (OEt 2 ) 3 [M(4-MeC 6 H 4 NN(NPhMe)C–– C(NPhMe)MN(C 6 H 4 Me- 4)N] was reported and discussed with the aid of semiempirical calculations.59 The crystal structure of ortho-lithio-b-(N,N@-dimethylamino)ethoxybenzene revealed a tetrahedral array of lithium atoms whereas the corresponding sodium compound was hexameric with an octahedron of sodium atoms.60 The crystal structures of a series of N-phenyl substituted lithium hydrazides showed that Li · · · Ph n interactions were only present when the lithium centres were not bound to donor molecules. The structures of sodium and caesium compounds showed increased coordination at the metal centre.61 Intramolecular motion of lithium in crystals of [LiN(SiMe 2 OBu5) 2 ] was investigated using X-ray di§raction and multinuclear solid state NMR spectroscopy; 62 ab initio calculations of 15N–6Li coupling constants in LiNH 2 and LiNMe 2 monomers their oligomers and mixed aggregates with LiCl have been reported.63 A novel triple ion complex 1 containing enolate amide and halide has been prepared and structurally characterized.The structure was discussed in the light of PM3 calculations. 64 Aggregates of lithium halides with either lithium amides or lithium enolates have been characterized by X-ray crystallography as heterodimers or heterotrimers. A reaction sequence for enolization and subsequent aldol additions involving halide containing aggregates was proposed and supported by ab initio calculations.65 The relationship between ligand structure and lithium amide aggregation was found to be a complex and sensitive function of the amine substituents after a study of the 6 I.B.Gorrell solvation and aggregation of lithium hexamethyldisilazide by more than 20 di§erent mono- and tri-alkylamines (and ammonia and dimethylethylenediamine).66 Multinuclear NMR spectroscopic studies of lithium hexamethyldisilazide coordinated by 29 polyamines polyethers and aminoethers revealed a range of structural types including g1-coordinated mono- and di-solvated dimers g2-coordinated monomers g1,g2-coordinated monomers g2,g2-coordinated monomers polymers triple ions and solventseparated ion pairs. Ligand binding constants for the monomers yielded information on chelate ring size and steric e§ects aza- and oxo-philicity mechanism and the macrocyclic e§ect.67 Individual diastereomeric solvates 2 (L\Me 2 O thf oxetane py) of a series of chelated organolithium reagents under slow exchange in Me 2 O solutions were detected using NMR spectroscopy enabling direct evaluation of donor-coordinating ability.68 Solvation of the dimer of lithiumM2-methoxy-(R)-1- phenylethylNM(S)-1-phenylethylamineN by (R)- and (S)-2-methyltetrahydrofuran has provided the first direct observation of diastereoselective solvation of a chiral organolithium compound by the enantiomers of a chiral ether.69 NMR spectroscopic studies showed that 2-(dimethylaminomethyl)phenyllithium formed three isomeric chelated dimers in thf–Me 2 O solution and that chelation between the dimethylamino groups and lithium was maintained in solvents containing thf tmen pmdien and hmpa although the latter formed a complex.70 The X-ray structure of bisMS-(1-lithio-3 3-diphenylprop-2-enyl)-N-methyl-Sphenylsulfoximine –thf(1/2)N was found to be in agreement with a calculated structure for a lithiatedN,S,S-trimethylsulfoxime a centrosymmetric dimer containing an eightmembered (LiNSO) 2 ring.71 Reaction of [VCl 2 (tmen) 2 ] with [Li(thf)] 4 (oepg) gave [(oepg)VLi 4 Cl 2 (thf) 4 ].X-Ray studies showed that the thf bound lithium centres were g5-bonded to the pyrrole rings and also participated in Li–Cl–Li links.72 Lithiation of (Me 2 NMe 2 Si) 3 CH gave a linear polymer in which two nitrogen atoms of each planar carbanionic (Me 2 NMe 2 Si) 3 C unit are attached to one lithium and the remaining nitrogen to another lithium atom.73 The first di§raction study of the cation present in 7 Alkali and alkaline-earth metals [Li(NH 3 ) 4 ] 3 P 11 ·5NH 3 has revealed a three-dimensional framework in which the tetrahedral cations and free ammonia molecules are linked by N–H· · ·N hydrogen bonds.74 Phosphorus-donor ligands Lithiation of PRH 2 [R\Pr* 2 (mes)Si] with a source of Li 2 O yielded [Li 18 O(PR) 8 ].The structure comprised a P 8 distorted cube surrounded by an Li 12 cuboctahedral shell and surrounding an Li 6 O octahedron. Lithiation of AsRH 2 [R\Si(Pr*Me 2 C)- Me 2 ] under similar conditions gave [(RAs) 12 Li 26 O] based on an As 12 icosahedron with all faces capped by lithium again surrounding an Li 6 O core.75 Lithiation of PRH 2 [R\Pri 2 (trip)Si] yielded (Li 2 PR) 2 which reacted with RF to give [(Li 2 PR)(RF)] 2 with a P 2 Li 4 F 2 ladder framework.76 The preparation and reactivity (with H 2 O D 2 O SiMe 2 Cl 2 and HgBu5Cl) of lithiumsilanidyl-lithiumsilylphosphanide trip 2 Si(Li)P(Li)SiR 3 ·4thf (R 3 \Pr* 3 Ph 2 Me) have been reported.77 The preparations and structures of 3 and 4 have appeared.78 The structure of [Li 4 (Bu5 2 P) 4 (thf) 2 ]·C 6 H 14 has been redetermined with inclusion of the hexane solvate giving a much lower crystallographic R value.79 Lithiation of P(C 6 H 4 OMe-2) 2 H and reaction of sodium with P(C 6 H 4 OMe-2) 3 yielded MP(C 6 H 4 OMe-2) 2 (M\Li Na); addition of diglyme (M\Na) gave [NaMk- P(C 6 H 4 OMe-2) 2N(diglyme)] 2 which contained six-coordinate sodium (2P]4O).80 The ab initio geometries of LiOCP NaOCP LiSCP and NaSCP were found to be n-type cyclic conformers which would dissociate in solution to give linear species; vibrational frequencies and ionization energies were also calculated.81 Oxygen- and sulfur-donor ligands The structures and conformations of the azaenolate lithium salts of several amides have been investigated using ab initio methods.82 Models for intermediates during lithiation of two di§erent organic precursors having -NHC––O units [2,2-dimethyl-N- (2-pyridinyl)propanamide and 2-tert-butylcarboxamido-3-methylthiophene] have been structurally characterized and shown to be complexed mono- and di-meric azaenolates with (-N––COLi·xB)n (B\Lewis base) units.The structures imply that the N (rather than O) centres of these species would direct second lithiations to nearby C–H bonds although the dilithiated systems could not be detected.83 A kinetic study has shown that the monomeric lithium enolate of 4-phenylsulfonylisobutyrophenone is the dominant reactant in mixtures of this enolate and LiBr used in alkylation reactions.However at higher LiBr concentrations the contribution from the dilithium enolate-bromide increases markedly.84 An ab initio study of the structure aggregation 8 I.B. Gorrell andNMRshifts of the lithium ester enolate of methyl isobutyrate has been reported.85 The lithium cation was found to bridge the two peroxide oxygens in [LiOOBu5] 12 . Calculations suggested that increasing aggregation led to stabilization of charge at anionic oxygen.86 The solid state and solution structures of a lithiated P-benzylphosphorinane- 1-oxide have been discussed.87 A rare example of an almost undistorted LiO 5 square pyramid was observed in the structure of the lithium benzohydroxamatebenzohydroxamic acid 1 1 adduct.88 The crystal structure of lithium N-isopropyl-2- (isopropylamino)troponiminate–bis(thf) revealed a tetrahedral metal centre.89 The oxidation of phenyllithium by various substituted orthoquinones led to the formation of the corresponding lithium semiquinone; EPR spectra of the 3,5-di-tert-butylsemiquinone compound indicated a trimeric structure in solution.90 The X-ray structure of [LiOC(Me)(c-CHCH 2 CH 2 ) 2 ] 6 [monomer shown as 5] has been reported and the short Li–C distances were found to characterize Li–cyclopropane edge interactions.The results were discussed in the light of ab initio calculations.91 Reaction of LiBu/ and KOBu5 with (SiMe 3 ) 2 O or reaction of KOSiMe 3 with LiOSiMe 3 yielded Li 4 K 4 (OSiMe 3 )x(OCMe 3 ) 8~x (x\5.7 6.8 8).The solid state structure contained two base-fused orthogonal prisms with a basal square plane of potassium atoms. In solution dissociation to smaller clusters occurred. The compounds served as catalysts for the anion-ring-opening-polymerization of octamethylcyclotetrasiloxane and produced a linear polymer of high molecular weight and low polydispersity. 92 The crystal structures of [M(Ph 2 SiOLi) 2 O(thf)N2 (dabco) 2 ] = and [M(Ph 2 SiOLi) 2 O(thf)N2 (4,4@-bipy) 2 ] = revealed pentacyclic units made up of two LiSi 2 O 3 rings and a folded ladder arrangement of three Li 2 O 2 rings.93 Treatment of alkaline-earth arenesulfonates readily prepared from the metal carbonates and an arenesulfonic acid with one of a range of organo-lithium -sodium or -potassium compounds a§orded the corresponding organo-alkaline-earth compound in high yield.94 The X-ray structure of LiAl[OC(Ph)(CF 3 ) 2 ] 4 revealed a rare trigonal prismatic arrangement around lithium with two LiO(C,Al) and four LiF(C) bonds.95 Reaction of 2,3-dimethylindole with Bu/Li and CO 2 in thf gave a carbamate complex which was tetrameric in the solid state with two boat shaped -LiOCOLiOCO-rings joined by four inter-ring Li–Olinks.The ring oxygen atoms were close to the 2-methyl groups of the indolyl moities suggesting a reason for the second lithiation of 2- alkylindoles at the 2-alkyl position.96 The preparation and X-ray structure of [MLi 4 (k3 -Cl)(k6 -C 4 H 12 O 3 Si 2 )(k-hmpa)(hmpa)N3 (k3 -Cl)(k9 -CO 3 )]·2thf in which three Li 4 O 3 Cl cubanes were linked by central chloride and carbonate anions have been reported.The cubes were also bridged by tetramethylsiloxanediolate and hmpa ligands.97 Natural energy decomposition analysis (a Hartree–Fock based approach) has been used to calculate electrostatic and polarization contributions for aqueous clusters of the alkali metals M(H 2 O)n ` (n\1–4).98 9 Alkali and alkaline-earth metals Reaction of LiR [R\C 6 H 4M(R)-CH(Me)NMe 2N-2 C 6 H 3 (CH 2 NMe 2 ) 2 -2,6 and C 6 H 4MCH 2 N(Me)CH 2 CH 2 OMeN-2] with sulfur yielded the corresponding lithium arenethiolates which crystallized as a hexanuclear prism a planar hexamer and a dimer respectively. The hexamer reacted with LiI thf (1 2) to give [Li 2 (SR)(I)(thf) 2 ].99 The crystal structures of [R1R2CHCS 2 Li·tmen] (R1\Ph R2\pyridyl; R1\H R2\2-methylpyrazine) have been reported as part of a study of the mechanisms of dilithiations in organic syntheses.The first contained a monodentate CS 2 unit whereas in the second both sulfurs were bonded to lithium. Only the pyrazine compound yielded evidence for dilithiation.100 The preparation and structures of [LiSC 6 H 2 -Ph 3 - 2,4,6] 4 [LiSC 6 H 3 -mes 2 -2,6] 3 and [MSC 6 H 3 -trip 2 -2,6] 2 (M\Li Na K Rb Cs) have been reported. The tetramer and trimer crystallize as four- and three-rung ladder frameworks while the dimers containM 2 S 2 cores. The metal centres also interact with the ortho-aryl groups to varying degrees in all structures to an extent determined by ionic size and geometric factors.101 The structures of [Li(pmdien)SCPh 3 ] [Li(thf) 2 SCPh 3 ] 2 [Li(pmdien)Strip] [Li(tmen)Strip] 2 [Li(thf)Smes*] 3 [Li(12- crown-4)SCPh 3 ] and [Li(12-crown)-4) 2 ][Smes*] have been determined in a study of the e§ects of ligand size and donor hapticity on the structures of lithium thiolates.102 3 Sodium The 1 4 reaction between [PPh 4 ]Cl and Na(cp) yielded [PPh 4 ][Na(cp) 2 ] whereas the 1 2 reaction gave [PPh 4 ]cp (cf.preparation of [Li(cp) 2 ]~). An ansa-sodocene [PPh 4 ] [Na(Me 4 C 2 Cp 2 )(thf)] was also prepared. All compounds were structurally characterized. 103 The crystal structure of Na[C 5 Ph 4 H]·2dme revealed discrete ion pairs containing nine-coordinate sodium cations.104 Two types of sodium environment were observed in the structure of [MNa(thf) 2N4 (rubrene)]; the metal atoms were either above and below the central tetracene skeleton (eight-coordinate) or between the peripheral bis(phenyl) arms (ten-coordinate).105 The crystal structure of the radical ion pair [Na(Et 2 O)(pyrene)] obtained via sodium reduction of pyrene in ether showed that each ether-solvated metal cation is g3- and g6-coordinated to one of the six-membered rings of two pyrene radical anions to form a polymer.106 The reduction of acenaphthylene and fluoranthene in diethyl ether with sodium led to the isolation of [Na(15- crown-5)C 12 H 8 (15-crown-5)Na] containing ten-coordinate sodium above and below the cyclopentadienyl ring and [NaL 2 C 16 H 10 NaL 2 ] = (L\dme diglyme) which contained a polymeric array again with ten-coordinate sodium above and below di§erent naphthalene six-membered rings.The metal in the lithium analogue was eight coordinate. 107 The structure of the product obtained via sodium reduction of azulene in diglyme showed doubly solvated sodium cations g5-bonded to the five-membered rings of the dimeric azulene dianions to form a polymer.108 The structure of the product of the sodium reduction of 1,3-diphenyl-4,5,6,7-tetrasilacyclohepta-1,2-diene in diethyl ether yielded a donor-free salt 6 of the allyl anion with five-coordinate sodium.109 The UV–VIS and EPR spectra of the electron-transfer products obtained by sodium reduction of 1,2,4,5-tetracyanobenzene tcnq and tetraphenyl-p-benzoquinone have been reported.110 The crystal structure of [Na 4 (OSiPh 3 ) 4 (H 2 O) 3 ] revealed an Na 4 O 4 cube containing one unhydrated sodium atom111 while that of [NaOC 6 H 4 (CH 2 NMe 2 )-2] 6 showed an 10 I.B.Gorrell Na 6 O 6 core of two face-sharing cubes and that of [NaMOC 6 H 2 (CH 2 NMe 2 ) 2 -2,6-Me- 4N(HOC 6 H 2 (CH 2 NMe 2 ) 2 -2,6-Me-4)] 2 showed each bridging phenolate contained one coordinating and one pendant NMe 2 group.112 Monomeric Na[Nd(OC 6 H 3 Ph 2 - 2,6) 4 ] revealed sodium to be coordinated to three bridging oxygen atoms and three phenyl groups; polymeric MCs 2 [La(OC 6 H 3 Pr* 2 -2,6) 5 ]N= contained caesium bonded solely to phenyl groups.113 The X-ray structures of [Na(k2 -g1-biphenyl-2,2@-diyl ketyl)(hmpa) 2 ] 2 and [Na(k3 -g1-biphenyl-2,2@-diyl ketyl)(hmpa)] 4 prepared from sodium and fluorenone in thf have provided the first structural characterization of an alkali metal ketyl.114 A combination of EPR magnetic susceptibility and powder neutron di§raction has been applied to the formation of sodium- and potassium-based ‘cluster crystals’ in zeolites Y and A respectively.The similarity of the interactions of alkali metals with dehydrated zeolites and the dissolution of those metals in nonaqueous solvents was noted.115 The bis(amido)sodate Na[NaMN(SiMe 3 ) 2 AlMe 3N2 ] has been prepared and structurally characterized; X-ray analysis revealed an infinite array of anions with cations interacting with the H 3 C(Al) groups.116 The structures of [NaNPr* 2 (tmen)] 2 and [NaNcy(Pr*)(tmen)] 2 were based on planar Na 2 N 2 rings. The deprotonating ability of the former complex was compared with that of [MNPr* 2 ] = (M\Li Na) in a series of simple organic reactions.117 The properties of the sodide LiNa(MeNH 2 )n have been studied as a function of n.118 4 Potassium rubidium and caesium The preparations and crystal structures of [K(OEt 2 )cp] [K(ind)(L)] (L\tmen pmdien) and [Na(ind)(pmdien)] have been reported.The potassium compounds formed polydecker chains whereas the sodium compound was monomeric.119 Reaction of Bi(XCN) 3 (X\S Se) containingKXCNas an impurity with dmpu (dmpu\N,N@- dimethylenepropylene urea) gave [K 3 (dmpu) 4 ][Bi(XCN) 6 ]. X-ray crystallography showed the complexes contained pairs of dmpu ligands which bridged between central and outer potassium centres and these units were linked into chains through K· · ·N interactions.120 Reaction of RSH (R\trip) with KH in thf or thf–tmen a§orded [MK(SR)N2MK(thf)(SR)N2MK(thf) 2 (SR)N2 ] and [MK(SR)N2MK(thf)(SR)N2MK(tmen)(SR)N2 ] ·thf which both exhibited box-shaped structures based on two face-sharing K 4 S 4 units.121 The rubidium and caesium dimetallated derivatives of octamethylcyclotetrasilazane have been prepared and crystallographically characterized.Comparison of the structures with those of the lighter alkali metal derivatives were made.122 Reaction of Cs(cp) with [PPh 4 ]Cl in thf yielded [PPh 4 ][Cs 2 cp 3 ] which adopted a bent ionic triple- 11 Alkali and alkaline-earth metals decker structure in the solid state.123 The preparation and crystal structures of [(Ph 2 CCPh 2 )MCs(diglyme)N2 ] = and [MPh 2 C–– (CHCH)·CPh 2NMCs(diglyme)N- (CsOCH 2 CH 2 OCH 3 ) 2 ] = have been reported.124 The structures of [Cs(MR 3 F)] 4 (M\Ga In; R\Et Pr*) were shown to be based on a heterocubane framework which could be described as (CsF) 4 units of the CsF structure stabilized by MR 3 groups.125 Reaction of Mmes 3 (M\Ga In) with CsF in acetonitrile yielded [MCs(MeCN) 2NMmes 3 MFN] 2 ·2MeCN while the analogous reaction with Ga(CH 2 Ph) 3 gave [CsMPhCH 2 ) 3 GaFN] 2 ·2MeCN.Both structures were based on (CsF) 2 rings and exhibited metal–phenyl interactions.126 Two intercalation compounds CsF·Br 2 and 2CsF·Br 2 were formed on reaction of CsF with bromine. Both contained CsF layers separated by perpendicular layers of bromine. Reactions of CsF and RbF with other halogens were also described.127 5 Berylium An IR study of the reaction of laser-ablated beryllium and magnesium atoms with acetylene in excess argon was interpreted as evidence for HBeCCH BeCCH and MgCCH as new product species; a mechanism was also proposed.128 Complex formation equilibria of beryllium(II) with five aliphatic a-hydroxycarboxylic acids have been studied.129 A crystal structure of K 2 Mn 2 (BeF 4 ) 3 revealed tetrahedral beryllium.130 Simultaneous gas phase electron di§raction and mass spectrometry showed that the vapour above BeCl 2 at 274 °C consisted of 97.5% monomer and 2.5% dimer.131 6 Magnesium A book on organomagnesium chemistry has been published.132 Carbon-donor ligands Crystals obtained from a solution of commercial MgBu4(Bu/) and tmen were shown to be [MgBu4 2 ·tmen] by X-ray crystallography.An equilibrium involving loss of tmen was observed in solution.133 The preparations and crystal structures of the dimeric di-n-butyl ether adduct of anthracenylmagnesium bromide134 and [MgBr(C 6 H 3 - mes 2 -2,6)(thf)] 2 135 have been reported.Treatment of C(Me 3 Si) 2 (MeOMe 2 Si)I with magnesium in diethyl ether gave [MgMC(SiMe 3 ) 2 (SiMe 2 OMe)N2 ] and [MgI 2 (OEt 2 ) 2 ] both of which were crystallographically characterized. The Grignard product was isolated from the same reaction in toluene and the X-ray structure of the lithium complex was also reported.136 Toluene solutions of alkylmagnesium chlorides partially solvated by diethyl ether have been investigated.137 EXAFS studies of MgRBr (R\Me Et) in Bu 2 O showed dimers to be present.138 IR and NMR spectroscopic studies of the structure and dynamics of some allylic magnesium compounds have been presented.139 The insertion of ethylene into Mg–C bonds catalysed by an alkyl chain transfer through chain growth polymerization on a lanthanonocene-based catalyst involving chains of 4–200 carbon atoms has been reported.140 The synthesis characterization and reactivity of ruthenocenes bearing pentamagnesiated cyclopentadienyl ligands have been reported.141 Ab initio studies 12 I.B.Gorrell on Mcp 2 (M\Mg Ca) have shown that their geometries (bent for Mg linear for Ca) can be understood in terms of repulsive interactions between the ligands and between the ligands and the distorted metal core,142 and also indicated ionic bonding in several magnesium–anthracene complexes.143 Nitrogen- and phosphorus-donor ligands An alternative preparation of [MgNPh(thf)] 6 (from MgRX rather than MgR 2 ) and its use as imide transfer reagent to for example carbon germanium tin lead phosphorus titanium zirconium and manganese have been reported.The synthesis of the 1-naphthyl derivative was also presented.144 Reaction of Mg(cp) 2 with NRH 2 (R\Bu5 dipp) yielded [Mg(NH 2 Bu5)(g5-cp)(g2-cp)(thf)] or [Mg(NHdipp)(g5-cp)] respectively while reaction of MgBu5 2 with NBu5H 2 a§orded [MgBu5MNH(Bu5)N(thf)] 2 . In contrast treatment of MgBu 2 with NRH 2 (R\mes triph) gave [Mg(NmesH) 2 (hmpa) 2 ] or [Mg(NtriphH) 2 (thf) 2 ]·thf. A bis amide [Mg(Ncy 2 ) 2 ] 2 was isolated from MgBu 2 and Ncy 2 H but N(dipp)H 2 and Mg[N(SiMe 3 ) 2 ] 2 yielded [Mg 3 (k-NdippH) 4 N(SiMe 3 ) 2 ] 2 and N(dipp)H 2 and MgEt 2 gave [MgEt(NdippH)] 12 . Most compounds were crystallographically characterized.145 Double deprotonation of 1,8-diaminonaphthalene with MgBu 2 hmpa yielded the first magnesium amide trimer the structure of which was based on an Mg 3 triangle within an N 6 trigonal prism.146 Ether free reactions of NR(2-pyr)H (R\Me Ph 2-pyr) with ‘MgBu 2 ’ yielded [MMgNR(2-pyr)BuNn] which gave the bis(amido) compound in polar solvents.The driving force was thought to be an increase in coordination number to give an octahedral metal centre.147 A series of amidino bridged complexes have been prepared by insertion of various carbodiimides into the Mg–C bond of [AlR1 2 (k-R2 2 N) 2 Mg(k- R)]n (n\2 4; R1\Me Et; R2\Et Pr*).148 Oxygen- and sulfur-donor ligands Controlled hydrolysis of Mg[TpA3,M%]Me [TpA3,M%\tris(3-M4-tert-butylphenyl-5- methylpyrazolylNhydroborato)] yielded MMg[TpA3,M%](k-OH)N2 the first structurally characterized magnesium hydroxide.149 Fast stereoselective ring-opening polymerization of L,L-dilactide by the acyl cleavage reaction to give isotactic poly(L,L-dilactide) has been achieved using [MgMHB(bpz) 3NOEt] as a catalyst precursor.150 The X-ray structure of [Mg(H 2 O) 4 (C 5 H 2 N 2 O 4 )]·H 2 O revealed an octahedral metal centre surrounded by the heterocyclic nitrogen and the adjacent carboxylate oxygen atom of the orotate group.151 Reaction of [Mg(th§o) 2 ] (th§o\2-tetrahydrofurfuroxide) with [VCl 3 (thf) 3 ] provided [V 2 Mg 2 Cl 4 (k3 ,g2-th§o) 2 (k,g2-th§o) 4 ] the structure of which revealed magnesium in a distorted octahedralMgO 6 environment.152 In the context of alkene polymerization catalysis reaction of [Mg(th§o) 2 ] with MgCl 2 yielded the centrosymmetric species [Mg 4 Cl 2Mk3 ,g2-th§oN2Mk,g2-th§oN4 ] which contained octahedral MgO 6 and trigonal-bipyramidal MgO 4 Cl centres.153 The structures of [Mg(thf) 2 (viph) 2 ] (viph\vinylphenyl) [Mg(thf) 6 ]2` and [Mg(thf) 5 Cl]2` have been reported.154 The first gas-phase evidence for a stable multiply charged metal–ligand unit [Mg(thf) 4 ]2` has been reported.It was suggested that stability was due to orbital overlap rather than electrostatic interactions.155 Reaction of [MMg(OEt) 2Nn] and [MCa(OEt) 2 (EtOH) 4Nn] with Htmhd (1 2) yielded the homoleptic b-diketonate compounds [MM(tmhd) 2Nn]. The triglyme derivative of the magnesium compound [M[Mg(tmhd) 2 ] 2 (triglyme)Nn] and the intermediate [Ca 2 (tmhd) 4 (EtOH) 2 ] were crys- 13 Alkali and alkaline-earth metals tallographically characterized.156 A chain of trigonal bipyramids linked by two common edges has been observed in the structure of MgBr 2 ·OEt 2 .157 The crystal structure of [MgMC 2 H 4 (CO 2 Et) 2N3 ][MgCl 4 ] showed that the cations were linked by other diethyl succinate ligands to form a linear polymer containing octahedral metal centres.158 The preparation and structure of trans-[MgCl 2 (thf) 4 ]·2AsCl 3 ·thf has been reported.159 The structure of [MgMS(C 6 H 4 -CH 2 NMe 2 -2)N2 ] 2 showed the metal centre to be five-coordinate with S N-chelation by a terminal ligand and two S-bridging ligands whose N atoms also coordinate to magnesium.160 7 Calcium strontium and barium Reaction of [CaMN(SiMe 3 ) 2N(thf)(C 5 Pr* 4 H)] with HC–– – CR (R\Ph Fc SiMe 3 SiPr* 3 SiPh 3 ) a§orded [Ca(C–– – CR)(thf)(C 5 Pr* 4 H)].An X-ray study showed the phenyl derivative to be dimeric with bridging acetylides.Solutions were stable in thf but in toluene when R\Ph Fc SiMe 3 or SiPh 3 partial disproportionation occurred.161 Several donor-functionalized chiral cyclopentadienyl complexes of calcium have been prepared and structurally characterized.162 The 1 1 reaction between Ca[N(SiMe 3 ) 2 ] 2 and SiPr* 3 (PH 2 ) in the presence of dme yielded [CaMN(SiMe 3 ) 2N(k-PHSiPr* 3 )(dme)] 2 while the 2 3 reaction in thf gave [CaMN(SiMe 3 ) 2Nk-PHSiPr* 3 ) 3 Ca(thf) 3 ]; a bicyclic structure containing a trigonal bipyramidal Ca 2 P 3 core was deduced for the latter from NMR measurements. A 1 2 reaction a§orded the octahedral complex [Ca(SiPr* 3 PH) 2 (thf) 4 ] which gave 7 on treatment with Sn[N(SiMe 3 ) 2 ] 2 .163 Reaction of Ca[N(SiMe 3 ) 2 ] 2 with P(SiMe 3 ) 2 H in thf yielded [CaMN(SiMe 3 ) 2NMk- P(SiMe 3 ) 2N·thf] 2 which reacted with more P(SiMe 3 ) 2 H to give octahedral Ca[MP(SiMe 3 ) 2 ] 2 ·4thf.If Sn[N(SiMe 3 ) 2 ] 2 is present then CaSn 2 (thf) 3 [k3 -P(SiMe 3 ) 2 ] 4 and CaSn 2 (thf) 2 [k-P(SiMe 3 ) 2 ] 2 [k3 -PSiMe 3 ] 2 can be isolated.164 The preparation and crystal structure of [CaMN(SiMe 2 CH 2 ) 2N(thf) 3 ] 2 has been reported.165 The in situ reaction of [Ca(OEt) 2 (EtOH) 4 ]n with Htmhd and 2,6-N,N-dimethylaminomethyl-4- methylphenol (ArOH) yielded [Ca(tmhd) 2 (OAr) 2 (EtOH)] 2 which was converted into [Ca(tmhd) 1.5 (OAr) 0.5 ] at high temperature and reduced pressure.166 The coordination geometry of divalent calcium ions has been investigated by analysis of the relevant crystal structures in the Cambridge Structural Database and the Protein Database and by ab initio calculation on [Ca(H 2 O)n]2`·mH 2 O (n\1–9; m\1,2).The results which showed that calcium binds to oxygen if possible and prefers coordination numbers 6–8 were compared with those obtained for beryllium magnesium and zinc.167 The structure of calcium 2-furancarboxylate contains three di§erent coordination polyhedra around the metal which are linked to form a three-dimensional framework.168 Surface models for the adsorption of a calcium b-diketonate complex on calcium sulfide have been studied using extended Hu� ckel calculations.169 14 I.B. Gorrell Deprotonation of [(2-C 5 H 4 N)CH 2 CMe 2 ]C 5 H 5 and (CH 3 OCH 2 CH 2 )C 5 H 5 with M[N(SiMe 3 ) 2 ] 2 (M\Ca Sr Ba) yielded the corresponding monomeric metallocenes with the Lewis base centre in the ligands coordinated to the metal.170 The preparations of M(ind) 2 (thf)n (n\1 M\Sr Ba; n\2 M\Ca) and M(ind@) 2 (thf)n (ind@\1,3-diisopropylindenide; n\1 M\Ca; n\2 M\Sr Ba) have been reported.X-ray crystallographic studies showed that the calcium and Ba(ind@) compounds possessed bent metallocene structures but the Sr(ind) and probably Ba(ind) compounds were polymeric.171 The crystal structures of [M(OSiPh 3 ) 2 (15-crown- 5)(thf)] (M\Sr Ba) showed the metals to be eight-coordinate. Heating the solids gave MSi 2 O 5 whereas refluxing toluene solutions yielded a metal oxo species.172 The synthesis characterization and reactivity of some polyether adducts M(O 2 CCF 3 )nL (M\Ba L\15-crown-5; M\Sr Ba L\tetraglyme) have been reported.The compounds decomposed at high temperatures to give MF 2 but in solution with Ti(OPr*) 4 yielded MTiO 3 when coated on silicon substrates below 600 °C.173 The crystal structure of [Sr(g5-C 5 H 2 Pr* 3 -1,2,4) 2 (thf)] revealed a C–Sr–C angle of 139.4(1)°.174 Reaction of barium with 2-pyridyl(phenyl)methane in liquid ammonia thf and diglyme a§orded [BaMg5-CPh(C 5 H 4 N-2)HN2 (diglyme)(thf)] the crystal structure of which was reported.175 Reaction of Ba[N(SiMe 3 ) 2 ] 2 with P(SiMe 2 Pr*) 2 H in thf yielded Ba[P(SiMe 2 Pr*) 2 ] 2 ·4thf which was in equilibrium with the dimer in toluene. Both monomer and dimer were crystallographically characterized.176 Reaction of 2,2,5,5- tetramethyl-2,5-disilaphospholane with Ba[N(SiMe 3 ) 2 ] 2 in dime yielded [Ba(dme) 3MP(SiMe 2 CH 2 ) 2N2 ] which in toluene converted into [Ba(dme)MP(SiMe 2 CH 2 ) 2NMk-P(SiMe 2 CH 2 ) 2N3 Ba(dme) 2 ]; both were crystallographically characterized.177 Reaction of Ba(OH) 2 with pivaloyltrifluoroacetone in MeOHH 2 O gave the acetonate Ba(H 2 O)(pta) 2 ; water s removed by sublimation.The X-ray structure of the hydrate revealed a chain structure while that of the unhydrated complex was found to be Ba 4 (pta) 8 based on a Ba 4 rhombus.178 A solution of Ba 4 (tmhd) 8 in water–ether in the presence of air yielded crystals of [Ba 6 (tmhd) 10 (O 2 )(H 2 O) 6 ] containing a Ba 6 octahedron.179 The X-ray structures and thermal behaviours of two Ba(facac) 2 (azapolyether) complexes have been reported.180 The metal centre in barium 1,3-dithiepan-2-ylidenemalonate adopted a nine-coordinate geometry consisting of three di§erent carboxylate bonding modes (chelated monodentate bidentate x 2 monodentate) and two water molecules.Each ligand was linked to five barium atoms to form a layer structure.181 A range of barium complexes of the new b-diketonates CR1R2(OCH 3 )COCH 2 COR3 have been prepared and investigated as possible CVD precursors to mixed oxides.182 Reaction of a 1 2 mixture of Y[N(SiMe 3 ) 2 ] 3 and Ba[N(SiMe 3 ) 2 ] 2 with Bu5OH (8 equiv.) yielded [YBa 2 (OBu5) 7 (Bu5OH)] the structure of which was based on a YBa 2 triangle with bridging (2 k3 ]3 k2 ) and terminal (1Y]1Ba) OBu5 groups and Bu5OH attached to the second barium.183 Reaction of Ba(OBu5) 2 with Y(tmhd) 3 or Cu(tmhd) 2 yielded [YBa 3 (OBu5) 6 (tmhd) 3 ] and [BaCu(OBu5) 2 (tmhd) 2 ]m respectively. 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ISSN:0260-1818    

