摘要:

Introduction 1 4 F. J. Berrya and N. G. Connellyb aDepartment of Chemistry The Open University Milton Keynes UK MK7 6AA bSchool of Chemistry University of Bristol Cantock’s Close Bristol UK BS8 1TS Volume 95 of Annual Reports Section A follows the format of previous years in covering developments in inorganic chemistry both by Group and by subjects of topical interest. This year an additional chapter covers the important and expanding area of Inorganic Pharmaceuticals; in Volume 96 the chapter on Si Ge Sn and Pb will cover both the 1998 and 1999 literature. Developments in transition metal chemistry include the synthesis of the first d0 4 4 alkyne complexes (of tantalum) the first stable CuII complex with an S donor set a unique and structurally characterised alkene-containing redox pair (of RuII and RuIII) species with l -PF and l -PO bridges and a variety of distibine derivatives.Particularly remarkable given the rarity of stable mononuclear Rh(II) complexes is the characterisation of the stable cation [RhIIH(CO)(PPh 3 ) 3 ]` formed simply by the oneelectron oxidation of the well known neutral complex [RhIH(CO)(PPh 3 ) 3 ]. While these advances might by conveniently categorised under the headings of organometallic and co-ordination chemistry the blurring of such traditional borderlines continues to lead to increasingly exciting discoveries. For example the synthesis of compounds in which an organometallic fragment is positioned in the larger opening of a calix[4]- arene cavity may lead to the promotion of sterically constrained metal-centred reactions and models based on [Fe(CN) (CO)Cp]~ a classically simple organometallic complex have been used to interpret the structure and IR spectrum of the iron centre of Ni/Fe hydrogenases.Also striking is the rapidly increasing use of density functional theory to underpin so many areas of molecular transition metal chemistry. 2 In Group 13 chemistry the synergic interaction between Al3` and NO has been observed in vivo and its possible influence on Alzheimers and other age-related neurological disorders are likely to be the subject of further investigation. Reports of the first tetrahedral aluminium clusters the stability of the Ga–Ga bond to protic reagents the characterisation of In 4 O 4 [C(SiMe 3 ) 3 ] 4 which completes the tetramer series In 4 X 4 R 4 and the huge Pt195–Tl205 nuclear spin–spin coupling constant for [(NC) 5 Pt–Tl(CN)] of 71,060 Hz (which is the largest coupling constant observed between two nuclei) illustrates the diversity of main group element chemistry.The development of new multidentate ligand systems particularly chiral derivatives containing mixed nitrogen and phosphorus donor atoms demonstrates another major 1 Annu. Rep. Prog. Chem. Sect. A 1999 95 1–2 area of interest in Group 15 chemistry. An undoubted highlight of work on Group 16 elements is the observation that stirring energy can be directly converted to chemical energy when Cu 2 O acts as a mediator/catalyst for the decomposition of water to oxygen and hydrogen.Although the mechanism is not clear it seems safe to assume that we have not heard the last of this reaction. Some other fundamentally important results include the observation that c irradiation of thiosulfate acts as a source of sulfide and the characterisation of the Te 6 N 8 core in [Te 6 N 8 TeCl 4 ]. The generation of the first Xe–S bond (the first noble gas bond to a second row element) albeit in a low temperature matrix is notable. In solid state systems we have seen the synthesis and characterisation by advanced di§raction methods of many novel zeolite-like phases such as the seven- and ninering-containing aluminosilicate denoted SSZ-23. Work on other open-framework phases templated by organic species continues apace.UFOs (organically-templated uranium fluorides) have been observed and the application of combinatorial chemistry to the solid state area has been impressively exemplified by the synthesis and characterisation of SrCe 2 O 4 . Two spectacular minerals; the aluminosilicate zeolite tscho� rtnerite containing a 96-membered cage and synthetic taranakite a layered potassium aluminium phosphate hydrate with an [95Å crystallographic axis remind us of the unlimited structural variety of the natural world. The characterisation of C 36 the smallest of all carbon cage molecules together with the synthesis and characterisation of a large range of ionic fullerides and improved methods for the preparation of carbon nanotubes which are likely to play an important role in the development of new technology illustrate impressive advancements in fullerene research. Finally in this volume we say farewell to one of our Scientific Editors–Professor Neil Connelly. Neil has been at the centre of the regeneration of Annual Reports Section A which has occurred over the past eight years and it is proper that these pages record the indebtedness of the inorganic chemistry community to his dedication and enthusiasm. With Neil’s departure we shall welcome Dr Chris Jones as a Scientific Editor of Volume 96 in the knowledge that Annual Reports Section A continues to demonstrate the health and vibrancy of all areas of inorganic chemistry. 2 Annu. Rep. Prog. Chem. Sect. A 1999 95 1&ndash

ISSN:0260-1818    

DOI:10.1039/IC095001

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

2 Alkali and alkaline-earth metals I. B. Gorrell Chemical and Forensic Sciences, University of Bradford, Bradford, UK BD7 1DP 1 Introduction This report follows the pattern set in previous years with the emphasis on the organometallic and co-ordination chemistry of Groups 1 and 2 published in 1998. In general, compounds with polydentate or macrocyclic ligands or those of more interest to solid-state chemists, which are covered elsewhere in this volume, have been omitted.As usual, lithium–nitrogen compounds dominate the field but interest in the heavier elements of both groups is increasing. A timely review of recent developments in the organometallic chemistry of the heavier alkali metals has appeared;1 there have also been reviews on the chemistry of cyclopentadienyl alkali metal derivatives2 and the chemistry of alkaline-earth metal bis[bis(trialkylsilyl)amides].3 A summary of work concerning well defined lithium –sodium and lithium–sodium–potassium compounds which can exhibit reactivity superior to that of conventional organolithium reagents has been published, and a new class of lithium–magnesium amide, based around an oxo or peroxo core, presented.4 The chemistry of a-heteroatom-substituted 1-alkenyllithium reagents, initially postulated to be short-lived intermediates in a-eliminations, has also been reviewed.Such species can act as nucleophilic carbanions or as electrophilic carbenoids, depending on the heteroatom substituent.5 The first thermally stable and structurally characterized neutral adducts of isonitriles with some Group 1 and 2 metal complexes have been described including the preparation and crystal structures of [LiMN(R)C(Ph)NC(Ph)–– CR 2N(CNPh)] 2 , [LiNR 2 (CNPh)] 2 , [Mg(CHR 2 ) 2 (CNC 6 H 3 Me 2 -2,6) 2 ] and [Mg(CHR 2 )(l- Br)(CNBu5)] 2 (R\SiMe 3 ).The magnesium compounds are especially noteworthy since they do not isomerise to give the insertion products.6 An in-depth X-ray di§raction study of a series of hydrated 2- and 4-nitrophenoxides of the Group 1 and 2 metals, together with their complexes with the parent phenols, has been published. In general, the lithium and magnesium compounds are discrete molecules whereas the heavier metals form polymeric species.Stacking of the aromatic rings is a persistent theme.7 Chiral lithium, potassium and barium metallocene complexes with a dialkylphosphonium bridge have been prepared.Solution NMR studies and X-ray crystal- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 3lography of [Ba(C 5 H 2 Me-2-Bu5-4) 2 PMe 2 (thf) 3 ][BPh 4 ] and [K(C 5 H 2 Me-2-Bu5- 4) 2 PMe 2 ] show that these compounds form as racemic diastereomers.8 The D([)- mandelate salts, [M(C 8 H 7 O 3 )] (M\Li, Na, K, NH 4 ) and [M(C 8 H 7 O 3 ) 2 (H 2 O)n] (n\0,M\Sr; n\1,M\Ca, Ba; n\2,M\Mg) have been prepared from D([)- mandelic acid and the appropriate hydroxide in water.The X-ray structure of the magnesium complex revealed distorted octahedral geometry at the metal centre and cis-water molecules.9 Several radical anion and dianion alkali metal salts of perylene have been described.All of the radical anion species, [C 20 H 12 ]·~[M` 40-7] and [C 20 H 12 ·~· · ·C 20 H 12 ][M` 40-7] crystallise as solvent-separated ion pairs whereas the dianionic salts, [C 20 H 12 2~(M` 40-7) 2 ] and [C 20 H 12 2~][M` 40-7] 2 strongly depend on optimum solvation of the counter ion for their stability. Calculations were also presented.10 Reaction of trimethylsilyl-substituted phosphanes with alkali metal butoxides has led to the isolation of a series of phosphanide compounds.The crystal structures of [M(thf)P(SiMe 3 ) 2 ] = revealed ladder frameworks with five-co-ordinate phosphorus and three-co-ordinate metal centres.11 A theoretical study of the interaction of alkali metal cations with glycine in the gas phase has been reported.12 A series of new Me 3 SiCH 2 –, (Me 3 Si) 2 CH–, Me2 Bu5Si– and Me 3 Si-substituted cyclopentadienes and their complexes with alkali metals (Li, Na, K) has been presented.13 The crystal structures of a series of adducts of 1,3,4,5-tetramethylimidazol-2-ylidene with MCp 2 * (M\Mg, Ca, Sr, Ba) have been published; the shortest M–C bond is to the former carbene centre but the di§erence between this distance and theM–Cp distance decreases as the atomic number of the metal increases.14 Reaction of Li[C(SiMe 3 )(PMe 2 ) 2 ] with MCl 2 in thf yields M[C(SiMe 3 )(PMe 2 ) 2 ] 2 ·n(thf) (M\Be, n\0; M\Mg, n\2; M\Ca, n\3); with an additional equivalent of the lithium compound the magnesium species yielded the MMg[C(SiMe 3 )(PMe 2 ) 2 ] 3N~ anion.15 2 Lithium Carbon-donor ligands Highly coloured paramagnetic lithium 5,5@- and sodium 6,6@-naphthalenide complexes have been prepared on polymer or oxide supports and characterized by CP MAS, PES, EPR and FTIR.Solutions of organoalkali reagents were obtained, free from arene by-products, by reaction of these supported complexes with organic halides, nitriles and phosphates.16 Electronic structure calculations have provided strong evidence for ate complexes being the key intermediates in lithium (magnesium halide) –halogen (metalloid) exchange reactions.17 Reaction of [Al(NHBu5) 3 ] 2 with LiBu/ generates a complex in which a dimeric LiBu/ fragment is trapped by [Li 3 Al 2 (NHBu5) 3 (NBu5) 3 ].18 Treatment of Bu 3 SnCH 2 PPh 2 with LiBu/ yields [Li(CH 2 PPh 2 )(thf)] = ; X-ray di§raction revealed chair Li 2 C 2 P 2 rings and planar Li 2 C 2 rings arranged alternately.19 Recrystallisation of [LiCH 2 NMe 2 ] from hexane– thf a§orded [LiCH 2 NMe 2 (thf)] 4 the crystal structure of which revealed an open Li 4 tetrahedron with two tetrahedral (CNO 2 ) and two pentaco-ordinate (LiNC 3 ) lithium centres.20 The doubly lithiated aminals [LiCH 2 NR]CH 2 (R\Me, Pr*) have been prepared as insoluble powders which dissolved in organic solvents in the presence of pmdien–thf or tmen–thf so that NMR spectra could be recorded.Ligand transfer Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 4reactions to zirconium were also reported.21 NMR studies indicate that triple ions form in thf–hmpa solutions of a variety of localized lithiated carbanions such as aryllithiums and sulfur- and silicon-substituted alkyllithiums.22 Within the context of the 1,2-addition of LiR to ArCOCF 3 mediated by LiOR occurring with a 50: 1 enantioselectivity, low temperature 6Li and 13C NMR spectroscopies have revealed lithium cyclopropylacetylide (LiR1) to be a dimer–tetramer mixture in thf and 1(R),2(S)-C 4 H 8 NCHMeCH(Ph)OLi (LiOR2) to be a complex mixture of oligomers.In thf, LiR1 and LiOR2 a§orded stoichiometry dependent mixtures of 3: 1, 2: 2 and 1: 3 mixed tetramers.23 A family of unsolvated lithiosilanes have been prepared and characterized as oligomers in non-polar solvents but monomeric in diethyl ether or thf; Li NMR provided a useful structural probe.24 The structures of MCCH (M\Li, Na, K) have been determined using millimetre/submillimetre spectroscopy.25 The transition- metal-like behaviour of lithium has been examined by means of ab initio calculations on the interactions of LiR (R\H, Me, Ph) with benzene and CO.26 1,1-Dilithio-2,2-diphenylethene undergoes rearrangement into (E)-1-lithio-2-(2- lithiophenyl)-2-phenylethene at temperatures above [100 °C; the (Z)-compound forms from the (E)-compound above [25 °C.27 1-Iodo-1-lithioethene has been prepared from 1-iodoethene and LiNPr* 2 in thf and can be trapped by electrophiles.Ab initio calculations suggest that the species is monomeric in thf and that hydride migration and a-elimination of LiI occur in a concerted process.28 Lithiation of 1,2-diphenyl-1,2-bis(trimethylsilyl)ethene using the metal in thf gives the dilithioethane derivative;NMRstudies show high quinoid character in the phenyl rings and relatively mobile cations.29 In the solid state the lithium salt of the octasilyl[4]radialene dianion is a contact ion pair with the metal ions situated above and below the four-membered ring.This structure is maintained in toluene but in thf one lithium dissociates and there is evidence for a ‘lithium walk’ on the eight-centred ten-electron system.30 A mechanism for the reduction of diphenylacetylene by metallic lithium has been proposed.31 The syntheses and structures of [Li 2 (tmen)(g5-C 5 H 4 SiMe 2 CHSiMe 3 )] 2 , a centrosymmetric dimer, [Li 4 (tmen)(g5-C 5 H 4 SiMe 2 )MNC(Bu5)CHSiMe 3N2 ], which contains four di§erent lithium environments32 and [Li(dme)] 2 [C 8 H 6 (SiMe 3 ) 2 -1,4] in which the two lithiums are coordinated to the dianion in a g3-allyl-like fashion33 have been reported.The crystal structure of fluorenyllithium revealed dimers in which the two metal centres are sandwiched between two six-membered rings;34 in the ether complex the metal interacts with the anion in a g2-fashion and this is the optimum structure from quantum chemical methods.35 The preparation and crystal structure of the dilithium salt of hexasilylfulvene have been reported; one of the lithium cations is located above the centre of the five-membered ring whereas the other is bonded to the two carbon atoms which are common to the six-membered rings.This structure persists in solution.36 The preparation and X-ray structure of g3-N-Boc-N-(pmethoxyphenyl)- 3-phenylallyllithium·([)-sparteine have been described together with its use for enantioenrichment.37 The solid state structure of unsolvated, base-free phenyllithium has been determined using synchrotron powder di§raction.The molecules form dimers which are linked to adjacent Li 2 Ph 2 units forming a polymeric ladder structure; the Li 2 C 2 rings are planar and the p-electrons of the phenyl rings interact with the metal centres of neighbouring units.38 The compound forms a mixture of dimers and tetramers in diethyl ether; Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 5complete conversion to dimeric solvates is achieved by addition of thf, dioxalane, dme or tmen but with pmdien in diethyl ether, a monomer is obtained. In thf, LiPh is a mixture of monomers and dimers; addition of tmen forms a series of complexes but the monomer/dimer ratio is una§ected.The e§ect of other donors such as hexamethyltriethylenetetramine, dimethylpropylene urea, 12-crown-4 ether and hmpa were also studied; all increase the reactivity of LiPh in thf.39 Ab initio calculations have been carried out on the lithium and sodium salts of doubly deprotonated benzene and the bridged ortho dianions were found to be remarkably stable (LiPh was found to be more acidic than benzene) and, indeed, ions corresponding to these species have been observed in electrospray mass spectrometry. 