DOI:10.1039/ic093003

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

3 Boron By M. A. BECKETT Department of Chemistry University of Wales Bangor Gwynedd LL57 2UW UK 1 Introduction This report takes a similar format to that used last year1 and reviews the chemistry of boron compounds reported during 1996. The literature has been surveyed by use of Chemical Abstracts Volumes 124 and 125 in conjunction with independent searches of BIDS and the principal chemical journals. 2 Reviews The reader is directed specifically to two chapters in Specialist Periodical Reports Organometallic Chemistry (Volume 26) for two reviews complementary to this report. The first review is a comprehensive account of the chemistry of carbaboranes and metallacarbaboranes,2a and the second review is a general account of the organometallic chemistry of Group 13 elements.2b Specific review articles2c–f have appeared on the following topics ‘Man and the elements of Groups 3 and 13’ ‘Boron–carbon multiple bonds’ ‘A new intermolecular interaction unconventional hydrogen bonds with element–hydride bonds as proton acceptor’ ‘Oxidation of B BH BH 2 and BmHn species thermochemistry and kinetics’.The ninth international meeting on boron chemistry IMEBORON IX took place in Heidelberg Germany over the period 14–18 July 1996; a book of abstracts covering all contributions has been published.2g 3 Polyhedral species Boranes The structures and stabilities of the BH 5 2` and BH 6 3` cations have been calculated at the MP2/6-31G** and QCISD(T)/6-311G** levels; the C 2v structure with two threecentre two-electron bonds was found to be a minimum for the BH 5 2` dication whilst the BH 6 3` trication has a stable minimum energy structure of D 3 symmetry.3a Deprotonation of the adduct Me 2 NH·BH 3 with LiBu resulted in Li[Me 2 NBH 3 ] and its solubility has been determined in various solvents; five solvates have been characterised by X-ray structure analysis.3b Royal Society of Chemistry–Annual Reports–Book A 21 Fig.1 ORTEP representation of (B 10 H 8 ) 2 (k-H)(k-OMCH 2N4 OMCH 2N2 CHMe 2 ) (Reproduced by permission from Angew. Chem. Int. Ed. Engl. 1996 35 2647) The reactions of 2-X-B 5 H 8 (X\Br Cl) with secondary or tertiary silylamines proceeded with attachment of amino groups to the clusters e.g. 2-[(Me 3 Si) 2 N]B 5 H 8 was prepared in 57% yield from 2-BrB 5 H 8 and (Me 3 Si) 2 NH; with (Bu5)(Me 3 Si)NH 2-BrB 5 H 8 produced hypho-2,3-k-(Bu5NH)B 5 H 10 in addition to the usual product.3c The closo anions [BnHn]2~ (n\6 10 or 12) were found to react with (SeCN) 2 in organic media to produce derivatives with one SeCN group bonded to the borane cage through Se; single-crystal X-ray di§raction structures of [PPh 4 ] 2 [(SeCN)B 6 H 5 ] [PPh 4 ] 2 [(SeCN)B 10 H 9 ] and [PPh 4 ] 2 [(SeCN)B 12 H 11 ] were reported.3d The synthesis and crystallographic structure of the analogous sulfur compound [PPh 4 ][2- (SCN)B 10 H 9 ]·CH 3 CN has also been described.3e The [2-(CH 3 CN)B 10 H 9 ]~ anion with its unique B–N bond has been analysed by ab initio geometry optimisation IGLO/NMR and FPT-INDO methods and compared with contiguous azaborane systems.3f The structure of [pyCH 2 py][1-IB 10 H 9 ] has been determined by singlecrystal X-ray di§raction at room temperature; the B–I distance M2.206(6)ÅN is signifi- cantly shorter than that found in the corresponding 2-isomer M2.230(2)ÅN.3g The N-fluoro reagent F-TEDA [1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo- [2.2.2]octane bis(tetrafluoroborate)] has been found to react with [B 10 H 10 ]2~ under mild conditions (24 h 25 °C H 2 O or H 2 O–DMF) to produce the first examples of the fluorinated derivatives [B 10 H 10~nFn]2~ (n\1–4) as mixtures of isomers.3h The synthesis solid state structures and spectral properties of O-alkyl and O-acyl derivatives of [(HO)B 12 H 11 ]2~ have been described.3i A one-step preparation of the dimethylsulfide- substituted icosahedral boranes 1,7-(SMe 2 ) 2 B 12 H 10 1,12-(SMe 2 ) 2 B 12 H 10 and [SMe 3 ][B 12 H 11 (SMe 2 )] has been reported from the self-condensation reaction of BH 3 ·SMe 2 in the absence of solvent; single-crystal X-ray structure determinations of the products were reported.3j Amine derivatives of the polyhedral borane anion 22 M.A.Beckett n-[B 20 H 18 ]2~ have been prepared by reaction with en which gave the ae- [B 20 H 17 (en)] 3 ~ anion (a\apical e\equatorial) in addition to a2-[B 20 H 18 ]4~; a more convenient synthesis of the previously known species ae-[B 20 H 17 (NH 3 )]3~ which employed CH 3 CN as the ammonia source has also been described.3k The synthesis and structure of the polyhedral borane anion [k-B 20 H 17 (OH)]2~ which contains both oxygen- and hydrogen-bridge bonds has been reported.3l Nucleophilic ring opening of thf by alkoxide anions was induced by n-[B 20 H 18 ]2~. Oxygen- and hydrogen-bridged species were obtained upon subsequent oxidation; the crystal structure of one such product is shown in Fig.1.3m When reacted with various proton sources the apical–apical isomer of the polyhedral borane anion a2-[B 20 H 18 ]4~ produced the protonated species a2-[B 20 H 19 ]3~ in high yield; the structure of this anion determined crystallographically as its mixed tetraethylammonium/pyridinium salt had a hydrogen-bridge connecting the two MB 10 H 9N cages with a BHB angle of 91(3)°.3n Metallaboranes For convenience this section is divided into three sub-areas tetrahydroborate complexes 4 metal-rich clusters,5 and boron-rich clusters.6 The results of ab initio calculations on [Y(H 2 O) 4 (BH 4 ) 2 ]` a model for [Y(thf) 4 (BH 4 ) 2 ]` revealed that electronic and electrostatic e§ects were of equal importance in determining the stability of the various isomers and co-ordination modes.4a The problem of intramolecular hydrogen-atom exchange in the [OsH 3 (BH 4 )(PR 3 ) 2 ] system was examined from both a theoretical (MP2 MP4 and CCSD(T) computational levels) and experimental (variable temperature 1H NMR) perspective; three exchange processes were fully characterised.4b The compound [MeZnBH 4 ] has been prepared by two routes and characterised by spectroscopic and single-crystal di§raction studies; the structure (Fig.2) revealed a helical polymer in which the MMeZnN` and MBH 4N~ units alternate with the latter functioning as a bidentate ligand with respect to both the adjacent metals.4c The synthesis and reactivity of [MC 5 R 4 PPh 2NU(BH 4 ) 3 ] (R\H Me) and their borane adducts [MC 5 R 4 PPh 2 ·BH 3NU(BH 4 ) 3 ] have been described.With R\Me the products were stable in solution and were isolated but with R\H the products were in equilibrium in solution with the biscyclopentadienyls [MC 5 H 4 PPh 2N2 U(BH 4 ) 2 ] and [MC 5 H 4 PPh 2 ·BH 3N2 U(BH 4 ) 2 ] and with uranium tetraborohydride [U(BH 4 ) 4 ].4d In the presence of CO the ZrIII tetrahydroborate complex [ZrCp(BH 4 )MN (SiMe 2 CH 2 PPr* 2 ) 2N] disproportionated to give two diamagnetic species [ZrCp(BH 4 ) 2MN(SiMe 2 PPr* 2 ) 2N] and the dicarbonyl derivative [ZrCp(CO) 2MN (SiMe 2 CH 2 PPr* 2 ) 2N]; the former compound underwent a slow further reaction with CO to a§ord the formyl-ylide species [ZrCp(BH 4 )(HCOPPr* 2 CH 2 SiMe)N (SiMe 2 CH 2 PPr* 2 ·BH 3 )] which was characterised by X-ray di§raction and by NMR spectroscopy.4e The addition of BH 3 ·thf to a CH 2 Cl 2 solution of [W 2 (k-COMe)(CO) 2 (k- dppm)Cp 2 ][BF 4 ] produced in high yield (79%) the four-vertex MBCW 2N cluster species [W 2 (k-CHBH 3 )(CO) 2 (k-dppm)Cp 2 ][BF 4 ]; both compounds were characterised by X-ray di§raction and spectroscopic studies.5a The reactions of [Co 2 (CO) 8 ] with the ferraboranes [B 2 H 6 Fe 2 (CO) 6 ] [HFe 3 (CO) 9 BH 4 ] [HFe 3 (CO) 10 BH 2 ] and [HFe 4 (CO) 12 BH 2 ] led to fragment addition and/or fragment exchange and several 23 Boron Fig.2 Helical polymeric structure of solid methylzinc tetrahydroborate at 150K determined by X-ray di§raction (Reproduced by permission from J. Chem. Soc. Dalton Trans. 1996 857) new mixed-metal metallaboranes Me.g.[B 2 H 5 FeCo(CO) 6 ] [Fe 2 Co(CO) 9 (k-CO)BH 2 ] [FeCo 2 (CO) 9 (k-CO)BH] [FeCo 2 (CO) 9 (BH) 2 ] and [HFe 3 Co(CO) 12 BH]N were isolated and characterised spectroscopically.5b A heteroborane analogue of nido- [B 4 H 7 ]~ viz. nido-[1,1,2,2-(CO) 4 -1,2-(PPh 3 ) 2 -1,2-FeIrB 2 H 5 ] was formed in low yield as a degradation product from the reaction between [Mk-Fe(CO) 4NB 6 H 9 ]~ and trans- [Ir(CO)Cl(PPh 3 ) 2 ]; the compound was fluxional in solution and has been characterised by single-crystal X-ray di§raction.5c The crystal structures of [RhRu 4 H 2 (Cp*)(k- Cl)(CO) 12 B] and [RhRuH(nbd)(CO) 12 B(AuPPh 3 )] displayed cluster core geometrical variations of the MBRhRu 4N skeletons consistent with valence-electron counts.5d Ligand substitution reactions of [RhRu 3 H(Cp*)(CO) 9 BH 2 ] clusters with bidendate phosphines yielded compounds of the type [RhRu 3 H 2 (Cp*)(CO) 8 (L-P)(BH)] (L\dppf and dppa) with the P-donor ligands replacing one carbonyl ligand from the wingtip butterfly site.5e A single-crystal X-ray di§raction study of [(CO)H(PPh 3 ) 2 -arachno-OsB 3 H 8 ] con- firmed the metal atom to be in the wingtip position; the overall dimensions were very similar to those of the ruthenium derivative [(CO)H(PPh 3 ) 2 -arachno-RuB 3 H 8 ].6a The compound [(PPh 3 )Mk3-HB(pz) 3N-arachno-RuB 3 H 8 ] has been established as the wingtip isomer with the PPh 3 ligand endo and the HB(pz) 3 ligand exo at the Ru centre.6b The electronically unsaturated chromaborane [Cp* 2 Cr 2 B 4 H 8 ] reacted with CS 2 to produce in high yield (90%) the saturated cluster [Cp* 2 Cr 2 (CH 2 S 2 )B 4 H 6 ] which contained the intracluster bridging methanedithiolato MH 2 CS 2N ligand.6c The reaction of the chromaborane [Cp* 2 Cr 2 B 4 H 8 ] with [Fe 2 (CO) 9 ] produced the trimetalla cluster [Cp* 2 Cr 2 B 4 H 8 Fe(CO) 3 ]; this was characterised by single-crystal X-ray di§raction and described as a MFe(CO) 3N fragment co-ordinated by a chelating chromaborane cluster (Fig.3).6d The polyhedral closo 7-vertex anion [NiCpB 6 H 6 ]~ was prepared as its [NBu 4 ]` salt in high yield (80–85%) from [NBu 4 ] 2 [B 6 H 6 ] with two equivalents of [NiCp 2 ] and one equivalent of Na–Hg amalgam in CH 3 CN at room temperature; an improved synthesis of [NBu 4 ] 2 [B 6 H 6 ] in yields of 20–25% from Na[BH 4 ] and BF 3 ·OEt 2 in diglyme was also described.6e The reaction of [TiCp 2 Cl] with K[B 6 H 9 ] yielded the blue air-sensitive dimeric compound [MCp 2 TiB 6 H 9N2 ] which had a structure reminis- 24 M.A.Beckett Fig. 3 Molecular structure of [Cp* 2 Cr 2 B 4 H 8 Fe(CO) 3 ] (Reproduced by permission from J. Am. Chem. Soc. 1996 118 8164) cent of the known Pt cluster [Pt 2 (B 6 H 9 ) 2 (PMe 2 Ph) 2 ] but without a metal–metal bond.6f The hexaborane(10) analogue [(PPh 3 ) 2 (CO)IrB 5 H 8 ] reacted with [Fe(CO) 9 ] in benzene to form the closo derivative [1,1,1-(CO) 3 -2,2-(CO) 2 -2,4-(PPh 3 ) 2 -closo-1,2- FeIrB 5 H 4 ] in 28% yield; its sodium salt Na[(PPh 3 ) 2 (CO)IrB 5 H 7 ] reacted with [MPt(PMe 2 Ph)Cl 2N2 ] in CH 2 Cl 2 to a§ord the nido seven-vertex cluster [2-(CO)-2,2- (PPh 3 ) 2 -7-Cl-7-(PMe 2 Ph)-nido-2,7-IrPtB 5 H 7 ] in low yield.6g The reaction of CS 2 with the open nido-6-iridadecaboranes [H(PPh 3 ) 2 -nido-6-IrB 9 H 13 ] and [H(PPh 3 )(ortho- Ph 2 PC 6 H 4 )-nido-6-IrB 9 H 12 -5 ] yielded closo 10-vertex species with boron-to-metal dithioformate bridges; the isocloso species [1,1,1-H(PPh 3 )(ortho-Ph 2 PC 6 H 4 )-isocloso- 1-IrB 9 H 8 -2 ] reacted similarly to produce the closo species [10-(PPh 3 )-2,6 2,9-(k- S 2 CH) 2 -2-(ortho-Ph 2 PC 6 H 4 )-closo-2-IrB 9 H 5 -1 ] by an unpredecented isocloso] closo conversion.6h The novel 18-vertex macropolyhedral diiridaborane [M(CO)(PMe 3 ) 2 Ir 2N2 B 16 H 14 ] isolated in low yield from the thermolysis of [(CO)(PMe 3 ) 2 IrB 8 H 12 ] and characterised by single crystal X-ray di§raction NMR spectroscopy and mass spectrometry comprised a closo 12-vertex MIrB 11N subcluster and a nido eight-vertex MIrB 7N subcluster fused together with two boron atoms in common (Fig.4).6i Heteroboranes The reader is directed to the Royal Society of Chemistry publication Specialist Periodical Report Organometallic Chemistry (Volume 26) for a comprehensive review of the 1996 literature concerning carbaboranes.2a Monocarbaboranes will be discussed first.7 An improved synthesis of the monocarbaborane arachno-4-CB 8 H 14 (from ortho-C 2 B 10 H 12 ) and the first definitive conforma- 25 Boron Fig. 4 Molecular structure of [MIr(CO)(PMe 3 ) 2N2 B 16 H 14 ]. (Reproduced by permission from J. Chem. Soc. Dalton Trans. 1996 3146) tion of the structure of its conjugate anion arachno-[4-CB 8 H 13 ]~ have been reported; the anion was characterised in the solid state crystallographically and in solution by an ab initio/IGLO/NMRinvestigation.7a The reactions of [CB 9 H 10 ]~ with (i) anhydrous HF (ii) N-chlorosuccinimide (iii)N-bromosuccinimide and (iv) I 2 led to regioselective mono- and di-halogenation of the lower belt; the anions [6-CB 9 H 9 F]~ [6,7- CB 9 H 8 F 2 ]~ and [6,8-CB 9 H 8 F 2 ]~ were the first examples of 10-vertex closo heteroborane clusters with B–F bonds.7b The new isocyanato carbaborane anion [7-OCN-7- CB 10 H 12 ]~ was prepared from the reaction of triphosgene with 7-H 3 N-7-CB 10 H 12 in the presence of NEt 3 ; the structure of the compound was established by NMR and IR spectroscopy.7c C-methylation of the anion [CB 11 H 12 ]~ followed by permethylation by methyltriflate in the presence of CaH 2 and 2,6-di-t-butylpyridine a§orded a 48% yield of the [CB 11 Me 12 ]~ anion which was characterised electrochemically spectroscopically and crystallographically as its dimethylanilinium salt.7d The stable free radical [CB 11 Me 12 ]· was obtained as shiny black tetrahedral crystals from the oxidation of Cs[CB 11 Me 12 ] by PbO 2 –CF 3 COOH; the free radical was stable in air for a few days and sublimable under reduced pressure but was destroyed by heating over 150 °C.7e Dicarbaboranes will be considered next.A recently developed Hu� ckel method has been used to study some closo-carbaboranes,C 2 BnHn`2 (n\5–12); relative energies of isomers were generally in good agreement with experimental observations although some discrepancies were found.8a The measured 13C NMR chemical shifts of over 40 carbaboranes correlated well with ab initio/IGLO/NMR calculated values at both the DZ//3-21G and DZ//6-31G* levels of theory and this combined with recently reported 11B NMR correlations of experiment with theory significantly adds to the 26 M.A.Beckett arsenal of carbaborane NMR structure proof methods.8b A mechanism for formation of 1,2-C 2 B 4 H 6 from B 4 H 10 and C 2 H 2 involving ‘B 4 H 8 ’ has been supported by a theoretical study.8c The synthesis and structural studies (NMR X-ray di§raction ab initio/IGLO/NMR methods) of several new subicosahedral carbaboranes with adjacent cage carbons have been reported closo-C 2 B 5 H 7 nido-2,3-C 2 B 4 H 8 nido-4,5- C 2 B 6 H 10 nido-[4,5-C 2 B 6 H 9 ]~ nido-[3,4-C 2 B 5 H 8 ]~ arachno-[5,6-C 2 B 7 H 12 ]~ arachno-[4,5-C 2 B 6 H 11 ]~.8d Strong evidence was obtained for the formation at low temperature of an ‘open’ cage axially positioned adduct from the interaction of trimethylamine with closo-1,6-C 2 B 7 H 9 .8e Definitive crystal structures of ortho- meta- and para-C 2 B 10 H 12 were obtained as their hydrogen bonded 1 1 adducts with hmpa.8f Reaction of closo-1,12-C 2 H 2 B 10 Me 10 in CCl 4 solution with Cl 2 under UV light resulted in a derivative in which all the methyl groups at the boron centres were halogenated; closo-1,12-C 2 H 2 B 10 (CH 2 Cl) 10 was characterised by a single-crystal Xray di§raction study.8g The single-crystal X-ray di§raction structures of a number of other substituted closo-C 2 B 10 H 12 derivatives have been reported 1-Ph-1,2- C 2 B 10 H 11 ,8h 1-Pr* 2 P-2-Ph-1,2-C 2 B 10 H 10 ,8i 1-Ph 2 P-2-Ph-C 2 B 10 H 10 ,8j 1,7-Ph 2 -1,7- C 2 B 10 H 10 .8k The deboronation of C-substituted ortho- meta- and closo-carbaboranes using wet fluoride ions has been described; thus hrated [Bu 4 N]F was found to be an e§ective reagent for the conversion of closo-R@RAC 2 B 10 H 10 into nido-[R@RAB 9 H 10 ]~ allowing access to a number of new nido-carbaborane derivatives which were inaccessible using other deboronating reagents.8l The reaction of 1,2-dehydro-ortho-carbaborane with thiothenes has been reported as an easy synthesis of ‘benzocarbaboranes’.8m Crystallographic evidence for the diene character of the ‘benzocarbaborane’ closo-1,2-C 2 B 10 H 10 -1,2-C 4 H 4 has been obtained and the nido analogue [C 2 B 9 H 10 (C 4 H 4 )]~ gave a Diels–Alder adduct with maleic anhydride.8n There were a number of reports of icosahedral carbaboranes species linked by organic residues.8o–s Thus methodology leading to a new class of rod-like paracarbaborane derivatives involving palladium-catalysed coupling of B-iodinated para-carbaboranes with terminal alkynes,8o the synthesis of bis- and tris(closo-1,2- C 2 B 10 H 11 -1-yl)-R (R\1,1@-biphenyl or -1,3,5-benzene) derivatives,8p and the synthesis of macrocyclic compounds composed of three or four ortho-carbaborane icosahedra linked by MCH 2N3 groups were reported.8q The synthesis and molecular structures of carbaboranes linked by a simple C–– C double bond e.g.trans-1,2-bis(2- Ph-1,2-C 2 B 10 H 10 -1-yl)ethene and a metallated analogue (Fig. 5) prepared by decapitation of the carbaborane by excess of KOH in EtOH followed by further reaction of the so-produced bis nido anion with [MRu(para-cymene)Cl 2N2 ] were described.8r The single-crystal X-ray di§raction structure of M2-Ph-(1,2-C 2 B 10 H 10 -1-yl)N2 -1,4-C 6 F 4 was studied to establish the structural consequences of modifying the steric and electronic properties of the phenyl ring in carbaboranes by substitution.8s A number of papers appeared during 1996 concerning carbaboranes with more than two carbon atoms.9 The synthesis of the parent nido-tricarbahexaborane nido-2,3,4- C 3 B 3 H 7 and several derivatives have been reported from the reaction of B 4 H 10 with 1-en-3-ynes.9a Monocarbon insertion into the neutral nido-5,6-C 2 B 8 H 12 and its anion nido-[5,6-C 2 B 8 H 11 ]~ using [CN]~ and Bu5NC as insertion reagents gave the ligand derivatives of the 11-vertex tricarbollide series of general formula 7-L-nido-7,8,9- C 3 B 8 H 10 (L\H 2 N~ Bu5NH 2 ); subsequent methylation of these products gave derivatives with L\Me 3 N Bu5(Me)NH.9b Thermal rearrangement of the zwitterionic 27 Boron Fig.5 Molecular structure of ethene linked closo-pseudocloso bis(carbametallaborane). (Reproduced by permission from Chem. Commun. 1996 1327) 7-(Me 3 N)-nido-7,8,9-C 3 B 8 H 10 and of the nido-[7,8,9-C 3 B 8 H 11 ]~ anion at 350 °C gave high yields of the isomeric tricarbollide species 10-(Me 3 N)-nido-7,8,10-C 3 B 8 H 10 and nido-[7,8,10-C 3 B 8 H 11 ]~ respectively.9c The first definitive X-ray structure of a 2,3,4,5- tetracarba-nido-hexaborane(6) derivative was obtained for nido-2,3,4,5-C 4 B 2 Me 5 -6- MNSFe 2 (CO) 6N.9d The ab initio/IGLO/NMR method established the structures of the three known isomers of nido-C 4 B 7 H 11 to be 7,8,9,10- 1,7,8,10- and 2,7,9,10-.9e The synthesis of the first ‘carbons apart’ tetracarbaborane (CSiMe 3 ) 4 B 8 H 8 has been achieved in 10% yield from the reaction of NiCl 2 with closo-exo-4,5-[(k-H) 2 Li(tmeda)] -1-Li(tmeda)-2,3-(SiMe 3 ) 2 -2,3-C 2 B 4 H 4 in a 1 1 stoichiometry; the solid state structure of this tetracarbaborane resembles a cuboctahedron.9f The room temperature reaction between a thf solution of 2,4,7,9-(Me 3 Si) 4 -nido-2,4,7,9-C 4 B 8 H 8 and finely cut excess of Li produced [Li(thf) 4 ][(Me 3 Si) 4 C 4 B 8 H 9 ] as an EPR silent transparent crystalline solid in 41% yield; with Mg in place of Li the magnesacarbaborane (thf) 2 Mg(SiMe 3 ) 4 C 4 B 4 H 8 was formed in 88% yield.9g The macropolyhedral carbaborane C 4 B 18 H 22 characterised by single-crystal X-ray di§raction was described as two nido-type M7,8-C 2 B 9 H 11N units symmetrically conjoined at the 9,10 positions with the B(9)–B(9@) distance at ca.1.65Å and the B(9)–B(10@) and B(10)–B(9@) distances at ca. 1.96Å.9h A number of papers appeared during 1996 concerning heteroboranes with heteroatoms other than carbon.10 The synthesis crystal structure and spectroscopic properties of Me 2 InB 3 H 8 were reported; this indatetraborane was synthesised from Me 3 In and B 4 H 10 at room temperature.10a The first closo monosilaborane [Et 4 N] [MeSiB 11 H 11 ] was formed in 93% yield from the reaction of [Et 4 N][MeSiB 10 H 12 ] with Et 3 N·BH 3 in boiling diglyme.10b A high-yield synthesis of the first arachno silaborane MeSiB 9 H 12 (NHMe 2 ) (Fig.6) from arachno-B 9 H 13 (SMe 2 ) with MeHSi(NMe 2 ) 2 was reported.10c 28 M.A. Beckett Fig. 6 Molecular structure of arachno-MeSiB 9 H 12 (NHMe 2 ) (Reproduced by permission from Organometallics 1996 15 2569) A rational synthetic route to silicon-containing heteroboranes was achieved for [7-R-7-SiB 10 H 12 ]~ (R\H Me Ph) from Na 2 [B 10 H 12 ] and HRSiCl 2 ; the reaction proceeded in an analogous manner to that found for CH 2 X 2 (X\halogen).10d Addition of three equivalents of KH·BEt 3 to [Me 3 NH][MeSiB 10 H 12 ] followed by addition of one equivalent of SnCl 2 or SbI 3 a§orded the heterosilaboranes [SnSiMeB 10 H 10 ]~ and SbSiMeB 10 H 10 respectively; the stannasilaborane was characterised crystallographically as its [MePh 3 P]` salt.10e Reaction of the phosphaalkyne Bu5C–– – P with B 10 H 12 (CH 3 CN) 2 yielded the nido 11-vertex phosphaborane cluster compound nido-Bu5(H)C––PB 10 H 13 in which the P atom is inserted directly into the polyhedral cage framework;10f the adamantyl phosphaalkyne reacted similarly.10g A new synthetic route to azacarbaborane clusters has been described nucleophilic attack of the isoelectronic nido-[5,6-C 2 B 8 H 11 ]~ or nido-[B 10 H 13 ]~ anions at a nitrile carbon followed by hydroboration and cageinsertion gave new azacarbaborane clusters in good yield e.g.nido-[B 10 H 13 ]~ formed arachno-[7-Me-7,12-CNB 10 H 13 ]~ with CH 3 CN.10h The aza-closo-boranes para- ClC 6 H 4 NB 9 H 9 and MeNB 11 H 11 were brominated iodinated or methylated under Friedel–Crafts conditions to give para-ClC 6 H 4 NB 9 H 4 Br 5 para-ClC 6 H 4 NB 9 H 7 I 2 and para-ClC 6 H 4 NB 9 H 4 Me 5 and MeNB 11 H 10 Br MeNB 11 H 10 I and MeNB 11 - H 5 Me 6 respectively; the upper boron belt adjacent to N was not involved in the substitution reactions.10i Comparative NMR spectroscopic studies of [OB 11 H 12 ]~ [MeNB 11 H 11 (OMe)]~ and [Me 2 CH(Me 2 CH)B 11 H 13 supported the view that the 12-vertex oxaborane anion was a contiguous nido-type12-vertex cluster species.10j Reactions between nido-NB 9 H 12 or nido-SB 9 H 11 and Lewis bases (L) gave two series of corresponding arachno compounds exo-9-L-arachno-6-NB 9 H 12 and exo-9-Larachno- 6-SB 9 H 11 (L included NEt 3 quinoline isoquinoline urotropine py MeCN MeNC NH 3 SMe 2 ,PPh 3 ).10k Mild thermolysis of SB 8 H 10 (SMe 2 ) resulted in the formation of the macropolyhedral S 2 B 17 H 17 (SMe 2 ) in low yield; the structure was described as a conventional nido-type 11-vertex MSB 10 H 9N subcluster fused to an unprecedented arachno-type 10-vertex MSB 9 H 8 (SMe 2 )N subcluster; the two parts shared two boron atoms.10l The crystal structure of 9-(PCy 2 Ph)-6-SB 9 H 11 has been determined;the cluster had the expected arachno 10-vertex MSB 9N geometry with the phosphine substituent exo.10m 29 Boron Metallaheteroboranes Following on from previous years a survey of the more important developments in metallacarbaborane chemistry is included in this section; a comprehensive review of this area is available.2a A number of papers relating to closo 12-vertex rhodamonocarbaborane species were published during 1996.11a–d The synthesis and molecular structure of the first hydridorhodacarbaborane [2,7-(PPh 3 ) 2 -2-H-2-Cl-1-(NMe 3 )-2,1-RhCB 10 H 9 ] with an icosahedral monocarbon carbaborane ligand has been described.11a Other clusters include the 16-electron metal products [RhX(PPh 3 )(g5-7-NH 2 Bu5-7-CB 10 H 10 )] (X\Cl Br) from [RhX(PPh 3 ) 3 ] and nido-7-NH 2 Bu5-7-CB 10 H 12 in toluene.11b In the presence of Ag[BF 4 ] these clusters reacted with arenes in CH 2 Cl 2 solution and a§orded [Rh(g6-arene)(g5-7-NHBu5-7-CB 10 H 10 )] [arene\PhMe mesH MeC 6 H 4 C 6 H 4 -4,4@ [2 2 ](1,4)-C 16 H 16 ] with deprotonation at the NH 2 Bu5 group.11c The complex [RhBr(PPh 3 )(g5 -7-NH 2 Bu5-8-CH 2 CO 2 Et-7-CB 10 H 9 )] was also prepared and characterised by X-ray crystallographic and spectroscopic techniques.11d The charge-compensated carbaboranes nido-7-NR 3 -7-CB 10 H 12 (NR 3 \NMe 3 NH 2 Bu5 NMe 2 Bu5) when reacted with [Ru 3 (CO) 12 ] in toluene at reflux temperatures a§orded the triruthenium complexes [Ru 3 (CO) 8 (g5-7-NR 3 -7-CB 10 H 10 )]; the structure of the NMe 3 derivative was established by X-ray crystallography.11e The first fully sandwiched lithiacarbaborane complex [Li(tmeda) 2 ][commo-1,1@- LiM2,3-(Me 3 Si) 2 -2,3-C 2 B 4 H 5N2 ] has been prepared and characterised crystallographically.12a The single-crystal X-ray structures of the holmium(III) ‘carbons adjacent’12b [Li(tmeda) 2 ][Li 2 (tmeda) 2MHoCl 2 (2,3-MMe 3 SiN2 C 2 B 4 ) 2 ] and the dinuclear ‘carbons apart’12c (Fig. 7) carbaborane clusters have been reported; similar ‘carbons adjacent’ species have been prepared with Sm Gd Dy and Er.12d Trinuclear lanthanide metal carbaborane species comprising three half-sandwich lanthanacarbaborane units three lithiacarbaboranes and three bridging Li atoms have been reported; the nine metal atoms form tricapped-trigonal-prisms with the lanthanide metals in the capping positions.12e The formation of nido-[7,8-(PR 2 )-7,8- C 2 B 9 H 10 ]~ from closo-1,2-(PR 2 ) 2 -1,2-C 2 B 10 H 10 (R\Ph Et Pr* OEt) in refluxing EtOH was enhanced by the complexation of the phosphinocarbaborane to transition metals; the crystal structures of [MCl 2M7,8-(PPr* 2 ) 2 -7,8-C 2 B 9 H 10Nn] (M\Au n\1; M\Ru n\2) were determined.12f Silver complexes of the nido-[7,8-(PPh 3 ) 2 -7,8- C 2 B 9 H 10 ]~ ligand have been similarly prepared and the AgI atoms displayed trigonalplanar or tetrahedral geometry with one or two additional neutral ligands respectively.12g Analogous AuI complexes were reported.12h New Rh complexes of nido-[7,8- (PPh 3 ) 2 -7,8-C 2 B 9 H 10 ]~ were prepared from [X 2 RhM7,8-(PPh 3 ) 2 -7,8-C 2 B 9 H 10N] [X 2 \cod (CO) 2 ] by ligand substitution reactions (X 2 \mono-amines and -phosphines and chelating di-amines and -phosphines).12i Modulation of agostic BH]Ru bonds observed by 1H NMR spectroscopy in exo-monophosphine-7,8-dicarba-nidoundecaborate derivatives was found to be dependent upon the nature of the trans ligand; this permitted an evaluation of the trans influence of a series of ligands and the following order was obtained H[PR 3[CO[BH[Cl.12j The closo-auracarbaboranes 1,2-(AuPPh 3 ) 2 -1,2-C 2 B 10 H 10 and 1,1@-(AuPPh 3 ) 2 -[2-(1@,2@-C 2 B 10 H 10 )-1,2- C 2 B 10 H 10 ] were synthesised and characterised by NMR spectroscopy and X-ray crystallography.12k Crystal structures of [Co 2 (CO) 2 (g5-7,8-C 2 B 9 H 11 ) 2 ] [Co 2 (CO)(PMe 2 Ph)(g5-7,8-C 2 B 9 H 11 ) 2 ] [CoCl(PMe 2 Ph) 2 (g5-7,8-C 2 B 9 H 11 )] and the 30 M.A.Beckett Fig. 7 Molecular structure of a dinuclear HoIII ‘carbons apart’ carbaborane cluster (Reproduced by permission from Acta Crystallogr. Sect. C. 1996 52 9) charge-compensated complex [Mn(CO) 3Mg5-7,8-C 2 B 9 H 10 -10-O(CH 2 ) 4N] were reported. 12l,m The first air-stable cationic metallacarbaborane [3-(MeCN)-3,3- (PPh 2 Me) 2 -3,1,2-closo-RhC 2 B 9 H 11 ][SbF 6 ] not containing a charge-compensating carbaborane ligand has been synthesised and characterised by X-ray crystallography and spectroscopic techniques.12n The synthesis and reactivity of several complexes of the type [Ru(CO) 2 L(g5-7,8-C 2 B 9 H 11 )] (L\donor ligand) have been reported; novel products were obtained from reactions with the alkynes Bu5C–– – CH and Me 3 SiC–– – CHin which the carbaborane ligand adopted a non-spectator role.12o The compounds [Ru 3 (CO) 12 ] and nido-[7,8-Me 2 -7,8-C 2 B 9 H 11 ] when reacted in CH 2 Cl 2 solution a§orded a 1 2 mixture of [Ru(CO) 3 (g5-7,8-Me 2 -7,8-C 2 B 9 H 9 )] and [Ru 3 (CO) 8 (g5-7,8- Me 2 -7,8-C 2 B 9 H 9 )]; treatment of the trinuclear species with tertiary phosphines produced carbonyl substitution and/or degradation to dinuclear species.12p An alternative route to closo-[3,3-(PPh 3 ) 2 -3-Cl-3,1,2-RhC 2 B 9 H 11 ] and its single-crystal X-ray structure was published.12q The reaction between [Ru([9]aneS 3 )(MeCN) 3 ][CF 3 SO 3 ] 2 and Tl[TlC 2 B 9 H 10 Ph] or Tl[TlC 2 B 9 H 9 Ph 2 ] a§orded respectively the closed 12-vertex species [1-Ph-3,3,3-[9]aneS 3 -k3-S,S@,SA-3,1,2-closo-RuC 2 B 9 H 10 ] or [1,2- Ph 2 -3,3,3-[9]aneS 3 -k3-S,S@,SA-3,1,2-pseudocloso-RuC 2 B 9 H 9 ] characterised by X-ray di§raction studies.12r Other pseudocloso Ir Rh and Ru diphenylcarbaboranes e.g.[3- MLxMN-1,2-C 2 B 9 H 9 -1,2-Ph 2 ] [MLxMN\Cp*Ir (g6-C 6 H 6 )Ru (g6-C 6 Me 6 )Ru (g6- cym)Ru (g5-heptamethylindenyl)Rh] were reported and these were characterised by the C(1) · · · C(2) connectivity being broken with the generation of an approximately square M(3)C(1)B(6)C(2) face.12s,t A new synthesis of Cs[commo-3,3@-Co(8,9,12-I 3 - 3,1,2-CoC 2 B 9 H 8 ) 2 ] and its subsequent reaction with MeMgBr–[Ph 3 PMe]Br to yield [MePPh 3 ][commo-3,3@-Co(8,9,12-Me 3 -3,1,2-CoC 2 B 9 H 8 ) 2 ] was described.12u The 31 Boron synthesis halide complexes and supramolecular chemistry of hydrocarbon-soluble [12]mercuracarborand-4 derivatives were reported.12v Reaction of [UBr 4 (NCMe) 4 ] with Li 2 [C 2 B 9 H 11 ] in CH 3 CN solution cleanly produced the bis(carbollide) complex anion [U(C 2 B 9 H 11 ) 2 Br 2 ]2~.12w The reactions of the tricarbaborane anion nido-[6-Me-5,6,9-C 3 B 7 H 9 ]~ with MX 2 salts (M\Ni Pd Pt) yielded a series of new bis(tricarbadecaboranyl) [(g4- MeC 3 B 7 H 9 ) 2 M] sandwich complexes; these new complexes were considered as analogues of [M(g3-C 3 H 5 ) 2 ].12x There was considerable interest in non-carbon-containing metallaheteroboranes during 1996 and thia derivatives were the most extensively studied.The molecular structures of the open 9- and 11-vertex arachno-[5,5-(PMe 2 Ph)-4,6,5-S 2 PdB 6 H 8 ] and nido-[8,8-(dppe)-7,8-SRhB 9 H 10 ] derivatives were established.13a,b The fluxional behaviour of MM(PR 3 ) 2N in closo-12-vertex metallaheteroboranes with MMZB 10N (Z\S Se Te) and MMX 2 B 9N (X\C or As) was characterised and a mechanism for the rotation of the MM(PR 3 ) 2N units above the heteroborane cage suggested.13c Reactions of anti-9,9@-S 2 B 16 H 16 with [MRhCl 2 Cp*N2 ] resulted in the syn and anti isomers of the macropolyhedral rhodathiaboranes [Rh 2 Cp* 2 S 2 B 15 H 14 (OH)] (Fig. 8); reaction with [NiBr 2 (PPh 3 ) 2 ] in the presence of base a§orded the 19-vertex cluster [(PPh 3 )NiS 2 B 16 H 12 (PPh 3 )] consisting of a nido shaped M1-NiB 8N subcluster and a closo shaped M1,4-NiSB 10N subcluster fused with the M1@,3@,4@ 1,2,3NMNiB 2N triangular face in common; a co-product in the reaction was the related 18-vertex non-metallated S 2 B 16 H 14 (PPh 3 ) cluster.13d,e Formation of 9- 10- and 11-vertex metallaheteroborane clusters by insertion of heteroatoms into existing metallaboranes was achieved for the cases of C N and S; thus the reaction of arachno-[(PMe 3 ) 2 (CO)HIrB 8 H 12 ] with H 2 S yielded nido-[2,2,2- (PMe 3 ) 2 H-2,6-IrSB 8 H 10 ] closo-[2,2,2-(PMe 3 ) 2 H-2,1-IrSB 8 H 8 ] and nido- [(PMe 3 ) 2 (CO)HIrS 2 B 8 H 8 ] but reaction with anhydrous hydrazine gave nido-[2,2,2- (PMe 3 ) 3 -2,9-IrNB 7 H 9 ].13f 4 Organometallic boron species Triarylboranes The molecular structure of Ph 3 B·thf was established by a single-crystal X-ray di§raction study the B–Odistance being 1.660(4)Å.14a The acceptor strength of a number of Lewis-acidic fluorinated triarylboron compounds was determined and shown to depend on the amount and position of fluorine substitution.14b The perfluorinated triaryl (C 6 F 5 ) 3 B is a convenient Lewis acid of comparable strength to BF 3 and its potential as a catalyst for organic transformations is beginning to be appreciated; thus the catalysed hydrosilation of aromatic aldehydes ketones and esters were reported.14c The silylene–borane adduct Bu5NC(H)––C(H)N(Bu5)S i]B(C 6 F 5 ) 3 was obtained from the reaction of the silylene and B(C 6 F 5 ) 3 ; it rearranged to a silylborane Bu5NC(H)––C(H)N(Bu5)Si(C 6 F 5 )MB(C 6 F 5 ) 2N with a half-life of about one month in toluene.14dA zirconocene–betaine system was formed by electrophilic substituion with B(C 6 F 5 ) 3 of a cyclopentadienyl ligand from [Cp 2 ZrC 4 Me 4 ]; the product contained a g5-CpB(C 6 F 5 ) 2 ligand with an additional ortho-F bridge interaction with Zr.14e Transmetallation of C 5 H 4 (SnMe 3 ) 2 by PhBCl 2 and ZrCl 4 led to the formation of 32 M.A.Beckett Fig. 8 ORTEP drawings of (a) syn- and (b) anti-[Rh 2 Cp* 2 S 2 B 15 H 14 (OH)] (Reproduced by permission from J. Chem. Soc. Dalton Trans. 1996 1776) 33 Boron [(k-PhB)(g5-C 5 H 4 ) 2 ZrCl 2 ]; the unstable ligand PhBCp 2 was isolated as its py (1 1) or dabco (2 1) adduct.14f The synthesis and structure of the half-sandwich compounds14 g [(mes) 2 B(g6-mes)Cr(CO) 3 ] [(mes)B(g6-mes) 2MCr(CO) 3N2 ] and [B(g6- mes) 3MCr(CO) 3N3 ] and the sandwich compounds14h [MR 2 B(g6-Ph)N2 M] (M\V Cr; R\mes Pr*O) and their redox behaviour were reported.Boratabenzene derivatives A new synthetic method a variation of the metallation/borylation theme was described for the synthesis of boratobenzene derivatives; thus reaction of CH 2 ––CRCH–– CMe 2 with BCl 2 NMe 2 in a three-step procedure produced [Li(tmeda)] [Me 2 NBCHCMeCHCRCH] in good yield.15a An evaluation of the exocyclic B–N interaction in metal complexes of aminoboratabenzene derivatives was made by dynamic NMR spectroscopy; the rate of B–N bond rotation was dependent upon the electron-withdrawing power of the co-ordinating metal group.15b The reaction of Li[Pr* 2 NBC 5 H 5 ] with [Cp*ZrCl 3 ] or [ZrCl 4 ] a§orded [Cp*(Pr* 2 NBC 5 H 5 )ZrCl 2 ] or [(Pr* 2 NBC 5 H 5 ) 2 ZrCl 2 ] respectively; in both complexes the boratabenzene ligand was g5-co-ordinated through the C atoms.15c The heterobimetallic cationic non-linear optic chromophore (1-ferrocenyl-g6-borabenzene)(g5-cyclopentadienyl)cobalt(1]) was prepared from the reaction of FeCp 2 BBr 2 and [Cp 2 Co] followed by oxidation with FeCl 3 .15d Neutral borabenzene ligand complexes C 5 H 5 B·L (L\py 2,6-lut NEt 3 PMe 3 CNBu5) were synthesised in three straightforward steps from 1-(trimethylsilyl)-1,4- pentadiyne.15e Nucleophilic aromatic substitution reactions of C 5 H 5 B·PMe 3 enabled convenient syntheses of 1-substituted boratabenzene derivatives M[C 5 H 5 BR] (M\Li Na K; R\H,C–– – CSiMe 3 OEt,NMe 2 PPh 2 ).15f The co-ordination chemistry of the negatively charged isosteric variant of triphenylphosphine [Ph 2 P(BC 5 H 5 )]~ (dpb) was investigated; [ZrCp 2 (PMe 3 )(dpb)] [FeCp(CO) 2 (dpb)] and [Rh(PMe 3 ) 3 (dpb)] were readily synthesised and characterised crystallographically.15g A series of new transition-metal complexes of 9,10-dihydro-9,10-dimethyldiboraanthracene was described; the isolation of mono- di- and tri-nuclear species indicated the diverse nature of its ligating properties (Fig.9).15h The crystal structure 9,10- dihydro-9,10-diiododiboraanthracene was established.15i Cyclopentadienylboranes The cyclopentadienylboranes CpBR 2 MR\NMe 2 Me 1/2(OCMe 2 ) 2 Pr*N synthesised from MCp (M\Li Na) and BCl(NMe 2 ) 2 BBrMe 2 ClB(OCMe 2 ) 2 BClPr* 2 respectively were readily metallated to form the salts M[(C 5 H 4 )BR 2 ] (M\Li Na).16a Reaction of CoBr 2 ·dme with M[(C 5 H 4 )BPr* 2 ] a§orded the new cobaltocene derivative [CoM(C 5 H 4 )BPr* 2N2 ]; oxidation of this material with [FeCp 2 ][PF 6 ] produced [CoM(C 5 H 4 )BPr* 2N2 ][PF 6 ].16b Hydrogenation of the Ta–borollide complexes [Cp*M(C 5 H 4 )BR 2NTaMe 2 ] (R\NPr* 2 Me) was investigated and the results suggested that reductive-elimination/oxidative-addition cycles may be operative in hydrogenation reactions of Group 4 metallocenes.16c Multi-decker sandwiches Triple-decker complexes with bridging boratabenzene ligands were prepared by electrophilic stacking reactions of [Cp*Fe(C 5 H 5 BMe)] with suitable reagents; examples 34 M.A.Beckett Fig. 9 Schematic drawings of metal complexes of 9,10-dihydro-9,10-dimethyl-9 10- diboraanthracene.(Reproduced by permission from J. Organomet. Chem. 1996 524 42) Fig. 10 Molecular structure of the triple-decker complex [CpCo(k,g5- Et 4 MeC 3 B 2 )Co(g5-1,10-C 2 B 7 H 9 ) (Reproduced by permission from Chem. Ber. 1996 129 215) 35 Boron of the compounds prepared include [Cp*Fe(k-CC 5 H 5 BMe)MCp*][CF 3 SO 3 ]n (M\Ru n\1;M\Rh Ir n\2).17a The 30-valence-electron triple-decker complex [CpCo(k-Et 4 MeMeC 3 B 2 )Co(g5-2,3-C 2 B 5 H 7 )] was formed from the three-component reaction of [CpCo(g5-Et 4 MeC 3 B 2 )]~ CoCl 2 and nido-[4,5-C 2 B 6 H 9 ]~; reactions of [CpCo(g5-Et 4 MeC 3 B 2 )]~ with CoCl 2 /RhCl 3 and arachno-[4,5-C 2 B 7 H 12 ]~ led to triple-decker complexes (Fig. 10).17b Derivatives of [Cp*Co(2,3-Et 2 C 2 B 4 H 4 )] containing substituents (X) at the apical boron [B(7)] were prepared in good yield via boron insertion into the nido- [Cp*Co(2,3-Et 2 C 2 B 3 H 3 )]2~ cage using BX 3 (X\Cl Br I) or XBCl 2 (X\Ph).17c Decapitation of [Cp*Ir(2,3-Et 2 C 2 B 4 H 4 )] with tmeda yielded colourless crystals of nido-[Cp*Ir(2,3-Et 2 C 2 B 3 H 5 )]; this sandwich complex was used as a precursor to a building block of several triple- and tetra-decker complexes containing Group 9 metals.17d 5 Metal-boryl derivatives The paramagnetic formally 17-electron CoII cis-bis(boryl) complex [Co(PMe 3 ) 3 (Bcat) 2 ] was prepared from the oxidative-addition reaction of B 2 cat 2 with [Co(PMe 3 ) 4 ]; the complex has a B–Co–B angle of 67.9° and a short B· · · B separation of 2.185Å.18a Tungstenocene [Cp 2 W] exclusively formed [Cp 2 W(Bcat@) 2 ] (cat@\4- Bu5C 6 H 3 O 2 ) by oxidative-addition of the B–B bond of cat@BBcat@ in benzene solution; photochemical studies led to the following order of stability [Cp 2 W(Bcat@) 2 ] [[Cp 2 W(H)(Ph)][[Cp 2 W(Bcat)(H)].18b The complex [Cp 2 W(Bcat)(H)] was prepared from the reaction of [Cp 2 WH]~ with ClBcat.18c Single-crystal X-ray structures of [Cp 2 W(Bcat@) 2 ] and [Cp 2 W(Bcat)(H)] were determined.18c The complex [Cp 2 Ti(CO) 2 ] was reported as an e¶cient and highly selective catalyst for alkene hydroborations by HBcat and [Cp 2 TiMe 2 ] was reported as an e¶cient and highly e§ective catalyst for alkyne hydroboration.18d The reaction of excess of HBcat with [Cp 2 TiMe 2 ] produced methane and precipitated the compound [Cp 2 Ti(HBcat) 2 ] in good yield; the structure was consistent with co-ordination of the H–B bond of the neutral catecholborane with a B–H distance of 1.268Å and a Ti–H distance of 1.779Å.18e Oxidative-addition of bis(pinacolata)diboron (Me 4 C 2 O 2 BBO 2 C 2 Me 4 ) to [Pt(PPh 3 ) 4 ] generated cis-[Pt(BO 2 C 2 Me 4 ) 2 (PPh 3 ) 2 ] which was characterised spectroscopically and by single-crystal X-ray di§raction.The compound exhibited high reactivity towards insertion into alkynes which produced cis-bis(boryl)alkenes.18f The synthesis and characterisation of PtII cis-bis(boryl) catalyst precursors for diboration of alkenes and diynes together with the molecular structures of [(PPh 3 ) 2 Pt(Bcat@) 2 ] [(PPh 3 ) 2 Pt(Bcat) 2 )] [(dppe)Pt(Bcat) 2 ] and [(dppb)Pt(Bcat) 2 ] were published.18g A mechanistic investigation of the insertion reactions of [(PPh 3 ) 2 Pt(Bcat) 2 ] into alkynes was reported; under stoichiometric conditions the complex mediated cis-diborylation of alkynes and the MPt(PPh 3 ) 2N fragment was trapped by alkyne and a§orded the corresponding Pt–alkyne complex.18h The first transition-metal substituted diborane(4) derivatives [Cl(Me 2 N)BB(NMe 2 )MCp(CO)n] (M\Fe n\2; M\W n\3) were prepared from the reaction of Na[MCp(CO)n] and B 2 (NMe 2 ) 2 Cl 2 ; the products were characterised by single-crystal X-ray di§raction (Fig.11).18i 36 M.A. Beckett Fig. 11 Molecular structure of [CpFe(CO) 2 B(NMe 2 )BCl(NMe 2 )] (Reproduced by permission from Chem. Ber. 1996 129 1100) 6 Boron–pnictogen species Various methods for the synthesis of tri-N-azolylboranes Az 3 B (Az\1-pyrrolyl 1-(2,5-dimethyl)pyrrolyl 1-indolyl 1-(2-methyl)indolyl 9-carbazolyl) have been compared and the molecular structures of the pyrrolyl derivatives determined by X-ray di§raction; the molecular structures and NMR data point towards weak rather than strong BN(pp)n interactions.19a 1,4-Diazobicyclo[2.2.2]octane (dabco) adducts of BCl 3 and B(NCS) 3 and their properties as polymerisation catalysts for epoxy resins were reported.19b Various 1,3-dipolar species (nitrile oxides nitrones Me 2 C–– SO 2 ) were found to react with (CF 3 ) 2 BNMe 2 by [2]3] cycloaddition reactions to give five-membered heterocycles.19c The crystal structure of an inorganic N-amino analogue of pyrrole PhBN(Me)N(H)B(Ph)N(NMeH) prepared from methylhydrazine and (Me 2 N) 2 BPh was reported.19d The synthesis and structure of the first mono-Balkylcyclotriborazane 2-(PhCH 2 CH 2 )B 3 N 3 H 11 was reported; the borazane was prepared by reaction of the borazene 2-(PhCH 2 CH 2 )B 3 N 3 H 5 with HCl and then Na[BH 4 ].19e The reaction of (Pr*NH) 3 B withNH 3 at room temperature led initially to B,B@,BA-tris(isopropylamino)borazene and then to polyborazenes; pyrolysis of (Pr*NH) 3 B at 1000 °C under NH 3 led to formation of BN containing less than 1% C.19f Syntheses of 1,3,2,4-diphosphadiboretane (Pr* 2 NBPH) 2 triphosphatriborinane (Pr*NBPH) 3 and aminodiphosphanylborane Pr* 2 NB(PH 2 ) 2 were reported together with their reactions with [Cr(CO) 5 (NMe 3 )] which led to the complexes [(Pr* 2 NBPH) 2 ·Cr(CO) 5 ] and [Pr* 2 NB(PH 2 ) 2 ·2Cr(CO) 5 ].19g Photolysis of the 1,3,2,4- 37 Boron diphosphadiboretane [Bu5PB(tmp)] 2 in dilute toluene solution yielded the bicyclic diphosphadiboretane P 2 B 2 (tmp) 2 whereas in concentrated solution a P,P@-connected dimer MBu5PB 2 (tmp) 2 PN2 was formed; reduction of this dimer with Na/K alloy followed by silylation with Me 3 SiCl led to [(tmp)BPSiMe 3 ] 2 and MHP[B(tmp)] 2 Si- Me 3N2 .19h The reactions of the 1,2,3,4-diphosphadiboretane (Bu5P) 2 B(NPr* 2 )B(NMe 2 ) with [Fe 2 (CO) 9 ] led to two isomeric MFe(CO) 4N complexes and a bisMFe(CO) 4N complex.19i The syntheses and structures of the five- and six-membered heterocyclic rings 1,2-(Me 2 N) 2 -3,4,5-Ph 3 -3,4,5-P 3 -1,2-B 2 and 1,2-(Me 2 N) 2 -3,4,5,6-Bu5 4 -3,4,5,6-P 4 - 1,2-B 2 were reported; the five-membered ring existed in the solid state in an envelope conformation whilst the six-membered ring adopted a boat conformation.19j 7 Boron–chalcogen species Single crystals of SrB 2 O 4 were grown from the melt by the Czochralski method and a detailed structure analysis performed; the Sr atom was dodecahedrally co-ordinated by eightOatoms from neighbouring infinite planes of (BO)n 2n~ anion.20a The diamagnetic species K 5 [BW 12 O 37 (H 2 O) 3 ]·13.5H 2 O was obtained from the six-electron reduction of a-K 5 [BW 12 O 40 ]·9H 2 O by photolysis in aqueous solution with MeOH at pH 1; single-crystal X-ray structures of both compounds were reported.20b The novel borosilicate compound [Bu5SiMO(BC 6 H 4 Br-4)ON3 SiBu5] which contained the Si(OBO) 3 Si cage was synthesised by reaction of Bu5SiCl 3 with 4-BrC 6 H 4 B(OH) 2 in toluene solution under reflux and characterised by X-ray di§raction (Fig.12) and spectroscopic techniques.20c The py:B catechol stoichiometry of Meulenho§’s salt 2M(pyH)[B(cat) 2 ]· H 2 catN·H 2 O was confirmed as 1 1 3 by an X-ray crystal structure; only two of the catechol units were directly bound to the B centre.20d The unexpected product [Cu 2 L 2Mk-PhB(O)(OH)N2 ] [HL\6-(2-hydroxyphenyl)-2,2@-bipyridine] was formed by reaction of Cu[BF 4 ] 2 with HL followed by precipitation by Na[BPh 4 ]; the bridging anions of PhB(OH) 2 were derived unexpectedly from an unusual decomposition of the [BPh 4 ]~ anion.20e The mechanism of the interaction of PhB(OH) 2 with ethan-1,2-diol in basic solution was investigated and the complexation reaction proceeded exclusively via a four-co-ordinate phenylboronate anion; comments were made on the trigonal/tetrahedral interconversion at boron as the rate-determining step.20f Boron as [B(OH) 4 ]~ when reacted in aqueous solution with the triols RC(CH 2 OH) 3 (R\Me Et NH 2 ) formed various amounts of mono-chelate bis-chelate and cage structures that were identified and measured by 13C 1H and 11B NMR spectroscopy; NMR spectra of the products of B(OH) 3 with N(CH 2 CH 2 OH) 3 or N(CHMeCH 2 OH) 3 were also recorded and assigned.20g A review on the use of arylboronic acids as molecular receptors for saccharide sensing has been published.20h The new orthothioborates Li 3 BS 3 and LiSrBS 3 have been prepared and their structures determined by X-ray di§raction; both structures contained isolated planar [BS 3 ]3~ anions.20i The synthesis characterisation and reactivity of the S-rich tridentate ligand tetrakis(2-thienyl)borate anion was reported; unlike [(MeS) 4 B]~ it does not co-ordinate MMo(CO) 3N when reacted with [(C 7 H 8 )Mo(CO) 3 ].20j 38 M.A.Beckett Fig. 12 Molecular structure of the cage compound [MBu5SiN2M4-BrC 6 H 4 BO 2N3 ] (Reproduced by permission from J. Organomet. Chem. 1996 526 196) Fig. 13 ORTEP view of the metallacyclic complex [Cp(PPh 3 )- FeC(Me)OBF 2 OP(OMe) 2 ] (Reproduced by permission from Organometallics 1996 15 4662) 39 Boron 8 Boron–halide species The isolation of the sterically encumbered arylborondihalides [2,6-(mes) 2 C 6 H 3 BX 2 X\Cl Br; 2,6-(trip) 2 C 6 H 3 BBr 2 trip\2,4,6-Pr* 3 C 6 H 2 ] have been reported.21a Reduction of these mes derivatives with Li metal gave novel lithium 9-borafluorenyl compounds in which the boranediyl intermediate had inserted into an o-Me ring C–C bond.21a Treatment of [FeCp(CO)MeMP(OMe) 3N] with BF 3 ·OEt 2 and then PPh 3 gave a six-membered metallacyclic species [Cp(PPh 3 )FeC(Me)OBF 2 OP(OMe) 2 ] which was best described as a carbene phosphite metallacycle (Fig.13).21b Phosphaneimine and phosphoraneiminato complexes of boron halides have been prepared and isolated; single-crystal X-ray di§raction structures of BF 3 (Me 3 SiNPEt 3 ) MBCl 2 (NPPh 3 )N2 MBCl 2 (NPEt 3 )N2 [B 2 Cl 3 (NPEt 3 ) 2 ][BCl 4 ] and [B 2 Cl 2 (NPPr* 3 ) 3 ] [BCl 4 ] have been reported.21c Displacement of Br~ by excess of pyridine from the adducts py·BF 2 Br and py·BFBr 2 led to the fluoroboron cations [py 2 BF 2 ]` and [py 3 BF]2` respectively; non-fluorine containing mixed-trihalide adducts of py also formed haloboron cations by heaviest-halide-ion displacement.21d IR spectra recorded from solutions in liquified Ar containing both BF 3 and CO showed the formation of the complexes BF 3 ·CO BF 3 ·(CO) 2 and BF 3 ·(OC).21e A convenient NMR method for determining the Lewis acidity at boron centres has been described and the results clearly confirm the Lewis acidity sequence for BX 3 (X\F Cl Br I) as F\Cl\Br\I.21f References 1 M.A.Beckett Annu. 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Laguna Inorg. Chem. 1996 35 41 Boron 1361; (i) F. Teixidor C. Vin8 as M. M. Abad C. Whitaker and J. Rius Organometallics 1996 15 3154; (j) C. Vin8 as R. Nun8 ez F. Teixidor R.Kiveka¡§ s and R. Sallanpa¡§ a¡§ Organometallics 1996 15 3850; (k) D.E. Harwell M.D. Mortimer C. B. Knobler and M. F. Hawthorne J. Am. Chem. Soc. 1996 118 2679; (l) S.L. Hendershot J. C. Je¡×ery P. A. Jellis D. F. Mullica E. L. Sappenfield and F. G. A. Stone Inorg. Chem. 1996 35 6561; (m)M. Gomez-Saso D. F. Mullica E. Sappenfield and F. G. A. Stone Polyhedron 1996 15 793; (n) G. Ferguson J. Pollock P. A. McEneaney D. P. O¡�Connell T. R. Spalding J. F. Gallagher R. Macia¢¥ s and J. D. Kennedy Chem. Commun. 1996 679; (o) S. Anderson D. F. Mullica E. L. Sappenfield and F. G. A. Stone Organometallics 1996 15 1676; (p) Y.-H. Liao D. F. Mullica E. L. Sappenfield and F. G. A. Stone Organometallics 1996 15 5102; (q) G. Ferguson P. A. McEneaney and T. R. Spalding Acta Crystallogr.Sect. C. 1996 52 2710; (r) A. J. Welch and A. S. Weller Inorg. Chem. 1996 35 4548; (s) P.T. Brain M. Bu¡§ hl J. Cowie Z. G. Lewis and A. J. Welch J. Chem. Soc. Dalton Trans. 1996 231; (t) U. Gra¡§ dler A. S. Weller A. J. Welch and D. Reed J. Chem. Soc. Dalton Trans. 1996 335; (u) M.D. Mortimer C. B. Knobler and M.F. Hawthorne Inorg. Chem. 1996 35 5750; (v) Z. Zheng C. B. Knobler M. D. Mortimer G. Kong and M.F. Hawthorne Inorg. Chem. 1996 35 1235; (w) D. Rabinovich C. M. Haswell B. L. Scott R. L. Miller J. B. Nielson and K. D. Abney Inorg. Chem. 1996 35 1425; (x) B.A. Barnum P. J. Caroll and L. G. Sneddon Organometallics 1996 15 645. 13 (a) G. Ferguson D. E. MaCarthy T. R. Spalding and J. D. Kennedy Acta Crystallogr. Sect. C. 1996 52 548; (b) G.M. Rosair A. J. Welch and A. S. Weller Acta Crystallogr.Sect. C. 1996 52 3020; (c) D. O¡�Connell J. C. Patterson T. R. Spalding G. Ferguson J. F. Gallagher Y. Li J. D. Kennedy R. Maci¢¥ as M. Thornton-Pett and J. Holub J. Chem. Soc. Dalton Trans. 1996 3323; (d) P. Kaur J. D. Kennedy M. Thornton-Pett T. Jel©¥¢¥ nek and B. S¢§ t©¥¢¥ br J. Chem. Soc. Dalton Trans. 1996 1775; (e) P. Kaur M. Thornton- Pett W. Clegg and J. D. Kennedy J. Chem. Soc. Dalton Trans. 1996 4155; (f) J. Bould N. P. Rath and L. Barton Organometallics 1996 15 4916. 14 (a)W. J. Evans J. L. Shreeve and J. W. Ziller Acta Crystallogr. Sect. C. 1996 52 2571; (b)D.C. Bradley I. S. Harding A. D. Keefe M. Motevalli and D. H. Zheng J. Chem. Soc. Dalton Trans. 1996 3931; (c)D. J. Parks and W. E. Piers J. Am. Chem. Soc. 1996 118 9440; (d) N. Metzler and M. Denk Chem.Commun. 1996 2657; (e) J. Ruwwe G. Erker and R. Fro¡§ hlich Angew. Chem. Int. Ed. Engl. 1996 35 80; ( f ) K.A. Rufanov V. V. Kotov N. B. Kazennova A. Lemenovskii E. V. Avtomonov and J. Lorberth J. Organomet. Chem. 1996 525 287; (g) C. Elschenbroich P. Ku¡§ hlkamp A. Behrendt and K. Harms Chem. Ber. 1996 129 859; (h) C. Elschenbroch P. Ku¡§ hlkamp J. Koch and A. Behrendt Chem. Ber. 1996 129 871. 15 (a)G. E. Herberich U. Englert M. U. Schmidt and R. Standt Organometallics 1996 15 2707; (b) A. J. Ashe III J. W. Kampf C. Mu¡§ ller and M. Schneider Organometallics 1996 15 2707 387; (c) G.C. Bazen G. Rodriguez A. J. Ashe III S. Al-Ahmad and C. Muller J. Am. Chem. Soc. 1996 118 2291; (d)U. Hagenau J. Heck E. Hendrickx A. Persoons T. Schuld and H. Wong Inorg. Chem. 1996 35 7863; (e) D.A.Hoic J. R. Wolf W.M. Davis and G. C. Fu Organometallics 1996 15 1315; ( f ) S. Qiao A. Hoic and G. C. Fu J. Am. Chem. Soc. 1996 118 6329; (g)D.A. Hoic W. M. Davis and G. C. Fu J. Am. Chem. Soc. 1996 118 8176; (h) P. Mu¡§ ller H. Pritzkow and W. Siebert J. Organomet. Chem. 1996 524 41; (i)H. Akutsu K. Kozawa and T. Uchida Acta Crystallogr. Sect. C. 1996 52 991. 16 (a) G. E. Herberich and A. Fischer Organometallics 1996 15 58; (b) G.E. Herberich A. Fischer and D. Wielbelhaus Organometallics 1996 15 3106; (c)C.M. Kowal and G. C. Bazan J. Am. Chem. Soc. 1996 118 10 317. 17 (a) G.E. Herberich U. Englert B. Ganter and C. Lamertz Organometallics 1996 15 5236; (b) W. Wienmann F. Metzner H. Pritzkow W. Wiebert and L. Sneddon Chem. Ber. 1996 129 213; (c) M.A. Curtis M. Sabat and R. N. Grimes Inorg.Chem. 1996 35 6703; (d)D.A. Franz E. J. Houser M. Sabat and R. N. Grimes Inorg. Chem. 1996 35 7027. 18 (a) C. Dai G. Stringer J. F. Corrigan N. J. Taylor T. B. Marder and N. C. Norman J. Organomet. Chem. 1996 513 273; (b) J.F. Hartwig and X. He Angew. Chem. Int. Ed. Engl. 1996 35 315; (c) J.F. Hartwig and X. He Organometallics 1996 15 5350; (d) X. He and J. F. Hartwig J. Am. Chem. Soc. 1996 118 1696; (e) J. F. Hartwig C. N. Muhoro X. He O. Eisenstein R. Bosque and F. Maseras J. Am. Chem. Soc. 1996 118 10 936; ( f ) T. Ishiyama N. Matsuda M. Murata F. Ozawa A. Suzuki and N. Miyaura Organometallics 1996 15 713; (g) G. Lesley P. Nguyen N. J. Taylor T. B. Marder A. J. Scott W. Clegg and N. C. Norman Organometallics 1996 15 5137. (h) C.N. Iverson and M.R. Smith III Organometallics 1996 15 5155; (i) H.Braunschweig B. Ganter M. Koster and T. Wagner Chem. Ber. 1996 129 1099. 19 (a) B. Wrackmeyer B. Schwarze and W. Milius Inorg. Chim. Acta. 1996 241 87; (b) B. Bonnetot H. Mongeot and V. Razafindrakoto Main Group Metal Chem. 1996 19 9; (c) D. J. Brauer H. Burger G. Pawelke and J. Rothe J. Organomet. Chem. 1996 522 129; (d) U. Engelhardt and S. S. Park Acta Crystallogr. Sect. C. 1996 52 3248; (e) A.E. Wille P. J. Carroll and L. G. Sneddon Inorg. Chem. 1996 35 5101; ( f ) F. Guilhon B. Bonnetot D. Cornu and H. Mongeot Polyhedron 1996 15 851; (g) D. Dou G.W. Linti T. Chen E. N. Duesler R. T. Paine and H. No¡§ th Inorg. Chem. 1996 35 3626; (h) B. Kaufmann H. No¡§ th and R. T. Paine Chem. Ber. 1996 129 557; (i) S. Grundei H. No¡§ th R. T. Paine Chem. Ber. 1996 129 1233; (j) B.Reigel H.-D. Hausen W. Schwarz G. Heckmann H. Binder E. Fluck A. Dransfeld and P. v. R. Schleyer Z. Anorg. Allg. Chem. 1996 622 1462. 20 (a) J.-B. Kim K.-S. Lee I.-H. Suh J.-H. Lee J.-R. Park and Y.-H. Shin Acta Crystallogr. Sect. C. 1996 52 498; (b) T. Yamase and E. Ishikawa J. Chem. Soc. Dalton Trans. 1996 1619; (c) G. Ferguson B. J. O¡�Leary 42 M.A. Beckett D.M. Murphy and T. R. Spalding J. Organomet. Chem. 1996 526 195; (d)W.P. Gri¶th A. J. P. White and D. J. Williams Polyhedron 1996 15 2835; (e) D.A. Bardwell J. C. Je§ery and M. D. Ward Polyhedron 1996 15 2019; ( f ) R.D. Pizer and C. A. Tihal Polyhedron 1996 15 3411; (g) M. J. Taylor J. A. Grigg and I. H. Laban Polyhedron 1996 15 3261; (h) T.D. James K. R. A. S. Samankumara and S. Shinkai Angew. Chem. Int.Ed. Engl. 1996 35 1911; (i) F. Hiltman C. Jansen and B. Krebs Z. Anorg. Allg. Chem. 1996 622 1508; (j) A.L. Sargent E. P. Titus C. G. Riordan A. L. Rheingold and P. Ge Inorg. Chem. 1996 35 7095. 21 (a)W. J. Grigsby and P. P. Power J. Am. Chem. Soc. 1996 118 7981; (b) H. Nakazawa Y. Yamaguchi and K. Miyoshi Organometallics 1996 15 4661; (c) M. Moehlen K. Harms K. Dehnicke J. Magull H. Goesmann and D. Fenske Z. Anorg. Allg. Chem. 1996 622 1692; (d)M. J. Farquharson and J. S. Hartman Can. J. Chem. 1996 74 1309; (e) E. J. Sluyts and B. J. van der Veken J. Am. Chem. Soc. 1996 118 440; ( f ) M.A. Beckett G. C. Strickland J. R. Holland and K. S. Varma Polymer 1996 37 4629. 43

ISSN:0260-1818    

DOI:10.1039/ic093021

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

4 Aluminium gallium indium and thallium By J. P. MAHER School of Chemistry University of Bristol Bristol BS8 1TS UK 1 Introduction This year’s review is based upon a search of the ACS Abstracts Volumes 124 and 125 obtained for the author with a ‘ChemScan’ profile of Group 13 elements provided by The Royal Society of Chemistry Search Services. This replaces the previous technique which was based on a search of the Current Contents database. The review has been arranged according to the elements. Reviews involving all of these Group 13 members and concerning multiple bonding involving organometallic compounds of the elements,1 and of general organometallic chemistry have appeared.2 2 Aluminium Aluminium is the most abundant metallic element in the Earth’s crust (8.3%) a review concerning how the distribution of aluminium in sedimentary rock and the hydrosphere has been achieved since the formation of the Earth shows how important chemistry was and still is in the distribution process.3 The toxicity of the AlIII ion is a continued source of review and discussion in view of aluminiums’ ubiquity nature must have evolved mechanisms to cope.For the chemical toxicologist there are three particular problems. First there is the very great complexity of biofluids and in particular blood plasma secondly the complicated speciation of AlIII in near-neutral solutions and thirdly there are the very low levels of AlIII in vivo and the consequent di¶culty in measuring aluminium concentrations. The latter problem could possibly be solved by increased use of the AMS (accelerator mass spectrometry) technique previously reviewed.4 Aluminium(III) has an undisputed e§ect upon bone formation and remodelling but its nephrotoxicity is less certain.5 Knowledge about aluminium toxicity particularly in infants and children receiving dialysis has been reviewed.6 Whilst AlIII is certainly neurotoxic in experimental animals and hyperaluminemia and encephalopathy can develop during dialysis the question as to whether aluminium is a hazard contributing to Altzheimer’s disease is still very open especially as to whether any e§ect can be encountered from aluminium in drinking water.Laser microprobe mass analysis has shown that aluminium is probably present in the neurofibrillary tangles observed in Royal Society of Chemistry–Annual Reports–Book A 45 brain tissue of victims of the disease but this is not certain.7 Chelation therapy for the toxic e§ects of aluminium with reagents such as desferrioxamine and the bidentate 3-hydroxypyridin-4-ones has been reviewed.8 Lipid peroxidation plays a major role in many degenerative processes in lipid biochemistry aluminium can facilitate ironmediated brain lipid peroxidation the pH and aluminium concentration conditions favouring peroxidation were examined.9 Chemical speciation studies in relation to aluminium metabolism and toxicity have been discussed in three important reviews.10–12 From the St Louis group,12 come some very specific requests for research into aluminium speciation.Namely to determine more accurate AlIII stability constants with critical low molecular mass ligands such as citrate and phosphate; to supplement the traditional potentiometric studies on AlIII complexes with data from other techniques such as 27Al NMR and AMS; to develop new methods for generating reliable AlIII complexation linear free energy relations; to determine equilibrium and rate constants for AlIII binding to transferrin at body temperature; to research the incorporation of kinetic considerations into the present equilibrium speciation calculations; to incorporate more detailed speciation data into studies on AlIII toxicity and pharmacokinetics develop future epidemiological studies on the relationship between AlIII toxicity and various water quality parameters; to improve methods for preparing chemically well defined stock solutions for toxicological studies.In addition to confirm the possible formation of low molecular mass AlIII–protein complexes following desferrioxamine therapy.From the latter observation some attention should possibly be given to cæruloplasmin involvement. Thus recent studies on blood cæruloplasmin show this to be a copper metalloenzyme with multifunctional properties among which may be complexation of FeIII and other metal ions.13 The crystal structures of over 200 heterometallic aluminium compounds have been reviewed.14 The synthesis of an unusual lamellar aluminophosphate [Al 4 P 2 O 11 ·2C 6 H 13 NH 2 ·4H 2 O]·3H 2 O from a mixture of H 3 PO 4 Al(OPr*) 3 ethylene glycol and an unbranched primary alcohol (n-CnH 2n~1 OH; n\4–8) with hexylamine as template has been described. Structural characterization shows that it is composed of PO 4 units with equal amounts of AlO 4 and AlO 6 units.15 The open framework aluminophosphate [NH 2 (CH 2 ) 3 NH 3 ][HAl 3 P 3 O 14 ]·H 2 O contains five- and six-coordinate aluminium but unlike other aluminium phosphate materials no AlO 4 tetrahedra.16 A molecular sieve-type of aluminophosphate has a novel 12-ring AlPO 4 structure.17 A methylphosphonate [Al(OH)PO 3 Me·H 2 O] 4 which was prepared hydrothermally has a structure consisting of parallel chains of AlO 6 units linked via bridging oxygens and methylphosphonate units to give sheets of inorganic material partially covered on both surfaces by the methyl groups.18 Several unusual aluminium compounds have been described. 1,4-Dimethylpiperazine reacts with AlCl 3 to form trichloro(1,4-dimethylpiperazine)aluminium(III) a crystal structure shows this to be a chelate complex with a trigonal bipyramidal AlIII with one axial and two equatorial chloride ligands.19 The first chiral four-co-ordinate AlIII cation has been characterised by X-ray di§raction.20 The solid was formed from the reaction of dilithium N,N@,NA-tris(trimethylsilyl)diethylenetriamine (ttsdt) with AlCl 3 and then anhydrous HCl and more AlCl 3 forming the cation [Al(ttsdt)Cl] [AlCl] 4 .46 J. P. Maher The crystal structure of trisodium tricalcium tetraarsenidoaluminate Na 3 Ca 3 [AlAs 4 ] shows that it contains slightly distorted [AlAs 4 ]9~ tetrahedra and has the Na 6 ZnO 4 structure.21 Metastable aluminium(I) iodide can be formed from liquid aluminium and gaseous HI at ca. 1000 °C by quenching with a mixture of toluene and diethyl ether. With NEt 3 as the donor (AlI·NEt 3 ) 4 can be isolated.This tetramer is the first room-temperature stable aluminium(I) iodide its structure shows a planar Al 4 ring with an Al–Al distance of 265 pm.22 The preparation structures and reactions of AlI and GaI halogen and organometallic compounds have been reviewed.23 Chromium-stabilized AlI and GaI complexes such as [(CO) 5 CrGaM(Me)(tmen)N] were prepared by reacting K 2 [Cr(CO) 5 ] with Cl 2 ER (E\Al or Ga; R\Me Et or Cl) in thf followed by treatment with tmen. These materials are useful in MOCVD (metal organic chemical vapor deposition) processes.24 The M 4 S 4 core of the aluminium- and gallium-sulfido cubane compounds [(Bu5)M(k3 -S)] 4 (M\Al or Ga) reacts with Cp 2 ZrMe 2 resulting in abstraction of a monomeric (Bu5)M(S) moiety to form [Cp 2 Zr(k-S)(k-Me)Al(Bu5)Me] and [Cp 2 Zr(k- S)] 2 ·[Ga(Bu5)Me 2 ] 2 respectively.The remaining [(Bu5) 3 M 3 S 3 ] fragment reacts with more Cp 2 ZrMe 2 to produce [(Cp 2 Zr)M 3 (k-S) 3 (Bu5) 3 Me 2 ] (M\Al or Ga).25 The reaction of AlMe 3 with [MnMN(SiMe 3 ) 2N2 (thf)] gave the novel manganese compound [MMn(k-Me)[N(SiMe 3 ) 2 AlMe 3 ]N2 ].26 In benzene solution 27Al NMR spectroscopy has been used to show that the monomeric compounds (C 5 Me 5 )AlR 2 (R\Me Et or Bu*) have g3-co-ordinated C 5 Me 5 ligands. With unsubstituted and monosubstituted Cp systems such as Cp@AlR 2 (Cp@\Cp or C 5 H 4 Me; R\Me or Et) an equilibrium between monomeric and dimeric species was observed. For the monomeric species 27Al NMR spectroscopy shows that the Cp rings are also bound in an g3-symmetry whereas for the dimeric alkyl-bridged species there is p-co-ordination of the Cp ring.However the novel monomeric monosubstituted complex (C 5 H 4 Bu5)Al(Bu*) 2 was g3-co-ordinated at the Cp ring.27 The isopropoxy-bridged dimer has an g1-co-ordinated Cp ring [g1- (C 5 H 5 ) 2 AlO(Pr*)] 2 according to a crystal structure determination.28 The complex [(g5-Cp)Al(2,6-Pr* 2 C 6 H 3 N)] 2 is the first solid-state example of a pentahapto Cp–Al co-ordination between a simple Cp ring and aluminium and was prepared by means of a double dealkylation reaction between Cp 3 Al and 2,6-diisopropylaniline forming the dimeric iminoalane.29 The reaction of (mes*AlH 2 ) 2 with azobenzene in hot toluene gave (mes*)AlN(Ph)(mes*)AlN(Ph)NPh. Whilst the Al 2 N 3 ring is a formal Al–N analogue of a Cp ring it showed no evidence of delocalisation.One of the N atoms deviates by 40pm from the averaged plane of the remaining atoms and bond lengths were normal.30 The first structurally characterized alkylperoxo–aluminium compound has been described it was formed by the reaction of the chelate complex (Bu5) 2 Al(mesal) with dioxygen resulting in the oxidation of both Bu5 groups to form the alkylperoxo compound (Bu5OO)(Bu5O)Al(k-OBu5) 2 Al(mesal) 2 . The compound has an unsymmetrical dinuclear structure containing four- and six-co-ordinated aluminium atoms bridged by alkoxide groups with the Bu5OO group on a four-co-ordinated aluminium. 31 Aluminium(III) chloride and potassium tris(3-phenylpyrazolyl)hydroborate reacted 47 Aluminium gallium indium and thallium to form [Mg3-HB(3-Phpz) 2 (5-Phpz)N2 Al][AlCl 4 ] the sterically demanding ligand has isomerized to relieve steric strain and the AlN 6 co-ordination octahedron was compressed along the N–Al–N axis on which the rearranged phenylpyrazolyl group is co-ordinated.32 The compounds [H(3-Bu5pz)B(3-Bu5pz) 2 -g2]AlEt 2 (A) and [H(3- Bu5pz)B(3-Bu5pz)(5-Bu5pz)-g2]AlEt 2 (B) have been prepared and their structure and dynamic solution behaviour examined.A 1,2-borotropic shift was observed for the conversion of A to B whereby the sterically less demanding 5-Bu5pz moiety is formed from 3-Bu5pz.33 3 Gallium Applied research into gallium and indium chemistry is dominated by interest in various optoelectronic materials. Presently there is very great interest in ultra-high brightness blue-light emitting diode and laser devices constructed from materials such as InGaN and InGaAlN.34 Gallium nitride can be formed by high-temperature thermolysis ([900 °C) of ammonia and gallium trialkyls but a more convenient source would be a single source precursor (compound containing all the necessary ingredients) which could also decompose at a much lower temperature.The tris(pyridine) complex of gallium tris(azide) has been prepared and structurally characterised with a view to its use for MOCVD processes. Surprisingly [Ga(N 3 ) 3 (py) 3 ] melts without decomposition at 58–60 °C and so far has not proven too hazardous. Preliminary studies indicated that it can act as a thermal source of gallium nitride via loss of pyridine and nitrogen.35 The organogallium azides [(R)a(N 3 ) 2~aGaM(CH 2 ) 3 - NMe 2N1~a] (R\Me or Bu5; a\0 or 1) (Et)(N 3 ) 2 Ga and (Et)(N 3 ) 2 Ga·L (L\quinuclidine py or H 2 NBu5) were synthesized by various metathesis reactions.36 Thus [Ga(N 3 ) 2M(CH 2 ) 3 NMe 2N] synthesized from [Cl 2 GaM(CH 2 ) 3 NMe 2N] and NaN 3 acts as a precursor for GaN films.The necessary conditions for optimum deposition of the GaN films using dinitrogen as a carrier gas and dihydrogen and ammonia as reactive gases were examined.37 The ligand [2-(N,N-dimethylamino)ethyl]cyclopentadienyl [2-(Me 2 NCH 2 CH 2 )C 5 H 4 ––([CpN]) forms various gallium complexes [CpN]GaX 2 [X\Cl Br I Me or H]. Su¶cient volatility and well behaved fragmentation makes [CpN]GaH 2 a suitable precursor for the deposition of gallium in the MOCVD process.38 Phenylated Group 13–15 compounds Ph 2 MEPh 2 (M\Ga or In; E\P or As) have been examined as convenient precursors to phase-pure gallium arsenide and gallium phosphide.39 The heterocubanes [(C 5 Me 5 )Ga(k3 -E)] 4 (E\S or Se) and [(C 5 Me 4 Et)Ga- (k3 -Se)] 4 have been synthesized and characterized and the use of the pentamethylcyclopentadienides as single-source MOCVD precursors for the low temperature (290–310 °C) growth of Ga 2 E 3 films has been described.40 The metastable cubane precursors [(CMe 3 )GaSe] 4 and [(EtMe 2 C)InSe] 4 were used to make well defined nanoparticles of InSe and GaSe under CVD conditions.41 The first example of a structurally characterized Ga thiocarboxylate compound Ga(SCOMe) 2 Me(dmpy) was synthesized and used to deposit crystals of Ga 2 S 3 thin films by aerosol-assisted CVD at low temperatures.The facile elimination of thioacetic anhydride provided a pathway to deposit high purity stoichiometric metal sulfide films according to equation (1).42 48 J.P. Maher M(SOCMe) 2 ·(dmpy) )%!5 ]MS](MeCO) 2 S]dmpy (1) The crystal structure of the black solid Al 2 Te 5 has been determined. In contrast to Ga 2 Te 5 and In 2 Te 5 the aluminium compound was very sensitive to hydrolysis. Its structure showed layers made up of chains of cis edge-sharing AlTe 4 tetrahedra and additional tellurium atoms. Both In 2 Te 5 -I and In 2 Te 5 -II were characterized by layers with a similar topology Ga 2 Te 5 however is di§erent in having no layer structure but containing chains of trans edge-sharing GaTe 4 tetrahedra and additional Te atoms it can be regarded as a variant of the TlSe-type structure. Mixed gallium and indium compounds Ga 2~xInxTe 5 (x\0.4) were observed but substitution of Te by Se in Ga 2 Te 5 was not detected.43 Crystal structures of europium digold pentagallide EuAu 2 Ga 5 and of strontium digold pentagallide SrAu 2 Ga 5 have been determined.44 The crystal structure of hexabarium di-k-phosphidobis[diphosphidogallate(III)] Ba 6 [Ga 2 P 6 ] is characterised by isolated [Ga 2 P 6 ]12~ ions consisting of pairs of edge-sharing GaP 4 tetrahedra isoelectronic to Al 2 Cl 6 .Barium and P build up a distorted NaCl structure with Ga occupying some of the holes.45 The inversion mechanism for dinuclear GaIII bis-bidentate catecholate helicate complexes containing discrete dinuclear [Ga 2 L 3 ]6~ anions with pseudo-octahedral GaO 6 cores has been examined by dynamicNMRspectroscopy. The complex exists in two isomeric cis and trans forms in D 2 O or (CD 3 ) 2 SO solution.The intramolecular inversion occurs by independent trigonal twisting of each metal centre without cis-trans isomerization and a§ording the heterochiral meso complex as an intermediate. Under slightly acidic conditions a proton-assisted pathway becomes dominant this involves protonation of both metal centres which simultaneously invert in order to interchange the helicate configuration.46 The incorporation of heteroatoms into aluminium phosphate frameworks leads to materials with potentially useful catalytic and exchange properties. To extend the range of such compounds a novel cobalt–gallium phosphate an analogue of the zeolite gismondine Ca 4 [Al 8 Si 8 O 16 ] has been prepared [C 4 NH 10 ][CoGaP 2 O 8 ].47 The intramolecularly co-ordinating ligands 2-(dimethylaminomethyl)phenyl (L) and 4-tert-butyl-2,6-bis(dimethylaminomethyl)phenyl (L1) have been used to prepare gallium and indium hallides L 2 InI LInI 2 L 2 InBr LInBr 2 LIn(Et)I LGaI 2 and L1InI 2 .The first neutral indium hydride L 2 InH has been prepared in situ from LiInH 4 and L 2 InBr.48 The compound Ga 4 [C(SiMe 3 ) 3 ] 4 with a tetrahedral Ga 4 core in the solid state evaporates to form the monomeric Ga[C(SiMe 3 ) 3 ]. This unique structure has a Ga atom solely co-ordinated by one singly bonded carbon ligand. The gas-phase molecular structure shows a Ga–C bond length of 206.4(17) pm similar to that found in the solid state for the tetramer. Whereas the (electrochemically) reduced organoindium tetramer did not exhibit any detectable EPR signals between 4 and 300 K the gallium analogue showed an EPR spectrum compatible with the formulation [(RGa 0.75 ) 4 ]·~ i.e.the unpaired electron was delocalized over all four metal centres [A(69Ga)\1.93 mT A(71Ga)\2.45 mT].49 Gallium–gallium bonds appear in a number of interesting situations. The compound Et 3 AsI 2 reacts with powdered gallium metal according to reaction (2). 2Et 3 AsI 2 ]2Ga][GaI 2 (AsEt 3 ) 2 ] 2 (2) The Ga–Ga bonds are 242.8(7) pm and the gallium is tetrahedrally co-ordinated to 49 Aluminium gallium indium and thallium iodine and arsenic.50 Reaction of Ga[GaCl 4 ] with two or more equivalents of Li(thf) 3 Si(SiMe 3 ) 3 in pentane gave [(Me 3 Si) 3 Si] 2 GaGa[Si(SiMe 3 ) 3 ] 2 .51 Proton NMR spectroscopy measurements of mixtures of dimethylgallane and diethylgallane in toluene provide evidence for dimeric and trimeric species undergoing both intra- and inter-molecular exchange.52 Insertion reactions have been observed for a number of gallium–gallium bonded compounds.The complex [GaMCH(SiMe 3 ) 2N2 ] 2 reacts with isocyanides RNC (R\CMe 3 Ph 2-MeC 6 H 4 2-MeOC 6 H 4 or 4-MeOC 6 H 4 ) by a two-fold insertion of the central carbon toms into the Ga–Ga bond and formation of C–C single bonds. The corresponding gallyldiazabutadienes were formed.53 The insertion of chalcogen atoms into the metal–metal bonds of [GaMCH(SiMe 3 ) 2N2 ] 2 (and [AlMCH(SiMe 3 ) 2N2 ] 2 ) using the chalcogen atom donors triethylphosphonium sulfide and selenide gives novel homoleptic compounds R 2 M–X–MR 2 [R\CH(SiMe 3 ) 2 ; M\Al or Ga; X\S or Se].54 The same metal–metal bonded dialane and digallanes reacted with dmso and H 2 O in di§erent fashions.The dialane forms a trimer probably via Al–OH–Al bridges M[R 2 Al(k-OH)] 3N but the digallane forms a hydroxy-bridged dimer.55 The tetromer [GaSi(SiMe 3 ) 3 ] 4 has a nearly regular tetrahedral framework of Ga atoms. The Ga–Ga distances average 258.4 pm. Ab initio calculations on various substituted gallium tetrahedrons showed a greater stability of silyl-substituted cages compared with their organyl congenors.56 The same Karlsru� he group have examined the reaction of LiSi(SiMe 3 ) 3 ·3thf with R 2 GaCl (R\tmpip Me or Cl) this forms (tmpip) 2 GaSi(SiMe 3 ) 3 and R 2 Ga(thf)Si(SiMe 3 ) 3 (R\Me or Cl). Both Ga–N bonds in (tmpip) 2 GaSi(SiMe 3 ) 3 are cleaved by protic reagents. Depending on the acidity of these agents the gallanes formed are trimers dimers or monomers.57 The very interesting cyclogallene (NB cyclogallene not cyclogallane) dipotassium tris[(2,6-dimesitylphenyl)cyclogallene] K 2 [(mes 2 C 6 H 3 )Ga] 3 has been prepared by two di§erent routes.The cyclogallene is arranged about the planar Ga 3 triangle constituted by extremely short Ga–Ga bonds 242.60(5) 243,17(5) and 241.87(5) pm. A theoretical study of the Ga 3 2~ core in other forms [GaH] 3 2~ Na 2 [GaH] 3 and K 2 [GaH] 3 suggests a well defined n molecular orbital. Thus both the theoretical and experimental results strongly support the formulation of a cyclogallene dianion [M(Mes 2 C 6 H 3 )GaN3 ]2~ as a well defined metallo-aromatic system exhibiting aromatic behaviour.58 It will be interesting to see how the chemistry of this fascinating species develops! There is much research into organogallium phosphorus compounds.Reaction of AlMe 3 and GaMe 3 with 1,2-(H 2 P) 2 C 6 H 4 in a 2 1 ratio gave the novel eight-membered tetrametallic ring compounds [(Me 2 M) 4M(k-PH) 2 (C 6 H 4 )N2 ] (M\Al or Ga). The corresponding amine 1,2-(H 2 N) 2 C 6 H 4 in 3 2 ratio with GaMe 3 gave [(Me 2 Ga) 3M(k- NH) 2 (C 6 H 4 )(k-NH)(C 6 H 4 NH 2 )N].59 The trimer [Me 2 GaPPh 2 ] 3 was prepared by reaction at ambient temperature of Me 3 Ga with Ph 2 PH in toluene. The crystal structure shows a six-membered Ga 3 P 3 ring in a chair conformation with a mean Ga–P bond distance of 243.3(1) pm.60 The reactivity of R 2 AlH (R\Me or Bu*) and Me 3 M (M\Al Ga or In) toward the silylphosphines P(SiMe 3 ) 3 and HP(SiMe 3 ) 2 has been examined various adducts were formed and some elimination reactions were observed.61 The four-membered ring compound I 2 GaAs(SiMe 3 ) 2 Ga(I) 2 P(SiMe 3 ) 2 is the first to contain two gallium atoms bridged by two di§erent Group 15 elements; it was 50 J.P. Maher synthesized by the equilibration of (1 1) [I 2 GaAs(SiMe 3 ) 2 ] 2 with [I 2 GaP(SiMe 3 ) 2 ] 2 and also by the reaction of (2 1 ) GaI 3 with As(SiMe 3 ) 3 and P(SiMe 3 ) 3 .62 Elimination of cyclopentadiene from Et 2 GaCp and the corresponding amine phosphine or thiol gives the dimers [Et 2 GaNEt 2 ] 2 [Et 2 GaN(H)(Me)] 2 [Et 2 GaN(H)- Bu5] 2 [Et 2 GaPPr* 2 ] 2 [Et 2 GaPBu5 2 ] 2 and [Et 2 GaS(SiPh 3 )] 2 .63 The tetrameric alkylimido –methylgallanes (MeGaNR) 4 (R\CHMe 2 or CMe 3 ) have been prepared by pyrolysis at 250–260 °C of the dimeric amido compounds [Me 2 GaN(H)R] 2 .64 Reaction of 2,2@-dipyridylamine (dpa) with R 3 M(R\Me M\Ga or Al) gave the Lewis acid–base adducts Me 2 Ga(dpa) and Me 2 Al(dpa).The crystal structure of the gallane showed a tetrahedral gallium and an unusual structure of dpa~ in the formation of a new anti–anti complex with two extremely short Ga–N bond distances of 197.6(3) and 1.978(3) pm.65 Trimethylgallium reacts with optically active amino alcohols ([)- (1R,2S)-2-dimethylamino-1-phenylpropanol and (])-(2S,3R)-4-dimethylamino-3- methyl-1,2-diphenylbutan-2-ol with methane elimination to form the dimer [Me 2 GaOCHPhCHMeNMe 2 ] 2 and the monomer Me 2 GaOCPh(CH 2 Ph)- CHMeCH 2 NMe 2 . The absolute configurations of the asymmetric centres in the ligands are retained in the product complexes.66 The first benzannelated diazabutadiene complex of gallium was prepared by treatment of C 6 H 4 [N(Li)SiMe 3 ] 2 with (2-Me 2 NCH 2 C 6 H 4 )GaCl 2 .67 The reaction of M(mes) 3 (M\Ga or In) with CsF in acetonitrile gave [MCs(MeCN) 2NM(mes) 3 MFN] 2 .Under the same conditions Ga(CH 2 Ph) 3 reacted with CsF forming [CsM(PhCH 2 ) 3 GaFN] 2 ·2MeCN.68 The reactions of Et 3 Ga with elemental sulfur S 8 in toluene or benzene at di§erent temperatures resulted in the insertion of sulfur in to the Ga–C bonds to form Ga[(S–S)Et] 3 and Ga[(S–S–S)Et] 3 . Trimethylgallium only forms Ga[(S–S)Me] 3 . An interesting de-insertion reaction occurs at [30 °C in pyridine with the formation of the six-membered Ga–S ring compounds [pyEtGaS] 3 and [pyMeGaS] 3 .69 Poly(pyrazolyl)borate complexes of gallium and indium have been reviewed.70 The most interesting aspect of the pyrazolylborates for Group 13 is their ability to stabilise univalent gallium and indium oxidation states.Thus a bulky poly(pyrazolyl)borate ligand stabilizes indium(I) in [HB(3-Phpz) 3 ]In,70 and monovalent gallium complexes are supported by the tris(3,5-di-tert-butylpyrazolyl)hydroborate ligand in (3,5- Bu5pz)Ga.71 4 Indium Indium(III) chloride has been intercalated into C 60 .72 A remarkable Zintl phase was observed for Na 3 K 23 Cd 12 In 48 . This was obtained by stoichiometric fusion of the elements and is composed of indium icosahedra indium triangular clusters and the novel Cd 12 In 6 tubular cluster. The latter which contains two Na` stu§s a 96-atom polyhedron (fullerane) and is sheathed by 20K` and 12Na`.The clusters are linked together through two-centre two-electron bonds within a three-dimensional anionic network.73 The black brittle and very air- and moisture-sensitive compound Ba 14 InP 11 was prepared from its elements the structure contains isolated P3~ linear [P 3 ]7~ and tetrahedral [InP 4 ]9~ anions.74 51 Aluminium gallium indium and thallium Interest in the synthesis of new microporous zeolitic materials in the form of open-framework metal phosphates has produced the first organically templated layered indium phosphate. Formed from a non-aqueous pyridine–butan-2-ol medium this has a unique two-dimensional structure consisting of [In(HPO 4 )(H 2 PO 4 ) 2 ]~ layers held together by hydrogen bonding to generate cavities in which pyridinium cations reside.The layers consist of corrugated sheets constructed from ribbons of edge-sharing four-membered rings of alternating InO 6 and PO 4 units linked via PO 2 (OH) groups.75 On the same theme a pillared layer structure of the organically templated indium phosphate with the crystal composition [In 8 (HPO 4 ) 14 (H 2 O) 6 ] [H 2 O) 5 (H 3 O)(C 3 N 2 H 5 ) 3 ] has been synthesised. This structure consists of layers assembled from InO 6 and InO 5 (OH 2 ) octahedra and PO 3 (OH) tetrahedra which are pillared through InO 6 octahedra to produce a three-dimensional framework. The framework contains a two-dimensional array of channels in which sit imidazolium cations hydroxonium ions and water molecules. Within the channels are 16-membered rings of alternating In and P polyhedra which have dimensions B860]970 pm.76 In another indium phosphate RbIn(OH)PO 4 the structure consists of spirals of cis corner-sharing InO 6 octahedra with hydroxyl O as the bridging atom and the In–O–In bonds nearly equidistant.77 The InI complex (3,5-Bu5pz)In has been synthesized by the reaction of Na(3,5-Bu5pz) with InCl it has a structure in which the 3,5-Bu5pz ligand adopts a highly twisted configuration due to steric interactions of the tert-butyl substituents in the 5 positions of the pyrazolyl groups.78 The compound (3,5-Bu5pz)In undergoes oxidative-addition reactions with I 2 and S 8 to give the InIII complexes (3,5-Bu5pz)InI 2 and (3,5- Bu5pz)In(g2-S 4 ) respectively.79 The novel redox properties of [HB(3-Bu5pz) 3 ]~ enabled the isolation and structural characterization of [In 2 I 3Mg3-HB(3-Bu5pz) 2 (5-Bu5pz)N(g1-5-Bu5pzH)] a novel In–In bonded species.80 Strong solutions of InI can be prepared by treatment of indium amalgam with silver triflate in dry acetonitrile in the absence of oxygen the solutions were stable for more than 5 d.Reducing the concentration by 300-fold dilution with water gave solutions which were stable for over 5 h. The solutions enabled kinetic patterns for reactions of [Co(NH 3 ) 5 X]2` (X\Cl~ Br~ I~ or HC 2 O 4 ~) with InI to be measured these show two consecutive one-electron reactions the first (slower) of which was predominantly an inner-sphere mechanism.81 The crystal structure of In 7 Br 9 was measured this is a mixed-valence compound which can be formulated as (In`) 6 (In3`)(Br~) 9 it crystallizes with a structure similar to In 7 Cl 9 .The InIII is octahedrally co-ordinated InIII–Br\268 pm InI has a slightly distorted bisdisphenoid geometry InI–Br\307–377 pm.82 The [N(SePPh 2 ) 2 ]~ ligand forms novel inorganic (carbon-free) chelate rings with InIII the stable [InMN(SePPh 2 ) 2N3 ] complex having a distorted octahedral co-ordination about the indium.83 A method to obtain pure trialkylindiums from indium metal with yields in excess of 80% has been described.84 When (mes*) 2 InBr was heated at 130–150 °C under reduced pressure a rearrangement to (mes*)(Br)In[CH 2 C(CH 3 ) 2 C 6 H 3 Bu5 2 ] occurred. Reaction of In(SePh) 2 I with (mes*)MgBr caused formation of (mes*)In(SePh) 2 .85 The compound (2,6-mes 2 C 6 H 3 ) 2 InBr was prepared either by reaction of InBr 3 with (2,6- dimesitylphenyl)lithium in Et 2 O or by disproportionation of Br 2 In–InBr 2 in the 52 J.P. Maher presence of (2,6-mes 2 C 6 H 3 )Li. The crystal structure showed the In–Br bond distance to be 250.5(4)pm and the two bulky ligands force a nearly T-shaped C–In–C bond angle of 157.3(8)° the widest angle reported for a three-co-ordinate indium.86 It is surprising that there have not been more investigations of reactions between boranes and Group 13 alkyls. The reaction between Me 3 In and tetraborane(10) gave dimethylindium octahydrotriborate the first reported example of a volatile indium hydride; the spectroscopic properties of the vapour indicated a molecular structure for Me 2 AlB 3 H 8 but the crystal structure implied the more ionic formulation [Me 2 In]` [B 3 H 8 ]~.87 Reaction of tetrakis[bis(trimethylsilyl)methyl]diindane (R 2 InInR 2 ) with the chalcogen atom donors propylene sulfide triethylphosphine selenide or triethyltelluride gave the homoleptic compounds R 2 InSInR 2 R 2 InSeInR 2 and R 2 InTeInR 2 by insertion of chalcogens atoms into the In–In bond.88 Organoindium phosphides have been prepared.One which incorporates two phosphido moieties in the same molecule is (Me 3 CCH 2 ) 2 In[k-PBu5 2 ](k- PPh 2 )In(CH 2 CMe 3 ) 2 .89 The compounds Pr* 2 InPPh 2 and (PhCH 2 ) 2 InPPh 2 and the tetramer [(mes)InP(mes)] 4 were prepared and characterized spectroscopically and by X-ray di§raction. The first two compounds were present as a monomer–dimer equilibrium mixture in benzene in the solid state they were trimers [Pr* 2 InPPh 2 ] 3 and [(PhCH 2 ) 2 InPPh 2 ] 3 ·OEt 2 with distorted In 3 P 3 six-membered rings in boat conformations.The compound [(mes)InP(mes)] 4 is tetrameric in solution but crystallised as [(mes)InP(mes)] 4 ·4.5thf a heterocubane with an In 4 P 4 core shielded by the bulky organic groups.90 The complex In 4 [C(SiMe 3 ) 3 ] 4 reacted with elemental sulfur and tellurium in boiling hexane to form In 4 X 4 [C(SiMe 3 ) 3 ] 4 (X\S or Te). These have indium chalcogen heterocubane structures.91 The compound In 4 [C(SiMe 3 ) 3 ] 4 reacts with Co 2 (CO) 8 to give two products depending on the ratio of the reactants and corresponding to the replacement of one and then the other bridging carbonyl.92 The compound In 4 [C(SiMe 3 ) 3 ] 4 reacts with (OC) 5 Mn–Mn(CO) 5 to form bright red octacarbonylbis Mk-[tris(trimethylsilyl)methyl]indanylNdimanganese in which two CO ligands are replaced by two InR fragments.93 The transition metal–indium complexes L(CO)nM–InBr 2 (D) and L(CO)nM–In[(CH 2 ) 3 NMe 2 ]Br ML\CO Cp or C 5 H 4 [(CH 2 ) 2 NMe 2 ];M\Fe Co or Ni; D\thf or NC 7 H 13N have been prepared.94 5 Thallium Stalderite TlCu(Zn,Fe,Hg) 2 As 2 S 6 another thallium mineral has been characterised this is a zinc equivalent of routhierite TlHgAsS 3 .95 Crystal structure determinations have been made on new thallium indium chalcongenides TlIn 3 S 5 ,96 TlIn 5 S 8 ,97 TlIn 5 S 7 and TlIn 5 Se 7 .98 A novel mixed-metal cluster of molybdenum sulfur and thallium [TlMo 6 S 8 ]8` was prepared by the NaBH 4 reduction of a solution of [Mo 3 S 4 (H 2 O) 9 ]4` in the presence of solid TlCl.A corner-shared double cuboidal cluster structure was proposed for this ion.99 In a search for discrete [TlCl 5 ]2~ anions new thallium-containing alkylammonium salts with di§erent chlorothallate cations have bene prepared and characterized by 53 Aluminium gallium indium and thallium X-ray crystallography bis(p-toluidinium) pentachlorothallate(III) [CH 3 C 6 H 4 NH 3 ] 2 - [TlCl 5 ]; 1,5-diammonium pentane pentachlorothallate(III) [NH 3 (CH 2 ) 5 NH 3 ]- [TlCl 5 ]; bis(piperazinium) decachlorodithallate(III) trihydrate [NH 2 C 4 H 8 NH 2 ] 2 - [Tl 2 Cl 10 ]·3H 2 O; pentakis(2-adamantaneammonium) bis[tetrachlorothallate(III)] hexachlorothallate(III) [C 10 H 18 N] 5 [TlCl 4 ] 2 [TlCl 6 ].The latter complex has three geometrically di§erent chlorothallate ions. Whilst the formation of the [TlCl 5 ]2~ anion is possible this was not observed and a thallium co-ordination of six was achieved either via formation of anionic chains or through dimerization giving [Tl 2 Cl 10 ]4~.100 Whilst there is less interest in thallium-containing high T# superconductor materials than a few years ago research into fabrication by various techniques continues e.g.by MOCVD,101 and by sputtering.102 Some new 1223 type layered superconducting (T#[100 K) cuprates (Tl,M)(Sr,Ba) 2 Ca 2 Cu 3 O 10`d (M\Cr or V) have been synthesised in order to examine the e§ect of other transition-metal substitutions and to make the preparations easier.103 Bearing a possible relation to these materials is Ba 3 Tl 2 O 5 Cl 2 which was synthesized and structurally characterised. It can be described either as a strongly distorted Sr 3 Ti 2 O 7 structure or as an intergrowth of rock salt layers [Ba 2 Cl 2 ] = with [BaTl 2 O 5 ] = layers similar to the [BaFeCuO 5 ] = layers observed in the YBaFeCuO 5 structure.104 The compound Na 23 K 9 Tl 15 is an unusual Zintl compound containing apparent Tl 5 7~ Tl 4 8~ Tl 3 7~ and Tl 5 ~ anions.The anion Tl 3 7~ is isoelectronic with CO 2 calculations reveal some bonding similarities with two good p(s,p) bonding and two weakly bonding n MOs. The Tl–Tl bond distance of 314pm was consistent with multiple bonding.105 In the thallium bicyclic phthalocyanine [14,28-3-(3-isoindolylimino)-1,1@-isoindolediylidenodiaminothallium( III)] the bicyclic phthalocyaninato macrocyclic hexadentate ligand was composed of six isoindole units forming a distorted trigonal prism of six N-donor atoms in which Tl` was encapsulated.106 In (meso-5,10,15,20-tetraphenylporphyrinato)( trifluoroacetato)thallium(III) [Tl(tpp)(O 2 CCF 3 )] the co-ordination sphere of the Tl3` ion was an approximately square-based pyramid in which the apical site was occupied by an asymmetric bidentate O 2 CCF 3 group.107 In dimethyl(diethylmonothiocarbamato)thallium(III) [TlMe 2MS(O)CNEt 2N] the crystal structure showed [TlMe 2MS(O)CNEt 2N] units in which the thallium atom was co-ordinated to the two methyl carbons and to the sulfur and oxygen atoms of the bidentate monothiocarbamato ligand.These were connected by additional� Tl–O bonds and weak Tl–S interactions giving a supramolecular polymeric ribbon along the b axis of the crystal with practically symmetrical Tl–O–Tl bridges.108 Hydrides such as In 2 H 6 and Tl 2 H 6 are thermodynamically unstable in both gas and solid phases according to ab initio MP2 calculations.However these compounds are kinetically stable in the gas phase and molecular structures and vibrational frequencies have been predicted.109 Thallium(II) is normally a very elusive species however it can be generated by c- irradiation of TlI-doped crystals and EPR spectra of the paramagnetic Tl2` centre can then be observed. In thallium-doped alkali nitrates the s- and p-character of the Tl2` ions were calculated from g and A parameters.110 The EPR of the Tl2` centre in Rb 2 Cd 2 (SO 4 ) 3 was studied between 10 and 140K in order to investigate phase transition structural changes in the crystal.111 54 J. P. Maher The open cluster [Pt 6 (k-CO) 6 (k-dppp) 2 (dppp) 2 ] was shown to encapsulate TlI with loss of dppp to give the closed cluster [Pt 6 (k6 -Tl)(k-CO) 6 (k-dppp) 3 ]`.112 In order to examine heavy metal–arene interactions bis(1,2,4-trimethylbenzene) thallium(]1)-tetrachloroaluminate(]3) and -tetrachlorogallate(]3) have been prepared.In the solid state the compounds can be described as dimeric thallium(I) tetrachlorometallates with a skeleton similar to that of (TeI 4 ) 4 shielded by four arenes co-ordinated in pairs at the thallium atoms. The study of these two compounds showed that thallium–arene n bonding was significantly weaker in the gallate than in the aluminate.113 The reaction of (dibromoboryl)ferrocene with pyrazole–NEt 3 gave the ferrocenyl tris(pyrazolylborate) ligand. Its thallium(I) complex provided an example of a solidstate polymeric structure with bridging tris(pyrazolylborate) units.114 Multinuclear magnetic resonance spectra (1H 11B 13C 15N and 205Tl) have been studied for the thallium hydridotris(3,5-dimethylpyrazol-1-yl)borate complex.The complex shows a dynamic NMR e§ect corresponding to breaking of the Tl–N bond.115 The addition of tris(3,5-dimethylpyrazolyl)methane to a thf solution of TlPF 6 resulted in the immediate precipitation of [MHC(3,5-Me 2 pz) 3N2 Tl]PF 6 . The structure showed that arrangement of the N-donor atoms about Tl was best described as a trigonally distorted octahedron. The Tl–N bonds range from 289.1(5) to 292.9(5) pm. 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ISSN:0260-1818    