40 Nitrogen- and phosphorus-donor ligands The preparation and X-ray structure of [LiMgMN(SiMe 3 ) 2N3 ] have been reported; a near-planar NMgNLi ring is present with trigonal planar (N 3 ) magnesium and tetrahedral (N 2 C 2 ) lithium due to two additional C–Li interactions with the bridging N(SiMe 3 ) 2 groups. In the presence of trace amounts of oxygen [Li 2 Mg 2MN(SiMe 3 ) 2N4 (O 2 )x(O)y] crystallises from solution and X-ray crystallography showed that the compound with x\0.715(7) and y\0.285(7) is the major component.The four indistinguishable metal centres are in a square planar arrangement with side-on co-ordination to the peroxide and bonded to two nitrogens in an eightmembered ring. With PhCN, [MPhC(NSiMe 3 ) 2N4 Li 4 Mg(O)] is obtained; its structure is based on a trigonal bipyramidal Li 4 MgOcore at the centre of which lies a l5 -oxygen atom.41 The compounds [Li 2 Mg 2 (O)MNCMe 2 CH 2 CH 2 CH 2 CMe 2N4 ] and [Na 2 Mg 2 (O 2 )x(O)yMN(SiMe 3 )N4 ] (x[32%, y[68%) have been prepared either by bubbling oxygen through the amine before reaction or placing a calcium chloride drying tube on the vessel containing the oxygen-free compounds.Their structures are similar to the LiMg peroxide compound described above.42 Rare examples of crystallographically characterized infinite one-dimensional ladders in lithium amide chemistry have been provided by [Li(NHCH 2 CH 2 NH 2 )], which contains double edgesharing LiN 4 tetrahedra,43 and the hemi-benzylamine complex of lithium benzylamide which possesses an infinite, twisted ladder of fused Li 2 N 2 rings; only one edge of the ladder is solvated with benzylamine molecules.44 Deprotonation of N,N-dimethyl-N@- Me2N N N Me2N Li Li(OEt2) SiMe3 SiMe3 1 trimethylsilylethane-1,2-diamine (HL) with LiBu/ yielded LiL in hexane but [LiL 2 Li(OEt 2 )] 1 in diethyl ether.The complex [LiLLiClLiL(thf)] 2 was formed as a side-product of the reaction of [LiL(thf)n] with [LiCl 3 (thf) 2 ] in thf. In the solid state a LiCl unit is bonded between LiL and LiL(thf) units generating a three-rung ladder which is further connected, by Li–Cl bonds, to a second LiLLiCl(thf) unit; the structure contains two rare Li 4 Cl moieties.45 The preparation and structure of [(tmen)Li(l- NPh 2 ) 2 LiClMl-Li(tmen)N2 NPh 2 ] have been published.46 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 6Lithiation of 1,8-bis(trimethylsilylamino)naphthalene in thf yielded [C 10 H 6MN[Li(thf) 2 ]SiMe 3N2 ] which, on stirring for ca. 15 h in dioxane or toluene, lost three molecules of thf to give [C 10 H 6MN[Li(thf)]SiMe 3NMN(Li)SiMe 3N] 2 in which the unsolvated cation is g3-bonded to one of the arene rings.47 The crystal structure of [Li(NPh)(NHPh)SiMe 2 (OEt 2 )] 2 , prepared from Me 2 Si(NHPh) 2 and LiBu/ in diethyl ether, revealed a centrosymmetric molecule based on a Li 2 N 2 ring.48 Treatment of the hydridosilylamines, NHR@SiR 2 H (R@\SiMe 3 ; R\Pr*, Bu5, Ph; R@\R\Bu5) with LiBu/ a§ords the hydridosilylamides, R 2 HSiN(Li)R@.These are dimeric in the solid state and possess a planar Li 2 N 2 ring with significant SiH · · ·Li and CH 3 · · ·Li interactions.49 New derivatives of general formula Li 2 [XMe 2 SiNSiMe 2 X] 2 (X\Ph, NMe 2 , NEt 2 , NHPr*, OPh, OSiMe 3 , C 4 H 3 O, C 4 H 3 S) have been synthesised and characterized. All possess a polycyclic arrangement with a central Li 2 N 2 ring to which four similar LiNSiY rings are fused along a common LiN edge (Y can be either a C atom of a p-system, N or O).These compounds appear to be dimeric in benzene but there is evidence of dynamic behaviour.50 X-Ray di§raction shows that Bu5N(Li)CH––CH(Li)NBu5 is an unsymmetrical dimer.51 The preparation of [Li 3 (thf) 3 N(CH 2 CH 2 NSiBu5Me 2 ) 3 ] has been published; distillation gave the base-free compound while cooling a§orded the bis-thf compound which was shown to be dimeric in the solid state with two Li 2 N 3 units each linked via Li–N bonds to a central Li 2 N 2 moiety.52 The thf adduct of lithiated 2,5-di(tert-butyl)pyrrolide is monomeric in the solid state and in solution.The three-co-ordinate metal is involved in agostic interactions with a methyl group from each Bu5 group.53 The competition between solvent thf and polyamine ligands for co-ordination sites around lithium has been studied by probing the solution structure of [6Li]-a-(phenylthio) benzyllithium using 1H–6Li HOESY.In most cases polyamine complexes, in the form of contact- and separated-ion pairs, are obtained and the amines bind more strongly when their nitrogen content is high.54 NMR (6Li and 15N) spectroscopic studies show that hexane solutions of LiNPr* 2 containing \1 equivalent of pmdien per lithium contain a mixture of unsolvated LiNPr* 2 oligomers, monosolvated open dimers and monosolvated monomers. With[1 equivalent of pmdien, monomers are the dominant species.Addition of pmdien to LiNPr* 2 in toluene gives open dimers at low pmdien concentrations and a mixture of LiNPr* 2 monomer and LiCH 2 Ph (via toluene deprotonation) at high pmdien concentrations. The results were compared to previous investigations of LiNPr* 2 with tmen and trans-N,N,N@,N@-tetramethylcyclohexanediamine. The reactivity of the LiNPr* 2 solutions was probed by studying the dehydrohalogenation of (^)-exo-2-bromonorbornane; all exhibited similar reactivity. 55 The binding of diamines to n-butyllithium dimers has been investigated using NMR (6Li and 13C) spectroscopies. Highly ligand-dependent solvation energies and correlated solvation e§ects were observed.56 The lithium salt of carbazole is a contact ion pair in thf whereas the caesium salt is a mixture of monomers and dimers; the monomers form a 1: 1 complex CsCb·CbH.57 Lithiation of 4H-imidazoles, using LiH, a§ords the stable delocalized anions.Surprisingly, X-ray di§raction studies revealed a coordinated water molecule and PM3 calculations predicted an increase in stability as diethyl ether ligands are substituted by water.58 Computational studies on lithium (2-methoxy-(R)-1-phenylethyl-(S)-1-phenylethyl)amide, using a solid state structure as reference showed that there are only small di§erences between X-ray, ab initio and PM3 structures.The distances from these structures can be used for the calculation of Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 7Li–H distances using Li,H NOE data. The solution structure of the thf adduct was found to be similar to the calculated and X-ray structures.59 The first example of a lithiated diazomethane, M[Me 3 SiC(Li)N 2 ] 2 ·3thfN= , has been reported.The repeat unit is tetrameric with two mono- and two bis-thf-complexed molecules. The former associate to form a central Li 2 C 2 ring; the latter which are terminally attached to the metal centres of this ring by N· · · Li contacts are also each lithiated at carbon. Further N· · · Li contacts cause polymerisation of these units.The structure is in marked contrast to that of the compound obtained when the lithiation is carried out in ether (see Ann. Rep. Prog. Chem., Sect. A, 1994, 91, 7). These results can explain the lower reactivity of lithiated diazomethanes in diethyl ether.60 Lithiation of 4-methyl-1,5-diphenyl-1,2-diazapenta-2,4-diene in diethyl ether yielded [(PhNLiNCHCMeCHPh) ·Et 2 O] 3 in which the cations are g1-co-ordinated to the nitrogen atoms of two W-shaped diazapentadienyl units as well as one diethyl ether molecule.61 The heteroatom assisted lithiation of 1,3-bis[1-(dimethylamino)ethyl]benzene with LiBu/ a§orded 2,6-bis[1-(dimethylamino)ethyl]phenyllithium. X-Ray di§raction revealed a dimeric structure in which four benzylic chiral centres are identical, pointing to stereochemical crystallisation. In contrast, 1,3-bis[1-(dimethylamino)propyl]benzene reacted to give a dimeric aggregate of the lithiated compound and LiBu/ in which two ArLi 2 units are bridged by two Bu/ groups in a ladder framework.62 The X-ray structures of [(Bu5NSiMe 2 C 6 H 4 X-2)Li] 2 (X\OMe, NMe 2 , CH2 NMe 2 , CF3 ) Ph3P O NC5H5 Li(thf) + + – NC5H5 2 revealed Li–X, as well as Li · · ·CH 3 (Bu5) contacts with almost planar Li 2 N 2 rings; [(Bu5NSiMe 2 C 6 H 4 OMe-2) 2 Mg] and [(Bu5NSiMe 2 C 6 H 4 CH 2 NMe 2 -2)(OMe)Mg] 2 were also reported.63 A stable betaine lithium salt, 2, stabilised by complexation with pyridyl ligands, has been observed during the course of a Wittig reaction.64 Enthalpies of Lewis base induced tetramer]dimer and dimer]monomer conversion, intramolecular Li–NMe 2 R complexation and stabilisation by a-SiMe 2 R have been reported for a group of primary alkyllithium compounds.65 The reaction of lithium morpholide with N,N-dibutylformamide and 1-formylpiperidine results in complex equilibria in which the mixed diamino lithium alkoxides derived from morpholine and the corresponding amide are formed first.These intermediates then collapse to the lithium morpholide carbamoyl anion which reacts with morpholine to give the lithium dimorpholinemethoxide.66 The p-pyrrole complexation of lithium by zirconium mesooctaalkylporphyrinogens to give encapsulated Li 4 H 4 and Li 2 Oin sandwich structures has been reported.67 The reactions between Li[CH(SiMe 3 ) 2 ] and RNC can yield an enamide, a b- diketiminate, a 1,3-diazaallyl or a 1: 1 adduct depending on reaction conditions and the nature of R (Bu5, Ph or C 6 H 3 Me 2 -2,6).68 Reaction of [Li(ER 3 )(thf) 3 ] with ArCN (Ar\Ph, C 6 H 3 Me 2 -2,6) yielded the 3-sila- and 3-germa-b-diketiminates [LiMN(R)C(Ar)E(R)C(Ar)N(R)N(D)n] (R\SiMe 3 , E\Si or Ge, D\thf or ArCN and n\0–2).The exact nature of the product was determined by the choice of starting Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 8material and work-up procedure. X-Ray structures of the compounds with E\Si, D\ArCN, Ar\C 6 H 3 Me 2 -2,6, n\2 (monomeric) and E\Ge, Ar\Ph, n\0 (dimeric) were determined and shown to have, in contrast to the carbon analogues, the anionic charge localised at Si or Ge.69 The alkali metal-1-azaallyl complexes [CH 3 CH 2 CH 2 C(H)C(Bu5)N(H)Li(hmpa)] 2 , [CH 2 C(Bu5)N(H)Li(hmpa)] 2 and [CH 3 CH 2 CH 2 C(H)C(Bu5)N(H)Na(hmpa) 2 ] 2 have been prepared by treating the appropriate metal alkyl with Bu5CNin the presence of hmpa.Each structure is centred on a M 2 N 2 rhombohedral ring but the nature of the azaallyl–metal bonding di§ers with the first two displaying a terminal g1-N arrangement and the third showing a chelating g3-NCC moiety. Ab initio calculations which examined the energetics of the ketimide–azaallyl isomerism involved in the formation of these compounds were also reported.70 The preparation and crystal structure of the lithium 1-azaallyl compound, [LiMg3-N(SiMe 3 )C(Bu5)CH 2N2 ] 3 have been published together with ligand transfer reactions to niobium.71 Detailed information concerning the structure of lithiated a-amino nitriles in the solid state and in solution has been presented along with a mechanism for their stereoselective reactions, especially Michael additions.72 X-Ray N NH LiL N LLi NH L = Me2N(CH2)2NHMe 3 crystallography showed the product of the reaction between ortho-methylbenzonitrile and [LiN(Me)(CH 2 ) 2 NMe 2 ] to contain a new type of (NCNLi) 2 core in the dimer 3; there are also very weak amido(N)–Li cross-ring contacts.In solution, co-ordination of the diamine varies with temperature.73 The 1: 1: 1 reaction of 3-methylpyridine with LiNPr* 2 and benzonitrile in the presence of pmdien a§orded the first monomeric iminolithium compound 4.This result together with the isolation of the cyclised N Ph HN Ph NLi(pmdien) 4 N NLi(thf)2 Ph 5 product, 5, using a 3: 10: 3 reactant ratio, suggested a mechanism for previously published cyclisation reactions of b-methylazines.74 An EPR study of argon matrices containing lithium atoms and HCN or MeCN has revealed a weak van der Waals, end-on complex, RCN· · · Li and a strong charge transfer, side-on complex, Li`(RCN)~ in agreement with MNDO predictions.Irradiation converts the former into the latter.75 Reaction of Bu5NCNBu5 with LiNHBu5 (1 equivalent) in thf yields Annu. Rep. Prog. Chem., Sect.A, 1999, 95, 3–22 9MLi[C(NBu5) 2 (HNBu5)]N2 ·(thf) which contains an Li 2 C 2 N 4 ring. Deprotonation of this species with LiBu/ (2 equivalents) gives MLi 2 [C(NBu5) 3 ]N2 after recrystallisation from pentane. The structure is based on a highly distorted Li 2 N 6 C 2 hexagonal prism containing planar C(NBu5) 3 2~ anions linked by four Li cations.76 Hydrolysis of MLi[Bu/C(NBu5) 2 ]N2 , prepared from LiBu/ and Bu5NCNBu5 in hexanes, produced the nineteen atom cluster MLi[Bu/C(NBu5) 2 ]N4 ·Li 2 O.X-Ray di§raction revealed a linear Li 2 O unit at the centre of a l6 -OLi 6 core and encapsulated by two Li 2 N 4 C 2 rings.77 The preparation and crystal structures of the triazenide compounds [Li(OEt 2 )(4- MeC 6 H 4 NNNC 6 H 4 Me-4)] 2 and [K(dme)(4-MeC 6 H 4 NNNC 6 H 4 Me-4)] = have been reported.78 Dilithiated hydrazine reacts with SiClMe 2 Ph to give the isomers (Me 2 PhSiNH) 2 and (Me 2 PhSi) 2 NNH 2 which, in turn, react with 1 and 2 equivalents of LiBu/ to a§ord [H(Li)NN(SiMe 2 Ph) 2 ] 2 and [(Me 2 PhSi)LiNNLi(SiMe 2 Ph)] 3 , respectively.Both were characterized by X-ray crystallography; the former contains two-co-ordinate lithium stabilised by additional g2-contacts to each phenyl ring and the latter contains an Li 6 N 6 polyhedron with three-co-ordinate lithium additionally involved in links to the ipso-carbon of each phenyl ring.79 The crystal structure of [LiNPPh 3 ] 6 reveals an Li 6 N 6 polyhedron which is peripherally shielded by the phenyl groups.80 The preparation and crystal structures of the heterocubane cis- [(Bu5NP) 2MBu5NLi(thf)N2 ] and the seco-heterocubane (cube with one corner missing) [Mg(thf) 2M(Bu5NP) 2 (Bu5N) 2N] have been reported81 as have those of the heterocubane, cis-[MMeSi(Bu5)NN2MBu5NLi(thf)N2 ].82 Metallation of PMCH(SiMe 3 ) 2N(C 6 H 4 CH 2 NMe 2 -2) 2 with LiBu/ a§ords Li[C(SiMe 3 ) 2MP(C 6 H 4 CH 2 NMe 2 -2) 2N] in which the ligand adopts an unprecedented tridentate PN 2 co-ordination mode with no short contacts between lithium and the planar carbanion centre.83 The syntheses and structures of the lithium derivatives of a variety of tridentate and macrocyclic ligands containing amides, amines and phosphines in a chelating array have been presented.84 The butane-1,4-diide salt, [Li(thf) 2 (Ph 2 P) 2 CCH 2 ] 2 has been prepared and structurally characterized; the lithium atoms are in distorted tetrahedral environments (2P]2O) at either end of the molecule.85 The crystal structure of [LiPBu5 2 (thf) 2 LiCl(thf)] 2 revealed a four-rung LiPLiClLiClLiP ladder; the structure of [Li(l-Cl)(thf) 2 ] 2 has been redetermined.86 Oxygen- and sulfur-donor ligands The 1: 1: 1 or 2: 1: 2 reactions of LiNHBu5, KOBu5 and tmen in hexane yields [Li 8 K 2 (O)(OBu5) 8 (tmen) 2 ] which consists of a discrete cage with a central O2~ anion co-ordinated to the eight cations of a surrounding Li 8 O 8 polyhedron, two opposing sides of which are capped by a tmen-chelated potassium cation.87 The corresponding 1: 1: 1 reaction involving RbOBu5, rather than KOBu5, a§orded [M(Bu5OLi) 5 (Bu5ORb) 4 (Li 2 O 2 )(tmen) 2N= ], the crystal stucture of which revealed (Bu5O) 9 (O 2 )Li 7 Rb 4 cages linked together via Rb–tmen–Rb bridges to give a sheet structure.88 The preparation and crystal structure of [Li(l2 -OAr)] 3 (Ar\2,6- diphenyl-3,5-di-tert-butylphenolato) have