DOI:10.1039/ic093045

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

(PhO)(PPri 3)2Rh C C CPh2 (OC)(PPri 3)2RhC CCPh2(OPh) Co Scheme 1 Cl(L)2Ru C C R H HC CR ( i) HC CCPh(R¢)OH AgOTf Cl(L)2Ru C C R¢ Ph AgOTf [RuCl2(L)2] + ( ii) Al2O3 C + 2 1 3 Scheme 2 5 Carbon silicon germanium tin and lead By D. A. ARMITAGE Department of Chemistry King’s College Strand London WC2R 2LS UK This review covers the literature for 1996. The preparation of carbon chains terminated by transition metal residues has been reviewed.1 The stretched dihydrogen complexes [Ru(H)(g2-H 2 )(LX)(PCy 3 ) 2 ] (LX\o-hydroxy or o-aminopyridine) react with SiEt 3 (CH––CH 2 ) to give the hydridovinylidene complexes [HRu––C–– C(H)(SiEt 3 )(LX)(PCy 3 ) 2 ].2 c-Functionalised alkynyl ligands result from the migratory insertion of an allylidene unit into the Rh–O bond of [(RO)(L) 2 Rh––C––C–– CPh 2 ] by reacting with CO at room temperature for five minutes (Scheme 1).3 Similar cationic derivatives 2 and 3 result from the ruthenium complex [RuCl 2 (L) 2 ] (L\Pr* 2 PCH 2 CH 2 OMe) 1 using AgO 3 SCF 3 with HC–– – CR [R\H aryl CPh(R@)OH where R@\Ph o-tolyl] as vinylidene or allenylidene complexes (Scheme 2).4 The allenylidene complex [ClL 2 Rh––C–– C––CRPh] (R\Ph CF 3 Bu5) 4 adds carbene to the a-carbon atom using CH 2 N 2 to give the red butatriene complex 5 n-bonded through the terminal double bond.Isomerisation occurs on heating to give the yellow 2,3-n-bonded derivative 6 which results directly from 4 and MeI while for R––Bu5 carbon monoxide displaces the free butatriene from 5 and 6 (Scheme 3).5 Royal Society of Chemistry–Annual Reports–Book A 59 ClL2Rh C C Ph R C H C H C C C R Ph ClL2Rh IL2Rh C C C H H C Ph Ph 4 5 CH2N2 MeI KI/Na2CO3 6 R = Ph Scheme 3 C C CH2 C NPh2H [Ru] C C C 4 [Ru] Me NPh2 + + Scheme 4 C CH)(CO)3Cp] [W(C C [Cp(CO)3WC8W(CO)3Cp] Cu(tmen)Cl O2 Scheme 5 The trienylidene complex [Ru(––C––C––C–– CH 2 )(PPh 3 )Cp]` is intermediate in the reaction of [(Ru(PPh 3 ) 2 (thf)Cp][PF 6 ] with buta-1,3-diyne since in the presence of NPh 2 H the heteroallenylidene derivative resulted (Scheme 4).6 Desilylation of [Re(Bu5 2 bipy)(CO) 3 (C–– – CSiMe 3 )] with base then oxidation using CuII gives the ReC–– – C–C–– – CRe rhenium(I)-carbon wire with C–C bonds of length 119 and 143 pm indicating dominant diyne features.The complex shows luminescent properties.7 A further range of diyne derivatives [W(C–– – CC–– – CH)(CO) 3 Cp] result with di§erent transition metals at the end while oxidising with Cu 2 Cl 2 ·tmen/O 2 under mild Hay conditions gives the dimetallated tetrayne (Scheme 5).8 The first neutral metallacumulene with five carbon atoms 7 results through coupling [IrH 2 Cl(L) 2 ] (L\Pr* 3 P) with the diyne HC–– – C–C–– – CCPh 2 OH followed by dehydroxyation using Tf 2 O/NEt 3 .A structure determination shows the cumulene almost linear with C–C bond lengths alternating thereby indicating participation of a diyne resonance form (Scheme 6).9 CouplingMe 3 SiC 6 Li with C(NMe 2 ) 3 Cl gives 8 which forms two metallopolyenes of 60 D.A. Armitage [IrH(L)2Cl(C CC CCPh2OH)] [Cl(L)2Ir C C C C CPh2] L i Pr3P Tf2O 2NEt3 7 6 Scheme 6 Me3Si(C C(NMe2)3 (CO)5W C C C C C NMe2 NMe2 C C SiMe3 Bun (CO)5W C C C C C NMe2 C C H NMe2 NMe2 (CO)5W C C C C C C C NMe2 NMe2 LiBun [W(thf)(CO)5] BF•OEt2 + 11 10 8 9 Scheme 7 tungsten 9 and 10; 10 is thought to result from the linear intermediate 11 through NMe 2 H addition (Scheme 7).10 In an attempt to prepare the C 60 isomer with five pentayne (C 10 ) units bridging two cyclopentadiene rings it has been necessary to prepare the pentaethynylcyclopentadienes and then fulvene derivatives.The latter oxidise in the presence of [Fe(CO) 5 ] or chloranil to the radical which shows a strong tendency to form the antiaromatic cation.11 The compound Ti 8 C 12 with T) symmetry has been shown to transform to the T$ isomer through a barrierless pathway while the cation Ti 8 C 12 ` readily complexes electron-rich donors and polar moleculesMto give Ti 8 C 12 (M)n ` (n\1–8).12 Combining [Ni(C 3 S 5 ) 2 ]~ with [MCp 2 ]` (M\Co or Ni) gives two products.The simpler [Ni(C 3 S 5 )Cp] results from the direct reaction with the NiC 3 S 5 unit planar and almost perpendicular to the C 5 H 5 ring. The cobalt derivative [CoCp 2 ] [Ni(C 3 S 5 ) 2 ] 3 ·2MeCN results through the electrochemical oxidation of [Bu/ 4 N] [Ni(C 3 S 5 ) 2 ] in the presence of [CoCp][PF 6 ]. The complex has a non-integral oxidation state and semiconductor properties. The structure shows the Ni-dithiole units in parallel stacked triads.13 The anion [Re 2 (C 3 S 5 ) 5 ]2~ shows all dithiol groups chelating to give octahedral co-ordination at each Re atom with sulfur atoms of two di§erent groups providing sulfide bridges to the Re–Re bond.14 The 4,5-disulfanyl-1,3-dithiole-2-thionate dianions (C 3 S 5 )2~ co-ordinate readily with SnIV.Reacting Sn(CH 2 CH 2 CO 2 Me) 2 Cl 2 with [Et 4 N] 2 [Zn(C 3 S 5 ) 2 ] gives 61 Carbon silicon germanium tin and lead S SPri PriS SPri PriS (PriSC)3[ClO4] + Na[CS2(SPri)] + S + NaClO4 Scheme 8 SiMe3 CO2H Me3Si Me3Si Me3Si SiMe3 Me3Si + [SbCl6]– ( i) (ClCO)2 ( ii) SbCl5 Scheme 9 Sn(CH 2 CH 2 CO 2 Me) 2 C 3 S 5 which has a distorted octahedral structure through coordination of the carboxylate groups with an Sn-O distance of 2.63Å and trans carbon atoms. A similar reaction with Sn(CH 2 CH 2 CO 2 Me)Cl 3 gives the five-coordinate derivative [Sn(CH 2 CH 2 CO 2 Me 2 )(C 3 S 5 )]2~ with the structure more closely resembling a square pyramid with the thiolato groups acting as the base.15 Reacting CBr 4 with [Cu(XR)(bipy)]n (X\S Se Te; R\2,4,6-Pr* 3 C 6 H 2 ) gives the tris(chalcogenato)carbenium ions as CuBr 2 ~ salts.They can be converted into the [PF 6 ]~ derivatives with AgPF 6 the structure of the Te derivative showing trigonal planarity for the CTe 3 group.16 The salt [(Pr*SC) 3 ][ClO 4 ] converts Na[CS 2 (SPr*)] to the tetrasubstituted thiophene (Scheme 8).17 Tris(trimethylsilyl)cyclopropenylium cation results from the cyclopropene-3-carboxylic acid as the hexachloroantimonate. The structure shows distortion from idealised D 3) symmetry due to close interionic C· · · Cl contacts and has C–C bonds of 1.38Å and ring Si–C bonds of 1.90Å a little longer than those of the SiMe 3 groups (Scheme 9).18 NMR spectroscopic studies of an extensive range of solvated complexes of the silylium cation indicate that four-co-ordinated monosolvates occur for (SiR 3 )` and (SiR 2 H)` while five-co-ordinated disolvates result for (SiR 3~nHn)` (n\1 2 or 3).Binding energies are in the range 170–250 kJ mol~1.19 The degree of silylium character increases with the weakly co-ordinating hexahalogenocarborane anions (CB 11 H 6 X 6 )~ (X\Cl Br I Pr* 3 SiY) indicating CSiC angles of 117.3° 117° and 115.6° for X\Cl Br I with 29Si downfield shifts indicating the chloro derivative least co-ordinating. This is therefore suggested as the most silylium-like condensed phase characterised to date with some 50% silylium-like character.20 However 29Si NMR spectroscopic studies suggest that the high electrophilicity of trivalent silicon in (SiEt 3 )` results in interactions with arenes (CB 11 H 5 Br 6 )~ H 2 O and MeCN resulting in little silicenium nature present.21 Similar studies with tin show no free trigonal stannyl cations in solution but a greater predominance of the five-co-ordinate rather than four-coordinate solvates.22 The compound N(SiCl 2 H) 2 H reacts with 3-methylpyridine to give the hypervalent derivatives Cl 2 H 2 Si(3-Mepyl) 2 and [SiH 2 (3-Mepyl) 4 ]Cl 2 ·4HCCl 3 with six-co-ordinate silicon.Both complexes are in equilibrium in chloroform but crystals of the latter show the 3-methylpyridine groups coplanar and N]Si bonds about 1.97Å.23 Heating [W(SiMe 3 )(GeMe 2 )Cp 2 ][OTf] in benzene or in the absence of solvent gives the dinuclear derivative 12 containing what is thought to be the germyl cation with two 62 D.A. Armitage GeMe2 W Ge Me Cp W Cp Cp H [W(SiMe3)(GeMe2)Cp2][OTf] [W(SiMe3)(GeMe3)Cp2] + + 12 –2Me3SiOTf SOi C6H6 Scheme 10 W–Ge bond lengths of 2.49 and 2.58Å respectively and planarity at germanium (Scheme 10).24 Reducing Me 4 C 4 SiBr 2 with three equivalents of potassium leads to the dianion 13 which with SiMe 3 Cl gives the tetrasilane 14.With four equivalents of potassium however the silole dianion 15 results which can be stabilised with 18-crown-6 or converted after desilylation into the silolyl anion 16; a similar one 17 results from 14 (Scheme 11). The silole dianion shows considerable n-delocalisation with C–C bonds of 1.38–1.44Å and C–Si bonds of 1.83–1.85Å. 25 The first pentaorganosilicate 19 results from the reaction of o-disubstituted biphenyl 18 with LiMe. The high field 29Si NMR spectroscopic signal (d\[116.9) supports pentavalency (Scheme 12).26 Reducing 20 with lithium gives the trigermole dianion which can be readily methylated to give 21 (Scheme 13).Structural data for the dianion supports a sandwich arrangement this complex the lithium cation and so reduces the delocalisation of the outer germole rings.27 The dianion of tetraphenyl germole can be similarly prepared in thf and can be recrystallised from dioxane as two distinct isomers. One is a reverse sandwich complex with two molecules of dioxane complexing to each lithium ion which are g5 to the germole ring. The second isomer has germanium co-ordinating g1 to one of the lithium ions the other g5 to the ring. In the former isomer the Ge–C bonds are 1.96Å in the latter 1.93Å.28 Ene reactions of Me 2 M––C(SiMe 3 ) 2 (M\Si Ge) take place both regio and stereospecifically with acceleration if there are electron-donating groups on the alkene or diene and retardation if bulky substituents.29 Thermolysis of Bu5 2 SiF– C(Li)(GeMe 3 ) 2 ·2thf gives the silene which isomerises to the germene 22 since ene adducts result for 22 and not the silene 23 (Scheme 14).30 The first stannagermene (Is) 2 Sn––Ge(mes) 2 results from GeH 2 (mes) 2 and SnF 2 (Is) 2 and adds MeOH gives the oxastannagermetane with benzaldehyde and eliminates :Ge(mes) 2 on heating to give the distannagermirane (Scheme 15).31 The kinetics of the reaction of chlorine atoms with silane supports hydrogen atom abstraction to give SiH 3 and HCl and while calculations give no evidence to support an intermediate SiH 4 ·Cl adduct transition state theory indicates the transition state geometry to be almost linear with a Si–H–Cl angle of about 170°.32 The FT ion 63 Carbon silicon germanium tin and lead SiBr2 Si Si Si Si thf SiMe3 Me3Si Si Si – SiMe3 – K+ 2Me3SiCl 3K – K+(18-crown-6) Si 2K+ 17 KCH2Ph 18-crown-6 14 13 Si(SiMe3)2 2– Si 15 4K thf KCH2Ph 18-crown-6 SiMe3 – 16 K+(18-crown-6) K+ Scheme 11 SiMe3 Br Me3 Si LiMe – 18 19 Scheme 12 cyclotron resonance MS examination of the interaction of W` with silane indicates initial dehydrogenation giving (WSiH 2 )` which reacts with more silane to give (WSi 2 H 2 )`.Further reactions with silane lead to (WSinHn)` (n\3 4) and eventually (WSi 10 H 6 )` with metal trapped in a silicon cage.33 Calculations indicate the cis isomer of [Mo(CO)(PH 3 ) 4 (HSiH 3 )] to be the more stable with g2-H–Si bonding to Mo,34 while for [OsCl(CO)(PH 3 ) 2 (‘H 2 SiH 3 ’)] calculations indicate that the MOs(SiH 3 )(g2-H–H)N and MOs(H)(g2-H–SiH 3 )N isomers are close 64 D.A.Armitage Cl Cl Et4 Ge Ge Et4 Li Ge Et4 Et4 Li(Sciv) Ge Ge Ge Me Me Et4 Et4 Et4 MeI Li/thf/tmen 20 21 Scheme 13 But 2FSi CLi(GeMe3)2•2thf Me2Ge C(GeMe3)(SiMeBut 2) F Li(thf)2 Me2Ge C GeMe3 SiMeBut 2 But 2Si C(GeMe3)2 100 °C C6H6 23 22 S h 14 Scheme 14 (Is*)2Sn Ge(mes)2 H F (Is*)2Sn Ge(mes)2 Li F (mes)2 Ge (Is*)2Sn (Is*)2Sn Ge(mes)2H2 LiBut ( i) LiBut (Is*)2Sn Ge(mes)2 ( ii) Is*2SnF2 (Is*)2Sn(F)GeMe(mes)2 MeI heat –(mes)2Ge –LiF Scheme 15 Me2 P Me2Pd P Me2 P P H2Si SiH2 H2Si SiH2 M SiH3 SiH3 + 24 Scheme 16 in energy. It was found that the g2-HSiR 3 bond to the metal is stronger than that of g2-H 2 in [OsCl(CO)(PH 3 ) 2 (H)(g2-HSiR 3 )] by about 43 kJ mol~1 which compensates for the greater strength of the H–H bond compared with the H–Si bond.35 Silyl derivatives of Fe and Ru result from the reduction of M(R 5 C 5 )(CO)–SiHCl 2 65 Carbon silicon germanium tin and lead N But Si But N N But Si But N N But Si But N B(C6F5)3 C6H5 B(C6F5)2 + B(C6F5)3 N B(C6F5)3 toluene 20 °C Me 25 N 26 Me toluene 20 °C 3 months Scheme 17 with LiAlH 4 and are photolytically substituted with phosphines without cleavage of the M–Si bond.36 Following the isolation of the tetrakis(silyl)platinum complex 24 (M–– Pt) the analogous PdIV derivative has been isolated from the reaction of PdMe 2 (dmpe) with excess 1,2-bis(silyl)benzene at 50 °C in toluene (Scheme 16).Di¶- culty in isolating the [PdIIM1,2-(H 3 Si) 2 C 6 H 4N(dmpe)] derivative suggests that tetrasilyl PdII intermediates may be important in Pd-catalysed reactions of silanes and disilanes.37 The silylene–borane adduct 25 slowly rearranges at room temperature with aryl migration to give the silylborane 26 while 4-methylpyridine displaces the silylene from the adduct (Scheme 17).38 The first arachno-silaborane arachno-(NHMe 2 )(SiMe)B 9 H 12 to be prepared results from arachno-B 9 H 13 (SMe 2 ) by reacting with Si(NMe 2 ) 2 MeH and the SiB 9 cluster has Si occupying position 6 of the (B 10 H 14 )2~ framework the amino group at position 9 the prow and stern of the open boat.39 The nido-silaborane B 10 H 12 (SiMe)~ 27 with an open B 4 SiMe ring readily reacts with NEt 3 ·BH 3 to eliminate hydrogen to give the first closo-monosilaborane 1-methyl-1-sila-closo-dodecaborate(1[) in excellent yield.The first-fold symmetry is supported by the 11B NMR spectroscopic intensity ratio of 5 1 5.40 Hetero sila-closo-boranes result from 27 using KH·BEt 3 followed by closo addition of SnCl 2 or SbI 3 to give heterosila-closo-boranes (Scheme 18).41 Reacting aluminium monochloride with NaSiBu5 3 gives the deep violet tetraalatetrahedrane Al(SiBu5 3 ) 4 which sublimes at 180 °C under high vacuum. Surprisingly indium(I) bromide and thallium(I) bromide both react with NaSiBu5 3 to give the diindium and dithallium compounds [M(SiBu5 3 ) 2 ] 2 as deep violet and black-green crystals respectively which are thermally unstable above 125 and 52 °C respectively and have long M–M bonds.42 Coupling Na[Mo(CO) 3 Cp] with Ge(2,6-mes 2 C 6 H 3 )Cl in thf gives the Mo-Ge derivative with metal–metal bond length of 2.27Å (compare 2.6–2.65Å for single bonds) suggesting multiple bond character possibly triple as would be expected for the 15-electron Mo fragment.43 The binary phase Ca 14 Si 19 possesses a novel two-dimensional silicon framework comprising 3,3,3-barrelane (Si 11 ) units linked by Si 3 bridges.The two ternary silicides SrMgSi 2 and Sr 11 Mg 2 Si 10 possess respectively branched and zig-zag chains.44 The 66 D.A. Armitage Si CH3 Si H CH3 H Si CH3 Si E – CH3 – K3 n 27 E = Sn n = –1 E = Sn n = 0 Et3N•BH3 –2H2. –Et3N thf 3KHBEt3 thf SnCl2/SbI3 Scheme 18 two ternary phases Ba 4 Li 2 M 6 (M\Si Ge) show remarkable Hu� ckel arene structures with 10 n electrons as heterographite-like nets comprising [Li 2 M 6 ]8~ units. The structure of the silicon derivative shows the Si 6 hexagons slightly puckered while that of the (Ge 6 )10~ ion in Ba 10 Ge 7 O 3 [comprising Ba2` O2~ Ge4~ and (Ge 6 )10~ ions] is planar.45 The ternary phase Y 2 AlGe 3 comprises a three-dimensional lattice of Al and Ge atoms with Al surrounded tetrahedrally by Ge atoms which form planar chains.It is superconducting at 4.5 K. The complex Eu 5 Ge 3 contains Ge4~ and (Ge 2 )6~ ions46 while EuGe 2 contains (Ge 2 )6~ ions with Ge–Ge bonds of 2.57Å. The ternary phase NaAuGe comprises layers with trigonal planar gold interconnected through Ge–Ge contacts so the Ge 2 Au 6 units resemble ethane.47 The trimetallic phase K 2 SnBi contains an infinite chain of alternating Sn and Bi atoms comprising [Sn 2 Bi 2 ]4~ repeating units that give a zig-zag chain with the central skeleton of tin atoms essentially linear.48 Reacting K 4 Ge 9 with [Ni(CO) 2 (Ph 3 P) 2 ] gives [Ge 9 (k10 -Ge)Ni(PPh 3 )]2~ with an interstitial Ge atom held within the NiGe 9 cage.49 Extraction of the alloys KSn 2.25 and KPb 2.25 using ethylenediamine and cryptand 222 gives solvated paramagnetic compounds K[(cryptand 222)] 6 M 9 M 9 (M\Sn Pb) with two di§erent M 9 clusters but both with a distorted tricapped trigonal prismatic polyhedral structure.50 Calculations on strain energies of silicon rings and clusters show the cyclotrisilane to be more strained than cyclopropane but the larger four- and five-membered cyclo(polysilanes) to be less strained than their cycloalkane analogues.While the tetrahedranes (CH) 4 and (SiH) 4 have considerable strain energy that of the cyclooctatetraene structures is negligible; those of other polyhedral silanes is smaller than their hydrocarbon analogues.The relative energies of polyhedral silanes (SiH) 2n enables a determination of the Si––Si double bond enthalpy to be 424 kJ mol~1.51 The water soluble polysilane [SiMeMNMe 3 (CH 2 C 6 H 4 C 2 H 4 )N]nCln in water/ethanol binary mixtures shows variations in the UV absorption and fluorescence properties attributed to p–p* transition in the Si–Si backbone the maximum depending on 67 Carbon silicon germanium tin and lead 4GeCl2.diox + 6ButSiNa (But 3SiGe)4 + (SiBut 3)2 19 28 Scheme 19 solvent composition. The band ranges from 280 to 304nm maximum in an approximately equimolar mixture of solvents.52 The first molecular compound with a Ge 4 tetrahedral structure (Bu5 3 SiGe) 4 28 results from the reductive coupling of GeCl 2 ·C 4 H 8 O 2 with NaSiBu5 3 .It forms as intense red crystals which slowly hydrolyse but rapidly oxidise in air. Crystals of 28 contain (SiBu5 3 ) 2 in the molar ratio 2 1 the germane having Ge–Ge bonds of 2.44Å and Ge–Si bonds of 2.38Å which are much shorter than the Si–Si bonds of the highly hindered disilane which are 2.72Å (Scheme 19).53 Heating Ba Yb and Si(NH) 2 gives BaYbSi 4 N 2 containing four SiN 4 units connected through a common N atom to give N(SiN 3 ) 4 as the building unit each connected through other such units so giving a formulation of Si 4 N 12@2 N. In this three-dimensional lattice the tunnels fill with Ba2` and Yb3` ions.54 Heating Na NaN 3 Sr and Ge in niobium tubes at 750 °C gives Sr 3 Ge 2 N 2 and Sr 2 GeN 2 .The former possesses a zig-zag chain of Ge2~ ions while both contain angular GeN 2 4~ ions with in the latter a NGeN angle of 113.6° and Ge–N bonds of 1.85–1.88Å.55 A reconsideration of the vapour phase structure of silyl isocyanate still supports a linear structure despite the non-linearity of R 3 SiNCO derivatives in the solid state.56 The cyanate MC(SiMe 3 ) 3 Si(CD 3 ) 2N(OCN) isomerises in the molten state at 150 °C to give the unrearranged isocyanate together with the rearranged [C(SiMe 2 )(SiMe 3 ) 2MSiMe(CD 3 ) 2N]NCO in the ratio 3 1 and in Ph 2 O at 220 °C in the ratio 6 1. This supports a mechanism involving initial ionisation of the cyanate. In CCl 4 with a trace of ICl no rearrangement accompanies isomerisation.57 Recrystallising LiBr LiN(SiMe 3 ) 2 LiOC(Bu5)–– CH 2 and tmen in the ratio 1 1 1 2 gives the amide complex LiBr·LiN(SiMe 3 ) 2 ·[LiOC(Bu5)––CH 2 ] 2 ·(tmen) 2 with a butter- fly skeleton 29 providing a new structural type in lithium chemistry.58 The compound Me 2 NNMeLi reacts with SiCl 4 to give the bis(hydrazino)dichlorosilane but with GeCl 4 gives the tetra(hydrazido) germane.Both decompose on heating and structure determinations of each indicate intramolecular N-co-ordination with Si · · ·N bonds of 2.51Å (compare Si–N 1.67Å); the germanium derivatives with Ge · · ·N bonds of 2.75Å(compare Ge–N 1.83Å) show much weaker intramolecular Ge · · ·N co-ordination. 59 Br Li O Li Li O Li N 29 Li Li Li Li P P Sn Sn Sn Sn 30 Reacting (SnNBu5) 4 with LiNH(R) (R–– napthyl) and LiPH(c-C 6 H 11 ) gives the clusters [Li(thf) 4 ][(NBu5)(C 10 H 7 N) 3 Sn 3 Li·thf]·thf·MePh and [MSn 2 (PC 6 H 11 ) 3N2 Li 4 ·4thf] ·2thf.The former has a cubane-like structure and the latter with the 14-membered cage Sn 4 P 6 Li 4 30 possesses two Sn 2 P 2 units bridged by two phosphides with each Li ion bridging three P atoms in the equatorial plane.60 68 D.A. Armitage (Is*)2Si E SiPri 3 (Is*)2Si N E O (Is*)2Si E SiPri 3 Ph N Si(Is*)2 E SiPri 3 N Ph2C Ph Ph SiPri 3 N PhC Ph2C O (E = P or As) Ph2CN2 Scheme 20 The ternary Cu/Si/P system gives Cu 4 SiP 8 as a three-dimensional lattice containing SiP 4 tetrahedra connected through P 4 units each P atom bonding to one P atom of a SiP 4 tetrahedral unit. The P–P distances are 2.18–2.21Å and inclusions in the lattice contain (Cu 2 )2` cations.61 The Si––P and Si–– As double bonds result from the thermolysis of the monomeric lithium (fluorosilyl)phosphanides and arsenides Is* 2 Si(F)P[LiLn]R [R\SiR@3 where R@3 –– Pr* 3 Me 3 Me 2 Bu5 Ph 2 Me Ph 3 (C 10 H 7 ) 3 HBu5 2 (M–– P) and Pr* 3 Ph 2 Me Cy 2 Me (M–– As); M\P As] and undergo an extensive series of addition reactions with electron-rich compounds (Scheme 20).62 Lithium adds to the Si–– P double bond of Is* 2 Si––PSiPr* 3 the dilithio derivative then hydrolysing or reacting with SiMe 2 Cl 2 to give the first disilaphosphacyclopropane or HgBu5Cl to give 31.This loses SiR 3 H to give 32 through Hg migration (Scheme 21).63 The arsanyl alanate LiAl(AsH 2 ) 4 reacts with Si(Is*)Cl 3 to give the tetraarsatetrasilacubane (Is*SiAs) 4 ; a structure determination indicates a distorted structure with Si–As bonds ranging from 2.40 to 2.41Å with angles at Si of about 100° and of 80° at As.64 The mixture Na 3 Bi/K 3 Bi reacts with SiMe 2 Cl 2 to give the decamethyl-1,4- dibismutha-2,3,5,6,7-pentasilabicyclo[2.2.1]heptane.65 The diphosphide K 2 [Bu5P(Bu5P) 2 PBu5] reacts with SnR 2 Cl 2 to give the stannatetraphospholanes while K 2 [Bu5P] 2 with SnCl 4 results in a redox reaction yielding (Bu5P) 3`4 along with the [2.2.2]octane ClSn(Bu5PPBu5) 3 SnCl with Sn–P bonds of 2.53Å.66 The transition metal monosilonyls M(SiO) (carbonyl analogues) were first characterised some years ago with an IR stretching frequency of 1163 cm~1 and a suggested triangular structure.The EPR spectra at 4K for M(SiO) (M\Cu Ag Au and V) suggest a non-linear structure for the first three compounds.67 Silicate minerals are usually four-co-ordinate at the earth’s crust surface and sixco- ordinate within the earth’s lower mantle.Five-co-ordination is not normally encountered in silicates but plays a role in dynamic processes. The oxide CaSi 2 O 5 synthesised at high temperature and pressure shows an NMR signal at d [150 suggesting five-co-ordination at Si. A structure determination shows that while octahedral SiO 6 co-ordination occurs at two silicon sites the third has one oxygen atom 69 Carbon silicon germanium tin and lead Si P Li(thf)2 SiR3 (thf)2Li Is* Is* Si P H SiR3 H Is* Is* Si P HgBut SiR3 ButHg Is* Is* Si P HgBut HgBut H Is* Me2C Pri Pri Is*2Si P SiMe2 32 31 –R3SiH SiR3 Me2SiCl2 HgBut 2Cl Scheme 21 displaced away from the octahedron by about 1.10Å to leave silicon pseudo-five-coordinate and with a geometry close to trigonal bipyramidal.68 Condensing the silane triol NR(SiMe 3 )Si(OH) 3 with SiMe 3 Cl gives the diol NR(SiMe 3 )Si(OSMe 3 )(OH) 2 while with Ti(OR@) 4 (R–– aryl; R@ –– Et Pr*) the Ti 4 Si 4 O 12 cage results.69 The compound GaMe 3 gives the gallium silicates (RSi) 2 (MeGa) 2 (Me 2 Ga) 2 O 6 Mfrom [R(OH)SiOGaMe(solv)] 2 and GaMe 3N and (RSi) 4 [Ga(solv)] 4 O 12 .70 The compound (c-C 6 H 11 ) 7 (Si 7 O 9 )(OH) 3 [L(OH) 3 ] reacts with MgBuEt to give [L(OH)O 2 Mg]n (n\1 2); with TiCl 4 [(c- C 6 H 11 ) 7 (Si 7 O 12 )MgTiCl 3 ]n results and in the presence of AlEt 3 it shows high catalytic activity for ethene polymerisation.71 Other incompletely condensed silasesquioxanes show similar activity.72 Condensing SiR(OH) 3 (R\Bu5 or MeCHMeCMe 2 ) using C(c-C 6 H 11 N) 2 as dehydrating agent gives (RSiO 1.5 ) 6 with six-membered Si 3 O 3 rings rather than the eightmembered ones while (HSiO 1.5 ) 8 can be derivatised using alcohols and silanols in the presence of catalytic amounts of amines.73 Oxidation of the germylene :Ge(mes*) 2 with trimethylamine N–oxide gives the unstable germanone which then isomerises to the germanol 33.The germylene slowly isomerises in Lewis acids through C–H insertion to give the germaindane 34 which does not oxidise to the germanol 33.74 Condensing SnClCp with KM(OBu5) 3 gives the novel half sandwich compounds CpSn(OBu5) 3 M (M\Ge Sn Pb) the Ge derivative 35 showing two bridged Bu5O groups and Cp acting g1/g3.75 Tin(II) oxide hydroxide Sn 6 O 4 (OH) 4 results from mildly alkaline solutions of stannous salts.It contains a Sn 4 O 8 belt comprising two 70 D.A. Armitage Sn 2 O 2 units and two Sn 2 (OH) 2 units connected through common tin atoms. The other tin atoms cap this belt top and bottom and hydrogen bonding connects the cages intermolecularly.76 Ge But But Me Me But But But OH Sn But O Ge O But OBut Ge But But Me Me But But But H 35 33 34 In the presence of Pb(OAc) 4 SnCl 4 provides a clean source of chlorine for chlorination to convert arenes into the chlorobenzene.77 Coupling [Co 3 (CO) 9 (k3 -CCO 2 H)] with Pb(OAc) 2 gives [PbM(CO) 9 Co 3 (k3 -CCO 2 )N2 ],78 while M[N(SiMe 3 ) 2 ] 2 (M\Ge Sn Pb) with (CF 3 ) 2 CHOH and amines gives monomeric M(OR&) 2 L (L\amine) (M\Ge Sn) but for M\Pb the bridged dimeric salts (Me 2 NH 2 ) 2 ) 2 [Pb(k- OR&)(OR&) 2 ] 2 result.79 Reaction of TsiSiH 3 with elemental sulfur gives the polythiadisilabicyclo[k.l.m] alkanes 36 37 and 38 with Si–S bonds ranging from 2.13 to 2.19Å.80 The disilene R(mes)Si––Si(mes)R MR\2,4,6-[C(SiMe 3 ) 2 H] 3 C 6 H 2N reacts with CS 2 in thf at 60 °C to give the 1,2,4-thiadisiletane-3-thione.The ring is not planar.81 S S Si Tsi S S S Tsi Si S S Si Tsi S S Tsi Si S S Si Tsi S Tsi Si S S S 36 37 38 Octamethyldibenzotetraaza[14]annulene [Me 8 taa] stabilises germanium and tin sulfur and selenium double bonds which readily react with MeI to give [M(g4- Me 8 taa)(EMe)]I. ICH 2 CH 2 I gives the diiodide [M(g4-Me 8 taa)]I 2 which with I 2 in THF forms the ionic salt [Sn(g4-Me 8 taa)I(thf)][I 3 ] add ethylene sulfide to give the five-membered heterocycle (M\Sn) or for M\Ge E\Se (g4-Me 8 taa)Ge––Se results.82 The two tin(II) amidates :Sn[CyNC(R)NCy] 2 L 2 Sn (R\Me Bu5) react with styrene sulfide to give L 2 Sn–– S (R\Bu5) with Sn–– S 2.28Å and (SnL 2 S) 2 (R\Me) with Sn-S bonds of 2.43–2.47Å.83 Amorphous GeS 2 reacts with dabco and silver acetate to give [(dabco) 2 (H 3 O)H 2 O] AgGe 4 S 10 . The silver ions provide the connection between sulfur atoms of three Ge 4 S 10 cages thereby building up a three-dimensional network.84 Tin(II) reacts directly with [Mo 3 S 4 (H 2 O) 9 ]2` 39 to give the [Mo 3 SnS 4 ]6` single cube which adds chloride to give the deeper yellow [Mo 3 (SnCl 3 )S 4 (H 2 O) 9 ]3`. With elemental tin 39 gives the red-purple double cube cation [Mo 6 SnS 8 (H 2 O) 18 ]8` with Sn as the bridge between the two Mo 3 S 4 units.85 Lead forms a similar double cube from lead shot and 39 as a blue-green air sensitive product.86 71 Carbon silicon germanium tin and lead Cl(L)2Ru C C R H HC CR AgOTf [RuCl2(L)2] + 2 1 Scheme 22 Extracting mixtures of the ternary alloys K/Sn/Se (3 2 6) or K/Sn/Te (3 2 5) in ethylenediamine with cryptand 222 gives the anions (Sn 2 Ch 6 )4~ and (Sn 2 Ch 7 )4~ (Ch\Se Te) the former with a Sn 2 Ch 2 four-membered ring 40 and the latter a Sn Ch Sn Ch Ch Ch Ch Ch Sn Sn Ch Ch Ch Ch Ch 4– Ch Ch 4– 40 41 Sn 2 Ch 3 five-membered ring 41.The novel [SnTe 3 (HO)]3~ anion also results and provides the first example of a simple mixed hydroxychalcogenide anion of tin.87 The compound [PtMe 2 (4,4@-Bu5 2 bipy)] 42 reacts with (Ph 2 SnS) 3 to give the luminescent PtSnSSnS 43 ring. Reacting 43 with (Me 2 SnS) 3 induces stepwise replacement of Ph 2 SnS units by Me 2 SnS with the mixed derivative with the PtSnMe 2 SSnPh 2 S preferentially formed from 42 (Ph 2 SnS) 3 and (Me 2 SnS) 3 .88 Desulfurisation of the tetrathiastannolanes 44 with PMe 3 gives the stannylene which can be trapped with 2,3-dimethylbuta-1,3-diene (Scheme 22) and itself adds sulfur from styrene episulfide or elemental sulfur to give the stannane thione which absorbs at 473nm and adds thiocumulenes to give cycloadducts.89 Reacting silicon powder with [NH 4 ]HF 2 at 400 °C gives crystals of [NH 4 ] [Si(NH 3 )F 5 ] and Si(NH 3 ) 2 F 4 the latter with a trans structure and Si–F bonds of 1.66–1.68Å for the two compounds and Si–N bonds of 1.90Å.90 Pyrolysing Si 2 Me 5 H with CCl 2 F 2 gives CF 2 ClH and chlorosilanes with evidence of radical intermediates.91 Carbon dioxide can be activated in the gas phase by co-ordination to (SiF 3 )`. The structure of the complex is slightly bent with an SiOC angle of 156.3° and the complex will react with aromatic C–H bonds to give (ArCO)` and SiF 3 OH.92 Condensing AuLiPMe 2 Ph with GeCl 2 ·diox gives the bright yellow photoluminescent derivative [Au(PMe 2 Ph) 2 ][Au(GeCl 3 ) 2 ] through GeCl 2 insertion into the Au–Cl bond followed by disproportionation.93 The anions (SnX 3 )~ (X\Cl Br) will complex with Pt to give square planar and trigonal bypyramidal derivatives,94 while the clusters [Pt 6 (k-CO) 6 (k-dppm) 3 ]n` (n\0 2) react with SnX 2 /NaX (X\F Cl Br) to give the bicapped trigonal prism adducts with (SnBr 3 )~ bridging the trigonal caps.95 The salt [Ph 4 P][SnCl 5 ] shows a trigonal bipyramidal structure with Sn–Cl bonds of 2.39Å (axial) and 234–229Å (equatorial) while [Ph 4 P][SnCl 5 OH 2 ]~ has equatorial Sn–Cl bonds of 2.39Å and trans to H 2 O of 2.34Å similar to those in [SnCl 5 (thf)]~.96 The compound Me 3 SnF readily fluorinates [WCl 4 Cp*] the tetrafluoride oxidising and hydrolysing to [WF 5 Cp*] and [WFO 2 Cp*].97 72 D.A.Armitage References 1 U.H.F. 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Soc. 1996 118 5997. 34 M.-F. Fan G. Jia and Z. Lin J. Am. Chem. Soc. 1996 118 9915. 35 F. Maseras and A. Lledos Organometallics 1996 15 1218. 36 W. Malisch S. Moller O. Fey H.-U. Wekel R. Pikl U. Posset and W. Kiefer J. Organomet. Chem. 1996 507 117. 37 S. Shimada M. Tanaka and M. Shiro Angew. Chem. Int. Ed. Engl. 1996 35 1856. 38 N. Metzler and M. Denk Chem. Ber. 1996 129 2657. 39 L. Wesemann and B. Ganter Organometallics 1996 15 2569. 40 L. Wesemann and U. Englert Angew. Chem. Int. Ed. Engl. 1996 35 527. 41 L. Wesemann Y. Ramjoie B. Ganter and H. Maisch Chem. Ber.1996 129 837. 42 N. Wiberg K. Amelunxen H. Noth M. Schmidt and H. Schwenk Angew. Chem. Int. Ed. Engl. 1996 35 65. 43 R. S. Simons and P. P. Power J. Am. Chem. Soc. 1996 118 11 966. 44 A. Currao S. Wengert R. Nesper J. Curda and H. Hillebrecht Z. Anorg. Allg. Chem. 1996 622 501; A. Currao J. Curda and R. Nesper Z. Anorg. Allg. Chem. 1996 622 85. 45 H. G. von Schnering U. Bolle J. Curda K. Peters W. Carrillo-Cabrera M. Somer M. Schultheiss and U. Wedig Angew. Chem. Int. Ed. Engl. 1996 35 984. 46 D. Johrendt A. Mewis K. Drescher S. Wasser and G. Michels Z. Anorg. Allg. Chem. 1996 622 589; P. Pottgen and A. Simon Z. Anorg. Allg. Chem. 1996 622 779. 47 U. Zachwieja Z. Anorg. Allg. Chem. 1996 622 1173. 48 M. Asbrand and B. Eisenmann Z. Naturforsch. Teil B 1996 51 1301. 49 D. R. Gardner J.C. Fettinger and B. W. Eichhorn Angew. Chem. Int. Ed. Engl. 1996 35 2852. 73 Carbon silicon germanium tin and lead 50 T. F. Fassler and M. Hunziker Z. Anorg. Allg. Chem. 1996 622 837. 51 M. Zhao and B. M. Gimarc Inorg. Chem. 1996 35 5378. 52 T. Seki A. Tohnai T. Tamaki and A. Kaito Chem. Lett. 1996 361. 53 N. Wiberg W. Hochmuth H. Noth A. Appel and M. Schmidt-Amelunxan Angew. Chem. Int. Ed. Engl. 1996 35 1333. 54 H. Huppertz and W. Schnick Angew. Chem. Int. Ed. Engl. 1996 35 1983. 55 S. J. Clarke G. R. Kowach and F. J. DiSalvo Inorg. Chem. 1996 35 7009. 56 T. Veszpremi T. Pasinszki and M. Feher J. Organomet. Chem. 1996 507 279. 57 A. I. Almansour G. A. Ayoko and C. Eaborn J. Organomet. Chem. 1996 514 277. 58 K.W. Henderson A. E. Dorigo P. G. Williard and P. R. Bernstein Angew.Chem. Int. Ed. Engl. 1996 35 1322. 59 N.W. Mitzel B. A. Smart A. J. Blake S. Parsons and D.W. H. Rankin J. Chem. Soc. Dalton Trans. 1996 2095. 60 R. A. Allen M. A. Beswick N. L. Cromhout M. A. Paver P. R. Raithby A. Steiner M. Trevithick and D. S. Wright Chem. Commun. 1996 1501. 61 P. Kaiser and W. Jeitschko Z. Anorg. Allg. Chem. 1996 622 53. 62 M. Driess H. Pritzkow S. Rell and U. Winkler Organometallics 1996 15 1845. 63 M. Driess and H. Pritzkow Z. Anorg. Allg. Chem. 1996 622 858. 64 M. Driess K. Merz H. Pritzkow and R. Janoschek Angew. Chem. Int. Ed. Engl. 1996 35 2507. 65 G.M. Kollegger H. Siegl K. Hassler and K. Gruber Organometallics 1996 15 4337. 66 D. Bongert H.-D. Hausen W. Schwarz G. Heckmann and H. Binder Z. Anorg. Allg. Chem. 1996 622 1167 1793. 67 A. P. Williams R.J. van Zee and W. Weltner jun. J. Am. Chem. Soc. 1996 118 4498. 68 R. J. Angel N. L. Ross F. Seifert and T. F. Fliervoet Nature (London) 1996 384 441. 69 R. Murugavel A. Voigt V. Chandrasekhar H. W. Roesky H.-G. Schmidt and M. Noltemeyer Chem. Ber. 1996 129 391; A. Voigt R. Murugavel V. Chandrasekhar N. Winkhofer H. W. Roesky H.-G. Schmidt and I. Uson Organometallics 1996 15 1610. 70 A. Voigt R. Murugavel E. Parisini and H. W. Roesky Angew. Chem. Int. Ed. Engl. 1996 35 748. 71 J.-C. Liu Chem. Commun. 1996 1109. 72 H. C. L. Abbenhuis H. W.G. van Herwijnen and R. A. van Santen Chem. Commun. 1996 1941. 73 M. Unno S. B. Alias H. Saito and H. Matsumoto Organometallics 1996 15 2413; A. R. Bassindale and T. Gentle J. Organomet. Chem. 1996 521 391. 74 P. Jutzi H. Schmidt B. Neumann and H.-G.Stammler Organometallics 1996 15 741. 75 M. Veith C. Mathur and V. Huch Organometallics 1996 15 2858. 76 I. Abrahams S. M. Grimes S. R. Johnston and J. C. Knowles Acta Crystallogr. Sect. C 1996 52 286. 77 H. A. Muathen Tetrahedron 1996 52 8863. 78 X. Lei M. Shang A. Patil E. E. Wolf and T. P. Fehlner Inorg. Chem. 1996 35 3217. 79 S. Suh and D. M. Ho§man Inorg. Chem. 1996 35 6164. 80 N. Choi K. Asano N. Sato and W. Ando J. Organomet. Chem. 1996 516 155. 81 N. Tokitoh H. Suzuki and R. Okazaki Chem. Commun. 1996 125. 82 M.C. Kuchta and G. Parkin Chem. Commun. 1996 1669; M. C. Kutcha and G. Parkin Polyhedron 1996 15 4599. 83 Y. Zhou and D. S. Richeson J. Am. Chem. Soc. 1996 118 10 850. 84 J. B. Parise and K. Tan Chem. Commun. 1996 1687. 85 J. E. Varey G. J. Lamprecht V. P. Fedin A.Holder W. Clegg M.R. J. Elsegood and A. G. Sykes Inorg. Chem. 1996 35 5525. 86 D.M. Saysell Z.-X. Huang and A. G. Sykes J. Chem. Soc. Dalton Trans. 1996 2623. 87 J. Campbell L. A. Devereux M. Gerken H. P. A. Mercier A.M. Pirani and G. J. Schrobilgen Inorg. Chem. 1996 35 2945. 88 L.M. Rendina J. J. Vittal and R. J. Puddephatt Organometallics 1996 15 1749. 89 M. Saito N. Tokitoh and R. Okazaki Chem. Lett. 1996 265; M. Saito N. Tokitoh and R. Okazaki Organometallics 1996 15 4531. 90 C. Plitzko and G. Meyer Z. Anorg. Allg. Chem. 1996 622 1646. 91 M.P. Clarke M. Conqueror G. H. Morgan and I. M. T. Davidson J. Organomet. Chem. 1996 521 395. 92 P. Cecchi M. E. Crestoni F. Grandinetti and V. Vinciguerra Angew. Chem. Int. Ed. Engl. 1996 35 2522. 93 A. Bauer and H. Schmidbaur J. Am. Chem. Soc.1996 118 5324. 94 J. H. Nelson W. L. Wilson L. W. Cary N.W. Alcock H. J. Clase G. S. Jas L. Ramsey-Tassin and J. W. Kenney III Inorg. Chem. 1996 35 883; E. Farkas L. Kollar M. Moret and A. Sironi Organometallics 1996 15 1345. 95 G. J. Spivak L. Hao J. J. Vittal and R. J. Puddephat J. Am. Chem. Soc. 1996 118 225. 96 U. Muller J. Siekmann and G. Frenzen Acta Crystallogr. Sect. C 1996 52 330; Z. Janas T. Lis and P. Sobota Inorg. Chem. 1996 35 5737. 97 K. Kohler A. Herzog A. Steiner and H. W. Roesky Angew. Chem. Int. Ed. Engl. 1996 35 295. 74 D.A. Armitage

ISSN:0260-1818    

DOI:10.1039/ic093059

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

6 Nitrogen phosphorus arsenic antimony and bismuth By K. K. HII Dyson Perrins Laboratory South Parks Road Oxford OX1 3QY UK and T. P. KEE School of Chemistry University of Leeds Leeds LS2 9JT UK 1 Introduction This report covers important aspects in the development of Group 15 chemistry during the year 1996.1 Since a comprehensive review is unfortunately beyond the remit of this particular article attention has been focused on the twin areas of metalloorganic and co-ordination chemistry. Within the field of phosphine chemistry alone where more than 1000 articles were published during 1996 according to the Chemical Abstracts Service only synthetic work on novel asymmetric phosphines and derivatives is described with particular emphasis on applications in asymmetric catalysis. 2 Nitrogen The development of the co-ordination chemistry of metals of Groups 16 and 17 with multiply bonded nitrogen or sterically demanding thiolate ligands has been reviewed and a brief outline of subsequent applications of metal complexes of these ligands in for example olefin metathesis methanol carbonylation and the general field of radiopharmaceuticals for diagnostic imaging and therapy has appeared.2 In addition aspects of the chemistry of highly stable nitride complexes of technetium in the]5 and ]7 oxidation states has also been reviewed.2 The synthetic and reaction chemistry of nitriles RCN where R is usually an organo function with transition-metal complexes developed during the period 1977 to early 19942 has been reviewed.In particular new reaction processes have been described such as insertion into metal–hydrogen and metal–carbon bonds coupling between one nitrile and an unsaturated metal fragment or between two nitrile molecules reduction to amines attack by protic and aprotic nucleophiles electrophilic attack and some catalytic transformations.3 The synthesis of tungsten (1-pyridino)imido complexes has been reported.3 These complexes have been found to be capable of inducing facile N–N bond cleavage resulting in the formation of pyridine from co-ordinated dinitrogen.4 Comparison of X-ray di§raction data recorded from five-co-ordinate molecular Royal Society of Chemistry–Annual Reports–Book A 75 bis(imido)- and imidoalkylidene-molybdenum complexes [Mo(NC 6 H 3 Pr* 2 - 2,6)(L)(L@)] where L is a tridentate pyridinediolato ligand and L@ is either [NC 6 H 3 Pr* 2 - 2,6] (1) or [CHCMe 2 Ph] has strongly supported the hypothesis that the nitrogen atom of the bent imido ligand in the bis(imido) complex is sp2 hybridised.5 The hydrazido complexes trans-[MX(NNH 2 )(dppe) 2 ]` and cis,mer- [MX 2 (NNH 2 )(PMe 2 Ph) 3 ] (M\Mo or W X\halogen) have been reported to undergo condensation with aldehydes or ketones (RR@C––O) to a§ord a series of diazoalkane complexes of the form trans[MX(NNCRR@)(dppe) 2 ]` and cis,mer- [MX 2 (NNCRR@)(PMe 2 Ph) 3 ].6 These diazoalkane complexes exhibit various classes of reactivity including nucleophilic addition deprotonation conjugate addition and reductive dimerization.For example condensation of hydrazido complexes with dialdehydes or their equivalent leads to the formation of complexes containing nitrogen heterocyclic ligands within which the terminal nitrogen atom has been incorporated by way of a cyclization process involving intermediate diazoalkane complexes.Various types of organonitrogen compounds such as acetone azine pyrazoles phthalimidines pyrroles and N-aminopyrrole have been found to be liberated from the above complexes in good yields. In this manner a synthetic cycle for the formation of pyrrole and N-aminopyrrole from dinitrogen has been established. The synthesis of a range of aliphatic tripodal tetramine ligands N(CH 2 CH 2 CH 2 NH 2 ) 3 (L1) N(CH 2 CH 2 CH 2 NH 2 ) 2 (CH 2 CH 2 NH 2 ) (L2) and N(CH 2 CH 2 CH 2 NH 2 )(CH 2 CH 2 NH 2 ) 2 (L3) has been reported.7 These potentially tetradentate N 4 ligands were found to react with Cu(OH) 2 in aqueous solution in the presence of NH 4 PF 6 to yield blue complexes of the type [Cu(N 4 )(NH 3 )][PF 6 ] 2 the molecular structures of several examples have been determined by X-ray di§raction.These complex dications were shown to possess a trigonal bipyramidal geometry in which the tertiary nitrogen of the tripodal ligand and the ammonia molecule occupy the axial positions. Complexes with the unsymmetric ligands have been prepared and shown to possess both five- and six-membered chelate rings. Two new atropisomeric bidentate nitrogen-donor chelating ligands namely ([)- (S,S)-3,3@-(1,2-dimethylethylenedioxy)-2,2@-bipyridine (L4) and (])-(R)-3,3@-(1-methylethylenedioxy)- 2,2@-bipyridine (L5) have been synthesised and characterised.8 The interaction of these new compounds with palladium(II) salts has resulted in the isolation and characterisation of palladium chelate complexes which have been found to act as very active catalyst precursors for the copolymerisation of styrene and carbon monoxide under mild reaction conditions (CO pressures of one atmosphere and 30 °C operating temperatures).Excess CO was found to have an inhibiting e§ect on reaction rate on these polymerisations. Low levels of asymmetric induction were observed together with short isotactic sequences in the copolymer chain. A number of aminoferrocenes and aminocobaltocenes have been synthesised and exploited as redox-active chelating ligands with a variety of metals. The formation of stable complexes of Zn2` and Co2` salts containing the ligand 1,1@-bis(di-2- aminomethylpyridine)-3,3@,4,4@-tetraphenylferrocene has been investigated.A singlecrystal X-ray di§raction analysis showed that the nitrogen atoms are directly bonded to the ferrocene and take part in the co-ordination of Zn2` ions.8 This nitrogen donor thus acts somewhat as a relay enhancing electronic communication between the redox-active ferrocene centre and the metal ion (Zn2` or Co2`) with the result that significant changes in the redox potential of the ferrocene unit in the corresponding 76 K.K. Hii and T.P. Kee cyclic voltammograms can be detected. On the basis of these results it was concluded that very large redox-switching e§ects can be observed by attaching donor atoms directly to the redox-active ferrocene unit.9 A number of six-co-ordinate nitrido complexes of the general form [LMV(bidentate ligand)(N)]n`Xn have been synthesised and characterised.Within this general format M\VV CrV or MnV; L\macrocycle such as [9]aneN 3 or its N-methylated derivative (L@); bidentate ligand\acac tacac pyca phen or ox; and X~\perchlorate or hexafluorophosphate. Photolysis of [LCrIII([9]aneN 3 )(ox)] in the solid state produces the k-nitrido-bridged mixed-valent species [L 2 Cr 2 (ox) 2 (k-N)][9]aneN 3 ).10 Both mononuclear and dinuclear complexes as well as several protonated and hydroxo chelates have been shown to be formed by the reaction of the hexaaza macrocyclic ligand bfbd (L6) with CuII ions.11 These cationic species have been shown to bind inorganic and organic anions through co-ordination and hydrogen bonding. Stability constants of the mono- and di-nuclear CuII complexes containing bfbd have 77 Nitrogen phosphorus arsenic antimony and bismuth been measured potentiometrically and their interaction with oxalate malonate and pyrophosphate anions investigated.Two of the new dinuclear CuII complexes have been examined by single-crystal X-ray di§raction. The e§ect of macrocyclic- and chelating-ring size on the complexation behaviour of a series of dibenzotetraaza macrocycles based on 14- to 17-membered inner rings has been investigated. A variety of nickel complexes with the general stoichiometry NiLX 2 ·xH 2 O (L\macrocyclic ligand; x\0 or 1; X\Cl NCS or NO 3 ) have been isolated and characterised. The result of five X-ray crystallographic analyses as well as studies on the molecular mechanics of these complexes have permitted a comparison of the e§ects of changing the chelate ring size on complex structure.Cyclic voltammetry suggests that the formation of the nickel(III) species is facilitated by rings of a smaller size; oxidation of the complex containing the 17-membered ring derivative is irreversible and probably ligand based.12 A corresponding series of zinc(II) and cadmium( II) complexes have also prepared and characterized. Single-crystal X-ray di§raction analysis of both new macrocycles and their respective cadmium(II) complexes have been determined. Comparison of these structures reveals that as the ring size increases the ligand binds cadmium(II) more tightly in the centre of the cavity thus aiding the formation of a six- rather than five-co-ordinate geometry in the complex of the 17-membered ring.13 Derivatives of the cofacial diporphyrin compound 1,8-bis(10,15,20-trimesityl-5- porphyrinato)anthracene (dpham) bound to ruthenium and nickel have recently been reported.14 Both Ru 2 (dpahm) and RuNi(dpahm) have been shown to be extremely reactive towards dioxygen dinitrogen and other small molecules capable of ligation to each metal centre.Moreover it has been reported that the electron-deficient RuII porphyrin complexes appear to bind aromatic solvents such as benzene and toluene. The complex Ru(tmp) and its metallodiporphyrin analogs Ru 2 (dpahm) and RuNi(dpahm) have also been shown to catalyse hydrogen-for-deuterium exchange in benzene solution. When adsorbed onto a non-polar carbon support these RuII porphyrins all show significant activity with respect to catalytic hydrogen-for-deuterium exchange. In addition these molecules slowly catalyse the exchange of hydrogen into deuteriated aromatic hydrocarbons and in the absence of solvent the exchange of 78 K.K.Hii and T.P. Kee deuterium into methane. Kinetic studies on hydrogen-for-deuterium exchange catalysed by these carbon-supported RuII porphyrins suggest that exchange is likely to be e§ected by one face of a single Ru(tmp) moiety. The quantitative synthesis of the new pendant arm macrocyclic compound thpc-14 (L7) has been accomplished through reaction of 1,4,8,11-tetraazacyclotetradecane (cyclam) with trimethylene oxide (oxetane) under high pressure conditions. The molecular and crystal structure of this compound reveals the presence of both intramolecular and intermolecular hydrogen bonding the former of which is su¶cient to preorganise the ligand into a conformation which proves to be unfavourable towards complexation.Formation constants have been determined by glass-electrode potentiometry for complexes of this ligand with a variety of metals including Co2` Ni2` Cu2` Zn2` Cd2` Hg2`and Pb2`. In all cases the [M(thpc-14)]2` complex is found to be less stable than the complex formed from the related ligand thec-14. Isolation of the octahedral complexes [Ni(thpc-14)][ClO 4 ] 2 and [Ni(thpc-14)(NCS) 2 ] and a study of their spectroscopic and magnetic properties indicates that co-ordination of the pendant hydroxyl functions occurs but that this bonding is relatively weak and is thus easily substituted by isothiocyanate.15 The synthesis and structural characterisation of several complexes based on the 14-membered macrocyclic trans-N 4 dibenzo molecule 5,6,7,8,9,14,15,16,17,18-decahydrodibenzo[ e.l][1,4,8,11]tetraazacyclotetradecine (L@) have been described.Single-crystal X-ray di§raction analysis of uncomplexed L@ and its CuII ZnII or PdII complexes have also been described and shown to possess saddle-shaped structures. The metal atoms are incorporated within the macrocyclic cavity in both [Cu(L@)(CF 3 SO 3 )]` and [Pd(L@)]2`. Zinc(II) adopts a five-co-ordinate geometry in the complex [Zn(L@)(Cl)]` in which the co-ordination polyhedron is perhaps best described as intermediate between a trigonal bipyramid and a square pyramid. In all of these complexes the metal-to-ligand distances to the nitrogen atoms in a b-position with respect to the aromatic ring are significantly shorter than those to the ‘anilinic’ nitrogen atoms.16 Among the now voluminous literature on Schi§-base ligands a manganese complex 2 containing such a ligand has been found to oxidise an imino group selectively to an amido group.17 Neutral and ionic methylpalladium compounds containing Schi§- base trinitrogen ligands [(N-N-N)Pd(Me)(Y)] (N-N-N\trinitrogen ligand; Y\Cl~ CF 3 SO 3 - or 4-MeC 6 H 4 SO 3 -) have been synthesized and characterized.18 The e§ects of solvent counter anion and structure of the trinitrogen ligands on subsequent insertion reactions with carbon monoxide and alkenes have also been investigated.Copper(II) complexes bound to the reduced forms of Schi§-base ligands based on amino acids possessing non-polar side chains with salicylaldehyde have been synthesized. 19 Ternary complexes with imidazole and py have been prepared and characterized for N-(2-hydroxybenzyl)-D,L-alanine.Such complexes have been proposed to serve as stable models for intermediates in enzymatic transformations of amino acids. A series of mono- and di-cationic palladium(II) complexes containing di§erent chiral tridentate nitrogen ligands pybox (L8) have been prepared.20 The molecular structures of two of these [Pd(CH 3 CN)(L8)][BF 4 ] 2 (R\Ph) and [Pd(PPh 3 )(L8)][BF 4 ] 2 (R\p-EtOC 6 H 4 ) have been determined by single-crystal X-ray di§raction. These complexes have been examined as catalysts for the aldol addition of CNCH 2 CO 2 Me to PhCHO. Under catalytic conditions the chiral tridentate pybox ligand is completely 79 Nitrogen phosphorus arsenic antimony and bismuth displaced thus explaining its failure as a chiral auxiliary.A series of chiral complexes of the form [Pd(L) 3 ]n`[BF 4 ]n have been prepared [L\4-methylpyridine 2,6-dimethylpyridine 4-methylaniline H 2 NCH 2 CH(OMe) 2 H 2 NCH 2 CH 2 OH H 2 N(CH 2 ) 5 CH 3 N 3 ~ HCO 2 ~ or Cl]. 3 Phosphorus Phosphides New vanadium complexes containing substituent-free (Pn n\1–4) phosphorus ligands have been synthesized upon photolysis of the half-sandwich complex [V(CO) 4 Cp*] in the presence of white phosphorus (P 4 ). A mixture of carbonylcontaining vanadium–phosphorus compounds such as [V(CO) 2 Cp*(Pn)] [Cp*(CO)V(k-g2 g2-P 2 ) 2 V(CO)Cp*] and [Cp*(CO) 2 V(k-g1 g1-P 4 )V(CO) 3 Cp*] were reported. Complete thermolytic and photolytic displacement of the carbonyl ligands (with or without P 4 ) always results in the triple-decker complex [Cp*V(k-g6 g6- P 6 )VCp*] presumably reflecting its thermodynamic stability.Carbonyl-free vanadium–phosphorus complexes were obtained upon thermolysis of [VO(CO) 4 R] [R\g5-C 5 H 5 g5-C 5 H 4 Me or g5-C 5 H 4 (CMe 3 )] and P 4 . The reactions result in the formation of both the triple-decker complex [RV(k-g6 g6-P 6 )VR] and a cluster complex [V 4 R 4 (P 3 )]. In the case of the sterically demanding indenyl ring ligand only the triple decker [(g5-ind)V(k-g6 g6-P 6 )V(g5-ind)] could be isolated.21 80 K.K. Hii and T.P. Kee Phosphoranes and phosphorus macrocycles The co-ordination and reaction chemistry of eight-membered polyphosphorus heterocycles has been reviewed with particular focus on the versatile tetraphosphorane ring system P 4 O 4 .22 Aryloxo derivatives of phosphorus(V) porphyrins of the type [(ttp)P(OR) 2 ][OH] where OR is an axial aryloxo [2,4-dimethylphenoxo 4-methylphenoxo phenoxo 4-nitrophenoxo 4-(4-nitrophenoxy)phenoxo or 4-(2,4-dinitrophenoxy)phenoxo] ligand have also been synthesized characterised and an octahedral co-ordination sphere at phosphorus proposed.The fluorescence quantum yield values of these porphyrins were found to be sensitive to the nature of both the aryloxo ligand and the solvent polarity.23 An ionic chlorophosphane of general form [L@P]`Cl~ (L9) containing the ligand L@\N,N@-bis(tert-butyl)-1,4-diaza-2-butene has been obtained and most surprisingly its analogue containing a fully saturated ligand [LPCl] [L\N,N@-bis(tert-butyl)-1,4- diaza-2-butane L10] found to be covalent. This remarkable di§erence can be attributed to the phosphenium cation possessing n stabilization reminiscent of an aromatic 6n-electron system.As expected the two chlorophosphanes di§er sharply in their volatility and solubility in organic solvents.24 The reaction of the molybdenum cation mer-[Mo(CO) 3 (bipy)]` containing a diamino- substituted phosphorus compound PN(Me)CH 2 CH 2 NMe(Y) [Y\OMe OEt SEt or N(CH 2 ) 3 CH 2 ] has been shown to proceed by a simple and reversible substitution of carbon monoxide by PN(Me)CH 2 CH 2 O(Y)25 and displacement followed by Y group migration to the co-ordinating phosphenium phosphorus atom to a§ord the complex [Mo(CO) 2 (bipy)MPN(Me)CH 2 CH 2 O(Y)N]`. The new compound 1,1-bis[N-p-tolylimino)diphenylphosphoranyl]ethane (1,1- bipe L11) has been synthesized and the molecular structures of H 3 CCH(PPh 2 ––NC 6 H 4 Me-4) 2 have been determined by X-ray crystallography.26 81 Nitrogen phosphorus arsenic antimony and bismuth Six-co-ordination of neutral phosphoranes containing potentially chelating ligands has been evidenced by their low frequency 31P NMR chemical shifts and further substantiated by single-crystal X-ray di§raction analyses.In both cases the compounds exhibit slightly distorted octahedral geometry in the solid state and fluxional behaviour in solution the latter being explored via dynamic 1HNMRspectroscopy.27 Regioselective synthesis of the first bis(transannular chiral cyclotriphosphazatriene) derivatives has been reported.28 Phosphanylphenolates have been prepared by the reactions of C,O-dilithium reagents or C,O-lithium–sodium reagents with chlorophosphanes.Subsequent treatment with SiMe 3 Cl a§ords 4-methyl- and 4,6-di-tert butyl-substituted o-phosphanylphenol silyl ethers. These compounds were subsequently used in the preparation of the corresponding o-phosphanylphenols derivatives which are asymmetric at phosphorus. 29 The versatility of o-hydroxyarylphosphanes and objectives of further studies were shown by preliminary results on complex formation and applications of these phosphanes in catalysis. Five-co-ordinate 1,2-azaphosphetidines bearing the Martin ligand have been prepared by the intramolecular dehydration of the corresponding b-amino phosphine oxides with the Mitxunobu reagent (Ph 3 P–EtO 2 CN––NCO 2 Et).30 A single-crystal X-ray analysis of the 1,2,4,4-tetraphenyl derivative shows it to possess a distorted trigonal bipyramidal structure with oxygen and nitrogen atoms occupying apical positions.Thermolyses of 1,2-azaphosphetidines gave the corresponding olefins along with a cyclic iminophosphorane which was readily hydrolysed to the cyclic phosphinate and aniline. The reactions of bis(trimethylsilyl) forms of the Schi§-base compounds N-(2-hydroxyphenyl) salicylideneamine N-(4-tert-butyl-2-hydroxyphenyl)salicylideneamine N-(2-hydroxy-4-nitrophenyl)salicylideneamineand the structurally related ligand 2,2@- azophenol with halogeno- and (trifluoromethyl)halogeno-phosphoranes have been shown to result in series of neutral six-co-ordinate phosphorus(V) compounds by means of trimethylsilyl halide elimination.31 In each case the ligands were found to chelate in a meridional conformation in which bicyclic five- and six-membered chelate rings are formed through structures containing two phenolic P–Obonds and one P–N bond.The six-co-ordinate nature of these compounds was further evidenced by their low frequency 31P NMR chemical shifts and their characteristic J(PF) coupling patterns and is further substantiated by selected single-crystal X-ray di§raction analyses. The silylated form of the related thiobis(phenol) 2,2@-thiobis(4,6-di-tert-butylphenol) reacted similarly with pentavalent halides to form six-co-ordinate complexes. 82 K.K. Hii and T.P. Kee In contrast to the above six-co-ordinate complexes this compound possesses a structure in which two phenoxy substituents form planar chelates centred on the bridging sulfur and intersecting at the P–S axis.Phosphine phosphite and phosphinite ligands The new multi-functional hemi-labile phosphorus–bis(nitrogen) compound N-[2- (diphenylphosphino)benzylidene][2-(2-pyridyl)ethyl]amine (L12) containing phosphine imine and pyridyl donor groups and its alkyl- allyl- and acyl-palladium complexes methylplatinum complexes and a zerovalent palladium complex have been synthesized and characterized.32 The compound L12 is capable of co-ordinating in either a tridentate or bidentate fashion. An unprecedented zerovalent palladium complex [Pd(L12)] has also been isolated which appears to be stable only in the presence of L12. Preliminary results show that palladium complexes of L12 are very active in allylic alkylation reactions. The syntheses of phosphorus–nitrogen (PN) ligands along with a selection of derivitised metal complexes with particular reference to applications in carbonylation reactions have been reported.33 Electronically neutral palladium and platinum compounds of the type [MX 2 (L)] [MX(Me)(L)] and [M(Me)(L)][O 3 SCF 3 ] in which X\Cl Br or I; L\2-(diphenylphosphino)benzylidene-S-([)-a-methylbenzylamine have been prepared and characterized.Within both classes of compound chelate co-ordination of the PN ligand a§ords a six-membered ring. The methyl-palladium and platinum derivatives were shown to react with carbon monoxide to a§ord the corresponding acetyl complexes. Temperature-dependent 1H 31P and 13C NMR experiments were used to delineate the influence of the chiral ligand on the structural aspects and dynamic features of these transformations. Calix[6]arene has been found to react with PCl 3 (two equivalents) to form a bidentate diphosphite L which is able to co-ordinate to palladium platinum and rhenium in a cis fashion and according to X-ray analysis with a bite angle of approximately 90° for the palladium complex [PdCl 2 L].34 Synthetic and conformational analyses of the sterically congested bis(phosphite) compound (4,6-Bu5 2 C 6 H 2 O)(PhO) 2 P (X) have been reported.35 Conformational flexibility of the molecule is severely restricted due to steric congestion.A through-space mechanism of coupling has been used to explain an observed eight-bond coupling between the two phosphorus atoms of 27.5 Hz in the 31P NMR spectrum of X and associated with the close proximity of the phosphorus atoms. These results support the proposed restriction of molecular motion by steric congestion which can be used in the rational design of a compound which favours a particular disposition of phosphorus atoms.A new ferrocene-based chiral auxiliary containing both phosphorus- and sulfur- 83 Nitrogen phosphorus arsenic antimony and bismuth donor atoms has been derived from thioglucose and used in enantioselective palladium- catalysed allylic alkylation reactions.36 A tripodal tris[4-(phenylphosphinato)-3-methyl-3-azabutyl]amine (H 3 ppma L13) based on the tren-type of ligand framework has been synthesized and its complexation properties with aluminium gallium and indium investigated.37 The structure of the bis-complex showed the ligand to co-ordinate in a tridentate manner through the three phosphinate oxygen atoms resulting in a bicapped octahedral structure of exact S 6 symmetry.The single-crystal X-ray structure of the [RRRSSS] diastereoisomer was solved where half of the molecule contained phosphorus atoms of R absolute configuration and the other half contained phosphorus atoms with the opposite absolute configuration. The aluminium complex [Al(H 3 ppma) 2 ][NO 3 ] 3 ·2H 2 O was found to exhibit an extremely rare example of aluminium–phosphorus coupling in both 31P and 27AlNMRspectra. Measurements of solution stability constants were carried out via a combination of 27Al 71Ga and 31P NMR spectroscopies. Variable-temperature 27Al and 31P NMR spectroscopic studies indicated that the [RRRSSS] diastereoisomer had a fixed solution conformation up to 55 °C in CD 3 OD. A synthetic route to unsymmetrical triphosphines has been developed.Chiral tridentate phosphines E 2 P(CH 2 ) 3 PPh(CH 2 ) 2 PPh 2 where E\C 6 H 5 p-ClC 6 H 4 or p-FC 6 H 4 have been shown to be readily accessible from simple starting materials [E 3 P I(CH 2 ) 3 I and Ph 2 P(CH 2 ) 2 PPh 2 ] involving phosphonium salts and phosphine oxides as intermediates. Their crystalline diamagnetic complexes with nickel(II) and palladium(II) have also been isolated and characterised.38 A new tripodal phosphorus compound containing a stereogenic carbon atom Ph 2 PCH 2 CH(Me)N(CH 2 CH 2 PPh 2 ) 2 (L14) has been prepared using L-alanine as an optically active starting material. A series of metal complexes of the general form [M(X)(L14)]BPh 4 (M\NiII or CoII X\NCS~ Cl~ Br~ or I~) have been prepared and characterised on the basis of electronic spectrophotometry.39 Phosphazenes and phosphaalkenes The reaction of monochloropentaphenoxycyclotriphosphazene with 3- (aminomethyl)pyridine yields 3-(aminomethyl)pyridylpentaphenoxycyclotriphosphazene a new N-donor ligand with five nitrogen atoms as potential co-ordination centres.40 The crystal structure analysis of the copper(II) nitrate complex showed co-ordination by two nitrogen atoms of the pyridine rings and four oxygen atoms of 84 K.K.Hii and T.P. Kee the unsymmetrical bidentate nitrate groups in a Jahn–Teller distorted octahedral arrangements. The phosphaalkene HP––C(F)NEt 2 has been shown to react with halogeno-phosphanes or -arsanes of the general form R 2 EX (X\Cl or I) in the presence of NEt 3 to give P-phosphino- or P-arsino-substituted fluorophosphaalkenes of the type (R 2 E)P––C(F)NEt 2 in high yields [R 2 E\(CF 3 ) 2 P Me 2 N(CF 3 )P Me 2 P (CF 3 )As or Me 2 As].41 The stability of the compounds decreased as a function of R 2 E from As to P and from CF 3 to Me respectively.These compounds have been found to favour the Z-configuration and have been characterized by spectroscopic investigations (MS IR 1H 19F 13C and 31P NMR). A single-crystal X-ray di§raction study on one of the derivatives provided support for a n-type interaction of the nitrogen lone pair with the P–– C bond presumably leading to an enhancement of the stability of the system as a whole. It has been shown that the (phosphaalkenyl)lithium carbenoid compound (Z)- mes*P––CClLi (mes*\supermesityl) may be transmetallated with MgBr 2 ZnCl 2 or HgCl 2 to furnish new (phosphavinylidene)metal carbenoids mes*P––CClMX (MX\MgBr ZnCl or HgCl) while with half an equivalent of the metal halide the bis(phosphaalkenyl)metal carbenoids (mes*P––CCl) 2 M (M\Mg Zn or Hg) are formed.42 Bromine–lithium exchange at [90 °C between (Z)-mes*P––CBrSiMe 3 and n-butyllithium furnished (E)-/(Z)-mes*P–– CLiSiMe 3 .Transmetalation of (E)-/(Z)- mes*P––CLiSiMe 3 with MgBr 2 or ZnCl 2 a§orded only the trans-metal isomer of mes*P––CMXSiMe 3 (MX\MgBr or ZnCl). The phosphaallene mes*P––C––CPh 2 was obtained by reaction with benzophenone. It has been demonstrated that 2-(diisopropylamino)phosphaethyne Pr* 2 NC–– – P reacts with certain Ni0 complexes to a§ord the novel complex [Ni(g2-Pr* 2 NCP)]. In reactions with either [Pt(C 2 H 4 )(PPh 3 ) 2 ] or [Co 2 (CO) 8 ] the products were found to be [Pt(g2-Pr* 2 NCP)(PPh 3 ) 2 ] in which the phosphalkyne is acting as a side-on bound ligand and [Co 2 (CO) 6 (k-g2-Pr* 2 NCP)] with the phosphalkyne ligand acting as a four-electron donor bridge.Reaction of the phosphalkyne with CuCl or CuI gave 1-j3,3-j5-diphosphetene (Pr* 2 N)CPC(Pr* 2 N)PO 2 .43 The novel molybdenum(VI) alkylidyne complex [Mo(CBu5)MOCMe 2 (CF 3 )NMN(R)P–– C(H)(CMe 2 PhN] (R\2,6-Pr* 2 C 6 H 3 ) has been shown to be formed in the reaction between tert-butylphosphaalkyne with the corresponding molybdenum alkylidene precursor.44 This alkylidyne which contains a formal (phosphaalkenyl)amido ligand rearranges at elevated temperature to form an alkoxide-shifted phosphamolybdacyclobutene in quantitative yield. The novel phosphametallacycle compound [MoM––C(Bu5)P(OR)C(H)(Bu5)N- (NR)(OR@) 2 ] [R\2,6-Pr* 2 C 6 H 3 R@\CMe(CF 3 ) 2 3] has been revealed as the product of the cycloaddition reaction between tert-butylphosphaacetylene and the high oxidation state molybdenum alkylidene [MoM–– C(H)(Bu5)N(NR)(OR@) 2 ] accompanied by an alkoxide metal-to-ligand shift.The resultant 1-phospha-3-molybdacyclobut-2- ene has been characterized by multinuclear NMR spectroscopy and its molecular structure determined by an X-ray crystallographic analysis.45 85 Nitrogen phosphorus arsenic antimony and bismuth 4 Arsenic The synthesis structure spectroscopic and chemical properties of arsaalkenes [R1As––CR2R3] and arsaalkynes [AsCR] have been reviewed.46 Arsaalkenes were shown to be significantly less stable and more reactive than the corresponding phosphaalkenes presumably explaining why only one kinetically stabilized example has so far been described in the literature.The controlled hydrolyses of azamacrocyclic complexes of the general form [MCl 3 L] (M\As Sb or Bi; L\Me 3 [9]aneN 3 ) has been studied.47 The synthesis and characterisation of five-co-ordinated triarylarsenic(V) complexes containing Schi§-base ligands of the general formula [AsLR 3 ] (R\C 6 H 5 p- CH 3 C 6 H 4 p-ClC 6 H 4 p-FC 6 H 4 or C 6 F 5 ; L\di-basic tri- and tetra-dentate ligands with ONO and ONNO systems) have been reported for the first time along with various triarylantimony complexes containing similar tridentate ligands.48 The reaction between sterically crowded dimeric arylalane (H 2 Almes*) 2 and some arylamines phosphines or arsines has been described.49 Treatment of (H 2 Almes*) 2 with the amines H 2 NPh and H 2 NR (R\2,6-Pr* 2 C 6 H 3 ) has been shown to a§ord monomeric bis(amino)alane products mes*Al(NHPh) 2 ·Et 2 O and mes*Al(NHR) 2 which contain three-co-ordinate aluminium and short aluminium-to-nitrogen distances.Heating a 1 1 mixture of H 2 Almes* and aniline under carefully controlled conditions a§ords the dimeric compound (mes*AlNPh) 2 whilst reaction of (mes*AlH 2 ) 2 with H 2 PPh or H 2 AsPh at ca. 160 °C a§ords the trimeric six-membered ring compounds (mes*AlPPh) 3 ·Et 2 O and (mes*AlAsPh) 3 ·Et 2 O which are formal valence analogues of borazine. 5 Antimony Aspects of the structural chemistry of inorganic and organoantimony complexes of diorganophosphorus ligands and their thio analogous have been reviewed.50 The complexes Ph 2 SbCl 2 [(OPPh 2 )(XPR 2 )N] (X\O or S R\Me or Ph) have been prepared by metathesis reactions between Ph 2 SbCl 3 and an alkali-metal salt of the corresponding imidodiphosphinic acid.All new compounds were characterised by 86 K.K. Hii and T.P. Kee IR multinuclear NMR and mass spectrometry; the molecular structures of Ph 2 SbCl 2 (OPPh 2 ) 2 N] and Ph 2 SbCl 2 [(OPPh 2 )(SPPh 2 )N] were determined by singlecrystal X-ray di§raction analyses.51 The salts SbCl 4 `Sb(OTeF 5 ) 6 ~ and SbBr 4 `Sb(OTeF 5 ) 6 ~ have been prepared by oxidation of Sb(OTeF 5 ) 3 with Cl 2 and Br 2 respectively.52 The SbBr 4 ` cation has been reported for the first time and is only the second example of a tetrahalostibonium(V) cation. Both salts are stable and have been characterized in the solid state by lowtemperature Raman spectroscopy and X-ray crystallography.Both salts are readily soluble in strongly polar solvents such as SO 2 ClF and have been characterized in solution by 121Sb 123Sb and 19F NMR spectroscopy. The SbCl 4 ` salt is stable in SO 2 ClF solution whereas the SbBr 4 ` salt decomposes slowly in SO 2 ClF at room temperature and rapidly in the presence of bromide anion and in CH 3 CN solution at low temperatures. The major products of the decompositions are SbBr 2 `Sb(OTeF 5 ) 6 ~ as an adduct with CH 3 CN in CH 3 CN solvent and Br 2 . The crystal structures of both salts are similar and reveal considerably weaker interactions between anion and cation than in previously reported SbCl 4 ` salts. The two stibocanes 1-oxa-4,6-dithia-5-stibocanediphenyldithiophosphinate O(CH 2 CH 2 S) 2 SbS 2 PPh 2 (4) and 1,3,6-trithia-2-stibocanediphenyldithiophosphinate S(CH 2 CH 2 S) 2 SbS 2 PPh 2 (5) have been prepared and reported.These new compounds have been characterized by IR mass spectrometry and multinuclear NMR spectroscopy. The relationship between transannular secondary binding interactions and conformations within diphenyldithiophosphinate stibocanes has also been investigated. 53 The reaction of antimony(III) chloride and antimony(V) chloride in acetonitrile in the presence of the azamacrocyclic ligand Me 3 [9]aneN 3 has been shown to provide the golden yellow ionic compound [SbCl 2 (Me 3 [9]aneN 3 )][SbCl 6 ] which has been characterised by single-crystal X-ray di§raction analysis.54 6 Bismuth Two related and comprehensive series of dithiabismuth heterocycles have been prepared by metathesis reactions.55 The compounds have been characterized by spectroscopic and X-ray crystallographic analysis.Monocycles 2-chloro-1,3-dithia-2-bismolane 2-chloro-1,3-dithia-2-bismane 2-chloro-1,3-dithia-2-bismepane 2-chloro- 1,3,6-trithia-2-bismocane and 2-chloro-1,3-dithia-6-oxa-2-bismocane are kinetically 87 Nitrogen phosphorus arsenic antimony and bismuth stable with respect to the tethered bicyclic derivatives 1,2-bis(1,3-dithia-2-bismolan-2- yl)thio- 1,3-bis(1,3-dithia-2-bisman-2-yl)thio-propane 1,4-bis(1,3-dithia-2-bismepan- 2-yl)thiobutane bis(1,3,6-trithia-2-bismocan-2-yl)thioethyl)sulfide and bis(1,3-dithia- 6-oxa-2-bismocan-2-yl)thioethyl ether. Monocyclic bismuth cations have been identi- fied as the principal products of thermal dissociation.Triarylbismuthanes bearing three di§erent aryl groups (R1R2R3Bi) have been synthesized by the action of aryl Grignard reagents on unsymmetrical diarylbismuth triflate–hmpa complexes R1R2Bi(OTf)(hmpa) 2 .56 The formation of the first bismuth–transition-metal bimetallic alkoxide [BiCl 3 (k- O)(k-OC 2 H 4 OCH 3 ) 2 (OC 2 H 4 OCH 3 )V] has been described.57 Within this compound the vanadium atom is in an unusual distorted octahedral co-ordination environment while the co-ordination environment of the bismuth atom is best described as octahedral capped by a long bonded interaction to an oxygen atom. There does not appear to be any evidence for a stereochemically active lone pair present on the bismuth atom. The bismuth(III) chloride ether complexes BiCl 3 ·O(CH 2 CH 2 OMe) 2 BiCl 3 ·O(CH 2 CH 2 OEt) 2 and BiCl 3 ·3thf have been prepared and characterised.The first two compounds form dimers in the solid state and exhibit distorted pentagonal bipyramidal co-ordination around the bismuth centres while the third is monomeric in the crystal lattice and shows approximate octahedral co-ordination for bismuth.58 The induction of chirality at a bismuth centre has been found to occur with exclusive stereoselectivity by using the planar chirality of substituted ferrocenes as a chiral auxiliary.59 The synthesis of [Bi 2 (biph) 3 ] and [N(PPh 3 ) 2 ][BiCl 2 (biph)] the first structurally characterized biphenylylene complexes of bismuth have been described.60 Synthetic and structural studies have been reported on a range of cationic four-coordinate diarylbis(ligand)bismuth(III) complexes.Reaction between BiBrPh 2 AgBF 4 and a two-electron donor ligand L (two equivalents) a§orded ionic complexes of the general form [BiPh 2 L 2 ][BF 4 ] (L\OPPh 3 or py).61 The syntheses and structures of a number of seven-co-ordinated tris(aryl)tropolonatobismuth(V) complexes with benzenoid and non-benzenoid arene ligands have been reported.62 References 1 K.K. Hii and T. P. Kee Annu. Rep. Progr. Chem. Sect. A 1995 92 71. 2 J.R. Dilworth Coord. Chem. Rev. 1996 154 163. 3 R.A. Michelin M. Mozzon and R. Bertani Coord. Chem. Rev. 1996 147 299. 4 Y. Ishii S. Tokunaga H. Seino and M. Hidai Inorg. Chem. 1996 35 5118. 5 V.C. Gibson E. L. Marshall C. R. Edshaw W. Clegg and M. R. J. Elsegood J. Chem. Soc. Dalton Trans.1996 4197. 6 M. Hidai and Y. Ishii Bull. Chem. Soc. Jpn. 1996 69 819. 7 A.M. Dittlerklingemann and F. E. Hahn Inorg. Chem. 1996 35 1996. 8 B. Milani E. Alessio G. Mestroni E. Zangrando L. Randaccio and G. Consiglio J. Chem. Soc. Dalton Trans. 1996 1021. 9 H. Plenio and D. Burth Organometallics 1996 15 4054. 10 A. Niemann U. Bossek G. Haselhorst K. Wieghardt and B. Nuber Inorg. Chem. 1996 35 906. 11 Q. Lu J. J. Reibenspies A. E. Martell and R. J. Motekaitis Inorg. Chem. 1996 35 2630. 12 I. M. Atkinson P. K. Baillie N. Choi L. Fabbrizzi L. F. Lindoy M. McPartlin and P. A. Tasker J. Chem. Soc. Dalton Trans. 1996 3045. 13 P. K. Baillie N. Choi L. F. Lindoy M. McPartlin H. R. Powell and P. A. Tasker J. Chem. Soc. Dalton 88 K.K. Hii and T.P. Kee Trans. 1996 3039. 14 J. P. Collman H.T. Fish P. S. Wagenknecht D. A. Tyvoll L. L. Chng T. A. Eberspacher J. I. Brauman J. W. Bacon and L. H. Pignolet Inorg. Chem. 1996 35 6746. 15 P. J. Davies M. R. Taylor K. P. Wainwright P. Harriott and P. A. Duckworth Inorg. Chim. Acta. 1996 246 1. 16 R. Feldhaus J. Koppe and R. Mattes Z. Naturforsch. Teil B 1996 51 869. 17 E. Gallo E. Solari N. Re C. Floriani A. Chiesivilla and C. Rizzoli Angew. Chem. Int. Ed. Engl. 1996 35 1981. 18 R. E. Rulke V. E. Kaasjager D. Kliphuis C. J. Elsevier P. W. N.M. van Leeuwen K. Vrieze and K. Goubitz Organometallics 1996 15 668. 19 L. L. Koh J. O. Ranford W. T. Robinson J. O. Svensson A. L. C. Tan and D.W. Wu Inorg. Chem. 1996 35 6466. 20 R. Nesper P. Pregosin K. Puntener M. Worle and A. Albinati J. Organomet. Chem. 1996 507 85. 21 M. Herberhold G.Frohmader and W. Milius J. Organomet. Chem. 1996 522 185. 22 E. H. Wong Comments Inorg. Chem. 1996 18 283. 23 T. A. Rao B. G. Maiya Inorg. Chem. 1996 35 4829. 24 M.K. Denk S. Gupta and R. Ramachandran Tetrahedron Lett. 1996 37 9025. 25 Y. Yamaguchi H. Nakazawa K. Kishishita K. Miyoshi Organometallics 1996 15 4383. 26 M.W. Avis C. J. Elsevier N. Veldman H. Kooijman and A. L. Spek Inorg. Chem. 1996 35 1518. 27 F. Carre C. Chuit R. J. P. Corriu A. Mehdi and C. Reye Inorg. Chim. Acta. 1996 250 21. 28 K. Brandt I. Porwolik A. Olejnik R. A. Shaw D. B. Davies M.B. Hursthouse and G. D. Sykara J. Am. Chem. Soc. 1996 118 4496. 29 J. Heinicke R. Kadyrov M.K. Kindermann M. Koesling and P. G. Jones Chem. Ber. 1996 129 1547. 30 T. Kawashima T. Soda K. Kato and R. Okazaki Phosphorus Sulfur Silicon Relat.Elem. 1996 110 489. 31 C. Y. Wong R. McDonald and R. G. Cavell Inorg. Chem. 1996 35 325. 32 R. E. Rulke V. E. Kaasjager P. Wehman C. J. Elsevier P. W. N.M. Van Leeuwen K. Vrieze J. Fraanje K. Goubitz and A. L. Spek Organometallics 1996 15 3022. 33 H. A. Ankersmit B. H. Loken H. Kooijman A. L. Spek K. Vrieze and G. van Koten Inorg. Chim. Acta. 1996 252 141. 34 F. J. Parlevliet A. Olivier W. G. J. Delange P. C. J. Kamer H. Kooijman A. L. Spek and P. W.N. M. Van Leeuwen Chem. Commun. 1996 583. 35 S. D. Pastor S. P. Shum A. D. Debellis L. P. Burke R. K. Rodebaugh F. H. Clarke and G. Rihs Inorg. Chem. 1996 35 949. 36 A. Albinati P. S. Pregosin and K. Wick Organometallics 1996 15 2419. 37 M.P. Lowe S. J. Rettig and C. Orvig J. Am. Chem. Soc. 1996 118 10 446. 38 G. Dyer and J.Roscoe Inorg. Chem. 1996 35 4098. 39 S. Utsuno T. Ando and M. Ishida J. Coord. Chem. 1996 38 29. 40 U. Diefenbach M. Kretschmann and O. Cavdarci Monatsh. Chem. 1996 127 989. 41 J. Grobe D. Levan J. Winnemoller B. Krebs and M. Lage Z. Naturforsch. Teil B 1996 51 778. 42 M. Van Der Sluis J. B. M. Wit and F. Bickelhaupt Organometallics 1996 15 174. 43 J. Grobe D. Levan F. Immel M. Hegemann B. Krebs and M. Lage Z. Anorg. Allg. Chem. 1996 622 24. 44 G.M. Jamison R. S. Saunders D. R. Wheeler T. M. Alam M.D. McClain D. A. Loy and J. W. Ziller Organometallics 1996 15 3244. 45 G.M. Jamison R. S. Saunders D. R. Wheeler M.D. McClain D. A. Loy and J. W. Zillier Organometallics 1996 15 16. 46 L. Weber Chem. Ber. 1996 129 367. 47 G. R. Willey L. T. Daly P. R. Meehan and M. G. B. Drew J. Chem.Soc. Dalton Trans. 1996 4045. 48 R. A. Siddiqui P. Raj A. K. Saxena Synth. React. Inorg. Met.-Org. Chem. 1996 26 1189. 49 R. J. Wehmschulte and P. P. Power J. Am. Chem. Soc. 1996 118 791. 50 C. Silvestru and I. Haiduc Coord. Chem. Rev. 1996 147 117. 51 C. Silverstru R. Rosler I. Haiduc R. A. Toscano and D. B. Sowerby J. Organomet. Chem. 1996 515 131. 52 W.J. Casteel P. Kolb N. Leblond H. P. A. Mercier and G. J. Schrobilgen Inorg. Chem. 1996 35 929. 53 M. Munozhernandez R. Ceaolivares and S. Hernandezortega Z. Anorg. Allg. Chem. 1996 622 1392. 54 G. R. Willey M. P. Spry and M. G. B. Drew Polyhedron 1996 15 4497. 55 L. Agocs N. Burford T. S. Cameron J. M. Curtis J. F. Richardson K. N. Robertson and G. B. Yhard J. Am. Chem. Soc. 1996 118 3225. 56 Y. Matano T. Miyamatsu and H. Suzuki Organometallics 1996 15 1951. 57 J. W. Pell W. C. Davis and H. C. Zurloye Inorg. Chem. 1996 35 5754. 58 J. R. Eveland and K. H. Whitmire Inorg. Chim. Acta. 1996 249 41. 59 T. Murafuki T. Mutoh and Y. Sugihara Chem. Commun. 1996 1693. 60 C. J. Carmalt A. H. Cowley A. Decken Y. G. Lawson and N. C. Norman Organometallics 1996 15 887. 61 C. J. Carmalt L. J. Farrugia and N. C. Norman J. Chem. Soc. Dalton Trans. 1996 443. 62 U. Dittes B. K. Keppler and B. Nuber Angew. Chem. Int. Ed. Engl. 1996 35 67. 89 Nitrogen phosphorus arsenic antimony and bismuth