been reported; an Li 3 O 3 ring forms the central core.89 An Li 4 O 4 cube with one unsolvated lithium centre forms the central core of [MLiOC 6 H 2 Me 3 -2,4,6N4 (thf) 3 ].90 X-Ray structure analysis of crystals grown from a photolysed LiOBu5–LiBu5 mixture revealed the presence of [Li 33 H 17 (OBu5) 16 ] with an inner hydride-rich core and a butoxide-rich periphery.Such species have Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 10potential as models of a soluble form of LiH.91 Reaction of LiN(Me)(CH 2 ) 2 NMe 2 with 2-CF 3 C 6 H 4 CHO a§ords a tetranuclear mixed aggregate containing three chiral a- amino lithium alkoxide units and one benzyl alkoxide, formed via LiH transfer.The structure is based on an Li 4 O 4 cube with only d-N-mono-co-ordination of the metal centres to give seven-membered chelates showing anti-isomerism about the a-N–C bond.92 Lithiation of dibenzylhydroxylamine, (PhCH 2 ) 2 NOH, yields an unsolvated, hexameric compound with a core of two stacked Li 3 O 3 rings.The metal centres are further co-ordinated via intra-monomeric chelation by hydroxylamide N-centres to give three-membered NOLi rings. Ab initio calculations were used to suggest reasons for the preference for a hexameric structure.93 Metallation of the disiloxane, OMSiMe 2 CH(SiMe 3 ) 2N2 , using LiMe in thf, yielded [SiMe 2 C(SiMe 3 ) 2 LiC(SiMe 3 ) 2 SiMe 2 OLi(thf) 2 ] the crystal structure of which was reported.94 Reaction of lithium or LiPh with a series of p-quinones gives the lithium semiquinonates; EPR spectroscopy identifies both monomeric and dimeric species. Adducts with 4-methylpyridine were also reported.95 Quantitative measurements of the aggregation equilibria in Claisen reactions of lithium enolates with phenyl esters show that the monomers are more reactive than the dimers and tetramers also present.96 The lithium enolate of 1-biphenylyl-2-methylpropanone exists as a mixture of monomer and tetramer ion pairs in thf.The most reactive species are the monomers, even though the tetramers are present in higher concentration.97 Rate studies of the ortholithiation of anisole by LiBu/–tmen have demonstrated that the reaction proceeds via the transition state [(LiBu/) 2 (tmen) 2 (PhOMe)]t.98 The structure, stability and electronic state of [Li(H 2 O)n]m` (n\1–6, 8; m\0 or 1) clusters have been investigated using ab initio methods which included electron correlation.The structure with four water molecules in the first co-ordination sphere and more in the second sphere was found to be the most stable for nq4.Li–O interactions play an essential role in dictating the structures in which 1pnp4 and the balance between Li–O bonding and hydrogen bonding becomes important in larger clusters.99 The structure of [Pt(C–– – CBu5) 2 (PPh 2 O) 2 Li 2 (l-H 2 O)(Me 2 CO) 2 ] 2 contains two coplanar Li 2 O 2 rings connected by two water molecules.100 The crystal structure of LiI·3thf, prepared from LiH and iodine, revealed a distorted tetrahedral geometry around the metal.101 The preparations and crystal structures of [LiX(dme) 2 ] (X\Br, Cl, AsH 2 , PH 2 ) have been reported.All possess trigonal bipyramidal metal centres with X in equatorial sites.102 The e§ect of polyether ligands on the solution structure of thf solutions of [6Li]-a-(phenylthio)benzyllithium has been reported (see ref. 54). Only the crown ethers were strongly bound.103 The preparation and crystal structures of [Li(E)CNBu5Bu/] (E\O, S) have been reported; the compounds are hexameric with cores of Li 6 E 6 hexagonal prisms.104 Halogen-donor ligands Reactions of NH 4 PF 6 with LiBu/ in toluene in the presence of hmpa or pmdien a§ord the ion-separated species [Li 2 (hmpa) 5 ][PF 6 ] 2 which contains three bridging hmpa ligands, or [LiPF 6 (pmdien)] 2 in which PF 6 ~ anions bridge Li(pmdien) units via Li · · ·F interactions. Ab initio calculations were used to help explain these di§erent structures.105 The 2: 1: 1 reaction of [TiCp*F 3 ] 2 , Me 3 SnF and LiCl in thf has resulted in the trapping of LiF formed in situ to give [(TiCp*F 3 ) 4 (LiF)].The structure consists Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 11of two [Ti 2 F 6 Cp* 2 ] units bridged by a lithium atom and a fluorine atom.106 The synthesis and crystal structure of [(C 6 H 3 mes 2 -2,6)AlBr 3 Li] 2 have been described. The X-ray structure revealed an Li 2 Br 4 octahedron with g6-interactions between the lithium centres and one of the mesityl rings on each phenyl group.107 3 Sodium The preparation and crystal structure of [Na(tmen) 3 (L)] (L\9,9-bianthryl), the salt of a radical trianion with three Na`–p(aryl) contacts in only one half of the bianthryl system, have been reported.108 The preparations of [MN(SiHMe 2 ) 2 ] (M\Li, Na, K) have been published; the structure of the sodium derivative revealed an infinite all-planar ladder structure with three-co-ordinate sodium also involved in SiH · · ·Na interactions.109 The crystal structure of [(NaNHBu5) 3 (NHBu5)] revealed an infinite wavelike polymer whereas [LiNa(NHBu5) 2 (tmen)] 2 adopted a four-rung ladder array with central Li–N rungs and outer Na(tmen)–N rungs.110 Metallation of NH(PPh 2 ) 2 with NaH in the presence of pmdien a§ords [NaN(PPh 2 ) 2 (pmdien)] with five-coordinate sodium (4N]P) and weaker g1-C contacts to the amine and a phenyl group. With 12-crown-4 ether rather than pmdien, M[NaN(PPh 2 ) 2 ] 2 [12-crown-4] 5N is formed; the structure is non-ionic according to mass spectrometry and conductivity measurements.111 The preparation and crystal structure of Na 4 [PMSiF(C 6 H 2 Pr* 3 - 2,4,6) 2N(SiPr* 3 )] 2 , in which a rhomboidally distorted planar Na 4 ring is stabilised between two silyl(fluorosilyl)phosphanide anions, has been reported.Each P atom is l-bonded to an Na 2 edge and each F atom coordinates to three Na centres.112 The preparation of [Na 2 P 5 (SiBu5 3 ) 3 (thf) 4 ] by (i) reaction of [Na 2 P 4 (SiBu5 3 ) 2 (thf)n] with CF 3 CO 2 H in thf, (ii) dissolution of the P 4 compound in toluene or (iii) reaction of [Na(SiBu5 3 )(thf) 2 ] with P 4 in benzene, has been reported; X-ray crystallography shows a P 3 ring with two cis-PNa(SiBu5 3 ) substituents and one trans SiBu5 3 group.113 The formation and X-ray structure of [MO(Ph 2 SiONa) 2N4 (NaOH)(H 2 O)(py) 7 ], incorporating a unique assembly of three fused Na 4 O 4 cubane units, which share a l6 -OH site, and a l3 -water molecule at one corner, have been presented.114 Reaction of fluorenone with Na (2 equivalents) in thf gave the green Na–fluorenone dianion.An X-ray structure analysis revealed both sodiums to be bonded to the carbonyl oxygen with one additionally coordinated by two thf molecules and the other also bonded to the carbonyl carbon and the carbon adjacent; further intermolecular interactions gave rise to a polymeric structure.115 The structures of hydrated Na` in concentrated aqueous solutions have been studied using X-ray di§raction and Raman spectroscopic methods.116 The synthesis and characterization of a series of sodium and potassium thiolates, [ML(SC 6 H 2 Pr* 3 -2,4,6)]n, (L\OEt 2 , thf, tmen, pmdien, dibenzo-18-crown- 6; n\1, 2, 6,O) have been described.Several were studied by X-ray di§raction and the choice of donor was found to influence structure.117 4 Potassium, rubidium and caesium Reaction of potassium with (Me 3 Sn) 2 in refluxing toluene–thf yields red [KCH 2 Ph] 2 - (thf) owing to metallation of toluene by the K[SnMe 3 ] intermediate.The dimeric units Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 12form a polymer through bridging benzyl groups.118 The synthesis and structure of the paramagnetic tweezer complex [(g5-C 5 HMe 4 ) 2 Zr(g1-C–– – CSiMe 3 ) 2 ]K has been reported. 119 The trimethylsilysilanyl compounds (Me 3 Si) 3 SiR [R\H, Et, SiMe 3 , Si(SiMe 3 ) 3 , SiMe 2 Si(SiMe 3 ) 3 ] and Me 3 SiSiR@ [R@\H 3 , Me 3 , MePh(SiMe 3 )] react with KOBu5 in dme or thf to give the corresponding polysilanylpotassium compounds and Me 3 SiOBu5; the usual route to such species involves the use of poisonous mercury compounds.120 The synthesis and X-ray structure of [KNPr* 2 (tmen)] 2 have appeared; the dimers are based on an asymmetric K 2 N 2 ring with secondary K· · ·CH 3 (Pr*) contacts.121 The diazapentadienyl complex, [(C 6 H 3 Pr* 2 - 2,6)NC(Me)C(H)C(Me)N(C 6 H 3 Pr* 2 -2,6)K ·PhCH 3 ] = has been prepared and structurally characterized. The compound is polymeric in the solid state via g5-aryl · · ·K interactions but monomeric in toluene.122 The 1,3-diazaallyl [LiMN(R)C(Ph)NC(Ph)––CR 2N], has been prepared from [LiC(SiMe 3 ) 3 (thf) 2 ] and 2 equivalents of PhCN; the tin derivative reacts with potassium–graphite to give the potassium analogue which was structurally characterized as a centrosymmetric dimer.The two metal centres are bridged by l-g2:g2-ligands; the nitrogens are coplanar and this plane forms the common base for the two distorted pyramids with an axial potassium.123 Several potassium pyrazolato complexes, [K(3,5-R 2 pz)(thf)/] (R\Bu5, n\0; R\Ph, n\1), have been prepared; a crystallographic study of a pyridine complex with R\Ph revealed a hexameric structure with the pz ligands adopting a slipped g2-bonding mode and also bridging with g1-interactions to adjacent metal centres.124 The crystal structure of [KPH(C 6 H 3 mes 2 -2,6)] 4 revealed a four-rung ladder stabilised by K· · · p(aryl) interactions and steric e§ects.125 The synthesis and solid state structure of [K 3 (PHmes) 3 (thf) 2 ] = have been described; the latter revealed a chain of KP 5 tetragonal pyramids which share common edges, and two additional K atoms located over two adjacent edges of one trigonal face of the pyramid.126 Reduction of [PBu5] 4 with potassium in the presence of pmdien followed by stoichiometric hydrolysis has provided the first fully characterized example of an organodiphosphide anion, [KM(PBu5) 2 HN(pmdien)] 2 , in which the anionic P centres of the two ligands form the central K 2 P 2 ring with secondary interactions with the neutral P centres and pmdien-solvation of the cations.127 Ab initio structure solutions using high resolution powder di§raction have been reported for KOPh·2PhOH and KOPh·3PhOH; both exhibited polymeric zigzag chains with the metal at the centre of distorted octahedra (5 O]ring centre).128 The molecular structures of the rubidium and caesium derivatives of supermesitylphosphane, PH 2 (C 6 H 2 Bu5 3 -2,4,6), as well as several base adducts of these have been presented.X-Ray di§raction studies revealed infinite ladder structures with M–P rungs and the bases (py, en, Meim, thf) bridging the metals.Structures depend on the size of the cation as well as the nature of the base. Sodium and potassium compounds were also prepared.129 The preparation and molecular sructures of [MP(H)R] (M\Rb, Cs; R\C 6 H 3 mes 2 -2,6) have been described. The rubidium compound contains an Rb 4 P 4 cube with Rb · · · p(aryl) contacts whereas the caesium compound consists of a two-dimensional polymeric framework of Cs`MCs 2 [P(H)R] 3N~ contact ion-pairs.130 A layer structure has been obtained for [CsOC 6 H 3 Pr* 2 -2,6] in which Cs–O and Cs–arene chains are held together by interactions between para-carbons in one chain and metals in an adjacent chain; interestingly this compound is solvent-free even though it was crystallized from thf.131 Investigation of the UV–VIS spectra of the Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 13caesium enolate of 1-biphenylyl-2-methylpropanone in thf shows that a mixture of monomers, dimers and tetramers is present. The caesium ion pair is more highly aggregated and much more basic than the analogous lithium ion pair.The ion pair monomer is the dominant reactant in alkylation displacement reactions.132 5 Beryllium A matrix-isolation and density-functional study of the reactions of laser ablated Be, Mg and Ca atoms with methane has been reported. Only CH 3 MH was observed for M\Mg and Ca but when M\Be, CH 3 BeH, CH 3 BeCH 3 , CH 3 Be, H 2 CBeH and HCBeH were found.133 The predominant species in alkaline hydroxyberyllate solutions have been identified as [(BeOH) 4 (OH) 6 ]2~; X-ray crystallography revealed a Be 4 tetrahedron with six bridging OH groups along the edges and one terminal OH on each metal atom in an adamantane-type structure.134 The preparation (in basic solution) and crystal structure of Ca[Be(OH) 4 ](H 2 O) 3@2 , containing the [Be 2 (OH) 7 ]3~ anion, have been reported.This species is probably an intermediate in the formation of the [Be 4 (OH) 10 ]2~ ion described above.135 The results of a thermodynamic and multinuclear NMRstudy of beryllium(II) hydrolysis and complex formation with oxalate, malonate and succinate ions in aqueous solution are consistent with the formation of [Be 2 OH]3`, [Be 3 (OH) 3 ]3`, [Be 5 (OH) 6 ]4`, [Be 6 (OH) 8 ]4` and Be(OH) 2 , as proposed previously.Complex formation is promoted by entropic contributions.136 The synthesis, structure and 9Be NMRspectrum of the picrate salt of [Be 3 (l-OH) 3 (H 2 O) 6 ]3` have been reported; the cation adopts a cyclic structure with a skew-boat six-membered Be 3 O 3 ring with two terminal water molecules also on beryllium.The H 2 O and OHgroups are hydrogen-bonded to the picrate anions and to waters of crystallisation to give a network which seems to be the stabilizing factor for the trimeric species.137 The succinato beryllates M 2 [Be(C 4 H 4 O 4 ) 2 ] (M\Na, K, NH 4 ) are prepared by reaction of BeSO 4 , succinic acid and Ba(OH) 2 (1: 2: 1) in aqueous solution; equimolar quantities yield [Be(C 4 H 4 O 4 )(H 2 O) 2 ].Potassium bis(maleato)beryllate is made similarly. The compounds undergo slow hydrolysis in water and in neutral solution the maleato complexes are in equilibrium withM 3M[Be(C 4 H 2 O 4 )OH] 3N.138 Equilibria in aqueous fluoroberyllate solutions have been studied as a function of beryllium and fluoride concentrations and pH and involve [Be(OH 2 ) 4 ]2`, [BeF(OH 2 ) 3 ]`, [BeF 2 (OH 2 ) 2 ], [BeF 3 (OH 2 )]~ and [BeF 4 ]2~.Fluoride exchange is slow on the NMR time-scale at room temperature and so sharp signals are observed in both 9Be and 19F spectra.139 Treatment of Be[N(SiMe 3 ) 2 ] 2 with PhSH resulted in acid–base reactions between NH(SiMe 3 ) 2 and PhSH so that in the presence of pyridine and 18-crown-6 ether, [Be(SPh) 2 (py)(NH 3 )] 2 ·18-crown-6 was formed.The structure consists of two [Be(SPh) 2 (py)(NH 3 )] units hydrogen bonded, via NH 3 , to either side of a central crown.140 Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 146 Magnesium Carbon-donor ligands Magnesium atoms generated by laser ablation have been reacted with methyl halide, MeX, in an argon matrix. The Grignard reagents, CH 3 MgX as well as MgX, MgX 2 , MgH, MgH 2 , CH 4 , C 2 H 6 , CH 2 X, CH 3 MgCH 3 , XMgCH 3 , XMgCH 2 , HMgCH 3 and HMgCH 2 X were also identified, together with associated Grignard species.The data provide the first experimental evidence for CH 3 MgF.141 A new general route to highly functionalized arylmagnesium halides, which proceeds via I–Mg exchange, has been published.142 Reaction of ‘MgBu 2 ’ with 6-methyl-6-phenyl- and 6,6-dicyclopropyl-fulvene gives the b-hydride transfer products 1,1@-bis(1-phenylethyl)- and 1,1@-bis(dicyclopropylmethyl)- magnesocene, respectively, whereas with MgMe 2 deprotonation occurs to give unstable 1,1@-bis(1-phenylethen-1-yl)magnesocene and 6, respectively. In the absence of b-hydrogen, only the addition reaction is possible and MgMe 2 and tetramethylfulvene give dimeric methylmagnesium ethyltetramethylcyclopentadienide in which the bridging methyl groups are shielded from further attack by the fulvene.143 A series of chiral ansa-magnesocene derivatives has been prepared and structurally characterized.The ring hapticities vary between one and five depending on the nature of the intramolecular bridge and the C 5 -ring substituents.144 The preparations and structures of the trigonal bipyramidal molecules [Mg(CH 2 SR) 2 (thf) 3 ] (R\Me, Ph) have been reported; [Mg(CH 2 SMe) 2 ] was also characterized.145 (thf)2Mg 6 Nitrogen- and phosphorus-donor ligands Treatment of N,N@-diphenylethylenediamine and N,N@-dibenzylethylenediamine with ‘MgBu 2 ’ in the presence of thf or hmpa yields [MgN(Ph)CH 2 CH 2 N(Ph)(thf) 2 ] 2 or [MgN(CH 2 Ph)CH 2 CH 2 N(CH 2 Ph)·hmpa] 2 .Both structures contain trans-5.4.5-fused rings with the former possessing a five-co-ordinate distorted trigonal bipyramidal metal centre instead of the more usual four-coordinate distorted tetrahedral geometry found in the latter structure. Replacement of the two thf molecules in the phenyl compound with hmpa molecules leads to the formation of the monomeric [MgN(Ph)CH 2 CH 2 N(Ph)·2hmpa] with tetrahedral magnesium.146 A series of fourco- ordinate magnesium amides, [MgL 2MN(SiMe 3 ) 2N], (L\2,3,5-trimethylpyridine, 2- or 4-methylpyridine, 3,5-dimethylpyridine) have been prepared and structurally characterized.Sublimation of the 2,3,5-trimethylpyridine and 2-methylpyridine derivatives a§ords [MgLMN(SiMe 3 ) 2N]; the 2,6-dimethylpyridine complex was made directly, in solution.147 The syntheses and structures of some g2-pyrazolato complexes Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 15of magnesium, [Mg(3,5-Bu5pz) 2 ] 2 and [Mg(3,5-Bu5pz) 2 L]n (L\tmen, n\1; L\thf, n\2) have been reported.148 The preparations and crystal structures of [ML 2 (4- MeC 6 H 4 NNNC 6 H 4 Me-4) 2 ] (M\Mg, L\thf; M\Ca, L\dme) revealed monomeric units with six-co-ordinate magnesium and eight-co-ordinate calcium.149 Metallation of Ph 3 P––NH with EtMgCl in the presence of hmpa yielded the N-magnesioiminophosphorane complex [Ph 3 P––NMgCl(hmpa)] 2 ; the dimer is centred on a planar Mg 2 N 2 ring with trans-chlorines. Retention of significant P––N double bond character is consistent with an electrostatic interaction between the anions and magnesium cations.150 The first solvent-free magnesium phosphanides have been prepared; Mg[P(SiHPr* 2 ) 2 ] 2 is dimeric in solution and Mg[P(SiMe 3 ) 2 ] 2 exists in a monomer–dimer equilibrium in frozen benzene and in a dimer–trimer equilibrium in toluene at [40 °C.Crystallisation at [30 °C yields the trimer, Mg[(Me 3 Si) 2 PMgMl- P(SiMe 3 ) 2N2 ] 2 , the X-ray structure of which was determined.151 Oxygen- and sulfur-donor ligands Reaction of [M(OMe) 2 ] = (M\Mg, Ca) with SO 2 in MeOH yields [M(O 2 SOMe) 2 (MeOH) 2 ] = ; with COS or CS 2 , [M(OCSOMe) 2 (MeOH)x]n (M\Mg, x\2;M\Ca, x\3, n\2) or [M(S 2 COMe) 2 (MeOH)x]n (M\Mg, x\6;M\Ca, x\4) are obtained.The analogous reactions with CO 2 gave [Mg(O 2 COMe)(OMe)(MeOH) 1.5 ]n and [Ca(O 2 COMe)(OMe)(MeOH)]n; recrystallisation of the magnesium compound from wet hydrocarbon led to the isolation of [Mg 9 (CO 3 )(O 2 COMe) 8 (MeOH) 13 ].The X-ray crystal structure of this compound revealed two Mg 4 O 4 cubes with a remote ninth Mg held in position via two bridging methylcarbonate groups and an unusual l5 -CO 3 ligand.The corresponding reaction of CO 2 with [M(OEt) 2 ] = gave [M(O 2 COEt)(OEt)(EtOH) 2 ]n; CO 2 with [Mg(OR) 2 ] = (R\Pr*, Bu5) in the parent alcohol gave [Mg(O 2 COR)(OR)(ROH)]n.152 A further investigation (NMR, IR, TGA) into the insertion of COS into the M–O bonds of alkaline-earth metal alkoxides has been reported, including the crystal structures of [Mg(OCSOPr*) 2 (Pr*OH) 4 ]·2Pr*OH and [Sr(OCSOPr*) 2 (Pr*OH) 2 ]n.153 A similar study involving CS 2 has also appeared which includes the crystal structures of [Ba(S 2 COEt) 2 ] = and [Ca(S 2 COPr*) 2 (Pr*OH) 3 ] · 2Pr*OH.154 The impetus for this work arises from the potential use of these compounds as MOCVD precursors for electroceramics.The Hauser base reagents MgX(NPr* 2 ) (X\Cl, Br) have been shown to react with a variety of enolisable ketones to give magnesium enolates.These compounds could not be isolated from thf but in ether in the presence of hmpa, [Bu5C(–– CH 2 )OMgBr- (hmpa)] 2 and [Pr*C(––CMe 2 )OMgBr(hmpa)] were isolated; both precipitate as mixtures with [MgBr 2 (hmpa) 2 ]. The results indicate that solvent plays a major role in the dismutation reactions of Hauser bases and halogenomagnesium enolates.155 The first examples of aqua-bridged dimagnesium cores have been described in the crystal structures of [Mg 2 L 4 (l-H 2 O)(l-OAc)(OAc) 2 ] (L\imidazole or benzimidazole).Implications of these structures, particularly the strong hydrogen bonds between H 2 O and ancillary OAc groups, for the hydrolytic activity of dimetallic hydrolases are discussed.156 The preparation and crystal structures of the octahedral cations [Mg(H 2 O) 2 (thf) 4 ][Mg(H 2 O) 4 (thf) 2 ][MnCl 4 ] 2 ·2thf,157 [Mg 2 Br 3 (thf) 6 ]` and [MgBr(thf) 5 ]`,158 have been described.Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 16The syntheses and structural characterization of a series of magnesium thiolates, [Mg(SR) 2 Ln]m (R\Ph, C 6 F 5 , -2-NC 5 H 4 ; L\py, 2,6-Me 2 py; n\1–4; m\1 or 3), and the first magnesiate thiolate, [Mg(SC 6 F 5 ) 4 ]2~, have appeared.159 7 Calcium, strontium and barium Metallocene syntheses using the metal (Ca, Sr or Ba) and pentaisopropylcyclopentadienyl radicals has been reported; the calcium and strontium compounds were stable in air for several weeks whereas the barium compound underwent slow decomposition.The structure of the barium species exhibited staggered, parallel rings.160 The transmetallation of Sn[N(SiMe 3 ) 2 ] 2 with the alkaline-earth metals in thf yields M[N(SiMe 3 ) 2 ] 2 ·2thf (M\Ca, Sr, Ba) which react with 6-methyl-6-phenylfulvene to give the 1,1@-bis(1-phenylethen-1-yl)metallocenes. Reaction of the strontium amide with equimolar amounts of the fulvene and acetophenone leads to the formation of 7 O Ph Me Ph Sr Sr O Ph Ph Me 7 with a planar Sr 2 O 2 ring.161 Reaction of 4-tert-butylacetyl-3-methyl-1-phenylpyrazol- 5-one (HQ) with CaCl 2 in ethanol–KOH yielded [CaQ 2 (EtOH) 2 ].The metal is in a distorted octahedral environment with the two b-diketonates in ‘anti-’ and the ethanol ligands in trans-positions; infinite chains are formed via hydrogen bonding.When R\Me, Et, Pr* complexes of general formula [CaQ 2 (ROH) 2 ] are obtained, whereas when R\Bu5, HC–– – CCH 2 or Pr*(Bu5)CH, [CaQ 2 (H 2 O) 2 ] is isolated.162 Recrystallisation of [(TiCp*F 3 ) 4 CaF 2 ] and [M(TiC 5 Me 4 Et)F 3N4 CaF 2 ] in the presence of hmpa a§orded the soluble 1: 1 adducts; X-ray di§raction of the latter showed calcium co-ordinated to eight fluorines from two [Ti 2 (C 5 Me 4 Et) 2 F 7 ]~ units and by an oxygen of hmpa.The behaviour of the Cp* compound in solution was also reported.163 The preparation and crystal structures of [Ca(SC 6 F 5 ) 2 (py) 4 ], [Ca(18-crown-6)(NH 3 ) 3 ]- [Smes*] 2 · 2thf and [Ca(18-crown-6)(Smes*) 2 ] · thf have been presented; the Ca–S bonds are weak and predominantly ionic.The structure of [CaBr 4 (thf) 2 (l2 -Li) 2 (thf) 4 ] was also given.164 The preparation and structures of [Sr(18-crown-6)(hmpa) 2 ][Smes*] 2 and [Ba(18- crown-6)(hmpa)(Smes*)][Smes*] have been reported; both metals are eight-co-ordinate. The factors a§ecting ion association in alkali and alkaline-earth chalcogenolates were discussed.165 Complexes M(hfac) 2 (Ln) (M\Sr, n\1, L\tetraglyme, dibenzo- 24-crown-8-ether; n\2, L\bipy, phen;M\Ba, n\1, L\tetraglyme, dibenzo-24- crown-8-ether) have been prepared and characterized including the X-ray structure of Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 3–22 17Sr(hfac) 2 (bipy) 2 which contains cis ligands around eight-co-ordinate strontium in the form of a square antiprism.166 Metallation of PH(SiMe 2 Pr*) 2 with Sr[N(SiMe 3 ) 2 ] 2 in thp yields Sr[P(SiMe 2 Pr*) 2 ] 2 ·4thp, which has two trans-phosphine ligands.Partial hydrolysis of this compound leads to the formation of Sr 4 O[P(SiMe 2 Pr*) 2 ] 6 which contains a central oxygen atom surrounded by a metal tetrahedron, the edges of which are bridged by phosphanide ligands; the metals are in trigonal planar environments. 167 The preparation and crystal structure of the linear polymer, [PPh 4 ][Ba(g5-Cp) 3 ] containing tetrahedral barium, have been presented.168 The crystal structure of [Ba(NH 3 ) 7 ]C 60 ·NH 3 revealed a monocapped trigonal antiprism around the metal.169 The synthesis and structure of [Ba 2MCyNC(Me)CHC(Me)NCyN3MN(SiMe 3 ) 2N], in which the diazapentadienyl group adopts three di§erent bonding modes, have been reported.170 Reaction of Ba[P(SiMe 3 ) 2 ] 2 ·4thf with diphenylbutadiyne yields dimeric 8.The alkenide moiety bridges two barium atoms forming a unique three-centre two-electron Ba–C–Ba bond. A mechanism for the formation of 8 is given; 9 is P Ph SiMe3 Ph Ph Ba thf Ba thf Ph P Ph Me3Si Ph Ph Ph Ph (Me3Si)2PMg Ph P(SiMe3)2 8 9 obtained when a similar reaction with magnesium species is carried out.171 Treatment of Ba[N(SiMe 3 ) 2 ] 2 with PH 2 (SiBu5 3 ) yields Ba[PHSiBu5 3 ] which reacts with Sn[N(SiMe 3 ) 2 ] 2 to give BaSn 3 [l-PSiBu5 3 ] 4 which contained a BaSn 3 P 4 cube with toluene g6-co-ordinated to barium.172 Metallation of As(SiMe 2 Bu5) 2 H with Ba[N(SiMe 3 ) 2 ] 2 ·4thf a§ords Ba[As(SiMe 2 Bu5) 2 ] 2 ·4thf; X-ray crystallography revealed a distorted pentagonal bipyramid with apical arsenic atoms and one free equatorial position shielded by the silyl groups.Recrystallisation from toluene gives [BaMAs(SiMe 2 Bu5) 2N2 (thf )] 2 .173 Reaction of BaCO 3 with the appropriate acid in the presence of 18-crown-6 ether a§orded Ba(OAc) 2 (18-crown-6)·nH 2 O and Ba[O 2 C(CH 2 ) 4 CO 2 ](18-crown-6)·nH 2 O.Various hydrates were formed but only those with n\4 (acetate) and n\8 (adipate) were characterized by X-ray di§raction. In both cases the metal sits in the centre of the crown but the acetate is monomeric with axial chelating ligands whereas the adipate is polymeric with one carboxylate chelating to one metal while the second bridges to another metal. Thermal decomposition and reactions with Ti(OPr*) 4 were also discussed. 174 Reaction of BaH 2 with CF 3 CO 2 H and a polydentate ligand leads to isolation of compounds of general formulae [Ba(O 2 CCF 3 ) 2 ]mLn (m\1 or 2; n\1 or 2; L\triglyme, cryptand-222, 12-crown-4, 18-crown-6–py, 2-(hydroxymethyl)-15- crown-5, 2-(hydroxymethyl)-18-crown-6). The bases are bonded to barium through all of their donor atoms and the anions adopt four di§erent bonding modes.All of the compounds decompose to BaF 2 , rather than sublime, between 250 and 600 °C.175 The synthesis and characterization of a series of volatile barium b-ketoimine–polyether Annu. Rep. Prog. Chem., Sect. 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ISSN:0260-1818    

DOI:10.1039/a804875d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

3 Boron Michael A. Beckett Department of Chemistry, University of Wales, Bangor, Gwynedd, UK LL57 2UW 1 Introduction This report takes a similar format to that used last year1 and reviews the chemistry of boron compounds reported during 1998. The literature has been surveyed by use of Chemical Abstracts, volumes 128 and 129, 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 Report Organometallic Chemistry (volume 28) 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 articles have appeared on the following topics: ‘Transition-metal complexes of boron’,2c ‘Five- and sixcoordinate nitrogen in azaborane clusters’,2d ‘Porphyrins like boron after all’,2e and ‘Chemistry of neutron capture therapy’.2f A special issue of J.Organomet. Chem. was published at the beginning of 1998 to celebrate the 65th anniversary of the birthday of Prof.K. Wade; the numerous articles on boron chemistry therein are included in the text of this report.2g The book ‘The borane, carborane, carbocation continuum’ titled after the symposium held in December 1995 to honour the 70th birthday of Dr R. E. Williams, has now been published and it contains 18 very relevant chapters organised into four sections: ‘Patterns of structures in boranes and carboranes’, ‘The carboranecarbocation continuum’, ‘Untangling molecular structures’, and ‘New species of boranes and carboranes’.2h 3 Polyhedral species Boranes Spectroscopic and theoretical studies have been reported on unusual hydrogen bonds involving hydride atoms of boron hydrides as proton acceptors; the interaction of Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 23di§erent proton donors with ionic [NBu 4 ][BH 4 ] and neutral BH 3 NEt 3 , BH 3 P(OEt) 3 species were described.3a The results of IGLO/NMR and GIAO/NMR calculations on [closo-R-XB 5 H 5 ]2~ (X\B: R\H, Me, CN; X\C: R\H, Me) and their monoprotonated counterparts have been correlated with experimental data.3b The isomeric composition of B 4 H 8 (CO) in the gas phase and in solution and its reactions with ethene or propene which a§orded R 4 B 4 H 4 (R\Et, Pr) with all four wing-tip H atoms of the tetraboranecarbonyl replaced by alkyl groups were described.3c Computational studies on eight-vertex clusters with nido electron counts were carried out using ab initio methods and the results indicated that the nido ‘six-membered open face geometry’ was usually the preferred configuration over the nido ‘five-membered open face’ geometry.3d The conventional preparation of 4-(L)-arachno-B 9 H 13 derivatives by ligand exchange on 4-(SMe 2 )-arachno-B 9 H 13 has been shown by NMR spectroscopy to also generate the previously unreported isomeric compounds, 5-(L)-arachno-B 9 H 13 ; the molecular structure of 5-(4@-PhC 5 H 4 N)-arachno-B 9 H 13 was determined.3e Relatively high potential barriers for the intramolecular rearrangement of [B 9 H 9 ]2~ were computed by ab initio methods via single (28.4 kcal mol~1) and double (21.3 kcal mol~1) diamond –square–diamond mechanisms.3f Two high-yield routes to nido-6-alkyldecaborane( 14) derivatives via one-pot syntheses were reported starting from either [nido-B 10 H 13 ]~ or arachno-6,9-(SMe 2 ) 2 B 10 H 12 with X-ray di§raction results described for the following intermediates/products: nido-8-(SMe 2 )B 10 H 12 , nido-6- (CMe 2 CHMe 2 )-8-(SMe 2 )B 10 H 11 , and nido-6-(CMe 2 CHMe 2 )B 10 H 13 .3g The partial insertion of the 9-BBN unit into the nido-B 10 H 14 framework was observed in the formation of (9-BBN)B 10 H 13 from Na[B 10 H 13 ] and 9-Br-BBN; the product was deprotonated with ‘proton sponge’ MPS, 1,8-bis(dimethylamino)naphthaleneNto a§ord [PSH][(9-BBN-B 10 H 12 ].3h Mechanistic experiments on the formation of arachno-6,9- (Me 2 S) 2 B 10 H 12 from nido-B 10 H 14 and its subsequent reaction with 2,3-dimethylbut- 2-ene to form nido-5-(Me 2 S)-9-(CMe 2 CHMe 2 )B 10 H 11 indicated that the movement of Me 2 S from B(6) to B(5) did not involve a concerted rearrangement of the boron cage but rather a migration of H and Me 2 S on an otherwise static borane cluster.3i An ab initio/IGLO/NMR investigation was undertaken on the structures of the following arachno- and hypho-MB 10N clusters and their possible Lewis base adducts: [B 10 H 12 ]2~, [B 10 H 12 L]2~, [B 10 H 12 L 2 ]2~, [B 10 H 13 ]~, [B 10 H 13 L]~, B 10 H 12 L 2 ; the recently proposed 6,6-(py) 2 B 10 H 12 structure was not supported computationally.3j The singlecrystal X-ray structures of the neutral substituted decaboranes closo-1,6- (PPh 3 ) 2 B 10 H 8 and arachno-2,4-Cl 2 -endo-6-exo-9-(PMe 2 Ph) 2 B 10 H 12 were reported. 