ISSN:0260-1818    

DOI:10.1039/ic093075

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

7 Oxygen sulfur selenium and tellurium By P. F. KELLY Department of Chemistry Loughborough University Loughborough LE11 3TU UK 1 Introduction This review highlights new developments in the chemistry of the Group 16 elements (the chalcogens) reported during 1996. I have tried as last year to emphasise results that demonstrate novelty of product or synthetic approach as their main feature. In addition I have again tried to limit the products reported to those in possession of a discrete molecular structure thus highlighting the extraordinary ability of these elements (sulfur selenium and tellurium in particular) to contribute to novel cluster arrangements. 2 Sulfur selenium and tellurium One of the most important aspects of the chemistry of the heavier chalcogens is their ability to exist in a variety of allotropic forms.While tellurium has traditionally been seen as the ‘poor relation’ in this sense the past few years have witnessed the appearance of a bewildering array of tellurium-based structures. An example of such a system is the Te 6 ring which is found in [Re 6 Te 16 Cl 6 ] a black crystalline material formed in the high temperature reaction of ReCl 5 with elemental tellurium (ratio 1 3).1 Its full structure consists of [Re 6 Te 8 ]2` clusters joined together by the Te 6 rings and two [TeCl 3 ]~ ligands. As expected the former exhibit a chair conformation. This reaction system has proven very fruitful as it also generates dark red needles of [Re 6 Te 16 Cl 18 ] in which the same rhenium cluster is present together with [Re 8 Cl 18 ]2~ ligands. The amazing ability of tellurium to exhibit new bonding arrangements is also very well demonstrated by the presence of the [Te 7 ]2` cation 1 in M[Te 7 ][AsF 6 ] 2N= which results from the treatment of [Te 4 ]2` with [Fe(CO) 5 ] in SO 2 .2 Unlike the analogous cation in other systems X-ray crystallography reveals it to consist of Te 6 rings (again in the chair configuration) linked by Te bridges in the 1,4 positions.This technique also proved invaluable in determining the products of the reaction of caesium carbonate with As 2 Te 3 in superheated methanol a reaction which appears to be very temperature dependent.3 Thus at 160 °C [Cs 2 Te 13 ] forms in which an isolated [Te 13 ]2~ chain (the longest so far characterised) is stabilised by co-ordination to the caesium atoms while at 180 °C [Cs 4 Te 28 ] is isolated.The latter exhibits three di§erent tellurium environments Te 8 crowns Te 4 squares and [Te 6 ]2~ chains. Cations of the type Royal Society of Chemistry–Annual Reports–Book A 91 [Te 6 ]2` are present in [Te 6 ][NbCl 4 O] which forms during the high temperature reaction of the element with TeCl 4 and [NbCl 4 O]; structurally they are identical to those previously reported in the tungsten analogue.4 The prediliction of the chalcogens for catenation is well demonstrated by two new sulfur systems which were reported in 1996. In the first it was shown that careful chlorination of S 6 leads to S 4 Cl 2 which in turns reacts with [Hg(SCN) 2 ] to give S 6 (CN) 2 .5 The presence of the S 6 chain was confirmed by crystallography though the compound itself rapidly polymerises at room temperature.An even longer sulfur chain is present in [MIr(k-SPr*)Cp*N2 (k-S 9 )] 2.6 It forms when a five-fold excess of sulfur is treated with [MIr(k-SPr*)Cp*N2 ] at ambient temperatures in toluene and constitutes the first example of a bridging nonasulfido chain. The latter degrades to a k-S 2 ligand upon reduction of the system with hydroborate. While there have been continuous developments in the chemistry of sulfur ring systems over the past few decades little progress has been made in the preparation of variable sized sulfur imides (i.e. SxNH). This has now been addressed by Steudel et al.,7 who have shown that [Ti(S 7 NH)Cp 2 ] reacts with SxCl 2 to give S 7`xNH(x\1 or 2)or with S 6 (CN) 2 to give S 11 NH. Structurally while S 8 NH 3 has been shown to be analogous to S 9 (as would be expected) S 9 NH has a conformation more akin to a combination of S 8 and an inserted SN(H) unit rather than the expected S 10 arrangement.Vibrational spectroscopy suggests that S 11 NH is also cyclic. As a general class of compound the main group chalcogenides continue to dazzle with the sheer range and variety of structural types they can display (and are reviewed here in ascending group order). Isolated planar [BS 3 ]3~ ions are present in the lithium salt which forms when Li 2 S 92 P.F. Kelly reacts with boron and sulfur (ratio 3 2 3) at elevated temperatures.8 Six-membered Ga 3 S 3 rings are present in compounds of the type [MGa(R)(py)SN3 ] (R\Et or Me) which form when the original products of the reaction of GaR 3 with elemental sulfur are treated with pyridine.9 One chalcogen atom ends up bridging two Group 13 elements in the products of the reaction of [MM[(Me 3 Si) 2 CH] 2N2 ] (M\Al or Ga) with triethylphosphine sulfide or selenide.10 The latter compounds are finding increasing use as sources of the chalcogenide (E) units and in this case they generate monomeric species of the type [MM[(Me 3 Si) 2 CH] 2N2 (k-E)].Phosphine tellurides can also perform this role; thus tributylphosphinetelluride reacts with tributylstannane to produce [(Bu 3 Sn) 2 Te].11 In this case the reaction is mediated by [TiHCp* 2 ] to the extent that a rate of some 10 turnovers per hour results at ambient temperature in the presence of 2–10 mol%of Ti. An astonishing range of Zintl-type anions have been prepared over the years and new techniques are still being developed for their preparation.One of the most interesting to have emerged over the past few years involves the use of main-group alloys as cathodes in electrochemical cells. For example it has been shown that passing current through cathodes of composition Ge 2 Se 3 and Sn 2 Se 3 (prepared by fusing the elements) in [Et 4 N]Br/ethylenediamine solutions results in a di§erent anion in each case. In the germanium case yellow crystals form by ether di§usion and have been shown to contain the [Ge 2 Se 6 ]4~ anion 4 which exhibits a four membered Ge 2 Se 2 ring.12 Electrolysis of the selenium compound produces yellow crystals directly; in this case the adamantane-like [Sn 4 Se 10 ]4~ anion 5 is present. Unusual tin-containing species are reported to form when the element reacts with P 2 Se 5 M 2 Se (M\K or Rb) and selenium.Two di§erent species result depending upon the ratios and temperatures employed black plates ofM 5 [Sn(PSe 5 ) 3 ] or orange rods of M 6 [Sn 2 Se 4 (PSe 5 ) 2 ]. In the former tin is octahedral to three bidentate PSe 5 units while the latter exhibits an extended structure 6.13 Chalcogen–nitrogen chemistry has a long history and continues to provide new reactions and structural types. The simplest sulfur–nitrogen unit [NS]` has been shown to react with caesium azide to give square S 2 N 2 which in turn polymerised to 93 Oxygen sulfur selenium and tellurium (SN)x.14 Of the likely intermediates in this reaction (neither of which was visible by 14N NMR spectroscopy) calculations suggest N 3 –N––S to be the most stable. The NS unit is also present in [Os(NS)(H 2 O)(S 4 )]~ the red/brown product of the reaction of [OsCl 4 N] with excess Na 2 S 4 .15 A longer N–S chain is present in the diimine [Fc 2 (k- N 2 S)] which forms when FcNH 2 is treated with SCl 2 in the presence of a base.16 When SOCl 2 is used [Fc(NSO)] results and this then reacts with Li[N(SiMe 3 ) 2 ] to give [Fc(NSNSiMe 3 )].The trimethylsilyl group is also present in the long chain system (Me 3 SiNSN) 2 S which has been shown to react with a range of simple platinum and palladium complexes to generate species such as [PdBr 2 (N 3 S 2 )]~ (which contains a six-membered sulfur–nitrogen metallocycle).17 A three-membered S–N–S chain is present in [(Me 3 PN) 3 SNS(NPMe 3 ) 2 ]Cl 2 the red crystalline product of the reaction of [NSCl] 3 with Me 3 SiNPMe 3 in acetonitrile,18 while three sulfurs bind to the central nitrogen in [(C 6 F 5 S) 3 N].19 The resulting NS 3 unit is planar and perpendicular to the C 6 F 5 rings.A detailed investigation into the kinetics and mechanism of the cycloaddition reactions of the [SNS]` cation with alkenes has been undertaken.20 When performed using unstrained alkenes with [SNS][AsF 6 ] in liquid SO 2 either the 1- or 2-cycloadducts form depending upon the ratio of reagents. A similar reaction with SF 5 (CN) generates F 5 SCNSNS (which contains the 1,3,2,4-dithiadiazolyl unit and which may be reduced to a radical species by triphenylantimony),21 while Hg(CN) 2 gives [Hg(CNSNS) 2 ]2` the first example of a metalladithiadiazolylium salt.22 The isomerisation of RCNSNS· radicals has been studied leading to the conclusion that dimer formation followed by photochemical symmetry-allowed rearrangement results in the formation of RCNSSN·.23 The latter class of compound has been the subject of much interest from the point of view of the novel solid-state properties they can exhibit.Thus p-NCC 6 F 4 (CNSSN) has been shown to be the first main-group radical to exhibit spontaneous magnetisation above liquid helium temperature (36 K),24 while the (CNSSN) 2 ·· diradical (formed when the product of N,N@-diaminooxamidine and excess SCl 2 is reduced with [SbPh 3 ]) forms a metallically conducting charge-transfer salt with iodine.25 Finally the properties of salts of the related species (CNSSS) 2 2`·· have been reported.26 EPR results suggest that in such systems each of the two unpaired electrons is e§ectively confined to isolated n systems which are separated by a C–C single bond.Thus the cations are alongside O 2 the only main-group non sterically-hindered diradicals to retain their paramagnetism in the solid state. Work on selenium–nitrogen systems continues apace. The observation that Se 4 N 4 reacts with AlBr 3 to give [(AlBr 3 ) 2 (Se 2 N 2 )] the first example of a main-group metal adduct of diselenium dinitride serves to strengthen the idea that polymeric (SeN)x may yet be a viable proposition.27 Four-membered rings are also present in [(Bu5N) 2 (Et)Se(BEt 2 )] (formed from the parent selenium diimide and triethylboron)28 and in the selenium–nitrogen halides [Se 2 NBr 3 ] and [Se 2 NCl 5 ].29 The last form when the relevant selenium tetrahalide is treated with N(SiMe 3 ) and both contain cyclic Se 2 NX units with Se–N bond lengths intermediate between single and double.The diimide used in the aforementioned boron reaction [(Bu5N) 2 Se] is a versatile and important reagent; it also reacts with Li[NHBu5] to give colourless crystals of [Li 2 Se(NBu5) 3 ] 2 which contains the first example of the triimidoselenite ion [Se- (NR) 3 ]2~.30 Finally an eight-membered ring cation [Me 2 SN 2 SeMe] 2 2` is formed when Me 2 S(NCl) 2 reacts with two equivalents of Me 2 Se 2 .31 X-Ray crystallography 94 P.F. Kelly reveals it to have the sulfur and nitrogen atoms in a plane above and below which are the selenium atoms in the 1,5 positions. Finally in the area of chalcogen–nitrogen compounds tellurium-containing species continue to exhibit an unexpectedly rich chemistry with the reaction of TeCl 4 with Li[NHBu5] being particularly fruitful.A four-membered ring is present in the product [(Bu5NTe) 2 (k-NBu5) 2 ] which also shows the terminal Te–– NBu5 groups to be cis to each other.32 The reaction also generates [Te 2 (NBu5) 4MLiTe(NBu5) 2 (NHBu5)NLiCl] 2 as a minor product and a general resume� /mechanism for this complex reaction system has been put forward.33 The aforementioned main product has been shown to react with K[OBu5] to give [MKTe(NBu5) 2 (OBu5)N2 ] M(which has dimeric structure brought about by the symmetrical chelation of [Te(NBu5) 2 (OBu5)]~ anions to the potassium cations)N and with Li[NHBu5] to give a cage species based on the pyramidal [Te(NBu5) 3 ]2~ anion. The latter species reacts with HCl to give [MLiTe(NBu5) 2 (NHBu5)N2 ·LiCl] 2 whose fluxional structure consists of a dimer made up of two [Te(NBu5) 2 (NHBu5)]~ anions their associated Li` cations and a ‘trapped’ LiCl molecule.34 Tellurium tetrachloride is also the starting material for three other interesting systems reported last year.Reaction with Li[NMe 2 ] generates [MTe(NMe 2 ) 2N= ] (a volatile monomer in solution; in the solid state intermolecular Te–N bonds of average length 2.96Å bridge the monomers),35 while with N(SiMe 3 ) 3 in hot toluene TeCl 4 generates crystalline [Te 11 N 6 Cl 26 ]·9C 7 H 8 .36 The key features of the structure are planar Te 5 N 3 units in which two Te 2 N 2 rings are fused together; the Te 11 -based units are then dimerised by long Te–Cl bonds. Finally the tetrachloride has been shown to react with C 6 F 4 (NH 2 ) 2 to give the unusually volatile and soluble telluradiazole C 6 F 4 (N 2 Te).37 A range of phosphorous-based systems were investigated during 1996 including the diiodo species P 4 S 3 I 2 and its reactivity towards alcohols and thiols [to give P 4 S 3 (OR) 2 and P 4 S 3 (SR) 2 respectively]38 and towards primary amines [resulting in P 4 S 3 (NHR) 2 and P 4 S 3 (k-NR)].39 The direct reaction of sulfur with red phosphorus and either calcium or strontium (ratio 3 1 1) at 900 °C for 20 days leads to colourless salts of the [P 2 S 6 ]4~ anion,40 while controlled hydrolysis of P 2 S 5 in absolute ethanol may be initiated by the addition of cadmium nitrate solution and leads to the formation of nano-sized CdS particles.41 The first example of a k3 -(P––S) complex [Fe 3 (CO) 3 (k- CO)Cp 3 (k3 -g2-PS)] results from the photolysis of the initial product formed when [MFe 3 (CO) 4 (k-CO)Cp 3 PN2 ] is oxidised with elemental sulfur.42 The chalcogenides of the heavier Group 15 elements continue to demonstrate an amazing capacity to exhibit unusual structures.For example treatment of Sb 2 Se 3 with potassium and cryptand 222 in acetonitrile leads to orange crystals containing the [Sb 2 Se 4 ]2~ anion 7. A salt of the analogous [As 2 S 4 ]2~ anion forms when As 4 S 4 is used; red needles of K 2 [As 10 S 3 ] 8 can also be isolated in this case. If As 4 Se 4 is used instead red/orange blocks of K 2 [As 4 Se 6 ] 9 form.43 Other techniques can also be used to generate new anions. For example isolated [SbSe 4 ]3~ anions 10 are present in [Ge(en) 3 ][Hen][SbSe 4 ] the product of the extraction of GeSbSe 4 with ethylenediamine under sonication.44 The [As 2 Se 4 Cl 12 ]2~ anion 11 results when As 2 Se 3 is treated with [PPh 4 ]Cl and thionyl chloride,45 while a new tellurium-based anion [SbTe 4 ]3~ 12 is produced when current is passed through a NiSb 2 Te 6 cathode in the presence of a solution of [NBu 4 ]I in ethylenediamine.46 95 Oxygen sulfur selenium and tellurium Metal complexes of As–S ligands reported last year include osmium and ruthenium complexes of the macrocyclic hexadentate [As 8 Et 6 S 10 ]2~ and [As 6 Et 4 S 10 ]2~ ligands47 together with iron and cobalt complexes of a range of As–S fragments that form when simple arsenic sulfides react with species such as [Co 2 (CO) 2 Cpj 2 ]48 or [Fe 2 (CO) 4 Cpj 2 ].49 Mixed-chalcogen species studied in 1996 include [Se(SCN) 2 ] (shown to be S–Se bonded in the solid state but demonstrating the N-bound linkage isomer in solution) 50 the [Se 3 O 10 ]2~ anion (which forms when SeO 2 is dissolved in nitromethane and allowed to react for a number of days),51 [Se(S 2 O 3 ) 2 ]2~ (which results from the reduction of selenous acid by aqueous thiosulfate and which demonstrates pH-dependent linkage-isomerism)52 and cations of the type [E 3 X 3 ]` (E\S or Se; X\Cl or Br).53 The latter form when [EX 3 ]` reacts with further chalcogen; thus treatment of [SeCl 3 ][AsF 6 ] with a two-fold excess of selenium in SO 2 yields red crystals of [Se 3 Cl 3 ][AsF 6 ].In the latter case 77Se NMR spectroscopy reveals that a chain structure with two halogens on one of the terminal selenium atoms exists at [70 °C; upon heating an exchange process flips the ‘extra’ halogen between the two.The presence of the [Se 2 ]~ anion has been reported in Nd-exchange Y zeolite,54 while the first examples of salts of the rcaptosulfonium cation [HSSH 2 ]` have been shown to form when H 2 S 2 is treated with the superacids HF–AsF 5 or HF–SbF 5 .55 The salts thus formed are colourless and stable below [45 °C; their insolubility has limited characterisation to IR and Raman spectroscopy. Finally substantially longer sulfur units are present in species of the type C 6 H 10 S 4 Sn where n\1–8.56 Such products in which one carbon of a cyclohexane ring is incorporated into a sulfur ring form when [Ti(S 4 C 6 H 10 )Cp 2 ] is treated with SnCl 2 . X-Ray crystallography reveals C 6 H 10 S 11 to have a CS 11 conformation identical to that of S 12 .The crystal structures of a range of salts of selenium chlorides such as [SeCl 4 ]2~ [SeCl 5 ]~ and [SeCl 3 ]` have been reported;57 improved routes to salts of the last and its sulfur analogue have also been developed.58 The first example of a square pyramidal [TeBr 5 ]~ anion has been reported in the product isolated from a saturated solution of TeBr 4 in wet 1,4-dioxane.59 Formulated as [H 3 O][TeBr 5 ]·3C 4 H 8 O 2 the 96 P.F. Kelly co-ordination sphere of the tellurium is completed via interaction with a dioxane molecule. A far more complicated tellurium halide species is present as the cationic component of the products generated when the element reacts with WBr 5 or WOBr 5 .60 Formulated as [Te 15 Br 4 ]n 2` it forms as a 1D strand composed of a band of interlinked Te 6 rings bound to a row of bromides somewhat akin to that of Te 2 Br.Tellurium halide ligands are present in [MFe 2 (k-Cl)(k-TeCl) 2 (CO) 6N2 (g2,k2 ,k2 - Te 2 Cl 10 )] which forms when [Fe 3 Te 2 (CO) 9 ] reacts with SOCl 2 in CH 2 Cl 2 . In solution this converts into [Fe 2 (g2,k2 ,k2 -Te 4 )(k-TeCl 2 )(CO) 6 ] which exhibits two tellurium- based bridging ligands TeCl 2 and [Te 4 ]2~.61 Transitional-metal complexes of chalcogenide ligands continue to provoke interest. Crystallography has revealed that the Pt 2 Se 2 core of [MPtSe(PPh 3 ) 2N2 ] is planar and comparable to the Te analogue rather than the bent sulfur species.62 The latter has been the subject of investigations into its reactivity towards BiCl 3 63 and CoCl 2 64 while the related species [Pd 2 (dppf) 2 (k-S) 2 ] has been shown to undergo nucleophilic addition with AgCl.65 Bidentate ligands of the type [Ex]2~ are well known.Examples of the smallest (x\2) form when [TiHCp* 2 ] reacts with two equivalents of selenium or tellurium.66 The products are of the type [Ti(g2-E 2 )Cp* 2 ] though either the g2-E 3 analogues or [(TiCp* 2 ) 2 (k-E)] (with Ti–E–Ti bonds) form if more or less chalcogen is employed. The latter bridged species may be formed from the monomeric complexes by removal of either selenium (with phosphine) or tellurium (with mercury). Larger ligands (x\4 or 6) are present in the iridium species [Ir(Se 4 ) 3 ]3~ and [Ir(S 6 ) 3 ]3~,67 while a lesscommon ligand arrangement is that seen in [La(NH 3 ) 9 ][Cu(S 4 ) 2 ] an orange material prepared by the reaction of the elements (La:Cu S ratio 1 1 8) in hot ammonia.68 In this case the copper is trigonal planar as one of the S 4 2~ ligands is monodentate.A similar arrangement occurs for the unprecedented g1-bonded [Te 3 ]2~ ligand in [Cr(CO) 5 Te 3 ]2~ formed when chromium hexacarbonyl reacts with one equivalent of K 2 [Te 4 ].69 When an excess of chromium is used the [MCr(CO) 5N2 Te 2 ]2~ anion which exhibits a ditelluro bridge results. A tri-seleno bridge is seen in [MW(CO) 3 CpN2 Se 3 ] the product of silica oxidation of the initial material formed when Li[W(CO) 3 Cp] is treated with three equivalents of selenium,70 while six-membered selenium rings link the PdX 2 units in [PdX 2 (Se 6 )] (X\Cl or Br).71 Only one selenium atom bridges the two magnesium atoms in [MMg(Tp1-50-)N2 Se]; the Mg–Se–Mg segment is linear and contains the shortest known Mg–Se bonds (2.406Å).72 On the subject of bridging units an unprecedented example of a bidentate S andObridging dmso ligand is found in [Ru 2 (k-Cl)(k-H)(k-dmso)Cl 2 (dmso) 4 ].73 Other chalcogen–oxygen ligands that have been the subject of recent study include [SeOCl]~ in [IrCl 2 (SeOCl)(CO)(PPh 3 ) 2 ],74 [SO 4 ]2~ in [Ir 2 H 4 (k-g2-SO 4 )(P(p-tolyl) 3 ) 6 ]75 and [S 3 O]2~.76 The last occurs in [Pt(PPh 3 ) 2 (S 3 O)] as a bidentate ligand bound to the platinum by sulfur atoms; this complex acts as a catalytically active intermediate in the transformation of H 2 S to S.Lack of space precludes a comprehensive survey of transition-metal chalcogenide cluster compounds. Some highlights from last year’s work include (in ascending order of nuclearity) [Ni 3 (k3 -Te) 2 (k-dppm) 3 ] (which is highly redox-active transferring electrons through three reversible redox states),77 [V 4 S 20 O 4 ]6~ (in which an unusual [S 4 ]2~ bridge holds the two component subunits together),78 [Ni 5 S(SBu5) 5 ]~ (which is capped by a k5 -S ion)79 and [MFe 2 (CO) 6 (k3 -Te)N2 MO(CO) 2 ] (in which the Mo atom 97 Oxygen sulfur selenium and tellurium sits at the apical site of two distorted square-pyramidal cores each containing Fe 2 TeSe rings).80 The hexanuclear species [Re 6 Te 6 Cl 6 (TeCl 2 ) 2 ] and [Re 6 Te 8 (TeBr 2 ) 6 ]2` form when ReCl 5 or Re 3 Br 9 is heated with tellurium.81 In the first the Re 6 octahedron is held together by k3 -Te ions and neutral TeCl 2 groups while the second consists of a Re 6 core within a cube of k3 -Te ions; again neutral TeBr 2 ligands are also present.Larger systems include [Pt 4 Ag 3 (dppy) 8 (k3 -S) 4 ]3` (an unprecedented example of a Pt 4 Ag 3 cluster),82 octanuclear[W 4 Ag 4 S 16 ]4~ 83 and [Cu 4 Mn 4 (SPr*) 12 S]2~ (the latter exhibiting a lone k4 -S atom at the centre of a Cu 4 Mn 4 cube).84 Supported [Rh 10 Se(CO) 22 ]2~ has been studied for its ability to convert CO 2 into ethanol85 while the massive selenium-based clusters [Hg 32 Se 14 (SePh) 36 ] and [Cd 32 Se 14 (SePh) 36 (PPh 3 ) 4 ] result when PhSeSiMe 3 reacts with either [Fe(CO) 4 (HgCl) 2 ] or [CdCl 2 (PPh 3 ) 2 ] respectively.86 Finally it is worth noting that an exhaustive survey of the reaction of gaseous sulfur with all the transition metals (bar Tc) has been completed and trends discussed.87 3 Oxygen Systems that hinge around catalytic oxidations continue to be of immense theoretical and practical interest.The oxidation of methane for example has been studied with respect to the catalytic activity of perovskite-type complex oxides of lanthanum (and manganese cobalt or nickel partially substituted with iron88 or silver89) and barium carbonate-supported vanadium oxides.90 The former species catalyses complete combustion while the latter catalyses an oxidative coupling to ethylene and ethane. In this case the activity is found to decrease with increasing V/Ba atomic ratio. The oxidative dehydrogenation of ethane to ethylene is e§ective at 580–620 °C over a lithium-doped La/CaO catalyst91 while complete oxidation of a range of hydrocarbons by O 2 has been shown to be catalysed by zirconia-based fluorite type oxides that are stabilised by 3d transition metals.92 Thus n-butane is taken to CO 2 and H 2 O at 100% conversion (reaction rate 26.9 kmol g~1s~1 523 K) by [Zr 0.2 Mn 0.1 O 2 ] fluorite.Irradiation (at 365 nm) of porphyrins bearing an OH axial ligand results in FeIII to FeII reduction and the production ofOH· radicals.93 In the presence of molecular oxygen this induces the oxidation of cyclohexane to cyclohexanone (and cyclohexanol when CH 2 Cl 2 is present in the solvent mix). In the presence of 1,4-dioxane as co-reductant MgO-supported polytitazane complexed with stannic chloride acts as a catalyst for the epoxidation of cycloalkenes with O 2 .94 In this way a 94.6% conversion of norbornene occurs (with 100% epoxide selectivity) under 1 atm oxygen at 80 °C for 20 hours.The new heteropolyperoxometalate [MWO(O 2 ) 2N2 (Ph 2 PO 2 )]~ has been shown to catalyse the epoxidation of a number of alkenes (both linear and cyclic) as well as the production of aldehydes and ketones from primary and secondary alcohols.95 Oxidation of nitrogen-containing species has also been the subject of close attention. For example molecular oxygen has been shown to oxidise acetonitrile to oxalic acid in the presence of metal-oxide doped magnesia catalysts.96 In terms of oxalic acid yield the best results are obtained using 10% ZnO in MgO at 500 °C. A mechanically mixed Mn 2 O 3 /Sn-2SM-5 catalyst is e§ective for the transformation of an NO propene and O 2 mixture into nitrogen carbon oxides and water.97 The rate of the reaction is 98 P.F.Kelly however greatly enhanced by the presence of water vapour with results suggesting that this e§ect comes directly from the involvement of water in the reaction rather than any e§ect of water upon the catalyst. Finally it has been shown that the complete reduction of NO to N 2 in the presence of oxygen is a§ected by a metal oxide (CuO on alumina) catalyst that has been pre-treated with liquid hydrocarbons.98 The work in question noted that diesel may be used as the hydrocarbon as can a system that has leaded petrol present raising the possibility that the system could be used in such a set-up to clean exhaust gases. The subject of singlet oxygen (1O 2 ) continues to provoke interest. An example of an inorganic reaction system based around this species came last year with the realisation that photolysis of a platinum diimine species in air results in a dehydrogenation reaction taking place.99 In this case the initially formed excited state of the diimine ligand transfers energy to generate 1O 2 which in turn attacks the resulting diimine ground state via production of H 2 O 2 .In another study 1O 2 was shown to react with [M(CO)(MeCN)(PPh 3 ) 2 ]` (M\Ir or Rh) to give the peroxo species [M(CO)(MeCN)(O 2 )(PPh 3 ) 2 ]`.100 The iridium complex is the more stable of the two; unfortunately neither show any olefin oxidation properties. A study of the higher energy singlet state (singlet sigma oxygen) has concluded that contrary to previous suggestions it does not have a role as an intermediate in photo-oxygenations.101 It now appears that chemical reactions do not compete e§ectively with the physical deactivation channels that convert it into ‘normal’ 1O 2 .Electroreduction of O 2 to H 2 O is catalysed by a cobalt nitrogen-donor macrocycle complex but only when the latter is adsorbed upon the surface of a graphite electrode. 102 The e§ect is not seen when the complex is in solution. The e§ect of surface exposure of caesium metal to O 2 has been investigated by XPS revealing that the oxygen species present varies as a function of exposure time.103 Hence theOd~ state is seen first followed by the oxide and finally the peroxo O 2d~. The first of these species reacts with CO to give the anionic form of adsorbed carbon dioxide CO 2d~. Nitrogen–oxygen species received their customary level of attention during 1996.Studies included investigations into the nitrosation of hydrogen peroxide by NO (which takes place only in the presence of O 2 and progresses through the ratedetermining formation of ONOONO),104 the oxidation of main-group species with peroxynitrite (which proceeds rapidly with AsIII SbIII and SnII but only slowly with phosphorus species),105 the autocatalytic oxidation of thiocyanate with nitrous acid (which forms red ONSCN)106 and the reaction of silver cyanate with either NO 2 or ClNO 2 (both of which progress through the short-lived OCN·NO 2 intermediate).107 The cis hyponitrite anion [N 2 O 2 ]2~ has been shown to form when N 2 O reacts with Na 2 O at elevated temperatures,108 while the first complex of the dinitramide ion [N 3 O 4 ]~ results when K[N 3 O 4 ] is treated with fac-[Re(CO) 3 (bipy)(OSO 2 CF 3 )].109 The yellow product [Re(CO) 3 (bipy)(N 3 O 4 )] contains the new ligand bound by the central nitrogen in monodentate fashion.Vibrational spectra of a range of salts of the aforementioned anion have also been reported with the conclusion that the very small N–NO 2 rotation barrier allows the anion to be easily deformed from ideal C 2 symmetry in solution.110 Other main-group/oxygen systems studied included the reaction of SeO 2 with Et 3 B to give colourless [Et 2 BOSe(Et)O] 2 (which exhibits an eight-membered B 2 Se 2 O 4 ring),111 the oxidation of CoII with peroxomonosulfate [HSO 5 ]~ (which in the 99 Oxygen sulfur selenium and tellurium presence of molybdate generates [Co 2 Mo 10 H 4 O 38 ]6~),112 the chain reaction of bisul- fite with O 2 (which is catalysed by MnII)113 and the first route to pure P 4 O 6 Se 3 .114 In the last case X-ray crystallography shows that all three selenium atoms are outside the P 4 O 6 cage; XANES has been used to investigate the related system P 4 O 6 Sn (n\1–4).115 The reactions of P 4 O 6 with a range of organic azides has been shown to result in species of the type P 4 O 6 NR(where R\Ph etc.) in which the nitrogen atom is bridging and one oxygen atom is present as a terminal P––O.116 A central As–O–As bond angle of 129° is observed in [Cl 3 AsO·AsF 5 ] Mformed when (Me 3 Si) 2 Oreacts with [AsCl 4 ][AsF 6 ]N,117 while three short and one long Cl–O bonds are found in the structure of ClO 4 .118 The latter the last hitherto unknown but expected mononuclear chlorine oxide may be prepared by vacuum thermolysis of Cl 2 O 6 and isolated in a neon matrix.Structural studies have now been performed upon two bromine oxides Br 2 O and BrO 2 .119 Both have C 2v symmetry with Br–O lengths of 1.84 and 1.65Å respectively. Finally an argon matrix study suggested that a weakly bound S 2 O 2 complex can be formed from the elements.120 The photolytically sensitive product is in e§ect intermediate between stable S 4 and very unstable O 4 . Although space restrictions clearly preclude detailed descriptions of all studies of transition-metal oxygen complexes undertaken in 1996 the following are noteworthy (and are listed in increasing nuclearity). A new technetium oxide fluoride [TcF 5 O] formed when KrF 2 reacts with [TcF 3 O 2 ] in HF; NMRstudies (19F and 99Tc) confirm an octahedral structure with terminal Tc–– O bond.121 The irreversible reaction of [RuCp*Cl(dippe)] with O 2 in air gives the mononuclear peroxo species [RuCp*(O 2 )(dippe)]` (O–O\1.37Å),122 while the first example of a crystal structure of a non-haem diiron–O 2 adduct has now been reported.123 One oxygen atom bridges two metal centres in [MRu(dmhd) 2 NN2 (k-O)]4`,124 in [(salen)VIVOVV(salen)O]` Mwhich forms during electroreduction of [(salen)VIVOVIV(salen)]2` in the presence of oxygenN125 and in gaseous Re 2 O 7 (as revealed by vibrational spectroscopy).126 Five such oxygen atoms are present in [(Ti 4 Me 2 Cp* 4 )(k-O) 5 ]127 while a Au 4 Rh 2 O 2 core with each oxygen bridging two gold and two rhodium atoms is found in [Rh(nbd)Mk- O(AuPPh 3 ) 2N] 2 2`.128 In [Mn 8 O 4 (O 2 CPh) 12 (Etmal) 2 (H 2 O) 2 ]2~ the two [Mn 4 O 2 ] units are linked by one k3 -O atom in each linking to a manganese in the other,129 while [Mn 13 O 9 (OEt) 6 (O 2 CPh) 12 ] has a core with both k3 and k5 oxygen atoms and is the largest cluster in which there are three oxidation states of a given metal in one molecule.130 Finally it has been observed that oxygen reacts slowly with [(C 8 H 17 ) 4 N] Br-stabilised cobalt clusters for form cobalt(II) oxide.131 The interesting thing about this reaction is the latter species being kept as nanostructured clusters solublised by the presence of the cation/anion; studies of their properties on solid alumina supports suggest they have the potential to behave as shell catalysts.References 1 Y.V. 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ISSN:0260-1818    