3k,l The molecular structures of closo-1,12-B 12 H 10 (CO) 2 and its dihydrate closo-1,12-B 12 H 10MC(OH) 2N2 ·4H 2 O were reported; the latter was the first structurally characterised species with two carbene diol groups.3m The palladium-catalysed coupling (trans-[Pd(PPh 3 ) 2 Cl 2 ] and CuI) of [closo-B 12 H 12 ]2~ with Grignard reagents (RMgBr) in thf or dioxane a§orded in good yields the corresponding arylated or alkylated borane anions, [closo-B 12 H 11 R]2~.3n A new class of inorganic self-assembled monolayers have been prepared by the spontaneous adsorption of [closo- B 12 H 11 S]3~ onto gold; the monolayers were characterised by surface-enhanced Raman spectroscopy using 735nm excitation.3o The structurally characterised [Ml- MeC(NH) 2NB 20 H 16 ]~ anion was obtained from the benzoquinone oxidation of a2- [Ml-MeC(NH) 2NB 20 H 16 ]3~ in acidic aqueous solution at room temperature.3p A new Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 24Fig. 1 ORTEP representation of the dianion cis-[B 20 H 18 ]2~ (reproduced by permission from Angew. Chem., Int. Ed., 1998, 37, 1869). isomer of [B 20 H 18 ]2~ was isolated and characterised: the oxidation of ae-[B 20 H 18 ]4~ resulted in the unprecedented polyhedral borane anion (Fig. 1) designated cis- [B 20 H 18 ]2~; the anion consisted of two intact [B 10 H 9 ]~ cages linked by two 3c–2e bonds.3q The thermodynamic stabilities of larger unknown closo-boranes [BnHn]2~ (n\13–17) have been calculated; the ‘three dimensional aromaticity’ of all of these larger closo species was demonstrated and the clusters with n\16 or 17 were calculated to be thermodynamically more stable than [B 12 H 12 ]2~.3r Quantum chemical calculations of proposed multicage boron fullerenes have also been reported.3s Metallaboranes There were a few reports on metal-rich polyhedral metallaboranes during 1998.4a–c An improved synthesis of [HRu 6 (CO) 17 B] was described.4a The formation of the octahedral hexaruthena derivatives [N(PPh 3 ) 2 ][Ru 6 (CO) 16 (PPh 3 )B], [HRu 6 (CO) 16 - (PPh 3 )B], and [Ru 6 (CO) 16 (PPh 3 )B(AuPPh 3 )], and some P(OMe) 3 -substituted species, including the crystal structure of [Ru 6 (CO) 16MP(OMe) 3NB(AuPPh 3 )] were reported. 4b Similarly, a selection of octahedral dirhoda-tetraruthena clusters, including the single-crystal structures of [Rh 2 Ru 4 (CO) 16 B(AuPPh 3 )] and [Rh 2 Ru 4 (CO) 14 - (PPh 3 ) 2 B(AuPPh 3 )] were reported.4c There were a number of papers during 1998 concerned with boron-rich metalla- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 25boranes.5a–y The reduction of TaCl 5 with Li[BH 4 ] in the presence of the bidentate ligand dmpm produced the novel [Ta 2 (l-BH 3 )(l-dmpm)(g2-BH 4 ) 2 ] metallaborane with an interesting bridging MBH 3N unit.5a The gas-phase molecular structure of H 2 GaB 3 H 8 was redetermined from electron di§raction data using the SARACEN method of analysis and structural trends in the family of compounds H 2 MB 3 H 8 (M\B, Al, Ga, or In) were investigated by ab initio molecular orbital calculations.5b Similarly, ab initio calculations for Me 2 MB 3 H 8 (M\B, Al, Ga, or In) and gas-phase electron di§raction studies of Me 2 MB 3 H 8 (M\Al, Ga) were reported.5c The dichromatetraborane, [MCr(CO) 4N2 (BH 2 BH 2MdmpmN)], was formed from BH 3 ·dmpm·BH 3 and [Cr(CO) 6 ] in toluene under vacuum using a medium pressure Hg lamp at 0 °C; the structure was comparable to that of arachno-B 4 H 10 with the MCr(CO) 4N fragments in the wing-tip positions.5d The first example of a alkylidyne metallatetraborane, [NBu 4 ][WBr(CO) 2 (CR)(B 3 H 8 )] (R\C 6 H 3 Me 2 -2,6), and its facile conversion via a metal templated triboronate condensation reaction to [NBu 4 ] 2 [B 12 H 12 ] was reported.5e The reactions of nido-2,4-(CoCp*) 2 B 3 H 7 with [Fe 2 (CO) 9 ] and [Co 2 (CO) 8 ] generated, by metal fragment substitution or metal fragment degradation, the seven skeletal electron pair nido or arachno species nido-1- MCoCp*N-2-MFe(CO) 3NB 3 H 7 and arachno-MCoCp*(CO)NB 3 H 7 , respectively.5f The reaction between [Cp*TaCl 4 ] and BH 3 ·thf at 40 °C yielded the pale-red electronically unsaturated air-stable cluster nido-2-MCp*TaCl 2NB 4 H 8 with an electron count two fewer than that required for its nido five vertex structure.5g The ‘unsaturated’ chromaborane MCp*CrN2 B 4 H 8 readily underwent reduction by Na/Hg to Na[MCp*CrN2 B 4 H 8 ] and changes in the paramagnetic 11B NMR spectra of mixtures of the two species indicated that their structures were closely related.5h It has been demonstrated by Fenske–HallMOcalculations that the dinuclear MCp 2 Cr 2N fragment in MCp*CrN2 B 4 H 8 is able to provide an additional low energy (filled) or high energy (unfilled) orbital to the cluster bonding with only a small distortion of the MCr 2 B 4N cluster core geometry.5i A new coordination mode for [closo-B 6 H 6 ]2~ has been described in the compound [NBu 4 ] 2 [Cd(B 6 H 6 ) 2 ] where the Cd(II) centre is symmetrically coordinated by two hexaborate clusters each g3-bound via one MB 3N face.5j A capped nido geometry, based upon a square-based pyramid, was obtained for MRuCp*N3 B 3 H 8 where a BH fragment capped the M1,2,3-Ru 3N triangular face; the cluster was formed in the reaction between [Cp*RuCl 2 ]n with Li[BH 4 ].5k The targeted high-yield synthesis of a number of new clusters was achieved by the controlled addition of MBHN, MFe(CO) 3N or MCo(CO) 3N fragments to dinuclear Group 6 metallaboranes; the synthesis and characterisation of (Cp*Cr) 2 B 5 H 9 , (Cp*Cr) 2 B 4 H 8MFe(CO) 3N, (Cp*Cr) 2 B 4 H 7MCo(CO) 3N and (Cp*Mo) 2 B 5 H 9MFe(CO) 3N have been described.5l The metallaboranes closo-(Cp*Re) 2 B 7 H 7 and closo- (Cp*W) 2 B 7 H 9 were found to display unusual and identical core structures and to have skeletal electron-pair counts of n[3; their structures were considered as molecular metallaborane counterparts of hypoelectronic main-group cluster Zintl phases.5m The first bimetallanonaborane, arachno-6,8-M(dppe)PtN2 B 7 H 11 , was characterised as the final product from the reaction of [PtCl 2 (dppe)] with nido-B 5 H 9 ; its structure was based on the uncommon n-B 9 H 15 cluster framework.5n The monometalla and bimetalla clusters 1-(g6-Pr*C 6 H 4 Me)-isocloso-1-RuB 9 H 9 and 1,5-(g6-Pr*C 6 H 4 Me) 2 -isocloso- 1,5-Ru 2 B 8 H 8 were reported as the first ‘clean’ examples of such cage geometries. 5o The bimetallaundecaboranes nido-[7,7-(PMe 2 Ph) 2 -9-(g6-Pr*C 6 H 4 Me)-7,9- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 26Fig. 2 Drawing of [(PMe 2 Ph) 2 PtB 16 H 17 PtB 10 H 11 (PMe 2 Ph)] with P-organyl groups omitted for clarity (reproduced by permission from J. Chem. Soc., Dalton Trans., 1998, 2777).PtRuB 9 H 11 ] and closo-[1-(g6-Pr*C 6 H 4 Me)-4,4-(PMe 2 Ph) 2 -1,4-RuPtB 9 H 9 ], each formally with two skeletal electrons fewer than expected for the observed geometries, were obtained from the reaction between nido-[6-(g6-Pr*C 6 H 4 Me)-6-RuB 9 H 13 ], KH, and [PtCl 2 (PMe 2 Ph) 2 ].5p The 11-atom boron rich cluster MCp*WN3 B 8 H 9 was obtained as a co-product with MCp*WN2 B 5 H 9 from the pyrolysis reaction of Cp*H 3 WB 4 H 8 ; the larger cluster’s structure was interpreted as close-packed.5q The synthesis of some new stanna- and germa-undecaboranes was described and the reaction of MX 2 (SnBr 2 or Gel 2 ) with a thf solution of Na 2 [B 10 H 12 ] a§orded the airand moisture-sensitive salts Na[7-X-7-MB 10 H 12 ] from which metathesis with [Ph 3 PMe]Br gave [Ph 3 PMe][7-X-7-MB 10 H 12 ]; treatment of [7-Br-7-SnB 10 H 12 ]~ with MeLi at [78 °C in thf gave the linked anionic species [7,7@-(SnB 10 H 12 ) 2 ]2~ which had the clusters joined by an Sn–Sn bond.5r The synthesis and molecular structures of 11-vertex metallaboranes with exocyclic thiobenzoate rings was described with reports of closo-(PPh 3 )(PhCOS) 2 RuB 10 H 8 ·CH 2 Cl 2 5s and nido- [(PPh 3 )(PhCOS)PtB 10 H 11 ·0.5CH 2 Cl 2 .5t The molecular structure of closo- MCpNiN2 B 10 H 10 has been reported; the Ni–Ni distance of 2.4233Å, although similar to that found in other dinickel metallaborane clusters, was the longest yet reported.5u Treatment of [Me 3 NH][nido-B 11 H 14 ] with 4 equivalents of lithium alkyl in thf at 5 °C followed by addition of [PdBr 2 (PMe 2 Ph) 2 ] gave in low yield the 12-vertex 1,4-Br 2 - Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 271,2,5-(PMe 2 Ph) 3 -closo-1-PdB 11 H 8 cluster as the first metallaborane complex to contain a doubly charge-compensated ‘ollide’ ligand.5v Multiple cluster fusion between [arachno-(PMe 2 Ph) 2 PtB 8 H 12 ] and molten nido-B 10 H 14 resulted in the novel macropolyhedral 26-boron species [(PMe 2 Ph) 2 PtB 16 H 17 PtB 10 H 11 (PMe 2 Ph)] (Fig. 2) in low yield.5w The syntheses of [NEt 4 ] 2 [Pt(anti-B 18 H 20 ) 2 ] and [PSH] 2 [Pt(syn- B 18 H 20 ) 2 ] from [Pt(cod)Cl 2 ] and anti-B 18 H 22 and syn-B 18 H 22 respectively have been reported with their crystal structures revealing intramolecular steric crowding and unusual intimately packed anion layers.5x The co-thermolysis reaction between [arachno-(PMe 2 Ph) 2 PtB 8 H 12 ] and anti-B 18 H 22 in benzene solution resulted in cluster fusion and generation of the contiguous triple-cluster species [(PMe 2 Ph)PtB 26 H 26 (PMe 2 Ph)] which consisted of a nido 11-vertex MPtB 10N cage, fused with a MPtB 2N triangular face in common, to a second nido-MPtB 10N cage, which in turn was fused to a nido 10-vertex MB 10N cage via a MB 2N edge.5y Heteroboranes The reader is directed to a Royal Society of Chemistry publication, Specialist Periodical Report Organometallic Chemistry for a comprehensive review of the 1998 literature concerning carbaboranes.2a Monocarbaboranes are reported first.6a–d A series of halogen derivatives of the monocarbaboranes, nido-7-Me 3 N-7-CB 10 H 12 , closo-2-Me 3 N-2-CB 10 H 10 and closo- 1-Me 3 N-1-CB 11 H 11 have been reported by electrophilic iodination or bromination (AlCl 3 –X 2 ) or electrophilically induced substitution (HI–AlCl 3 ) of nido-7-Me 3 NCB 10 H 11 with subsequent oxidation, or insertion by reaction with PhBCl 2 , of the readily deprotonated nido cage halogenated products.6a Treatment of the unsolvated [CpA2 Ln] (Ln\Sm, Eu) or [MCpA2 LnIN2 ] with, respectively, 1 or 2 equivalents of [Ag(CB 11 Br 6 H 6 )] in pure toluene at room temperature gave the ‘Lewis-base free’ cationic lanthanide metallocene complexes [CpA2 Ln][CB 11 Br 6 H 6 ] in good yield.6b Trialkylation of 1-amino-1-carba-closo-dodecaborane with 1-bromo-3,3-bis(2-bromoethyl) octane a§orded in 29% yield the closo quinuclidin-1-yl derivative 1-(4-penthylquinuclidin- 1-yl)-1-carba-closo-dodecaborane; this was iodinated to the corresponding closo 12-iodo species in 40% yield and was characterised by X-ray crystallography.6c Comprehensive ab initio calculations at the RMP2(fc)/6-31G* level on the closo-monocarborane anions [CBn~1 Hn]~ and the neutral closo-dicarbaboranes, C 2 Bn~2 Hn, (n\5–12) showed that the relative energies of all the positional isomers agreed with the qualitative connectivity considerations of Williams, and with the topological charge stabilization rule of Gimarc.6d The highly fluorinated, chlorinated, brominated and iodinated icosahedral carbaborane anions [1-H-CB 11 X 11 ]~, [1-MeCB 11 X 11 ]~ (X\F, Cl, Br, and I) and [1-BrCB 11 Br 11 ]~ have been described; 6e,f the fluorinated derivatives were weakly coordinating and the structure of [NBu/ 4 ][ClCuCB 11 F 11 ] was determined by X-ray di§raction methods.6f Dicarbaboranes are considered next.7,8a–d The molecular structure of nido-1,2- C 2 B 3 H 7 was determined in the gas phase by electron di§raction; this dicarbaborane was the principal volatile product from the quenched gas-phase reaction of B 4 H 10 with ethyne at 70 °C whilst other carbaboranes identified in this complicated reaction included 2,3-C 2 B 4 H 8 , 2-Me-2,3,4-C 3 B 3 H 6 , 4-Me-2-CB 5 H 8 , 2,4-Me 2 -2,3-C 2 B 4 H 6 , 5- Et-2,3-C 2 B 4 H 7 , 2,5-Me 2 -2,3-C 2 B 4 H 6 , 4-Et-2,3-C 2 B 4 H 7 , 1-Me-2,3,4-C 3 B 3 H 6 , 2-Me-2- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 28CB 5 H 8 , 3-Me-2-CB 5 H 8 , and 2,3,4,5-C 4 B 2 H 6 .7a The experimentally observed C 2 B 4 Et 6 H 2 , claimed to be the first nido-2-carbapentaborane(8) derivative, has been shown by the ab initio/GIAO/NMR method to be a substituted nido-2,4-dicarbahexaborane( 8) cluster.7b A computational study of the reaction of B 4 H 10 with ethene leading to the basket compound (CH 2 CH 2 )B 4 H 8 has been undertaken and the preferred mechanism found to involve H 2 dissociation from B 4 H 10 as the rate determining step.7c A convenient route to carbon-substituted derivatives of nido-5,6-C 2 B 8 H 12 , based upon the reaction of 4-(Me 2 S)-arachno-B 9 H 13 with alkynes in toluene under reflux, was reported.7d A topological analysis of the electron density distribution in the crystal of 8,9,10,12-F 4 -1,2-C 2 B 10 H 8 was performed with the aid of high resolution low-temperature (120 K) single-crystal X-ray di§raction data; it was concluded that the fluorine atoms cause considerable redistribution of electron density within the molecule with a shift from the more electron rich C–C bond to B–C bonds.7e The analysis of 13C NMR data and UV–VIS spectra for a series of substituted aryl-pcarborane (1,12-dicarba-closo-dodecaborane) derivatives established that the p-carborane moiety was able to transmit electronic e§ects.7f Deboronation of o-carborane to [nido-C 2 B 9 H 12 ]~ was achieved in high yield by the use of KF supported on alumina in dry acetonitrile; addition of [PPh 3 Me]Br to the reaction solution allowed isolation of the product as [PPh 3 Me][nido-C 2 B 9 H 12 ].7g In the presence of aqueous [NBu 4 ]F the addition of o-carborane to various aldehydes proceeded smoothly at room temperature and gave in high yields the corresponding carbinols.7h The Barton reaction has been adapted to carborane chemistry in a report where the reaction of deca-B-methyl-1-hydroxymethyl-1,12-dicarbadodecaborane(12) with NOCl followed by UV light to yield nona-B-methyl-1-hydroxymethyl-2-hydroxyimino-1,12-dicarbadodecaborane( 12) was described.7i There were a number of reports of polyhedral ligands and their complexes where either a substituted [nido-7,8-C 2 B 9 H 12 ]~ cage7j–m,x–z,8a or a substituted closo-1,2- C 2 B 10 H 12 cage7n–w supported substituents with donor atoms of P, N, S, or Si; examples included [7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 11 -7-(AuPPh 3 )-8-(AuC 6 F 5 )]·CH 2 Cl 2 ,7j [IrCp*Cl(7,8-l-(SCH 2 CH 2 S)-7,8-C 2 B 9 H 10 )],7k [RhCp*Cl(7,8-l- (SMCH 2 CH 2 (OCH 2 CH 2 ) 3NS)-7,8-C 2 B 9 H 10 )],7k [Ru(p-cymene)ClM7,8-(SPh) 2 -7,8- C 2 B 9 H 11N],7l [Pd 2 (l-Cl) 2M7,8-(PPr* 2 ) 2 -7,8-C 2 B 9 H 10N2 ],7m 2,6-bisM[(1-methyl-1,2- dicarba-closo-dodecaboranyl)thio]methylNpyridine,7n [AgM1,2-(C 5 H 4 NS) 2 -1,2- C 2 B 10 H 10N(PPh 3 )]OTf,7o [Au 2 (1-S-1,2-C 2 B 10 H 11 ) 2 (l-dppe)],7p rac- and meso-1,2- (PPhH) 2 -1,2-C 2 B 10 H 10 ,7q 1-(PPhH)-1,2-C 2 B 10 H 12 ,7q l-S-1,2-(PMSNPh) 2 -1,2- C 2 B 10 H 10 ,7q rac-[MMo(CO) 4N-1,2-(PPhH) 2 -1,2-C 2 B 10 H 10 ],7r rac- and meso- [MCuCl(PPh 3 )N-1,2-(PPhH) 2 -1,2-C 2 B 10 H 10 ],7r [1-MAuClN-1-PPh 2 -2-Ph-1,2- C 2 B 10 H 10 ],7s [MNi(PEt 3 ) 2N-1,2-(SiMe 2 ) 2 -1,2-C 2 B 10 H 10 ],7t 4@-(ortho-carboranyl)- 2,2@: 6@,2A-terpyridine,7u [4-MeC 5 H 4 NMe] 2 [Pd(S 2 C 2 B 10 H 10 )I 2 ],7v and (R,R/S,S)- [PdCl 2 (1,2-PPhCl) 2 C 2 B 10 H 10 ].7w The synthesis and applications in organolanthanide chemistry of the new versatile ligand Me 2 Si(Cp)C 2 B 10 H 11 , obtained from the reaction of Me 2 SiCpCl with Li 2 [C 2 B 10 H 10 ] followed by hydrolysis, together with the analogous monoanionic, dianionic and trianionic species was described.8b Treatment of Li[RC 2 B 10 H 10 ] (R\Me, Ph) with [M(CO) 6 ] (M\Cr, W) followed by quenching with [Me 3 O][BF 4 ], a§orded in moderate yields the first examples of a new class of ‘Fischer-type’ carbene complexes, [(CO) 5 MMC(OMe)(RC 2 B 10 H 10 )N].8c The dicarbaborane derivative [rac-Zr(g5;g1-CpCMe 2 CB 10 H 10 C) 2 ], prepared from the reaction Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 29of [ZrCl 4 ] with Li 2 [CpCMe 2MCB 10 H 10 CN], catalysed the formation of syndiotactic poly(methyl methacrylate) in thf in the absence of any alkylating reagent or cationic centre generator.8d A few papers appeared during 1998 concerned with carbaboranes containing more than two carbon atoms.Hydroboration of diethyl(1-propynyl)borane with tetraethyldiborane( 6), in the presence of catalytic amounts of tributyl- or trimethyltin chloride gave organosubstituted carbaboranes with either 2,3,4- or 2,3,5-tricarba-nido-hexaborane( 7) skeletons along with polymeric material and the known 1-carba-arachnopentaborane( 10) derivative and pentaethyl-1,5-dicarba-closo-pentaborane(5).8eA new hexacarborane system based on the hexacarba-arachno-dodecaborane(12) structure, was also described.8f A few reports appeared during 1998 concerned with heteroboranes containing heteroatoms other than, or in addition to, carbon.The transformation of 3,4- bis(isopropylidene)-2,5-dichloro-1,2,5-dithiaborolane, obtained from 3,4-bis(dichloroboryl)- 2,5-dimethylhexa-2,4-diene and (Me 3 Si) 2 S, by reaction with Li[RBH 3 ] (R\H, Ph, C 6 H 4 Me) to the corresponding derivatives of nido-4,5-diisopropyl-2,4,5- thiadicarbahexaborane in low yield was reported; the formation of the nine-vertex cluster closo-5,6-Pr* 2 -4,5,6-SC 2 B 6 H 6 was also detected by GC-MS and identified by the ab initio/IGLO/NMR method.9a The single-crystal molecular structure of the mono-ligand adduct 9-(PPh 3 )-arachno- 6-SB 9 H 11 has been reported.9b The primary amines RNH 2 (R\Bu/, Pr*, Bu5) were found to react with 4-arachno-B 9 H 13 (SMe 2 ) to yield the hypho-type azaboranes, (RH 2 N)B 8 H 11 NHR, in an analogous manner to that reported for R\Et; the crystal structures of (Pr*H 2 N)B 8 H 11 NHPr* and (Pr*H 2 N)B 8 H 11 NHBu5 were reported.9c Treatment of an acidified solution of [nido-7,8-C 2 B 9 H 12 ]~ with Na[NO 2 ] at 0°C resulted in the formation of two 11-vertex dicarbaazaundecaboranes, nido-10,7,8- NC 2 B 8 H 11 and arachno-1,8,11-NC 2 B 8 H 13 in yields of 15 and 35% respectively; the arachno cage was converted in 68% yield to the nido species by treatment with PS and acetone.9d A range of nido 11-vertex thia- and phospha-boranes, thia- and phosphadicarbaboranes, and the first thiaphosphaborane, nido-10-Ph-7,10-SPB 9 H 9 , have been produced by synthetic sequences involving the reaction of an organophosphorus dihalide or sulfur dihalide with monoanionic boron clusters followed by in situ dehydrohalogenation initiated by PS.9e The reaction of closo-1,2-(MeSi) 2 B 10 H 10 with [Zr(NEt 2 ) 4 ] in thf gave a surprising closo 12-vertex cluster anion adduct as observed in the salt [Zr(NEt 2 ) 3 (thf) 2 ][(Et 2 N)(MeSi) 2 B 10 H 10 ] (Fig. 3); the Si–Si cluster edge was bridged by the diethylamido group.9f A number of sulfur containing macropolyhedral double-cluster species have been reported: thus, treatment of [S 2 B 17 H 18 ]~ with oxidising acids quantitatively yielded [S 2 B 17 H 17 ] characterised as its anion [S 2 B 17 H 16 ]~,9g and the double cluster anion [S 2 B 18 H 19 ]~ was prepared from the interaction of elemental sulfur with [syn-B 18 H 21 ]~.9h Metallaheteroboranes Continuing the tradition of 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 elsewhere.2a Non-carbon containing metallaheteroboranes are described first.Reaction between Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 30Fig. 3 PLATON representation of the cluster anion [(Et 2 N)(MeSi) 2 B 10 H 10 ]~ (reproduced by permission from Angew.Chem., Int. Ed., 1998, 37, 1412). arachno-4,6-S 2 B 7 H 9 and the metal organophosphine complexes [Pt(PPh 3 ) 3 ], [PtCl 2MP(OMe) 3N2 ] and [RhCl(PPh 3 ) 3 ] yielded the ten-vertex MMS 2 B 7N cluster compounds [9,9-(PPh 3 ) 2 -9,6,8-PtS 2 B 7 H 7 ], [9,9-MP(OMe) 3N2 -9,6,8-PtS 2 B 7 H 7 ] and [9,9- (PPh 3 ) 2 -9,6,8-RhS 2 B 7 H 8 ]; heating a solution of the rhodadithiadecaborane in benzene isomerised it to [5,5-(PPh 3 ) 2 -5,6,10-RhS 2 B 7 H 8 ].10a An 11-vertex MM 2 S 2 B 7N cluster [(PPh 3 ) 2 HRh(PPh 3 )ClS 2 B 7 H 7 ] was also reported.10a The ten-vertex oxametallaborane [9,9-(PMe 2 Ph) 2 -arachno-9,6-PtOB 8 H 10 ] was found by X-ray crystallography to have the classical arachno ten-vertex geometry, with the MON and MPt(PMe 2 Ph) 2N vertices in the prow 6- and 9-positions, and with the oxygen bound contiguously to three boron atoms.10b The orange–yellow [6-Cp*-nido-6-RhB 9 H 12 -l- 8,9-(NEt 2 )] and yellow [5-Cp*-nido-5-RhB 9 H 12 -l-9,10-(NEt 2 )] cluster compounds, obtained by reaction of 4-(NHEt 2 )-arachno-B 9 H 13 with [MRhCl 2 Cp*N2 ] and NaH, have been characterised by single-crystal X-ray di§raction studies and NMRspectroscopy. 10c The structures of [8,8-(PPh 3 ) 2 -8,7-nido-RhSB 9 H 10 ] and [9,9-(PPh 3 ) 2 -9,7,8- RhC 2 B 8 H 11 ] were analysed by RMS-misfit calculations which in apparent contravention of Wade’s rules confirmed their 11-vertex cluster geometries as nido.10d The unique cluster compound [2-I-2-(Bu5NC)-3-(Bu5NHCH)-closo-2,1-PdTeB 10 H 9 ] contained the secondary carbene (Bu5NHCH) bonded to a cage boron atom.10e The monometallic closo cluster anion in [NEt 4 ][1-MRu(CO) 3N-2-(MeSi)B 10 H 10 ] was obtained in almost quantitative yield from the interaction of 3 equivalents of [NEt 4 ]- [MeSiB 10 H 12 ] with 1 equivalent of [Ru 3 (CO) 12 ]; equimolar amounts of the two reagents a§orded [NEt 4 ][Ru 3 (CO) 8 (g5-MeSiB 10 H 10 )].10f The platinathiaborane species [(PMe 2 Ph) 2 PtSB 8 H 12 ], [(PMe 2 Ph) 2 PtSB 10 H 10 ] and [(PMe 2 Ph) 2 PtS 2 B 15 H 14 (NHCOMe)] were obtained by reaction of [PtMe 2 (PMe 2 Ph) 2 ] with arachno-4-SB 8 H 12 , nido-7-SB 10 H 12 , and (anti)-9,9@- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 31Fig. 4 Molecular structure of the macropolyhedral anion [Cp*IrSB 18 H 19 ]~ (reproduced by permission from Inorg.Chem. Commun., 1998, 1, 97). S 2 B 16 H 16 , respectively.10g Reaction of syn-[Cp*IrB 18 H 20 ], obtained from [MIrCl 2 Cp*N2 ] with syn-B 18 H 22 and base, with elemental sulfur a§orded by direct heteroatom insertion the 20-vertex cluster anion [Cp*IrSB 18 H 19 ] (Fig. 4).10h Small metallacarbaborane species are considered next. The disodium or dilithium salts of [nido-2,4-(SiMe 3 ) 2 -2,4-C 2 B 4 H 4 ]2~ reacted with gaseous HCl in 1: 1 stoichiometry in thf and a§orded the monoprotonated species [1-M-(thf) 2 -2,4- (SiMe 3 ) 2 -2,4-C 2 B 4 H 5 ] (M\Na, Li) in excellent yields.10i Pale-yellow crystals of [1,1-(Bu5OH) 2 -1-(Bu5O)-2,3-(SiMe 3 ) 2 -l-4,5-MLi(thf)ClN-closo-g5-1-Sm-2,3-C 2 B 4 H 4 ]· thf were obtained from reaction of anhydrous SmCl 3 with the dilithiocarbaborane [closo-exo-l-4,5-Li(thf) 2 -1-Li(thf) 2 -2,3-(SiMe 3 ) 2 C 2 B 4 H 4 ] in 1: 1 ratio in dry benzene at 0 °C.10j A synthetic spectroscopic and structural investigation of C-trimethylsilylsubstituted half- and full-sandwich magnesacarbaboranes of 2,3- and 2,4-MC 2 B 4N carbaborane ligands was reported.10k The dichlorotantalum cluster species [CpCl 2 Ta(Et 2 C 2 B 4 H 4 )] gave the dimeric system [MCpTa(H)(Et 2 C 2 B 4 H 4 )N2 -l-Cl] upon treatment with Li[AlH 4 ] in thf; this hydrido species underwent alkyne insertion with p-tolyl acetylene and generated exclusively [trans-CpCl(p- MeC 6 H 4 CH––CH)Ta(Et 2 C 2 B 4 H 4 )].10l The thermally stable tantalum carbaborane complex [CpTaMe 2 (Et 2 C 2 B 4 H 4 )] was cleanly converted to the vinyl tantalum species Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 32Fig. 5 Molecular structure of [CpCrMl-g6:g6-(l-1,2-C 3 H 6 -1,2-C 2 B 4 H 4 )NCtrCp] (reproduced by permission from Inorg. Chem., 1998, 37, 608). [CpTaMe(CR––CRMe)(Et 2 C 2 B 4 H 4 )] by photochemical insertion of alkynes; the analogous diphenyl complex [CpTaPh 2 (Et 2 C 2 B 4 H 4 )] was thermally active, and reacted by elimination of benzene followed by trapping reactions involving alkynes and the derived benzyne intermediate.10m The enyne insertion of HC–– – CCMe–– CH 2 with arachno-[(CO)(PMe 3 ) 2 (H)Ir(B 8 H 12 )] in xylene at 138 °C a§orded two iridadicarbaboranes [7-MCMeCH 2N-9,9,9-(CO)(PMe 3 ) 2 -nido-9,7,8-IrC 2 B 8 H 10 ] and [5,5,5- (CO)(PMe 3 ) 2 -l-6,7-MCHCMeCH 2N-nido-5,6-IrCB 8 H 11 ] in low yields.10n The synthesis and crystal structure of the EPR-silent polymeric caesium carbaborane system [Mexo-Cs(tmen)-1-Cs-2,4,7,9-(SiMe 3 ) 4 -2,4,7,9-C 4 B 8 H 8Nn] has been reported.10o The synthesis of molybdenum and tungsten carbonyl multidecker sandwiches e.g.[Cp*Co(Et 2 C 2 B 3 H 3 )M(CO) 4 ] (M\Mo, W), [MCp*Co(Et 2 C 2 B 3 - H 3 )N2 Mo(CO) 2 ] were described with the compounds being characterised by X-ray di§raction studies.10p The triple-decker complex [(CpCr) 2 -l-g6:g6-(l-1,2-C 3 H 6 -1,2- C 2 B 4 H 4 )N] (Fig. 5) with an unusual 24-electron count contained a metal-stabilised planar tetraborabenzene bridging ligand.10q There were a number of reports of metalladicarbaborane clusters based upon Annu. Rep. Prog. Chem., Sect.A, 1999, 95, 23–43 33Fig. 6 A view of the ‘head-set’ and ‘ear-mu§’ molecular structure of [M(nido- C 2 B 9 H 11 )Zn(NMe 3 )N2 ] (reproduced by permission from Chem. Commun., 1998, 1713). derivatives of the icosahedral 12-vertex closo MMC 2 B 9 H 11N11a–e or MMC 2 B 9 H 10 LN11f–j cage structures, examples include: [3,3-(PEt 3 ) 2 -1-Ph-3,1,2- PtC 2 B 9 H 10 ]·0.5CH 2 Cl 2 ,11a [Cp*(g5:g1-4-CHMeO-C 2 B 9 H 10 )Ti],11b [Ru(CO) 2 (MeCCPh)(g5-7,8-C 2 B 9 H 11 )],11c [1-M(g5-C 5 H 4 )FeCpN-3-(p-cym)-3,1,2- RuC 2 B 9 H 10 ],11d [1-C 4 H 3 S-3-(cod)-3,1,2-MC 2 B 9 H 10 ] (M\Pd, Pt),11e [3-(PPh 3 )- 3,3-(I) 2 -4-SMe 2 -3,1,2-RhC 2 B 9 H 10 ],11f [3-Cp*-4-SMe 2 -3,1,2-RuC 2 B 9 H 10 ],11g [3-(g3- C 3 H 5 )-3,3-(CO) 2 -4-SMe 2 -3,1,2-MoC 2 B 9 H 10 ],11h [FeMC 2 B 9 H 10 (SMe 2 )N2 ],11i and [1,8-Ph 2 -2-(g3-C 3 H 5 )-2,2-(CO) 2 -6-SMe 2 -2,1,8-MoC 2 B 9 H 8 ].11j The alkane elimination reaction between ZnMe 2 and [NMe 3 H][C 2 B 9 H 12 ] gave the macropolyhedral dimer [M(nido-C 2 B 9 H 11 )Zn(NMe 3 )N2 ], which contained an unprecedented planar diamond- shaped MZn 2 B 2N ring at its core (Fig. 6).11k The synthesis and structural characterisation of the thioether bridged commometallabis( dicarbollide) species, [3,3@-Co-(l-1,1@-MCH 2 SCH 2N-1,2-C 2 B 9 H 10 ) 2 ]~, was described and developed as a model for ‘venus-flytrap’ radiotransition metal carriers. 11l The cobaltabis(dicarbollide) [3,3@-Co-(1-Me-2-R-1,2-C 2 B 9 H 9 ) 2 ]~ (R\MCH 2N6 OMCH 2N3 Me) showed a higher e¶ciency in transport of 152Eu at low acidity than the well known calixarene derivatives.11m The sandwich complexes [3,3@- Co(1-Ph-1,2-C 2 B 9 H 10 ) 2 ]~ and [3,3@-Co(1,7-Ph 2 -1,2-C 2 B 9 H 9 ) 2 ]~ were tested for liquid–liquid extraction and transport for 137Cs, 90Sr, and 152Eu;11n [3,3@-Co-(1-Me-2- M(CH 2 ) 3 OEtN-1,2-C 2 B 9 H 9 ) 2 ]~ was also tested for its 137Cs- and 90Sr-extracting capacity. 11o Electrochemical studies on [Li(thf) 4 ] 2 [(g5-C 2 B 9 H 11 ) 2 UBr 2 ] were also reported. 11p Metallamonocarbaboranes are reported next. The synthesis and crystal structures of the platinacarborane complexes [PtCl(PMe 2 Ph) 2 (g5-7-CB 10 H 11 )], [Pt 2Ml- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 34r,g5: r,g5{-8,9@-I(H)-(7-CB 10 H 10 ) 2 (PMe 2 Ph) 4 ] and [Pt 2 (PEt 3 ) 4Mg5:g5{-9,9@-I(H)-(7- CB 10 H 10 ) 2 ] were described following protonation reactions of [Na][Pt(PR 3 ) 2 (g5-7- CB 10 H 11 )] salts;12a reactions of the PEt 3 derivative with PhSeCl, PhSeSePh, and PhTeI yielded products with chalcogen substituents on platinum, or platinum and boron.12b The salts [X] 2 [Re(CO) 3 (g5-CB 10 H 11 )] [X\N(PPh 3 ) 2 , NEt 3 (CH 2 Ph)] were synthesised from the reaction of Na 3 [nido-7-CB 10 H 11 ] with [ReBr(thf) 2 (CO) 3 ] followed by addition of [X]Cl.12c Neutral bimetallic species [RePt(CO) 3 L 2 (g5- CB 10 H 11 )]12c (L\PPh 3 , PEt 3 , 1/2dppe) and [ReM(CO) 3 Cp*(g5-CB 10 H 11 )]12d (M\Rh, Ir) were prepared by treatment of [N(PPh 3 ) 2 ] 2 [Re(CO) 3 (g5-CB 10 H 11 )] with [PtCl 2 L 2 ] in the presence of Tl[PF 6 ], or [M(NCMe) 3 Cp*][BF 4 ] 2 , respectively; CO/PR 3 exchange reactions of the Group 9 bimetallic clusters were also reported.Treatment of Na[MeSi(C 2 B 10 H 11 )(C 5 H 4 )] with SmI 2 (thf)x gave [MeSi(C 2 B 10 H 11 )(C 5 H 4 )Sm(thf) 2 ] as the first structurally characterised example of a mixed lanthanacarborane incorporating g5-cyclopentadienyl and g6-carboranyl ligands.12e The three new metallacarboranes [closo-1-CoCp-2-(NC)-2,3-C 2 B 10 H 11 ], [nido-2-FeCp-8-(CH 3 OCO)-6,7,8,9-C 4 B 7 H 11 ] and [arachno-CoCp-8-(CH 3 OCO)- 7,8,9,10-C 4 B 7 H 12 ], with cage geometries derived from supraicosahedral frameworks, were produced by metal insertion reactions into the [arachno-8-(NC)-7,8-C 2 B 10 H 14 ]~ and [arachno-8-(MeOCO)-7,8,9,10-C 4 B 8 H 12 ]~ anions.12f 4 Organometallic boron species General The synthesis and structure of the first terminal-borylene complexes were reported with a ‘nearly linear’ arrangement observed for the W–B–N unit of [(CO) 5 WBN(SiMe 3 ) 2 ].13a Treatment of Cp*BCl 2 with K 2 [Fe(CO) 4 ] gave [(CO) 4 FeMBCp*N]; a single-crystal X-ray di§raction study confirmed that the complex displayed a Fe–B r bond and that the Cp* was g5-bonded to boron.13b The reaction of aminodichloroboranes, R 2 NBCl 2 , with Na[C 5 R 5 Fe(CO) 2 ] yielded, depending upon the nature of the amino group bound to boron, either boryl or bridging borylene complexes of iron.13c The reaction of the organodiborane M(l-H)(BC 5 H 10 )N2 with Lewis bases NMe 3 , PMe 3 , NH 3 , orH~ produced cyclic adducts L·HBC 5 H 10 through symmetric cleavage of the hydrogen-bridge bonds.13d The synthesis of a series of cyclic hydroborate complexes of metallocenes have been described and the structures of zirconoceneboracyclohexane derivatives [Cp 2 Zr(X)M(l-H) 2 BC 5 H 10N] (X\H, Me, H 2 BC 5 H 10 )] reported.13e Pentafluorophenylborane derivatives The neutral compound H 2 O·B(C 6 F 5 ) 3 ·2H 2 O was formed in the interaction of H 2 O with B(C 6 F 5 ) 3 whilst the reaction of KOH/H 2 O in the presence of dibenzo-18- crown-6 gave [K(dibenzo-18-crown-6)][(HO)B(C 6 F 5 ) 3 ] co-crystallised with H 2 O·B(C 6 F 5 ) 3 ; the new binuclear borate anion [M(C 6 F 5 ) 3 BN2 (l-OH)]~ was also reported. 