DOI:10.1039/ic093091

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

8 Halogens and noble gases By E. G. HOPE Department of Chemistry University of Leicester Leicester LE1 7RH UK 1 Introduction This chapter reviews the 1996 literature for the elemental halogens and noble gases and compounds containing these elements in their positive oxidation states only. Publications which include reference to halide polyhalide or oxohalide anions as counter ions are not described. 2 Halogens Two reports have detailed recent developments in the production of elemental fluorine; the first outlined fundamental modifications to the established fluorine cell technology1 while the second o§ered an alternative solid-state electrochemical source of pure fluorine gas based on the electrochemical decomposition of a conducting solid- fluoride electrolyte.2 In the latter paper the authors outlined the use of a solid solution of LaF 3 containing 3–10% BaF 2 as the electrolyte and suggested that this system o§ers significant practical advantages over the established methodology which is derived directly from Moissan’s 1886 extraction of fluorine.The most common reactions of the halogens are oxidations and the expansion in the scope and application of elemental fluorine in this context is continuing. Reports during 1996 have included the fluorination of cyclic 1,3-diketones,3 1,3-dithiolanes,4 purines (where regiospecific derivatisation at the 8-position has been reported for the first time)5 and [60]-fullerene and some higher fullerenes,6 and the generation of some new N-fluoro nitrogen systems.7 The value of fluorine gas as a reagent in a wide range of organic chemistry even for the synthesis of products which do not contain fluorine has been reviewed8 and elegantly illustrated.9 Consecutive papers describe the surprising room-temperature fluorination of some of the platinum metals by elemental fluorine in anhydrous HF in the presence of alkali-metal fluorides or ammonium fluoride.10 An apparatus designed for the preparation and characterisation using matrix-isolation infrared spectroscopic techniques of molecular species formed when fluorine reacts with high-temperature metal surfaces has been reported.11 Oxidation reactions involving the heavier halogens are more widespread papers of note include an important hazard warning associated with the generation of explosive nitrogen –chlorine derivatives during the reaction of chlorine with ammonium complexes,12 Royal Society of Chemistry–Annual Reports–Book A 105 the synthesis of the [SbX 4 ][Sb(OTeF 5 ) 6 ] (X\Cl or Br) salts13 and the crucial function of bromine in the synthesis of a luminescent conjugated polymer for LED applications.14 Although equilibrium constants for the hydrolysis of aqueous Br 2 have been extensively investigated for 85 years considerable disagreement exists over the values of K 1 [equation (1)] (K 1 \k 1 /k ~1 ).The reinvestigation of this reaction as a function of ionic strength at 25 °C and as a function of temperature at constant ionic strength (kV0M) o§ers definitive kinetic data.15 Br 2 (aq)]H 2 O k”k k~1 HOBr]Br~]H` (1) Donor–acceptor complexes particularly involving the halogens have been extensively studied since the interactions in such species are one of the most fundamental processes in chemistry and may play a key role in many chemical and biological processes.The structure of M1,2,4,5-(EtS) 4 C 6 H 2 · · · Br 2N= nicely illustrates this type of interaction where the Br–Br bond length is increased from 228 (gas phase) to 241pm (adduct).16 Two intercalation compounds CsF·Br 2 and 2CsF·Br 2 were isolated from the reaction of CsF with bromine.17 In the 1 1 compound a single-crystal X-ray investigation revealed eclipsed Cs · · ·F layers (Cs` positioned above Cs`) whereas from X-ray- and neutron-powder di§raction data the layers in the 2 1 compound are staggered (Fig. 1). In both compounds the Br–Br distance is larger than that for free gaseous bromine suggesting some charge transfer from fluoride to bromine.The interaction between iodine and porous materials investigated spectrochemically has been proposed as a molecular probe for the quantitative evaluation of zeolite donor strength18 and may be controlled by topotactical insertion in for example porosils.19 A feature article on the formation and characterisation in the gas phase by groundstate rotational spectroscopy of pre-reactive intermediates of halogens (and interhalogens see below) with a series of Lewis bases o§ered a general introduction including experimental details and a summary of most of the results in this area.20 New linear HCN· · ·F 2 and CH 3 CN· · · F 2 intermediates have been described.21 A theoretical paper on H 2 O· · ·F 2 H 2 O· · · Cl 2 and H 2 O· · · ClF adducts has suggested that a lone pair on water interacts with chlorine and chlorine monofluoride; however in the fluorine adduct the fluorine nuclei are more e§ectively screened such that the water lone pairs have little involvement in complex information and the interaction this adduct is therefore more like a classical van der Waals interaction.22 3 Interhalogen compounds and polyhalide anions The generation of an extensive range of pre-reactive intermediates of ClF with Lewis bases23–26 have been described; the H 2 O adduct 124 compares well with an earlier theoretical prediction,22 whilst the data for the ammonia25 and trimethylamine26 pre-reactive intermediates indicate increasing ionic contributions to the valence-bond descriptions and the formation of Mulliken inner-complexes e.g.[(CH 3 ) 3 NCl]F. Bromine trifluoride reacts with M(C 6 F 5 ) 2 (M\Zn Cd or Hg) to give (C 6 F 5 )BrF 2 whilst in the presence of additional Lewis acids bromonium cations [(C 6 F 5 ) 2 Br]` are formed.27 The molecular structures of [(C 6 F 5 ) 2 Br]BF 4 and [(C 6 F 5 ) 2 Br]AsF 6 reveal distorted square-planar co-ordination at bromine with asymmetric hypervalent 106 E.G.Hope Fig. 1 ORTEP plots of the (i) CsF·Br 2 and (ii) 2CsF·Br 2 structures (Reproduced by permission from Chem. Eur. J. 1996 2 1303.) bonds in which the anions and cations form infinite –Br–F–B/As–F– zigzag chains.27 New cations containing the unusual Se–Se bridge have been synthesized by the reaction of selones with IBr or ICl28 and the binding energy (8.06 kcal mol~1) in the donor–acceptor ICl–diethyl ether complex has been determined by iodine PES.29 Polyiodides continue to provide a rich area for investigation o§ering various degrees of catenation and a wide variety of geometrical arrangements.In contrast to the intercalation compounds formed in the reaction of CsF with bromine CsF and iodine react to give Cs 2 I 8 and probably CsIF 6 .17 The conformations of the triiodide and tribromide anions in a series of crystal structures have been classified30 and phase transitions in triiodide salts of binuclear ferrocene derivatives with long alkyl chains have been investigated by 129IMo� ssbauer spectroscopy.31 Slow cooling of the product 107 Halogens and noble gases obtained by the reaction of NH 4 I–I 2 –Au at 500 °C a§orded crystals of [NH 4 ] 2 [(AuI 4 )AuI 2 (k-I 4 )] where the near-linear bridging I 4 2~ ligands link to form a chain network.32 The nature of the cation can have a pronounced e§ect on the structure of the anion; [N-propylurotropinium]I 5 and [N-propylurotropinium]I 7 crystallize with ‘normal’ anions (I 5 ~ V-shaped; I 7 ~ pyramidal)33 whilst the I 5 ~ anion in [Pr/ 4 N]I 5 consists of almost-squared nets of I~ ions connected by four I 2 molecules in which the cations are enclosed by a mesh made up of twelve iodine atoms.Similarly the I 7 ~ anion in [Pr/ 4 N]I 7 adopts a centrosymmetric Z-shape in which linear symmetrical I 3 ~ units and two iodine molecules form twisted rope ladders.34 Four types of polyiodide anions (I 3 ~ I 13 3~ I 12 2~ and I 16 2~) have been structurally charactered as their dimethyldiphenylammonium salts.35 The I 13 3~ anion consists of zigzag chains of iodide ions and iodine molecules in which the iodide ions are co-ordinated to I 5 ~ groups.The I 12 2~ anion 2 consists of two I 5 ~ groups bridged by an iodine molecule and the I 16 2~ anion 3 consists of two I 7 ~ groups also bridged by an iodine molecule. In a further development of the co-ordination chemistry of thioether crown ligands with main-group centres Schro� der and co-workers36 have described the synthesis of the binuclear [([16]aneS 4 )MIM([16]aneS 4 )]I 11 from the reaction of [M([16]aneS 4 )] [PF 6 ] 2 (M\Pd or Pt) with [Bu/ 4 N]I 3 . The anion which can be described either as two I 5 ~ groups linked via an iodide ion or two I 3 ~ groups and two iodine molecules linked via an iodide ion forms a 14-membered polyhalide ring (9.657]12.640Å) around the complex cation with the metal-bridging iodide at the centre of the ring (Fig.2); these rings also link into an infinite two-dimensional sheet. The authors proposed 108 E.G. Hope Fig. 2 Structure of [([16]aneS 4 )PdIPd([16]aneS 4 )][I 5 ] 2 I (Reproduced by permission from Chem. Commun. 1996 2207.) that this represents the first synthesis of a cyclic polyhalide array in which the complex cation acts as a template.36 Raman spectroscopy and X-ray crystal structure analysis of [(Bu5NH)Ph 3 P]ICl 2 and [(Bu5NH)Ph 3 P]IBr 2 showed linear non-centrosymmetric and linear centrosymmetric anions respectively.37 In contrast the anion in [K(crypt-2- 2-2)][I(ICN) 2 ] is bent at an angle of 89° at the central iodine atom.38 4 Halogen oxides and organoiodine oxygen compounds The focus of attention in halogen–oxygen chemistry is the action of these compounds in the atmosphere.The transcripts of the 1995 Nobel lectures include discussions on the role of halogen radicals in ozone destruction39 whilst the influence of chloro- fluorocarbons and their replacements are reviewed40 and demonstrated.41 Timeresolved flash photolysis of iodine and ozone gave in addition to evidence of IO 109 Halogens and noble gases O Cl O O O O I O ButOO R (R = H or NO2) 153 pm 142 pm 4 5 electronic bands attributed to the OIO radical42 whilst ab initio calculations on HBrO 2 indicated that it may play a role in night-time stratospheric bromine chemistry. 43 Rotational spectra for Br 2 O and OBrO have been recorded and interpreted.44 The ClO 4 radical 4 is generated by thermal decomposition of Cl 2 O 6 or Cl 2 O 7 and characterised by IR and UV/VIS spectroscopies under matrix-isolation conditions.The structural parameters were calculated from normal co-ordinate analysis and indicate a dynamic Jahn–Teller e§ect.45 The kinetics of the reaction of ClO 2 with lignin as a model compound for the pulp bleaching process have indicated that chlorination does not occur via direct reaction but via released HOCl or Cl 2 .46 The harmonic force field for ClO 3 F has been refined during a study of the microwave FT spectrum of an 18O-enriched monolabelled sample.47 The rate of Friedel–Crafts acylation using lanthanum triflate as a catalyst has been shown to be significantly enhanced by the addition of lithium perchlorate; the combined system reputedly o§ers significant advantages over the established procedures.48 During the past 15 years 200 articles have been published on the chlorite–iodide reaction; Lengyel et al.49 have recently obtained for the first time a self-consistent set of rate constants from kinetic measurements and modelling studies of the four components within this system. The X-ray crystal structures of MIO 4 (M\K Rb or Cs) first structurally characterised between 1926 and 1937 and now redetermined using modern facilities,50 have revealed isolated IO 4 tetrahedra. The structure of Be(H 4 IO 6 ) 2 ·4H 2 O was first reported incorrectly in 1941; a redetermination of the structure has indicated that this complex is the first beryllium periodate in which slightly deformed Be(OH 2 ) 4 tetrahedra and cis-IO 2 (OH) 4 octahedra are held together by eight hydrogen bonds.51 The same workers have also determined the structures of the related Mg(IO 3 ) 2 ·10H 2 O52 and [Ni(OH 2 ) 6 ][H 3 IO 6 ]53 complexes.Further work on the tetrabutylammonium periodate oxidation of alcohols54 and the syn-dihydroxylation of alkenes using the RuCl 3 –NaIO 4 catalyst has been reported.55 The last decade has witnessed a substantial renaissance in hypervalent iodine chemistry and a number of new reactions have been discovered exploiting the low toxicity ready availability and ease of handling of many of these reagents; the literature in this area (1970–1995) has been comprehensively reviewed.56 Reactions using iodosylbenzene have been preeminent in this area including a recent report of high yield b-functionalization in the treatment of triisopropylsilylenol ethers with PhIO–trimethylsilyl azide.57 The related iminoiodine ArINTs compound (Ar\C 6 H 5 or 2-MeC 6 H 4 ) have found application in the asymmetric catalytic synthesis of sulfimides58 and exhibit unusual polymeric association.59 The determination of two crystal structures of (o-tolyl) INTs compounds have revealed quasi-two-coordination at iodine but while one contains centrosymmetric dimers held together via I · · ·N interactions which link via I · · ·O associations into ladder polymers the second contains no short I · · ·N distances and polymerises exclusively via I · · ·O interactions 110 E.G.Hope Fig. 3 ORTEP Plots of two structures of (o-tolyl)INTs compounds (Reproduced by permission from Inorg. Chem. 1996 35 275.) (Fig. 3).59 In spite of the extensive interest in organoiodine oxygen compounds little is known about the related peroxy systems probably because of their tendency to decompose.One such type of compound 5 has been found to o§er a new route to the room-temperature oxidation of benzyl and allyl ethers.60 5 Cationic iodine and other organoiodine compounds 4-Methyl(difluoroiodo)benzene has been structurally characterised61 and used for the selective fluorination (at the a-position) of b-ketoesters.62 Phenyliodine(III) bis(tri- fluoroacetate) has been used in a novel and e¶cient synthesis of sulfur-containing heterocycles,63 in the intramolecular oxidative phenol coupling of phenol–ether derivatives 64 and in the asymmetric synthesis of isostegane derivatives.65 Penta- fluoroiodobenzene has been oxidised regiospecifically to iodoheptafluoro-1,4-cy- 111 Halogens and noble gases I F F2I F (2) C6F5I IF5–BF3 F2–N2 6 clohexadiene using IF 5 –BF 3 .Subsequent cautious oxidation using diluted elemental fluorine in dichloromethane at [78 °C has a§orded the first perfluorovinyliodine(III) compound 6 [equation (2)].66 Treatment of CF 3 I with [Me 4 N]X (X\Cl or Br) gave [Me 4 N][CF 3 IX]; the related CF 3 IF~ anion was obtained via thermal degradation of the intermediate resulting from the treatment of the heavier halide species with CF 3 OCl.67 Ph l O l Ph OTf OTf 7 The ligand-free palladium acetate-catalysed coupling of various aryl-alkenyl- and -alkynyl-iodonium salts (including [Ph 2 I]BF 4 [(PhC–– – C)IPh]BF 4 PhI(OH)(OTs) and Zefirov’s reagent 7) with terminal alkynes has been reported.68 Stang and coworkers 69 in a continuation of their work on cationic tetranuclear macrocyclic squares have described the self-assembly of optically active nanoscale-size assemblies linked via iodonium units.6 Noble gases The fundamental high-resolution molecular spectroscopy of small van der Waals clusters of SF 6 in liquid helium droplets (ca. 4000 He atoms) has been described.70 The observation of rotational structure indicates that the embedded species rotate nearly freely even at 0.37 K suggesting that these droplets are probably superfluid and provide a uniquely cold yet gentle matrix for high-resolution spectroscopy. Xenon has been used to catalyse the isomerisation of CH 3 NO 2 to CH 3 ONO within the reaction region of a selected-ion flow tube (SIFT) masspectrometer.71 The authors proposed a mechanism involving direct ‘interaction’ of xenon with nitromethane promoting the methyl-cation shuttle.The heavy-atom e§ect of xenon has been reported to be enhanced by adsorption to zeolites72 and further work on the structures of zeolites by 129XeNMRhas been outlined.73 Early work on the incorporation of noble gases into fullerenes indicated a very low gas uptake; concentration to 30% enrichment by column chromatography has now been reported.74 Fundamental vibrational spectroscopic studies of unstable adducts such as BF 3 ·CO and CH 2 CHF·HCl in liquid argon have been carried out under equilibrium conditions.75 The first time-resolved IR study of the photolysis of [M(CO) 6 ] (M\Cr Mo or W) in supercritical argon krypton or xenon has permitted the observation of the established [M(CO) 5 (noble gas)] adducts.Further competitive kinetic studies gave data on the strength of the metal–noble-gas interaction.76 112 E.G. Hope 7 Noble-gas compounds Noble-gas compounds have continued to captivate theoretical scientists.77–79 The 129Xe NMR chemical shifts of XeF 2n XeF 2n~1 ` and XeOnF 6~2n (n\1–3) have been studied theoretically by ab initio finite perturbation theory. The calculated values agree with experimental data and indicate that the dominant term in the xenon chemical shift is the paramagnetic term.80 Following its spectroscopic identification in 1995 XeH 2 has been identified as a transient species obtained by annealing xenon–hydrocarbon systems irradiated with fast electrons at 15 K;81 following reaction with trans-but-2-ene XeH 2 has been described as either a highly reactive hydrogenation agent or an ‘active form’ of molecular hydrogen.A new thermal catalytic synthesis of XeF 2 and KrF 2 has been proposed.82 The principal application of noble-gas compounds outside noble-gas chemistry is oxidation with or without fluorination. Xenon difluoride has been used for the oxidation of Te(C 6 H 5 ) 4 in the synthesis of Te(C 6 H 5 ) 6 the first neutral compound comprising a hexaarylated element.83 The reaction of tetrafluorobenzenes with XeF 2 in anhydrous HF has been shown to occur either by addition of fluorine to the ring or substitution of hydrogen by fluorine.84 In water in the presence of HF XeF 2 acts as an electrophilic oxygenation agent in the production of cyclohexa-1,4-dienones from pentafluoroarenes.85 Krypton difluoride has been used in the synthesis of [NF 4 ]BF 4 82 and [TcOF 5 ].86 Seppelt and co-workers87,88 have reported X-ray structural analyses of complexes containing the XeF 7 ~ Xe 2 F 13 ~ and XeF 8 2~ anions (Fig.4). In CsXeF 7 obtained from CsF and XeF 6 in BrF 5 at 4 °C the anion is a capped octahedron a geometry which is strictly obeyed due to the symmetry constraints of the cubic lattice system; this should be compared to most other main-group seven-co-ordinate compounds which are pentagonal bipyramidal. The Xe–F#!1 bond is unusually long (210 pm cf. average Xe–FOh \195 pm) which may arise by interaction with the non-bonding electron pair or from the interaction with three caesium cations (the other fluorine atoms only show short contacts to two cations). In [NO 2 ]Xe 2 F 13 the anion can be described as an adduct of XeF 7 ~ with XeF 6 .As such this would represent the first structural determination of a discrete XeF 6 molecule; in the solid state XeF 6 is a complicated mixture of fluorine-bridged tetramers and hexamers. In this description of the anion structure the XeF 7 ~ part adopts a capped trigonal-prismatic arrangement in which the Xe–F#!1 distance is the shortest bond and the lone pair appears to point between the two Xe–F bonds trans to Xe–F#!1. The XeF 6 part has C 2v symmetry with two short two intermediate and two long Xe–F bonds and exhibits significant deviation from a regular octahedral structure as seen previously for IF 6 ~ and SeF 6 2~. In the solvated structure of Cs 2 [XeF 8 ]·4BrF 5 the anion adopts a near-regular square-antiprismatic structure as seen 25 years ago for the NO` salt which may be compared to that for IF 8 ~.The Xe–F bonds are longer than the I–F bonds which can be rationalised in terms of shielding by the centrosymmetric non-bonding electron pair or by increased polarity of the A–F bonds due to the increased negative charge. The systematic investigations of the xenon–carbon bond by Frohn and coworkers89,90 have been continued. The reactions of (nonafluorocyclohexen-1- yl)xenon(II) hexafluoroarsenate with halide ions have been shown to be solvent dependent. With iodide and bromide in acetonitrile and anhydrous HF xenon(II) is 113 Halogens and noble gases Fig. 4 Structures of units of (i) [NO 2 ][Xe 2 F 13 ] and (ii) Cs 2 [XeF 8 ]·4BrF 5 (Reproduced by permission from Angew. Chem. Int. Ed. Engl.1996 35 1123 and Chem. Eur. J. 1996 2 398.) F F (3) [C6F5Xe]AsF6 XeF2•H2O HF Xe+AsF6 – Xe+AsF6 – O O O + F F (4) Xe+AsF6 – Xe+AsF6 – O 8 XeF2•H2O HF displaced by the halide giving RX (X\Br or I). Chloride and fluoride do not react with the xenon salt in anhydrous HF but in acetonitrile the fluoride ions initiate the formation of alkenyl radicals which abstract hydrogen from the solvent a§ording RH. Chloride shows intermediate behaviour in acetonitrile giving both RH and RCl.89 As outlined above the XeF 2 -H 2 O–HF system acts as a strong electrophilic oxygenation agent. Treatment of [C 6 F 5 Xe]AsF 6 and [C 6 F 7 Xe]AsF 6 8 with this system resulted in only the second report of the transformation of an organic moiety bonded to xenon without Xe–C bond cleavage equations (3) and (4).90 References 1 G.Hodgson and M. P. Hearne Br. Pat 96 08589 A2 960321 (Chem. Abstr. 1996 125 043743). 2 V.N. Bezmelnitsyn A. V. Bezmelnitsyn and A. A. Kohnakov J. Fluorine Chem. 1996 77 9. 3 R.D. Chambers J. Hutchinson A. S. Batsanov C. W. Lehmann and D. Y. Nanmov J. Chem. Soc. Perkin Trans. 1 1996 2271. 4 R.D. Chambers G. Sandford M. E. Sparrowhawk and M.J. Atherton J. Chem. Soc. Perkin Trans. 1 1996 1941. 114 E.G. Hope 5 J.R. Barnio M. Navnavari M.E. Phelps and N. Satyamurthy J. Am. Chem. Soc. 1996 118 10 408. 6 Y. Matsuo T. Kakajima and S. Kasamatsu J. Fluorine Chem. 1996 78 7; O.V. Boltalina L. N. Sidorov V. F. Bagryantsev V. A. Seredenko A. S. Zapol’skii J. M. Street and R. Taylor J. Chem. Soc. Perkin Trans. 2 1996 2275. 7 See for example R. E. Banks M.K. Besheesh S. 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ISSN:0260-1818    