13f The phosphorus ylide Ph 3 P––CH 2 when reacted with B(C 6 F 5 ) 3 a§orded the zwitterionic species Ph 3 PCH 2 B(C 6 F 5 ) 3 characterised by an X-ray crystal structure Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 35analysis.13g The interaction of B(C 6 F 5 ) 3 with oxo- and peroxo-molybdenum, and nitrido-rhenium and -osmium complexes has been reported and the products, typified by cis-[MoOMOB(C 6 F 5 ) 3N(g2-ONEt 2 ) 2 ]13h and [ReMNB(C 6 F 5 ) 3N(PMe 2 Ph)(S 2 CNMe 2 ) 2 ] were described.13i The reaction of [MCp@YMeN2 ] (Cp@\Cp, C 5 H 4 SiMe 3 ) with B(C 6 F 5 ) 3 a§orded the complexes [Cp@YMMeB(C 6 F 5 ) 3N] in which the ‘anion’ was co-ordinated to the metal via one ortho-fluorine atom and agostic interactions from two of the methyl hydrogens; these compounds acted as initiators for carbocationic polymerisation of isobutene.13j The zwitterionic compound [Cp 2 Zr(PPh 2 Me)CH 2 CH 2 B(C 6 F 5 ) 3 ], formed from the reaction of B(C 6 F 5 ) 3 with [ZrCp 2 (g2-CH 2 CH 2 )(PPh 2 Me)], was an ethene polymerisation catalyst either with or without additional B(C 6 F 5 ) 3 .13k Addition of B(C 6 F 5 ) 3 to [(ArO) 2 TiMe 2 ] gave unstable species which were also able to polymerise ethene and propene.13l The cationic benzyl derivative of [(C 10 H 6 CH 2 ) 2 NMe]Zr(CH 2 Ph) 2 with [B(C 6 F 5 ) 4 ]~ as counter ion catalytically polymerised olefins, whereas with the g6-[PhCH 2 B(C 6 F 5 ) 3 ]~ counter ion the system was inactive.13m The triamide complex, [NEt 4 ]- [MC 5 H 4 B(C 6 F 5 ) 3NZr(NMe 2 ) 3 ], formed from [NEt 4 ][C 5 H 5 B(C 6 F 5 ) 3 ] and [Zr(NMe 2 ) 4 ] in good yield, was readily converted to the crystallographically characterised dimeric trichloride [NEt 4 ] 2 [(MC 5 H 4 B(C 6 F 5 ) 3NZr(l-Cl)Cl 2 ) 2 ].13n The bifunctional boranes RCH–– CMB(C 6 F 5 ) 2N2 (R\Bu5, Ph, C 6 F 5 ) were formed from the regioselective hydroboration of corresponding 1-boraalkynes using HB(C 6 F 5 ) 2 .13o The synthesis and characterisation of the amino(pentafluorophenyl)boranes (Me 3 Si)HNB(C 6 F 5 ) 2 , HNMB(C 6 F 5 ) 2N2 , and (Me 3 Si) 2 NB(C 6 F 5 ) 2 together with the structure of the latter were reported.13p Unsaturated ring systems containing boron and related derivatives The first heterometallic borole complexes of Fe and Au were prepared by the reaction of [HFeMg5-C 4 H 4 BPhN(CO) 2 ]~ with [Au(PPh 3 )Cl] inCH 2 Cl 2 which yielded [Fe(g5- C 4 H 4 BPh)(CO) 2MAu(PPh 3 )N2 ]; the cationic MFeAu 3N cluster species with a tetrahedral metal core was obtained by further reaction with [Au(PPh 3 )Cl] and Tl[PF 6 ].14a The polymeric salt catena-[MRh(l,g5:g6-C 4 H 4 BPh)N(BF 4 )]x was obtained by loss of acetonitrile under vacuum from [Rh(NCMe) 3 (C 4 H 4 BPh)][BF 4 ].14b X-Ray structure determinations of [Cp*Mg5-C 4 H 4 BNH(CHMe 2 ) 2NHfCl(C–– – CSiMe 3 )], [Cp*Mg5- C 4 H 4 BN(CHMe 2 ) 2NHfCl(PMe 3 )] and [Cp*Mg5-C 4 H 4 B(C–– – CSiMe 3 )NHfCl(PMe 3 )] were reported.14c The reaction of TaCl 5 with 2 equivalents of AlCl 3 and Li[C 4 H 4 BN(CHMe 2 ) 2 ]·thf gave in 47% yield [MC 4 H 4 BN(CHMe 2 ) 2NTaCl 3 ], and from which a number of tantalum borollide complexes were prepared.14d The synthesis of the bridged boratabenzene zirconium complexes [ZrCl 2Mg6:g6- (C 5 H 4 BNPr* 2 ) 2 -l-CH 2 CH 2N], [ZrCl 2Mg6:g6-(C 5 H 4 BNPr* 2 ) 2 -l-SiMe 2N] and [ZrCl 2Mg5:g6-(C 5 H 4 )(C 5 H 4 BNPr* 2 )-l-CMe 2N] were reported and the bridging SiMe 2 and CMe 2 derivatives characterised by X-ray crystallogoraphy.14e The lithium salt of the new benzothiaborolide heteroaromatic anion [C 6 H 4 SC(H)B(NPr* 2 )]~ has been prepared by a multistep synthesis starting from thioanisole; the anion was converted to a MCp*RuN-g5 adduct and characterised crystallographically.14f The synthesis of the cycloheptatrienyl(dipropyl)borane, C 7 H 7 BPr 2 , was accomplished by an exchange reaction of C 7 H 7 SnMe 3 with Pr 2 BCl; it was found to equilibrate with its valence tautomer 7-exo-(dipropylboryl)norcaradiene.14g The bisboryl cobaltocenes Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 36[Co(g5-C 5 H 4 BR 2 ) 2 ] (R\NMe 2 , NEt 2 ) were prepared from [CoBr 2 (dme)] and M[C 5 H 4 BR 2 ] (M\Li, Na) and were oxidised to ionic cobaltocenium chlorides by C 2 Cl 6 .14h The synthesis of borylindenides has been achieved by borylation of the lithium indenide and the structure of [Li(N,N@,NA-Me 3 -1,3,5-C 3 H 6 N 3 )]- [1-C 9 H 6MB(NMe 2 ) 2N] was reported.14i The formation of 1,5-bis(dimethylamino) dibenzo[b,f ]-1,5-bidorocane was accomplished via sodium reduction of 1-(Me 2 NCH 2 )-2-BCl 2 C 6 H 4 .14j 5 Catecholate derivatives and boration reactions The synthesis and characterisation of a series of bis-catecholate, bis-dithiocatecholate, and tetraalkoxydiborane(4) compounds have been described together with the bis(adducts) [B 2 (cat) 2 (NHMe 2 ) 2 ] and [B 2 (1,2-O 2 -3,5-Bu5 2 C 6 H 2 ) 2 (NHMe 2 ) 2 ];15a XRay structures were reported for [B 2 (cat) 2 ], [B 2 (1,2-O 2 -4-Bu5C 6 H 3 ) 2 ], [B 2 (1,2-O 2 - 3,5-Bu5 2 C 6 H 2 ) 2 ], [B 2 (1,2-S 2 C 6 H 4 ) 2 ], [B 2 (1,2-S 2 -4-MeC 6 H 3 ) 2 ], and [B 2 (OCH 2 CMe 2 CH 2 O) 2 ] which revealed planar MB 2 O 4N or MB 2 S 4N units.15b Oxidative-addition reactions of B–B, B–Cl, and B–Br bonds to Pt(0) complexes to yield mono(boryl) Me.g.trans-[PtX(PPh 3 ) 2 (Bcat)] (X\Cl, Br)N or bis(boryl) Me.g. cis-[Pt(PPh 3 ) 2 (Bcat) 2 ]N derivatives were reported.15c Oxidative addition of [B 2 (cat) 2 ] with either [RhCl(PPh 3 ) 3 ] or [MRh(l-Cl)(PPh 3 ) 2N2 ] a§orded the colourless Rh(III) bis(boryl) species [RhCl(PPh 3 ) 2 (Bcat) 2 ]; the Rh coordination sphere was squarebased pyramidal with a boryl group apical and the two PPh 3 ligands mutually trans in the basel plane.15d A number of neutral and cationic six-coordinate osmium boryl complexes derived from [Os(Bcat)Cl(CO)(PPh 3 ) 2 ] have been prepared and characterised crystallographically.15e The reactions of [L 2 Rh(acac)] (L\alkene, triorganophosphine) with B 2 (cat) 3 cleanly yielded the zwitterionic complexes [L 2 Rh(g6-cat- Bcat)] with [(acac)Bcat]; [(dppm)Rh(g6-catBcat)] was found to be an excellent catalyst for the diboration of vinylarenes and the unstrained internal alkenes cis- and trans-stilbene, and trans-b-methylstyrene.15f The clean and quantitative platinumcatalysed diborations of a range of prochiral 1,3-dienes with the compounds [B 2MR,R-O 2 CH(CO 2 Me)CH(CO 2 Me)N], [B 2 (S-O 2 CH 2 CHPh) 2 ] and [B 2 (R,RO 2 CHPhCHPh) 2 ] were studied but the observed de values were low or non-existent. 15g Di§erences between the Pd(0) and Pt(0) catalysts and between thioboration and diboration reactions have been studied by hybrid density (B3LYP) calculations.15h 6 Boron–pnictogen species The elimination of HF from mes*B(F)CH 2 CH 2 B(F)mes* (mes*\2,4,6-Bu5 3 C 6 H 2 ) resulted in mes*B–– – NCH 2 CH 2 N–– – Bmes* as the first example of a compound containing B–– – N triple bonds; this compound was thermally stable but readily hydrated to a§ord mes*B(OH)NHCH 2 CH 2 NHB(OH)mes*.16a The preparation of a series of differently substituted 2-chloro-, 2-fluoro-, and 2-iodo-2,3-dihydro-1H-1,3,2-diazaboroles were reported.16b Eleven new 2-aminoethyl- and 3-aminopropyl-borinate derivatives with a coordinate N]B bond have been synthesised by condensation reactions between piperidine- and piperazine-alcohols and diphenylborinic acid.16c Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 37Fig. 7 A CAMERON drawing of MFe(g5-C 5 H 4 Me)(CO) 2N2 ClB 3 N 3 H 3 (reproduced by permission from Eur. J. Inorg.Chem., 1998, 291). The first tricyclic N-pyrrollylborane with an exceptionally stable B–N bond was obtained from hydroboration of 2,5-diallylpyrrole using a mixture of Et 2 BH and Et 3 B; this borane was readily converted into adducts or borates.16d Theoretical and experimental evidence for a S N 2-type mechanism for the dissociation of B–N coordination bonds has been obtained for 2,6-bis(dimethylaminomethyl)phenylborane derivatives. 16e The electronic structure of [Cr(g6-B 3 N 3 H 6 )(CO) 3 ] was investigated in detail using high quality density functional calculations; puckering of the borazine ring was associated with repulsive interactions between high lying boron dominated ring r-bonding orbitals and the metal’s ‘lone-pairs’.16f A theoretical study of the structures, energetics and magnetic properties of B 3 E 3 H 6 (E\N, P, As) and B 3 E@3 H 3 (E@\O, S, Se) has been reported and the discussion centered on the relative aromaticity of these ring compounds.16g The synthesis and structures of the first g1-borazine complexes were reported from the reaction of Na[(g5-C 5 R 5 )Fe(CO) 2 ] with Cl 3 B 3 N 3 H 3 ; Fe–B p-interactions were ruled out from spectroscopic and structural results (Fig. 7).16h New silylborazines have been prepared by the interaction between Li[Si(SiMe 3 ) 3 ] with ClMe 2 B 3 N 3 Me 3 , Cl2 MeB 3 N 3 Me 3 , Cl3 B 3 N 3 Me 3 , and Cl 3 B 3 N 3 H 3 ; pyrolysis of an oligomer obtained from M(Me 3 Si) 3 SiNCl 2 B 3 N 3 H 3 and (Me 3 Si) 2 NH in hexane resulted in composites containing BN and SixNyCz.16i Bicyclic cage compounds containing B, P and transition metals (Ni, Pd, Pt) were isolated and characterised from 1: 1 reactions of (Pr* 2 N)BP(H)B(NPr* 2 )PLi·dme and Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 38Fig. 8 Molecular structure of [B 2 O 2 (BCl 3 ) 2 (tcp)] (reproduced by permission from Angew. Chem., Int. Ed., 1998, 37, 1112). (tmp)BP(H)B(tmp)PLi·dme with [(R 3 P) 2 MCl 2 ].16j Skeletal bonding in closo-1,5- X 2 B 3 Y 3 (X\N, P; Y\NH 2 , CH 3 , H) cages was shown by bonding, energetic, and magnetic analyses to be dependent upon the substituents at boron.16k 7 Boron–chalcogen species Solid state NMR spectroscopy has provided evidence for the selective association of [Na]` with tetrahedral MBO 4N units and [H]`with trigonal MBO 3N units in the dehydrated zeolite B-ZSM-5.17a A new 1-D inorganic chain polymer [H 2 en] 4 - [Hen] 2 [V 6 B 22 O 53 H 8 ]·5H 2 O consisting of [V 6 B 20 O 50 H 6 ] cluster sub-units linked together through diborate bridges has been synthesised by a molten boric acid ‘flux’ method in which H 3 BO 3 , V 2 O 5 , and en were heated together at 180 °C for 3 days.17b Boronic acids were used for selective fluorescence detection of fluoride17c and for optical sensing properties of sugars.17d The crystal structure of the adduct (Ph 3 SiO) 3 B·Ph 3 SiOH consisted of molecules of (Ph 3 SiO) 3 B and Ph 3 SiOH linked by a weak B · · ·O (silanol) donor–acceptor bond and additionally stabilised by a OH(silanol) · · · O(siloxy) hydrogen bond; the MBO 3N fragment remained ‘trigonal’ with the interaction to the silanol axial.17e New divinyl- and diallyl-borasiloxanes have been synthesised in good yield from corresponding boronic acids and their behaviour Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 23–43 39in metathesis reactions initiated by organometallic catalysts was investigated.17f The synthesis and characterisation of a series of amine adducts of Ar 3 B 3 O 3 (Ar\4- BrC 6 H 4 , 3-NO 2 C 6 H 4 , 3-NH 2 C 6 H 4 ) derivatives have been reported together with the crystal structure of one such adduct, 3-picoline·(4-BrC 6 H 4 ) 3 B 3 O 3 .17g The preparation and crystal structure of a porphyrin complex containing a coordinated MB 2 O 2N ring has been described (Fig. 8)17h and the synthesis of a boronbridged tetrathiaporphrinogen, M(SC 4 H 2 )B(NPr* 2 )N4 , in 62% yield was reported.17i 8 Boron halide species A combined ab initio, Monte Carlo, and FTIR investigation of the behaviour of BF 3 in liquified Ar,N 2 and Ar–N 2 cryosolutions has been reported; solvation of BF 3 occurred in Ar, but with N 2 and Ar/N 2 van der Waals complexes were observed.18a A vibrational analysis of the van der Waals complex between cyclopropane and BF 3 in liquified inert gases has also been reported.18b EPR evidence for radical stabilization through electronic e§ects of the halogen substituents was obtained for the paramagnetic cluster ions [B 6 HalnHal@6~n]·~ (Hal, Hal@\Cl, Br, I).18c References 1 M.A.Beckett, Annu. 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ISSN:0260-1818    

DOI:10.1039/a804876b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

4 Aluminium, gallium, indium and thallium J. P. Maher School of Chemistry, University of Bristol, Bristol, UK BS8 1TS 1 Introduction This year’s review was compiled via an ISI Personal Alert. This resulted in over 9000 references, and illustrates just how di¶cult it has become to cover such a diverse subject. By comparison with previous years the searches gave a di§erent proportion of papers: Al: 39%; Ga: 24%; In: 12%; Tl : 25%.There has been a discernable shift in interest towards the heavier elements in the group. A microcosm of the current chemistry for Group 13 can be seen in the abstracts to papers relating to Group 13 presented at the 1998 meeting of the ACS.1 There have been Group 13 reviews on the distribution of the M–M distances in the oxides of the elements and their spinels and delafossites,2 and a new database of the thermodynamic properties of the nitrides and related species is available.3 2 Aluminium The health hazards associated with environmental Al3` continues to attract attention. The current medical situation concerning the possible role of aluminium in Alzheimer’s disease has been reviewed.4 For a healthy adult the (safe) daily dietary intake of aluminium can be up to 60 mg.The aluminium content of German foodstu§s has been investigated,5 and the oral exposure of adults to aluminium was the subject of a recent long term survey.6 A huge amount of beer is consumed from aluminium cans so that it is surprising that this source of aluminium has evaded investigation until now! It was shown that the aluminum cans are corroded over time by canned beer, but that the corrosion may be reduced through refrigeration; in any case the quantities are minute compared to the allowed intake of aluminium.7 Bentonite is often used for fining wines and thus is another possible aluminium source, however \3mgL~1 is contained in red or white wines.8 The pros and cons of the risk of exposure to aluminium from drinking water for the development of Alzheimer’s disease have been discussed.9 Aluminium salts are also the major constituent of many widely used antiperspirants, the use of which has been linked with the systematic in vivo accumulation of aluminium. 10 Whatever the risk for healthy people, for patients undergoing renal dialysis aluminum toxicity is a major clinical hazard associated with anaemia, disturbed lymphocyte function and immunosuppression–the e§ects can be lethal.11 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 45The term ‘ultratrace element’ has been defined as an element with an ‘established, estimated, or suspected requirement generally indicated by lg day~1 for humans’. Whilst aluminium has been so classified since 1984, its possible beneficial role in biochemistry is still only suspected, and swamped by potentially hazardous e§ects.12 Neither is the molecular mechanism of aluminum neurotoxicity understood. Some synergic e§ects have recently been investigated.Thus an association with nitric oxide has been discovered. Major alterations in nitric oxide regulation in Altzheimer’s disease have been observed.13 Chronic exposure to aluminum impairs the neuronal glutamate-induced activation of nitric oxide synthase and nitric oxide-induced activation of guanylate cyclase, so that impairment of the glutamate–nitric oxide–cyclic guanosine monophosphate (GMP) pathway in neurons may contribute to aluminum neurotoxicity.14 Aluminium salts apparently have the capacity to promote prooxidant events in the central nervous system in rats, measured levels of nitric oxide synthase were increased.15 It is also possible that Al3` neurotoxicity may be related to an alteration of the intracellular calcium regulatory system.Thus Al3` modifies Ca2` uptake in the endoplasmic reticulum, accelerates Ca2` release from mitochondria and strongly inhibits Ca2`–ATPase activity with a consequent high-level calcium accumulation inside the cell.16 The e§ect of aluminum on acetyl–CoA and acetylcholine metabolism in nerve terminals has been studied.The ion [Al(PO 4 )(OH)]~ may be the active form of aluminium which interacts with the verapamil binding sites of Ca2` channels, so restricting the Ca2` influx to the synaptoplasm. MVerapamil is a class IV antiarrythmic drug which blocks voltage sensitive Ca2` channelsN.This may inhibit the provision of acetyl–CoA to the synaptoplasm as well as the Ca-evoked ACh release. The authors suggest that excessive accumulation of aluminium in some encephalopathic brains may, by this mechanism, suppress still-surviving cholinergic neurons and exacerbate cognitive