DOI:10.1039/ic093105

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

9 Zinc cadmium and mercury By I. B. GORRELL School of Chemistry Physics and Environmental Science University of Sussex Falmer Brighton BN1 9QJ UK 1 Introduction This chapter summarises results published during 1996 with the focus on organometallic and co-ordination chemistry. Compounds containing macrocyclic ligands are not included. 2 Zinc Carbon-donor ligands The crystal structure of [Zn(C 5 HPr* 4 ) 2 ] has revealed one g1- and one approximately g5-ring; [Zn(C 5 H 2 Pr* 3 ) 2 ] has also been prepared and the structure and bonding discussed.1 The preparations and crystal structures of [Zn(tmen)XMCH(SiMe 3 )PhN] (X\Cl or Me) [ZnMN(SiMe 3 ) 2NMC(SiMe 3 ) 3N] 2 2 and [Li(tmen)] 2 [Zn(CH 2 SiMe 2 SiMe 2 CH 2 ) 2 ] have been reported.3 A vibrational spectroscopic study of M[Si(SiMe 3 ) 3 ] 2 (M\Zn Cd or Hg) together with X-ray analyses of the cadmium and mercury compounds have appeared.4 The o-phenylenezinc compound C 6 H 4 Zn·2thf was shown to be dimeric in the solid state and trimeric in solution.5 The X-ray crystal structure of a zinc carbenoid cyclopropanating agent IZnCH 2 I·L (L\18-crown-6 or benzo-18-crown-6) has been reported.6 Studies of EtZnCH 2 I and IZnCH 2 I using 13C NMR spectroscopy have shown that equilibria involving such reagents follow those observed for ethylzinc-derived complexes.7 The di§erent structures of the homochiral and heterochiral dinuclear complexes formed from (2S)- or (2R)-3-exo-(dimethylamino)isoborneol and Me 2 Zn have been used to rationalise the chirality amplification observed in the asymmetric reaction of PhCHO with Me 2 Zn in the presence of small amounts of these complexes.Data have been supported by ab initio calculations.8 A comparison of the abilities of di§erent co-ordinating agents to complex [RMg]` and [RZn]` (R\Et or CH 2 Bu5) has shown that zinc has a lower tendency to form dative bonds and prefers to bond to nitrogen rather than oxygen.9 A theoretical study of the electronic structures of [ZnXH 2 ]n` (n\0–2 X\C or Sn) together with a study of the ZnCH 2 –HZnCH photolytic rearrangement has been reported.10 The kinetics and mechanism of the thermal decomposition of Et 2 Zn have been investigated.11 X-Ray crystallography has revealed a diamond-type framework Royal Society of Chemistry–Annual Reports–Book A 117 in [Me 4 N]LiZn(CN) 4 ,12 and a pseudo-tetrahedral zinc centre in [(PhC–– – C) 4 ZnMLi(tmen)N2 ] with the two [Li(tmen)]` cations linked to the anions via acetylide–lithium n interactions.13 Nitrogen- and phosphorus-donor ligands The reaction of ZnR 2 (R\Et or CH 2 SiMe 3 ) with a variety of primary amines has a§orded [MZnEt(NHPh)(thf)N3 ] [MZnEt[NH(mes)](thf)N2 ] [Zn 4 Et 4MNH(dipp)N4 (OEt) 2 ] [MZnEtNHBu5N3 ] and [MZnCH 2 SiMe 3 [NH(dipp)]N2 ] which were crystallographically characterised.14 The heterocubanes [MZnR(NPMe 3 )N4 ] (R\Me or Bu/) have been prepared by the reaction of [MZnBr(NPMe 3 )N4 ] with RLi.With Bu/Li [MZnI(NPMe 3 )N4 ] gave [Zn 4 IBu/ 4 (NPMe 3 ) 3 ].15 Fusion of ZnI 2 with Me 3 SiNPMe 3 in the presence of sodium fluoride yielded [ZnI(NPMe 3 )] 4 .16 A mixture of ZnH 2 and ZnCl 2 in thf–tmen afforded [ZnHCl(tmen)]; reactions of complex zinc hydrides with a range of organic substrates have also been reported.17 X-Ray crystallography has revealed octahedral geometry for zinc in [Zn(tipb) 2 ] ClO 4 .The tipb molecules connect three metal centres to form a two-dimensional polymer.18 The structure of [Zn(tpt) 2@3 (SiF 6 )(H 2 O) 2 (MeOH)] has been shown to contain eight [Zn 3 (tpt) 2 ]n interpenetrating networks four of one handedness and four of the other.19 Networks of M–Cl–M and M–L–M chains have been observed in the structures of [MLCl 2 ] (M\Zn or Cd L\pyz; M\Zn L\pyrimidine).20 Both [Zn(L1) 2 (SCN) 2 ]·2H 2 O and [Zn(L2)Br 2 ] [L1\cyanoguanidine L2\1- (ethoxyiminomethyl)guanidine] have been found to contain tetrahedral metal centres with a chelating ligand in the latter.21 A distorted tetrahedral geometry around the metal has been observed in dichloro[1-(4-chlorophenylmethyl)-2-(1-pyrrolidinylmethyl) benzimidazole-N,NA]zinc22 and in [Zn(1-mim) 4 ][ClO 4 ] 2 .23 Neutron powder di§raction measurements on [Zn(ND 3 ) 4 I 2 ] have revealed tetrahedral zinc centres linked with two- and three-centre hydrogen bonds.24 The reaction of [Zn(py) 2 (NCS) 2 ] with tris(2-pyridyl)phosphane L yielded [ZnL 2 ][Zn(NCS) 4 ]; X-Ray crystallography revealed an octahedral cation and tetrahedral anion.25 The preparation and spectroscopic properties of [Zn(Him) 2 (OAc) 2 ] have been presented26 and complexes of tris(N-piperidinomethyl)phosphine oxide with zinc and cadmium have been prepared.27 The reaction of [(Me 3 Si) 3 CZnCl] with LiPH(SiPr* 3 ) yielded [MZn[C(SiMe 3 ) 3 ]N2 P- (SiPr* 3 )] which is monomeric in the solid state and in solution.28 The preparations and crystal structures of [ZnCl 2 (PMe 3 ) 2 ] and [Cl 3 Zn(k-Cl)Zn(PMe 3 ) 3 ] have appeared.29 The reaction of Et 3 AsI 2 with zinc powder gave [MZnI 2 (AsEt 3 )N2 ] whereas that of Me 3 AsI 2 gave a 1 1 mixture of [ZnI 2 (AsMe 3 ) 2 ] and ZnI 2 .Both arsine complexes have been crystallographically characterised.30 Oxygen-donor ligands The reactions of [(TpC6.,M%)ZnOH] with hydroxamic acids and hydroxyketones yielded the hydroxamates and ketoalcoholates respectively. Crystal structure data have revealed ZnN 3 O 2 co-ordination and it has been suggested that these compounds could serve as transition-state analogues of enzyme-catalysed reactions.31 The reaction of [(TpC6.,A3)ZnOH] with H 2 S gave [(TpC6.,A3)ZnSH] and these compounds are converted to [M(TpC6.,A3)ZnN2 E] (E\O or S) on heating; the reactions of the hydrox- 118 I.B.Gorrell ide with CO 2 CS 2 SO 2 and PhNCS have also been described.32 The synthesis of [Zn(OTeF 5 ) 2 ] and its interaction with PhCH 3 2,4,6-Me 3 C 6 H 3 MeNO 2 PhNO 2 MeCN Me 2 CO Et 2 O or thf have been reported; [MZn(OTeF 5 ) 2 (PhNO 2 ) 2N2 ] and [Zn(OTeF 5 ) 2 (PhNO 2 ) 3 ] have been crystallographically characterised.33 The crystal structure of [(ZnL 2 )n][ClO 4 ] 2n [L\O 2 CCH 2 CH 2 N(CH 2 CH 2 ) 3 NCH 2 CH 2 CO 2 ] has revealed eight-co-ordinate zinc in a structure of mutually interpenetrating zinc– betaine networks.34 The crystal structure of [ZnM(EtO) 2 S 2 PN2 (bipy)] has been shown to contain polymeric zig-zag chains with monodentate dithiophosphate groups and bipy linking tetrahedral metal centres.35 The preparations of [MZn[OSi(OBu5) 3 ]- 2N2 ] and [ZnOSi(OBu5) 2 O] = and their use as precursors for Zn 2 SiO 4 have been presented; the former has been crystallographically characterised.36 A series of polynuclear complexes of zinc or cadmium containing cis- [Cr(OH) 2 (en) 2 ]` as a ligand have been reported; zinc is in a tetrahedral environment whereas cadmium is octahedral.37 The preparations and crystal structures of bis[2-(1- methyliminoethyl)phenolato]zinc and [2-(1-methyliminoethyl)phenolato]ethylzinc have been reported; both are dimeric and contain Zn 2 O 2 rings with ZnO 3 N 2 and ZnO 2 NC co-ordination respectively.38 The nature of the zinc carboxylates formed by the neutralization reaction between aliphatic carboxylic acids and Zn(OH) 2 has been found to depend on the spatial structure of the alkyl chain.39 Sulfur- and selenium-donor ligands The preparation and characterisation including X-ray crystal structure for L\3,5- lutidine of [Zn 10 S 4 (SEt) 12 L 4 ] (L\py or 3,5-lutidine) have revealed an adamantane (sphlarite) core with four [k3 -S]2~ and twelve [k-SEt]~ groups.40 The crystal structure of [Zn(Et)(S 2 NEt 2 )] 2 has shown each dithiocarbamate group to be chelated to one zinc atom and bridged to the other.41 The synthesis and crystallographic analysis of [MME 2 CN(Me)(CH 2 ) 3 NMeN2 ] (M\Zn or Cd; E\S or Se) have been reported.The zinc compounds are polymeric whereas the cadmium–sulfur compound is dimeric. High quality ZnS films have been obtained.42 The preparation and X-ray crystal structures of [MZn(S 2 CNMeR) 2N2 ] 1 (R\Et Pr/ Pr* or Bu/) have appeared.CVD of the butyl compound yielded polycrystalline ZnS.43 The reaction of the elements in liquid ammonia yielded amorphousME(M\Zn or Cd; E\S or Se).44 The preparations of [Ph 4 E][M(SOCPh) 3 ] (M\Zn Cd or Hg; E\P or As) have been reported together with the crystal structures of [Ph 4 P][M(SOCPh) 3 ] (M\Zn or Hg) and [Ph 4 As][Cd(SOCPh) 3 ]. The metal centres are trigonal planar and are further coordinated to one (Hg) or two (Zn Cd) thiobenzoate oxygen atoms. Bonding has been discussed using the bond-valence approach.45 The preparations of [M[(Bu5O) 3 SiS] 2 - Zn(H 2 O)nNm] [M[(Bu5O) 3 SiS] 2 Zn(NH 3 )N2 ] and [M(Bu5O) 3 SiSN2 Zn(MeCN)] have been 119 Zinc cadmium and mercury described; reactions with donor bases gave [M(Bu5O) 3 SiSN2 ZnLn] (n\1 L\bipy or phen; n\2 L\py or 1-mim).The crystal structures of the acetonitrile and bipy complexes have revealed trigonal-bipyramidal (2S]2O]N) and tetrahedral (2S]2N) geometries for zinc respectively.46 A spectroscopic electronic and structural study of charge-transfer complexes of 2,2@- and 4,4@-bipyridinium and 1,10- phenanthrolinium acceptors with dithiooxalate zinc donors has been presented.47 Halogen-donor ligands The X-ray crystal structures of [Et 4 N] 2 [MCl 4 ] (M\Zn Cd or Hg),48 [LH 2 ][ZnBr 4 ] (L\1,4-dimethylpiperazine)49 and the 7-methyladeninium salt of the trichloro(7- adenine)zinc anion50 have been reported; all contain tetrahedral anions. 3 Cadmium Structural data for nearly 40 organometallic and transition-metal carbonyl compounds of cadmium have been reviewed.51 Carbon-donor ligands The preparation and structure of [MgMeL][CdMe 3 ]·C 6 H 6 (L\1,4,7,11-tetramethyl- 1,4,7,11-tetraazacyclotetradecane) has been reported; cadmium is trigonal planar.52 Infrared spectroscopic studies of the complexes formed between Me 2 Cd and Me 2 E MeEH (E\O S or Se) and Me 2 CO,H 2 S,H 2 Se NH 3 PH 3 and AsH 3 in argon matrices and cold thin films have been reported.53 Nitrogen- and phosphorus-donor ligands In a continuation of a study of the use of [Ag(CN) 2 ]~ as a rod-shaped ligand to bridge cadmium centres to form multidimensional co-ordination polymers the crystal structures of [Cd(Him) 4MAg(CN) 2N2 ] [Cd(Him) 5MAg(CN) 2N][Ag(CN) 2 ] [Cd(1- mim) 4MAg(CN) 2N][Ag(CN) 2 ] and [Cd(2-mim) 4MAg(CN) 2N][Ag(CN) 2 ]·H 2 O have been determined.Geometries at cadmium were described as four-blade propellers and umbrellas.54 A two-dimensional structure has been observed for M[Cd(4-ampy) 2Mk- Ag(CN) 2N2 ][Cd(ae)(4-ampy)MAg(CN) 2NMk-Ag(CN) 2N] 2Nn.55 The structures of [Cd(ae)(L1)MNi(CN) 4N] and [Cd(ae)(L2)MNi(CN) 4N]·H 2 O (L1\1,5-diaminopentane L2\1,6-diaminohexane) have been shown to consist of doubly or triply penetrating frameworks respectively.56 X-Ray crystallography has revealed a new type of clathrate structure for [Cd(C 12 H 12 N 2 ) 2 ][Ni(CN) 4 ]·2C 6 H 4 Me 2 -1,3 with an octahedral cadmium centre surrounded by two cyanide and four bis[1,2-di-(4-pyridyl)ethane] nitrogen atoms.57 The clathrate [MCd(Him)NMCd(CN) 3 (Him)NMCd(CN) 3N]·C 6 H 6 has been shown by X-ray di§raction to consist of a three-dimensional cyano-linked framework containing both tetrahedral and octahedral cadmium centres.58 The reaction of dilithio-1,2,3-triphenylguanidide Li 2 [(PhN) 3 C] with [CdMN(SiMe 3 ) 2N] gave [M(Me 3 Si) 2 NN2 CdM(PhN) 3 CNLi 2 (thf) 3 ] with cadmium in a distorted trigonal planar environment.59 The crystal structures of [CdL 2 F 2 ]·3H 2 O [CdL 2 Br 2 ] and [HgLCl 2 ] (L\cyanoguanidine) have shown each cadmium to be bonded to four halogen atoms to form polymeric chains and to two guanidine molecules.Similar chains occur in the mercury compound but they are connected by 120 I.B. Gorrell bidentate bridging guanidine ligands.60 In [CdCl 2 (C 7 H 7 NO 2 ) 2 ] the cadmium atom has been shown to be surrounded by four chlorine atoms and two nitrogen atoms from two 4-aminobenzoic acid groups to form infinite zigzag chains of edge-sharing octahedra.61 The reaction of CdBr 2 with 2,2@-biimidazole L yielded the linear polymer [CdBr 2 L]n with octahedral metal centres.62 Crystals of [Cd(Htcmel)]·3H 2 O have shown to contain sheets of hydrogen-bonded pairs of planar ligands linked together by metal centres in a three-dimensional framework.63 The metal centre in [Cd(NCS) 2 (C 7 H 18 N 2 ) 2 ] has been shown to have a distorted-octahedral co-ordination with equatorial bidentate N1-isopropyl-2-methylpropane-1,2-diamine ligands.64 The structure of [Cd 2 (S 2 O 3 ) 2 (dmphen) 2 ] has revealed a thiosulfate group acting as both a bridging and bidentate ligand with five-co-ordinate cadmium.65 The cadmium centre has been shown to adopt a distorted-octahedral geometry in [CdCl 2 (phen) 2 ].66 The X-ray crystal structure of [pyH][Cd(py) 4 (ONbF 5 ) 2 ] has revealed a trans-octahedral arrangement around the metal.67 The preparations and structures of the nanoclusters [Cd 32 Se 14 (SePh) 36 (PPh 3 ) 4 ] [PEt 2 (Ph)C 4 H 8 OSiMe 3 ] 5 [Cd 18 I 17 (PSiMe 3 ) 12 ] [NEt 3 C 4 H 8 OSiMe 3 ] 5 [Cd 18 I 17 (PSiMe 3 ) 12 ] and [Hg 32 Se 14 (SePh) 36 ] have been reported.68 Oxygen-donor ligands The structure of an adduct of CdCl 2 with an olefinic double betaine [M(CdCl 2 ) 3 (EtOH) 2 (H 2 O) 4Nn]·n(C 18 H 20 N 4 O 4 )·nH 2 O has been shown to be based on an infinite zig zag chain of corner-sharing CdCl 2 units with H 2 O or EtOH ligands around the metal forming an octahedral CdCl 4 O 2 co-ordination polyhedron. The adduct of Cd(NO 3 ) 2 with the betaine meso-2,5-bis(trimethylammonio)adipate (L) [MCd 2 L 2 (NO 3 ) 2 (H 2 O) 3Nn][NO 3 ] 2n has also been shown to contain an infinite zigzag chain but with pentagonal-bipyramidal and highly distorted octahedral geometries.69 A polymeric complex of an olefinic double-betaine-containing cadmium in four di§erent co-ordination environments [Cd 3 L 3 I 2 (H 2 O) 6 ]n[CdI 4 ] 2n·nH 2 O [L\cis-(4- Me 2 N`C 5 H 4 ) 2 C 2 (CO 2 ~) 2 ] has been prepared and characterised by X-ray di§raction.Polymeric cadmium(II) complexes [MCdLX 2 (H 2 O) 2Nn]·nH 2 O (X\Cl or Br) and [MCdLI 2Nn]·nH 2 O [L\O 2 CCH 2 N(CH 2 CH 2 ) 3 NCH 2 CO 2 ] have also been prepared. 70 The X-ray crystal structures of [MCd 4 L 2 X 8 (H 2 O) 2Nn] [X\Cl Br or I; L\O 2 CCH(NMe 3 )CH 2 CH 2 CH(NMe 3 )CO 2 ] have been reported. The chloride has a two-dimensional layer structure while the bromide and iodide have three-dimensional networks of zigzag cross-linked chains.In [MCd(L)X 2Nn] (X\Cl or Br) and [MCd 2 (L)I 4Nn] [L\O 2 CCH(C 5 H 5 N)CH 2 CH 2 CH(C 5 H 5 N)CO 2 ] the chloride and bromide have been shown to contain zigzag chains but a two-dimensional polymeric layer structure has been found in the iodide.71 The crystal structure of M[CdMPh 3 P(CH 2 ) 2 CO 2N(H 2 O(k-Cl) 2 CdClMPh 3 P(CH 2 ) 2 CO 2 ](H 2 O) 2 ]ClO 4Nn has revealed chains containing CdCl 2 O 4 and CdO 3 Cl 3 octahedra.72 The cadmium malonates [MCd 2 (mal) 2 (H 2 O) 4Nn] [MCd(mal)(H 2 O)·H 2 ONn] and [MCd(mal)(H 2 O) 3 ·H 2 ONn] have been characterised by X-ray crystallography and solid-state 113Cd NMR spectroscopy and form a layer structure a three-dimensional network and a chain structure respectively.73 Cadmium complexes of deprotonated 2,3-pyrazinedicarboxylic acid (H 2 L) have been prepared and characterised by X-ray crystallography; [H 3 O] 2x[CdL 2 ]x contains anionic chains of metal centres linked by double-bridgingL groups while [CdL(H 2 O) 3 ]x·xH 2 Oconsists of chains of metals with 121 Zinc cadmium and mercury single-bridging L groups.74 The reaction of CdSO 4 with 5,7-dimethyl-1,2,4- triazolo[1,5-a]pyrimidine (dmtp) in aqueous solution yielded [Cd(dmtp)SO 4 (H 2 O) 2 ].Each metal centre is linked to two water molecules one dmtp ligand and three oxygen atoms from di§erent sulfate groups each of which is itself bound to three cadmium atoms to form a polymeric chain. Spectroscopic data and antimicrobial activity have been reported.75 The crystal structure of dichloro(L-piperidine-3-carboxylic acid)cadmium( II) has revealed a one-dimensional polymer chain.76 Treatment of a suspension of Cd(acac) 2 with HBF 4 ·OEt 2 in thf yielded [Cd 2 (thf) 5 ] [BF 4 ] 4 as an intermediate which gave [Cd(thf) 4 ][BF 4 ] 2 on crystallisation from thf–CH 2 Cl 2 .The reactions of the intermediate to give tris(pyrazolyl)methane and tris(pyrazolyl)methane–tris(pyrazolyl)borate complexes have also been reported along with X-ray structural and 113Cd NMR data.77 113Cd NMR spectroscopy has been used to detect many species in aqueous solutions of cadmium(II) with fulvic acid78 and has indicated that cadmium monocarboxylates undergo fast exchange in solution.79 Sulfur- and selenium-donor ligands The three-dimensional complex [MCd 17 S 4 (SPh) 24 (MeOSC 2 ) 4@2Nn]·nMeOH has been prepared and crystallographically characterised.80 Identification of [Cd(SPh) 4 ]2~ [Cd 4 (SPh) 10 ]2~ and [Cd 10 S 4 (SPh) 16 ]4~ has been achieved using electrospray mass spectrometry.81 The preparation of [Cd(SCPh 3 ) 2 (tmen)] from Cd[N(SiMe 3 ) 2 ] 2 has been reported.X-Ray crystallography revealed that cadmium adopts a highly distorted tetrahedral co-ordination geometry.13 Both compounds [PPh 4 ] [Cd(S 2 CNEt 2 ) 2 X] (X\Cl or Br) have been shown to contain five-co-ordinate cadmium in a geometry half way between trigonal bipyramidal and square pyramidal.82A crystallographic study of [CdMS 2 P(OMe) 2N2 ] has shown that the ligands bridge two adjacent cadmium centres forming a linear chain.83 Electrochemical oxidation of cadmium in a solution of 4-methyl-6-(trifluoromethyl)pyrimidine-2-thione L in acetronitrile gave [CdL 2 ] the crystal structure of which revealed polymeric chains of octahedrally co-ordinated N 2 S 4 metal centres.84 Nanoparticles of CdS have been prepared by controlled hydrolysis of P 2 S 5 using Cd(NO 3 ) 2 ·4H 2 O.85 The reaction of [Cd(C–– – CPh) 2 (tmen)] with selenium (1 2) produced [MCd(SeC–– – CPh) 2 (tmen)N2 ] a loosely linked dimer with cadmium in a highly distorted five-co-ordinate environment.86 Halogen-donor ligands Crystallographic studies have revealed two-dimensional sheets of CdCl 6 octahedra in [C 6 H 4 (NH 3 ) 2 -1,4][CdCl 4 ],87 and discrete CdCl 4 tetrahedra in the bis(2-methyl-4- nitroanilinium)88 and 1,2-bis(1-aza-4,7-diazonia-1-cyclononyl)ethane89 salts. X-Ray analysis of [Et 3 S][CdI 4 ] have also revealed isolated anionic tetrahedra.90 Crystal structures of six species [Me 3 SOCdCl 3~xBrx] (x\0.286–2.116) have shown that it is not possible to describe the compounds in terms of continuous solid-solution series.91 The reaction of CdI 2 with LiE(SiMe 3 ) 3 (E\Si or Ge) a§orded [Li(thf) 4 ] [(Me 3 Si) 3 ECd(k-I) 3 CdE(SiMe 3 ) 3 ]; the germyl derivative has been crystallographically characterised.92 122 I.B.Gorrell 4 Mercury Carbon-donor ligands Full details of the preparations of the first examples of post-transition-element carbonyls [Hg(CO) 2 ][Sb 2 F 11 ] 2 and [Hg 2 (CO) 2 ][Sb 2 F 11 ] 2 have appeared with in the case of the mercury(II) compound an X-ray crystal structure. Both species contain linear cations.93 The preparations spectroscopic properties and thermal stabilities of [Me 3 Si) 3 CHgR] (R\Me Pr* Bu/ Bu5 or Ph) and [(Me 2 PhSi) 3 CHgR] (R\Me Bu/ CH 2 Ph or Ph) have been reported.A crystal structure [(Me 3 Si) 3 CHgC(Me 2 PhSi) 3 ] has also been determined.94 The cyclic trimer perfluoroo- phenylenemercury has been found to bind SCN~ in acetone solution. A crystal structure of [Bu/ 4 N][(o-C 6 F 4 Hg) 3 (SCN)] showed an infinite helical chain of alternating trimers and anions linked via Hg· · · S interactions.95 The reaction of 4- Bu/OC 6 H 4 NO 2 with [Hg(O 2 CCF 3 ) 2 ] and LiCl yielded RHgCl (R\C 6 H 3 NO 2 -3- OBu/-6) which was converted toR 2 Hg by [Me 4 N]Cl; a crystallographic study showed R 2 Hg to be linear at mercury.96 Bis(4-pyridylethynyl)mercury has been prepared and characterised by X-ray di§raction.The metal has a T-shaped co-ordination geometry and is bound to two ethynyl groups and a pyridyl group from a neighbouring molecule to form chains.97 Reactions of Hofmann’s base [MCHg 4 O(OH) 2 (H 2 O)Nn] with concentrated nitric and sulfuric acids to give [C(HgNO 3 ) 4 ]·H 2 O and [C(HgSO 4 ) 2 (HgH 2 O) 2 ] have been reported. X-Ray data have revealed the central carbon to be tetrahedrally surrounded by four mercury atoms.98 The reaction of 2-S-methylthiobarbituric acid (H 2 TbSMe) with PhHgOAc a§orded [(HgPh) 2 (TbSMe)] the crystal structure of which has been reported.99 The reaction of Hg(ClO 4 ) 2 ·3H 2 O with 2-(2@-pyridyl)quinoxaline L in acetone yielded [MHg(k- CH 2 COCH 3 )(ClO 4 )LN2 ] which has been crystallographically characterised.100 The reaction of Hg(CN) 2 with [SNS][AsF 6 ] yielded [Hg(CNSNS) 2 ][AsF 6 ] which initiated polymerisation of thf and was converted into the halide salts by treatment with [Bu/ 4 N]X (X\Cl Br or I).Attempts at reduction led to decomposition but halogenation gave [XCNSNS]` salts. The reaction of [SNS][AsF 6 ] with PhHgCN gave [Ph 2 S 4 N 3 ][AsF 6 ].101 The first vinylmercury hydrides R1(H)C–– CR2HgH (R1\R2\H; R1\H R2\Me; R1\Me R2\H) have been prepared by reduction of the corresponding chlorides with Bu 3 SnH in the presence of a radical inhibitor. Bonding has been discussed with reference to photoelectron spectra and ab initio calculations.102A series of new organomercury hydrides including aromatic and fluoroaromatic compounds have been characterised by mass and NMR spectroscopy.103 The compounds ArHgCl ArCH 2 HgCl Ar 2 Hg and (ArCH 2 ) 2 Hg in which the aryl group possesses a substituent in the 2-position which contains a nitrogen atom have been prepared.However no evidence for nitrogen–mercury interaction has been obtained.104 Mercury photosensitization of ArCH 2 X (X\alkyl alkoxy or amido) causedC–X cleavage in order C–O[C–N[C–C the key step being the formation of the exciplex Hg(g2- ArCH 2 X) which dissociates to give a vibrationally excited triplet arene.105 An increase in the electron donating ability of Ar [Ar\3-CF 3 C 6 H 4 3,4-Cl 2 C 6 H 3 or 4-XC 6 H 4 (X\Me 2 N Me H F or Cl) has been shown to increase the hardness of [ArHg]` in 4-fluorothiophenoxides 4-nitrophenoxides chlorides and acetates.106 Ab initio calculations have shown that the CH 3 –Hg bond is broken by HX (X\Cl Br or I) in a 123 Zinc cadmium and mercury one-step mechanism involving a four-centre transition state in which bond forming and bond breaking are not completely synchronous.Activation energies have been shown to parallel Hg–C bond strength and are influenced by the electronegativity of the ligands attached to Hg.107 Mono- and di-substituted ferrocenes reacted with excess Hg(OAc) 2 to give highly insoluble polymercurated ferrocenes. Full mercuration failed to occur due to the extreme insolubility of the higher mercurated products.108 A series of arylmercury compounds have been synthesised in a microwave oven in higher yields and shorter reaction times than those achieved using conventional techniques. 109 Nitrogen- and phosphorus-donor ligands The reaction of HgIMe with 2-(2@-pyridyl)quinoxaline L yielded [Hg 2 I 4 L 2 ] the crystal structure of which has been reported.110 The reactivity of 4-amino-6-methoxy- 2-methylthiopyrimidine (HL) with mercury(II) ions has been studied using potentioimetric methods and [HgLCl]·H 2 O and [Hg 2 (HL) 2 Cl 4 ] have been isolated and structurally characterised.111 The reaction of [2-(pyridin-2-yl)phenyl]mercury(II) acetate with 2-thiouracil (H 2 tuc) in 1 1 and 2 1 mole ratio a§orded [Hg(C 6 H 4 C 5 H 4 N)(H 2 tuc)] and [MHg(C 6 H 4 C 5 H 4 N)N2 (tuc)] 2 respectively.112 The reaction of [RHg]` (R\Me or Ph) with bidentate phosphines L (2 1) yielded binuclear complexes [RHg(L)HgR]2` [L\Ph 2 P(CH 2 )nPPh 2 n\1–3].With excess phosphine HgR 2 and [HgL 2 ]2` were obtained.113 Oxygen- and sulfur-donor ligands The synthesis and characterisation including one X-ray crystal structure of four mercury derivatives of 1-phenyl-3-methyl-4-acyl-5-pyrazolone (L) RHgL (R\Me or Ph; acyl\acetyl benzoyl) has been described.114 The products from the reactions of HgX 2 (X\Cl or Br) with thione ligands L have been characterised by multinuclear NMR spectroscopy as [HgL 2 X 2 ].115 The crystal structure of [NMe 4 ][Hg 2 (SPh) 6 ] has revealed the presence of the tetrahedral [(PhS) 2 Hg(k-SPh) 2 Hg(SPh) 2 ]2~ anion in contrast to the known [NBu/ 4 ]` salt which contains trigonal [Hg(SPh) 3 ]~ species.Vibrational and NMR spectroscopic studies have been reported.116 The preparations of the bis(tetrathiafulvalenedithiolate) complexes [NMe 4 ] 2 [Hg(R 2 C 6 S 8 ) 2 ] (R\Et or Bu) and the corresponding oxidised neutral complex [Hg(Et 2 C 6 S 8 ) 2 ] together with the crystal structure of the anionic ethyl derivative have been reported.Cyclic voltammetry and ESR studies revealed little interaction between the two ligands.117 The crystal structures of [Hg(2-pvbt) 2 ]·0.5H 2 O and [HgM2,6-bis(pvbt)N2 ] have revealed two conformers with di§erent C–S–Hg–S–C angles in the former and a linear S–Hg–S unit and weak Hg· · ·OC interaction in the latter.118 Intramolecularly stabilised divalent mercury selenolates [Hg(SeR) 2 ] [R\2-Me 2 NCH 2 C 6 H 4 (S)-2- Me 2 NCHMeC 6 H 4 (R,S)-(Cp)Fe(2-Me 2 NCHMeC 5 H 3 ) (S,R)-CpFe(2-Me 2 - 124 I.B. Gorrell NCHMeC 5 H 3 )] have been prepared from the corresponding diselenides and elemental mercury. Although the environment of mercury was found to be four-co-ordinate in the solid state spectroscopic studies suggested di-co-ordination in solution.The iron-containing compounds decomposed on heating to give HgSe whereas the others were vapourised unchanged.119 Halogen-donor ligands A crystal structure of [Hg 4 P 2 Br 4 ] has revealed a tridymite-like three-dimensional net of almost linear mercury atoms and tetrahedral phosphorus atoms with tunnels crossing the net filled with columns of HgBr 5 trigonal bipyramids. Interatomic distances suggest [Hg 2 P] 2 [HgBr 4 ].120 The crystal structure of [Cs 2 (18-crown-6][HgI 4 ] has been reported.121 X-Ray analysis of [et] 8 [Hg 4 Cl 12 ]·2C 6 H 6 has revealed layers of centrosymmetric anions consisting of four trigonal HgCl 3 units with secondary Hg· · ·Cl bonds.122 Mercury–transition-metal complexes The reaction of [PPh 4 ] 2 [S 2 WS 2 HgCl 2 ] with acetone a§orded [PPh 4 ] 2 [S 2 WS 2 Hg(CH––CH 2 ) 2 ]·0.5Me 2 CO which on standing in a desiccator for 3–4 months transformed to [PPh 4 ] 2 [S 2 WS 2 Hg(C–– – CH) 2 ]·0.5MeCHO.123 The preparation and characterisation of [M(CO) 3M(g5-C 5 H 4 )Z([g5-C 5 H 4 )N(CO) 3 M]Hg [M\Cr Mo or W Z\C(O)CH 2 CH 2 C(O); M\Mo Z\CH 2 CH 2 OCH 2 CH 2 ] has been reported124 and the X-ray crystal structures of [MPt(diphos)(RNC)N2 Hg][PF 6 ] 2 [diphos\cis-PPh 2 CH––CHPPh 2 PR@2 (CH 2 )nPR@2 (R@\Bu5 n\2; R@\Ph n\3) R\mes xylyl] have been described.125 References 1 D.J. Burkey and T. P. Hanusa J. Organomet. 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ISSN:0260-1818    

DOI:10.1039/ic093117

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

10 Inorganic and Organometallic Polymers By IAN MANNERS Department of Chemistry University of Toronto 80 St. George St. Toronto M5S 1A1 Ontario Canada 1 Introduction Inorganic polymeric materials continue to attract attention as a result of their interesting and unusual properties and applications as speciality materials.1–4 This review focusses on developments in inorganic and organometallic polymer science published in 1996 and has a similar format to and follows on from the five previous articles in the series which cover the years 1991–1995.5–9 The first section of review covers new developments concerning well-established inorganic polymer systems namely the polysiloxanes polyphosphazenes and polysilanes.1–3 A brief introduction to each of these classes of inorganic polymer systems was included in the appropriate sections of the first article of this series.5 Recent developments concerning other polymers based on main-group elements and transition metals are discussed.4 As with previous articles in this series,5–9 the main emphasis is placed on polymers with inorganic elements within the main chain rather than in the side group structure.A review of inorganic polymer science which focusses mainly on new polymer systems prepared recently was published in 1996 and may also be of interest to readers.10 2 Polysiloxanes (silicones) polyphosphazenes and polysilanes Vancso and co-workers have established a route to well-defined liquid crystalline polysiloxanes with narrow polydispersities (PDI\1.2) via the anionic ring-opening polymerization of pentamethylvinylcyclotrisiloxane followed by the attachment of mesogens using a hydrosilylation strategy (Scheme 1).11 The resulting polymers showed very fast electrooptic switching times which is a vital consideration for many device applications.Other developments in the siloxane area include studies of block copolymers of poly(diethylsiloxane) with polystyrene which build regular phase separated structures in the solid state where the siloxane block exists as a mesophase.12 The controlled synthesis of polysiloxanes with organosulfur side groups has also been described in detail.13 Attention in the past year has focussed particularly on the new condensation route Royal Society of Chemistry–Annual Reports–Book A 129 O Si O Si O Si Me Me Me Me Me (ii) ButMe2SiCI Me3SiO Si Me Me O Si Me Me O Si Me (i) LiOSiMe3 n O Si Me Me But Me3SiO Si Me Me O Si Me Me O Si Me n O Si Me Me But Si O Si Me Me (CH2)m O Pt catalyst H Si Me Me O Si (CH2)m Me Me O CN CN Scheme 1 to polyphosphazenes which was reported by Manners and Allcock in 1995.The cationic polymerization of the phosphoranimine Cl 3 P–– NSiMe 3 has been shown to be a ‘living’ process and provides routes to polyphosphazenes with narrow polydispersities (Scheme 2).14 Samples of poly[bis(trifluoroethoxy)phosphazene] with molecular weights of Mn 5800–66 400 with PDIs of \1.25 were prepared. Species such as PCl 5 and SbCl 5 and Ph 3 C[PF 6 ] were found to function as initiators. In other developments studies of the molecular motion of phosphazene-bound non linear optical chromophores have been described by Allcock and Haw and studies of calcium-deficient hydroxyapatite–polyphosphazene composites have been described by Brown and Allcock.15,16 Further studies of polyphosphazene–polysiloxane hybrid materials and polyphosphazene solid electrolyte materials have also been reported.17,18 In addition gas permeation studies of poly(methylphenylphosphazene) 130 I. Manners have been reported by Wisian-Neilson.19 The same group has reported a route to poly(phospholenazene) a new type of phosphazene polymer.20 In the area of polysilanes studies of the energy and electron transfer distances in Langmuir–Blodgett films have been described and further studies of the synthesis and properties of dendritic polysilanes have been reported.21,22 3 Other polymer systems based on Main Group elements The design synthesis and development of new polymer systems containing Main Group elements in the polymer main chain continue to attract significant attention.Poly(thionylphosphazenes) which possess backbones of sulfur(VI) nitrogen and phosphorus atoms continue to be of interest. The synthesis of amino derivatives were reported in the past year (Scheme 3).23 These materials were shown to possess an atactic structure by 31P NMR spectroscopy. Scheme 3 The reactions of poly(thionylphosphazene) with aryloxides has previously been shown to give rise to materials in which substitution of halogens only occurs at phosphorus. Studies have been reported which show that the reactions of cyclic thionylphosphazenes display the same regioselectivity.24 Applications of poly(thionylphosphazenes) as matrices for phosphorescent sensors were also reported in 1996.25 Phosphorescence quenching has been used to provide measurements of oxygen di§usion in poly(n-butylaminothionylphosphazene) 1.26 This material was found to possess a very high permeability for oxygen making it ideal for use as a matrix in gas sensors.S N P N P N O NHBu NHBu NHBu NHBu NHBu n 1 Further significant developments have been reported in the last year in the area of polystannanes. Highly branched materials have been prepared via a dehydropolymerization/ rearrangement process.27 Whereas Ti and Zr metallocene complexes have previously been shown to a§ord linear polystannanes via dehydropolymerization of Bu/ 2 SnH 2 the RhI complex [RhH(CO)(PPh 3 ) 3 ] was found to a§ord either cyclic oligomers of polymers depending on the reaction conditions (Scheme 4).Moreover the dark yellow gum-like polymer formed 2 (M8 \50 240 PDI\1.43) was found to possess a branched structure by 119Sn NMR spectroscopy and by analysis of the cleavage products after treatment with I 2 followed by MgPhBr which included SnBuPh 3 as well as SnBu 2 Ph 2 . As a result of the branching the j.!9 in the 131 Inorganic and Organometallic Polymers Bun 2SnH2 [RhH(CO)(PPh3)3] Bun Sn Bun n 2 Scheme 4 UV/VIS spectrum of the material (in pentane) was 394 nm slightly red-shifted from that of linear poly(di-n-butylstannane) (j.!9 \378–380nm in the same solvent). The branched material was reported to possess greater stability to air-oxidation and light in the solid state than the linear polymer. The first successful and detailed report of polystannanes via Wurtz coupling in a refereed journal was reported in 1996.28 Poly(di-n-butylstannane) was prepared from the reaction of SnBu 2 Cl 2 with a sodium dispersion in toluene in the presence of 15- crown-5 at 60 °C in the dark (Scheme 5).The maximum yield of polymer was reached after 4 h when very high molecular weight materials was formed (Mn[106). Prolonged reaction gave rise to chain scission. The spectroscopic data were consistent with the earlier reports for the same polymer by Tilley and co-workers using the dehydrocoupling route. Bun 2SnCI2 Na Bun Sn Bun n Scheme 5 15–crown–5 Tilley and co-workers have now reported high molecular weight poly(diarylstannanes) by dehydrocoupling reactions.29 These materials were found to possess even smaller band gaps than their alkyl analogous.For example poly[bis(tert-butylphenyl) stannane] was isolated as an orange solid. Another exciting development in Main Group polymer chemistry involved the discovery of a demethanative coupling route to polygermanes.30 The reaction reported by Berry et al. involved the coupling of GeHMe 3 with the ruthenium catalyst [Ru(PMe 3 ) 4 (GeMe 3 ) 2 ] (Scheme 6). GeHMe3 [Ru(PMe3)4(GeMe3)2] Me Ge Me n Scheme 6 H H The polygermane formed was found to have a highly branched structure. The proposed mechanism for the formation of linear and branched chains in this reaction is shown in Schemes 7 and 8 below. In other areas further developments concerning the use of poly(borazylenes) as precursors to boron nitride ceramic fibres have been described.31 In addition further studies of poly(carbosilanes) with a variety of side groups have been reported by Interrante.32 Studies of materials with alkyl side groups with between four and six carbon atoms have been published by Frey.33 132 I.Manners GeMe3 Ru GeMe2GeMe2R Me Ru GeMe2 GeMe2GeMe2R GeMe3 Ru Ge Me Me GeMe2R Me Ru GeMe2GeMe2GeMe2R Ge Ru Me GeMe3 GeMe2R Me a-Me migration a-Me migration 1,3-Me migration linear branched Scheme 8 4 Polymers containing skeletal transition-metal atoms Macromolecules containing skeletal transition-metal atoms represent a continually growing area of research.4 133 Inorganic and Organometallic Polymers An interesting class of self-oscillating gels have been reported by Yoshida et al.34 These materials 3 which possess [Ru(bipy)] complexes in the side group structure undergo the Belousov–Zhabotinsky (BZ) reaction and exhibit spontaneous mechanical oscillations.CH2 CH C O NH CH CH3 CH3 CH2 CH2 CH2 CH C O NH CH2 NH C CH N N CH3 Ru N N N N O CH2 2+ x y 3 Further advances have also been reported concerning high molecular weight poly(ferrocenes) which are accessible via a ring-opening polymerization route. Full details of the ‘living’ anionic ring-opening polymerization of silicon-bridged [1]ferrocenophanes were published in 1996.35 This methodology allows access to materials with controlled molecular weight and architectures such as di- tri- and penta-block materials (see Scheme 9). ‘Living’ anionic polymerization of phosphorus-bridged [1]ferrocenophanes was also reported for the first time.36 This allows similar control of molecular weight and polymer architecture; block copolymers with other poly(ferrocenes) and also poly(siloxanes) were described.Manners and Geiger have reported the synthesis of linear oligo(ferrocenylsilanes) with between two and nine ferrocene units by anionic oligomerization methods.37 Detailed electrochemical studies of the resulting species have provided convincing evidence for the concept of initial oxidation at alternating iron atoms originally postulated for these materials. The structure of the pentamer in the solid state was obtained by single-crystal X-ray di§raction and provided insight into the likely conformations of the analogous high polymer in the solid state. Interesting studies of n-hexyl-substituted oligo(ferrocenylenes) and low molecular weight polymers have also been reported by Nishihara et al.38 O’Hare and co-workers have reported a molecular mechanics study of oligomeric models of high molecular weight poly(ferrocenylsilanes).39 The calculations utilized the new generalized ESFF force field and showed that the neutral molecules are conformationally flexible with the lowest energy configurations having close contacts between the electropositive iron atoms and the electronegative cyclopentadienyl ligands of their neighbors.For the isolated molecules and conformations are governed by intramolecular interactions whereas in the solid state intermolecular interactions are more important. In another development spirocyclic ferrocenophanes have been used as novel crosslinking agents for poly(ferrocenes) prepared via ring-opening polymerization.40 Full details of the properties of poly(ferrocenylsilanes) with methylated Cp ligands and 134 I.Manners 135 Inorganic and Organometallic Polymers their charge transfer complexes with electron acceptors have also been described.41 Detailed studies of a series of poly(ferrocenylgermanes) were described in 1996.42 Further developments concerning the transition-metal-catalyzed ROP of siliconbridged [1]ferrocenophanes which was discovered in 1995 have been reported in the past year. Manners and Foucher reported that whereas [1]silaferrocenophane containing Si–Cl bonds undergoes thermal ring-opening polymerization at more elevated temperatures transition-metal-catalyzed ring-opening polymerization occurs at room temperature in the presence of ca. 1 mol% of PtCl 2 (Scheme 10).43 The resulting poly(ferrocenylsilanes) were found to be tunable and halide replacement yielded polymers with di§erent side groups.Fe Si Me CI trace PtCI2 Fe Si Me CI n Scheme 10 Transition-metal-catalyzed copolymerization of silicon-bridged [1]ferrocenophanes with silacyclobutanes was also reported in 1996 (Scheme 11).44 The first step in the transition-metal-catalyzed ring-opening polymerization reactions of silicon-bridged [1]ferrocenophanes is believed to involve insertion into the strained ipso-carbon-bridging-atom bond. The first example of this type of reaction has been reported and involves the reaction of [Pt(PEt 3 ) 3 ] with a silicon-bridged [1]ferrocenophane (Scheme 12).45 Fe Si Me Me trace PtCI2 Fe Si Me Me Si n Scheme 11 Si Me Me + Me Me CH2 A review concerning the mechanisms for the thermal and transition-metal-catalyzed ring-opening polymerization reactions of [1]ferrocenophanes was published in the past year.46 A series of novel dendritic systems has been reported in the past year.Cuadrado and co-workers have recently reported the synthesis of a series of novel ferrocenyl-functionalized poly(propylenimine) dendrimers 4 which undergo oxidative precipitation 136 I. Manners Fe Si Me Me Pt(PEt3)3 Fe Pt PEt3 Scheme 12 PEt3 Si Me Me –PEt3 onto electrode surfaces.47 Moss has described large organoruthenium dendrimers with 48 ruthenium atoms from ‘dendritic wedge’ precursors such as 5.48 Constable and co-workers have described a convergent approach to metallocentric metallodendrimers 6 containing up to seven metal atoms with poly(pyridyl) ligand 137 Inorganic and Organometallic Polymers O O O O X O O O M O M OC OC OC OC O O O M OC OC O O M CO OC M O O O M OC OC CO CO O M OC OC O O M CO CO M OC CO O O O M OC OC O O M CO OC M O O O M OC OC CO CO O M OC OC O O M CO CO M OC CO M = Ru 5 environments.49 The same research group has also described convergent routes to organoruthenium dendrimers with organic centres.50 Peng and Yu have reported the synthesis of conjugated polymers 7 containing ionic ruthenium bipyridyl complexes in the main chain using the Heck reaction.51 The resulting polymers possess a delocalized backbone and exhibit photoconductive properties.Rigid-rod polymers containing metals in the backbone continue to attract attention. 138 I. Manners N N M N N N N O O O O O O O N N N Ru N N N O N N N Ru N N N O O N N N Ru N N N N N N Ru N N N O N N N Ru N N N O N N N Ru N N N 14+M = Fe 14+M = Co 6 (M = Fe or Co) 14+ OR N N N N RO Ru N N OR OC6H13 C6H13O RO xn Polymer I x = 0 y = 1 Polymer II x = 0.1 y = 0.9 Polymer III x = 1 y = 0 [h] = 0.48 dI g–1 [h] = 0.58 dI g–1 [h] = 0.60 dI g–1 2X– 7 yn Butler52 has reported a vibrational spectroscopic investigation of platinum acetylide polymers and Puddephatt53 has reported the synthesis of oligomers and polymers with Pt–Pt bonds in the main chain.Endo and co-workers have described the 139 Inorganic and Organometallic Polymers synthesis and characterization of liquid crystalline polyesters with cyclobutadienecobalt moieties in the backbone.54 Further interesting work has been reported concerning polymers with metallacyclopentadiene units in the main chain.Nishihara and co-workers described full details of the synthesis and properties of a range of poly(cobaltacyclopentadienes) which were prepared via the reactions of conjugated diacetylenes with [Co(PPh 3 ) 2 (g-C 5 RH 4 )].55 In the cases where R\H the polymers were insoluble but soluble materials were prepared where R\n-hexyl with values ofM8 up to 104. The UV/VIS band edge was found to shift on moving from the monomer to the dimer and on to the polymer; the optical band gap values for the polymers were 2.1–2.3 eV which are similar to the value for poly(thiophene) (2.0 eV). Photoconductivity was detected for the polymer (g-C 5 RH 4 )CoC 4 Me 4 C 6 H 4 ]n where the photocurrent was four times greater than in the dark. Further significant developments in the area of well characterized lanthanide-based polymers have also been reported by Archer and co-workers.56 The first linear luminescent polymers with europium(III) in the backbone have been synthesized and characterized.Mixed metal Y and Eu polymers were also prepared and possessed enhanced emission properties over the homopolymers. References 1 Silicon-Based Polymer Science eds. J. M. Zeigler and F. W.G. Fearon Advances in Chemistry 224 American Chemical Society Washington D.C. 1990. 2 Siloxane Polymers eds. J. A. Semlyen and S. J. Clarson Prentice Hall Englewood Cli§s NJ 1991. 3 J.E. Mark H. R. Allcock and R. West Inorganic Polymers Prentice Hall Englewood Cli§s NJ 1992. 4 I. Manners Chem. Br. 1996 32 46. 5 I. Manners Ann. Rep. Prog. Chem. Sect. A Inorg. Chem. 1991 88 77. 6 I. Manners Ann. Rep. Prog.Chem. Sect. A Inorg. Chem. 1992 89 93. 7 I. Manners Ann. Rep. Prog. Chem. Sect. A Inorg. Chem. 1993 90 103. 8 I. Manners Ann. Rep. Prog. Chem. Sect. A Inorg. Chem. 1994 91 131. 9 I. Manners Ann. Rep. Prog. Chem. Sect. A Inorg. Chem. 1995 92 127. 10 I. Manners Angew. Chem. Int. Ed. Engl. 1996 35 1602. 11 M.A. Hempenius R. G. H. Lammertink and G. J. Vancso Macromol. Rapid Commun. 1996 17 299. 12 A. Molenberg S. Sheiko and M. Moller Macromolecules 1996 29 3397. 13 K. Rozga-Wijas J. Chojnowski T. Zundel and S. Boileau Macromolecules 1996 29 2711. 14 H. R. Allcock C. C. Crane C. T. Morrissey J. M. Nelson S. D. Reeves C. H. Honeyman and I. Manners Macromolecules 1996 29 7740. 15 H. R. Allcock C. G. Cameron T. W. Skloss S. Taylor-Meyers and J. F. Haw Macromolecules 1996 29 233. 16 C. S.Reed K. S. TenHuisen P. W. Brown and H. R. Allcock Chem. Mater. 1996 8 440. 17 H. R. Allcock S. E. Kuharcik and C. J. Nelson Macromolecules 1996 29 3686. 18 H. R. Allcock S. E. Kuharcik C. S. Reed and M. E. Napierala Macromolecules 1996 29 3384. 19 P. Wisian-Neilson and G.-F. Xu Macromolecules 1996 29 3457. 20 J. A. Gruneich and P. Wisian-Neilson Macromolecules 1996 29 5511. 21 R. Kani Y. Nakano Y. Majima and S. Hayase Macromolecules 1996 29 4187. 22 J. B. Lambert J. L. Pflug and J. M. Denari Organometallics 1996 15 615. 23 Y. Ni P. Park M. Liang J. Massey C. Waddling and I. Manners Macromolecules 1996 29 3401. 24 D. P. Gates P. Park M. Liang M. Edwards C. Angelakos L. M. Liable-Sands A. L. Rheingold and I. Manners Inorg. Chem. 1996 35 4301. 25 Zh. Pang X. Gu A. Yekta Z. Masoumi J.B. Coll M. A. Winnik and I. Manners Adv. Mater. 1996 8, 768. 26 Z. Masoumi V. Stoeva A. Yekta Zh. Pang I. Manners and M.A. Winnik Chem. Phys. Lett. 1996 261 551. 27 J. R. Babcock and L. R. Sita J. Am. Chem. Soc. 1996 118 12 481. 28 N. Devylder M. Hill K. C. Molloy and G. J. Price Chem. Commun. 1996 711. 29 V. Lu and T. D. Tilley Macromolecules 1996 29 5763. 30 J. A. Reichl C. M. Popo§ L. A. Gallagher E. E. Remsen and D. H. Berry J. Am. Chem. Soc. 1996 118 9430. 31 T. Wideman and L. G. Sneddon Chem. Mater. 1996 8 3. 32 I. L. Rushkin and L. V. Interrante Macromolecules 1996 29 3123. 140 I. Manners 33 F. Koopmann and H. Frey Macromolecules 1996 29 3701. 34 R. R. Yoshida T. Takahashi T. Yamaguchi and H. Ichijo Adv. Mater. 1997 9 175. 35 Y. Ni R. Rulkens and I. Manners J. Am. Chem.Soc. 1996 118 4102. 36 C. H. Honeyman T. J. Peckham J. A. Massey and I. Manners Chem. Commun. 1996 2589. 37 R. Rulkens A. J. Lough I. Manners S. H. R. Lovelace C. Grant and W. E. Geiger J. Am. Chem. Soc. 1996 118 12 683. 38 T. Hirao M. Kurashima K. Aramaki and H. Nishihara J. Chem. Soc. Dalton Trans. 1996 2929. 39 S. Barlow A. L. Rohl S. Shi C.M. Freeman and D. O’Hare J. Am. Chem. Soc. 1996 118 7578. 40 M. Maclachlan A. J. Lough and I. Manners Macromolecules 1996 29 8562. 41 J. K. Pudelski D. A. Foucher C. H. Honeyman P. M. Macdonald I. Manners S. Barlow and D. O’Hare Macromolecules 1996 29 1894. 42 T. J. Peckham J. A. Massey M. Edwards I. Manners and D. A. Foucher Macromolecules 1996 29 2396. 43 D. L. Zechel K. C. Hultzsch R. Rulkens D. Balaishis Y. Ni J. K. Pudelski A. J. Lough I.Manners and D. A. Foucher Organometallics 1996 15 1972. 44 J. B. Sheridan P. G. Elipe and I. Manners Macromol. Rapid Commun. 1996 17 319. 45 J. B. Sheridan A. J. Lough and I. Manners Organometallics 1996 15 2195. 46 I. Manners Polyhedron 1996 15 4311. 47 I. Cuadrado M. Mora� n C.M. Casado B. Alonso F. Lobete B. Garci� a M. Ibisate and J. Losada Organometallics 1996 15 5278. 48 Y.-H. Liao and J. R. Moss Organometallics 1996 15 4307. 49 E. C. Constable and P. Harverson Chem. Commun. 1996 33. 50 E. C. Constable P. Harverson and M. Oberholzer Chem. Commun. 1996 1821. 51 Z. Peng and Y. Lu J. Am. Chem. Soc. 1996 118 3777. 52 R. D. Markwell I. S. Butler A. K. Kakkar M.S. Kahn Z. H. Al-Zakwani and J. Lewis Organometallics 1996 15 2331. 53 M.J. Irwin G. Jia J. J. Vittal and R. J. Puddephatt Organometallics 1996 15 5321. 54 I. L. Rozhanskii I. Tomita and T. Endo Macromolecules 1997 30 1222. 55 T. Shimura A. Ohkubo N. Matsuda I. Matsuoka K. Aramaki and H. Nishihara Chem. Mater. 1996 8 1307. 56 H. Chen and R. D. Archer Macromolecules 1996 29 1957. 141 Inorganic and Organometallic Poly

ISSN:0260-1818    

DOI:10.1039/ic093129

出版商:RSC    

年代:1997

数据来源: RSC