deficits caused by already-existing structural losses in the cholinergic system.17 There may also be links between magnesium deficiency and aluminium, whereby the uptake of aluminium is accelerated by magnesium deficiency during age-related neurodegenerative processes.18 Aluminium at concentrations as low as 0.015mM has been found to induce changes in the rheological properties of mucin, the important glycoprotein which forms mucus in solution.Aluminium will cause precipitation of the mucin biopolymer. Considering the ubiquitous nature of mucin in plants and animals this observation may have wide ranging implications for biological systems.19 Aluminum tris(8-hydroxyquinoline) is presently considered to be one of the most reliable electron transporting and emitting materials for molecular-based organic light-emitting diodes.Intense blue colours can be obtained from devices constructed using the quinolines and related compounds.20 Doping the materials with laser dyes gives other colours, for example, red–orange and yellow.21 The reactions of AlMe 3 with di-2-pyridylamine gave three compounds, all emit an intense blue color in solution and the solid state when irradiated with UV light.22 Materials with similar properties based on the 7-azaindole anion,23 and 2-hydroxypyridine, 2-pyridinemethanol, 8-hydroxyquinoline and 8-quinolinemethanol,24 have been described.The fluorescence behavior of the aluminium quinolinates have been studied in reverse micellar systems and very large fluorescence enhancement factors observed.25 Aluminium tris(2,6-diphenylphenoxide) acts as an intriguing bowl-shaped Lewis acid host which can protect various substrates which would otherwise react and Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 46promote regio- and stereo-specific reactions for groups which can coordinate to the aluminium.26 Highly selective b-diketone type ligands have been designed for Group 13 metal ions, in which the complexation of the Al3` was found to be dependent on the inter-ligand contact.27 The reaction of 2,2@-(buta-1,3-diyne-1,4-diyl)bis[6-(1,1- dimethylethyl)-4-methylphenol] with AlBu* 3 gives the corresponding bis(di-isobutylaluminium phenoxide), this holds two strongly Lewis acidic atoms of aluminum in a potentially convergent orientation. A 1: 1 adduct is formed with dme.An X-ray crystallographic study showed that the adduct is a linear oligomer in which the two Lewis acidic sites each bind a basic oxygen atom from di§erent molecules of dme.However, low-temperatureNMR solution studies indicated that a discrete 1: 1 adduct is favored, in which the two Lewis acidic sites each bind one of the two basic sites in a single molecule of dme. Formation of this adduct provides an example of the recognition and binding of a multidentate Lewis base by a complementary multidentate Lewis acid.28 Reaction of AlBu5 3 with Bu5 3 Al[O(H)CH 2 CH 2 CH 2 NMe 2 ] yielded the Lewis acid-base complex [(Bu5 2 AlMl-OCH 2 CH 2 CH 2 N(Me) 2 AlBu5 3N] 2 A.Compound A is also formed directly when 2 equivalents of AlBu5 3 reacts with 1 equivalent of [Bu5 2 Al(l-OCH 2 CH 2 CH 2 NMe 2 )] 2 .In contrast, the reaction of 2 equivalents of AlBu5 3 with 1 equivalent of [Me 2 Al(l-OCH 2 CH 2 NMe 2 )] 2 yielded Me 2 Al(l- OCH 2 CH 2 NMe 2 )AlBu5 3 B. The molecular structure of B shows the AlMe 2 chelate moiety bound to the anionic bidentate ligand, while the AlBu5 3 moiety is bonded to the anionic terminus of the ligand. The formation of compound A may occur via the Bu5-analogue of compound B, i.e., Bu5 2 Al(l-OCH 2 CH 2 CH 2 NMe 2 )AlBu5 3 , which is unstable due to significant Bu5 · · · Bu5 interligand interactions.29 A theoretical investigation using ab initio methods concerning the nature of the Al-containing species present in dilute aqueous alkaline solution, together with associated IR spectra measurements, confirms that the dominant species present is the [Al(OH) 4 (H 2 O) 2 ]~ anion.At high concentrations of sodium aluminate it was predicted that dimerization to the doubly hydroxy-bridged species [(OH) 3 Al(OH) 2 Al(OH) 3 ]2~ can occur and that this is assisted by the coordination of two or more water molecules.30 X-Ray structural and IR spectral measurements were carried out on mitryaevaite, ideally Al 10 [(PO 4 ) 8.7 (SO 3 OH) 1.3 ]p10 AlF 3 ·30H 2 O, a new mineral species from a Cambrian formation and occurring in the weathered zone of a vanadium-bearing black shale in carbonaceous concretions containing clay and fluorapatite.The mineral comes from southern Kazakhstan, and its name honours Dr Nonna Mikhailovna Mitryaeva for her contributions to mineralogy in Kazakhstan.31 A new aluminium vanadium oxide hydroxide, [Al 2 (OH) 3 (VO 4 )], an analog of the mineral augelite has been prepared.The structure contains clusters of edge sharing AlO 6 octahedra and AlO 5 trigonal bipyramids joined together by VO 4 tetrahedra.32 A series of aluminophosphate-based tubular mesoporous molecular sieves with and without substituted Si have been synthesized and characterised by a variety of techniques.The incorporation of the Si appears to make the aluminophosphate framework more flexible and facilitates the formation of an aluminophosphate-based mesoporous structure.33 A new two-dimensional aluminophosphate layer [Al 2 P 3 O 10 (OH) 2 ]- [C 6 NH 8 ] with an Al 2 P 3 O 12 3~ stoichiometry has been prepared from an alcoholic system using 4-methylpyridine as a template.The structure has alternating aluminum units, AlO 4 and AlO 5 , and PO 4 , PO 3 (OH), PO 2 (––O)(OH) units with rows of edge- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 47sharing bridged six-membered rings and zigzag four-membered rings. The layers are held together by strong H-bonds. The organic ammonium cations [C 6 NH 8 ]` are located in the large cavities between the interlayer regions.34 A novel type of tridecameric cation consisting only of interconnected AlO 6 units is found in [Al 13 (OH) 24 (H 2 O) 24 ]Cl 15 ·13H 2 O.35 Unusual Al–Si, Al–P and Al–As bonds have been stabilised by the bulky ligand 2,2,6,6-tetramethylpiperidine (tmp) in the compounds [(tmp) 2 AlY] [Y\OR, SR, NR 2 , PR 2 , AsR 2 , CR 3 , Si(SiMe 3 ) 3 ; R\organyl, H].In contrast to the situation in the analogous [(tmp) 2 BY] compounds, quantum mechanical calculations rule out aluminium to nitrogen p-p to p-p bonding.36 Mono-adducts between (tmp) 2 AlX, (X\Cl, Br, I) complexes and Lewis bases, (tmp) 2 AlX·L, (L\py,thf) were observed, subsequent reaction with AlX 3 formed the tricoordinate alane, [(tmp) 2 AlL][AlX 4 ].37 The unique cluster (2,6-mes 2 H 3 C 6 Al) 2 [As(H)Ph 2 ](l-PhAsAsPh), which has a basket-shaped Al 2 As 4 core, was prepared by heating (H 2 AlC 6 H 3 mes 2 -2,6) 2 with an excess of H 2 AsPh.38 The chemistry of low valent aluminium compounds is fascinating.The first tetrahedral aluminium clusters containing r-bonded alkyl groups such as [M(Me 3 Si) 3 CNAl] 4 and [Cp*Al] 4 has been reported.These compounds complete the Group 13 tetrahedrane series.39 Oxidative addition of (mes)N––CHCH––N(mes) to [Cp*Al] 4 results in the monomeric AlIII derivative, [(g5-Cp*)AlN(mes)CH––CHN(mes)], which was characterised by X-ray crystallography.40 Potential precursors for low-valent aluminum compounds, bulky alkylaluminum dihalogenides [(Me 3 Si) 3 CAlX 2 ·thf] (X\F, Cl, Br, I) and dialkylaluminum halogenides [(Me 3 Si) 3 CAl(Me)X·thf] (X\Cl, Br, I) have been prepared.41 Reaction of AlCl 3 or AlBr 3 with R*Na (R*\SiBu5 3 ) gave the rubycoloured dialane R* 2 Al–AlR* 2 .An X-ray structure determination showed an Si 2 Al–AlSi 2 unit with the longest Al–Al bond to date [275.1(2) pm].42 R 2 Al–AlR 2 [R\CH(SiMe 3 )] reacts with LiCH 2 SMe with insertion of a carbene CH 2 into the Al–Al single bond.The product has a central R 2 Al–CH 2 –AlR 2 group with two coordinatively unsaturated Al atoms.43 Disproportionation of metastable AlX-solutions (X\Cl, Br, I) generates donor-stabilized (DAlX 2 ) 2 species, the Al–Al bond lengths in these are significantly shorter than in the organometallicR 2 Al–AlR 2 species, being strongly influenced by the donor molecule as well as by the halogen ligands.44 Reaction of Cp*Al with Al 2 I 6 proceeds by insertion of three Cp*Al moieties into the bridging Al–I bonds to form a curious Cp* 3 Al 5 I 6 compound with a cage structure in which an Al 2 unit is bridge bonded to an Al 3 unit by iodines.The compound is important in that it demonstrates the potential ro� le ofAlII species during the reactions between aluminium metal and alkyl iodides.45 Cationic alkyl aluminiums based on monoanionic N,N,N-pyridyliminoamide ligands catalyse ethylene polymerization.46 H 2 AlMN(Et)C 2 H 4 NMe 2N, H 2 AlMN(Me)C 2 H 4 NMe 2N and H 2 AlMN(Et)C 2 H 4 NEt 2N have been proposed as new precursors for the deposition of Al films.47 Novel organoaluminium–antimony compounds such as [Et 2 AlSb(SiMe 3 ) 2 ] 2 and [Bu* 2 AlSb(SiMe 3 ) 2 ] 2 may also be useful as precursor compounds.48 3 Gallium Gallium–gallium bonding is a regular topic for gallium chemistry.In the gas phase Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 48mass spectrometry measurements of diatomic metal–metal dissociation energies give Ga 2 \110.8^4.9 kJ mol~1, GaIn\90.7^3.7 kJ mol~1, In2 \74.4^5.7 kJ mol~1.49 The stability of the Ga–Ga bond in R 2 Ga–GaR 2 [R\CH(SiMe 3 ) 2 ] is further demonstrated by the observation that it is cleaved by some protic reagents such as phenols and also by C–F containing compounds, but that reagents such as dibenzoylmethane and dicarboxylic acids release two bis(trimethylsilyl)methanes leaving the dimer intact. The dicarboxylic acid products [e.g. 1,4-benzenedi(methylcarboxylic) acid, 1,4-cyclohexanedicarboxylic acid, 1,6-hexanedicarboxylic acid, and 1,4-butanedicarboxylic acid) have very short Ga–Ga bonds (237.7pm average), with two carboxylates e§ectively connected in each compound by two ‘spacers’ (dimethylbenzene, cyclohexane, hexane or butane) to form macrocyclic compounds with up to 22 atoms in the resultant heteroatomic rings.50 Double reduction of (Trip) 2 GaGa(Trip) 2 with Na/Et 3 Ngave Na 2 [GaMGa(Trip) 2N3 ] C with a planar GaGa 3 moiety in which the average Ga–Ga distance is 238.9(1.7) pm.This is longer than in the radical anion [(Trip) 2 GaGa(Trip) 2 ]~, 234.3(2) pm, with a formal bond order of 1.5, but shorter than in cyclic materials such as Na 2 [Ga(2,6- mesC 6 H 3 ) 3 ], 244 pm, with a formal bond order of 1.33.Dry oxygen reacted with C to form Ga[Ga(Trip) 2 ] 3 , here the average Ga–Ga bond length is 247.6(7)pm consistent with a bond order of one.51a The indium analogue In[In(Trip) 2 ] 3 was discovered in 1996.51b The formation of gallium ‘triple bonds’ has recently been disputed.52 [Tp(Bu5 2 )]Ga reacts with sulfur to form [Tp(Bu5 2 )]GaS providing evidence for gallium forming a double bond to sulfur; the corresponding indium compound gave a tetrasul- fido compound [Tp(Bu5 2 )]In(g2-S 4 ).53 Several compounds with potential as CVD precursors (chemical vapour deposition) have been described: [Bu5 4 Ga 4 (l3 -Ex)(l3 -Te) 4~x] (x\0–4; E\S, Se);54 [MeGaMl- N(H)PhN] 4 ;55 Me 3 Ga·Sb(SiMe 3 ) 3 and [Me 2 GaSb(SiMe 3 ) 2 ] 3 ;56 [Pr/(Cl)GaAsBu5 2 ] 2 and [(PhCH 2 ) 2 InAsBu5 2 ] 2 .57 EPR studies were reported for various isotopomers of GaH 2 and HGaCH 3 .58 Stepwise dehydrogenatioof [H 2 GaNH 2 ] 3 in supercritical ammonia at 15 °C generated the poly(imidogallane), [HGaNH]n.59 Various cluster compounds have been prepared: [(tmp)GaS] 4 ;60 Ga 4 [XC(SiMe 2 - R) 3 ] 4 (R\Me, Et) heterocubanes by reaction of Ga 4 [C(SiMe 3 ) 3 ] 4 with X\S, Se and Te;61 the quasi double cubane, [Ga 4 (OH) 6 (3-Bu5pzH) 10 ]6`, but no discrete Ga 4 O 4 , as yet, has been identified;62 heterometallic derivatives of [Mo 3 S 4 (H 2 O) 9 ]4` such as [Mo 3 GaS 4 (H 2 O) 12 ]5`,63 the tungsten–gallium cluster [W 3 GaO 4 (O 2 CEt) 8 ] 2 2~;64 the dinitrogen complex trans,trans-[MWX(PMe 2 Ph) 4 (l3 -N 2 )N2 (GaX 2 ) 2 ] (X\Cl, Br);65 gallium–iron clusters such as [(CO) 4 Fe–Ga 3 (OH) 4MSi(SiMe 3 ) 3N3 ] and [M(CO) 3 FeN2MGaSi(SiMe 3 ) 3N2 Cl]~;66 a gallium(I) pyrazolylborate compound with a short, two-electron dative bond [Ga: Fe[HB(3,5-Me 2 pz) 3 ]GaFe(CO) 4 ];67 CN~ reacts with GaMe 3 to form polymers [CsMCN(GaMe 3 ) 2N]n and [Cs(C 6 H 5 Me) 2MCN(GaMe 3 ) 2N]n.68 A wide variety of organogalliums have been studied: the benzylgallium compounds M[Mg 3 Br 2.4 Cl 1.6 (OEt 2 ) 6 ][Ga(CH 2 Ph) 4 ] 2 ·0.5C 6 H 5 MeN and [(3,5-Me 2 C 6 H 3 CH 2 ) 2 GaBr] 2 ;69 [(mes* 2 C 6 H 3 )GaCl 2 ] 2 ;70 Bu5 3 SiGaX 2 and (Bu5 3 Si) 2 GaX, (X\halide);71 heterocycles with Ga 2 Si 2 and a Ga 3 Si frameworks;72 [(PhMe 2 CCH 2 ) 2 GaNH(Bu5)] 2 and [(H 4 C 6 )Me 2 CCH 2 ]Ga[NH(Bu5)] 2 Ga(CH 2 CMe 2 Ph) 2 ;73 various SalenBu5 ligand dervatives of GaMe 3 and GaEt 3 ;74 [R 2 AlM(SePPh 2 N)N (R\Me, Et, Bu*) and Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 49[Et 2 GaM(SePPh 2 ) 2 NN];75 [(Me 3 SiCH 2 ) 2 GaP(SiMe 3 ) 2 ] 2 ;76 (mes) 2 Ga(facac) and Me 2 Ga(facac)·py;77 chalcogenides of GaIII (and AlIII) derived from Lewis base adducts of gallane (and alane), [Ga(TePh) 3 (NMe 3 )], [Ga(SeEt) 3 ·NMe 3 ] and [Ga(TePh) 3MP(C 6 H 11 ) 3N], trans-[MGaCl(l-Se)[P(C 6 H 11 ) 3 ]N2 ].78 GaMe 3 induced trimerization of acetonitrile leads to a hexanuclear gallium complex [(Me 2 Ga) 4 (MeGa) 2MHNC(Me)C(CN)CH(NCMe) 2N2 ].79 Four-coordinate dimethylgallium complexes containing bidentate ligands with O,O; O,N and S,N donor atoms were evaluated for their stability toward decomplexation in water, this is a key property in determining their potential as radiopharmaceuticals. The most hydrolytically stable compounds were those based on an N-alkylsalicylaldimidate donor.80 Triethylenetetraminehexaacetic acid (H 6 ttha) forms a strong complex with Ga3`, [Ga 2 (OH) 2 (ttha)][Na 2 (H 2 O) 6 ]·2H 2 O.The ligand is a potential chelating agent relevant to radiopharmaceutical applications involving Al3`, Ga3`, and In3`.81 The gallium(III) and indium(III) complexes of tris(2-mercaptobenzyl) amine and tris(2-hydroxybenzyl)amine were investigated in solution and in the solid state to help interpret their contrasting in vivo behavior as diagnostic imaging probes.82 Molecular-seive-type gallium phosphates have been prepared: Ga 4 (PO 4 ) 5 HF·1.5(tmen)·H 2 O (or ULM-18) an oxyfluorinated gallium phosphate was obtained by hydrothermal template synthesis using tmen;83 an aza-crown ether 1,4,7,10,13,16-hexaazacyclooctadecane acted as a template for Ga 5 F 2 (HPO 4 ) 2 (PO 4 ) 4 , C 12 H 27 N 6 (MIL-1);84 a new gallophosphate containing a gallium organic complex macrocycle 1,4,8,11-tetraazacyclotetradecane as part of the framework;85 a 14-membered ring gallium oxyfluorophosphate, Ga 7 P 6 O 28 F 3 C 10 N 2 H 16 , has 4,4@-bipyridyl and pyridine in the 14-ring channels;86 [NH 3 (CH 2 ) 4 NH 3 ][Ga(PO 4 )(PO 3 OH)], is a one-dimensional gallophosphate;87 and a gallium phosphonate cluster (Bu5 7 Ga 3 P 3 O 8 )·Bu5OH.88 4 Indium The preparation of nanometer size isolated particles of semiconductor materials is of considerable current interest, these are particles small enough to show quantum confinement and electronic e§ects dependent on the size of the particles.Group III–V materials have been di¶cult to prepare until now. In(PBu5 2 ) 3 can be used to form quantum dot indium phosphide, and it is likely that the method can be applied to InAs and GaP.89 (C 6 H 11 )PH 2 with InMe 3 cleanly forms thin films of crystalline InP under pyrolytic CVD conditions.90 Thin films of CuInSe 2 for solar cell devices have been grown by low-pressure MOCVDusing In[Se 2 CNMe(n-C 6 H 13 )] 2 and Cu[Se 2 CNMe- (n-C 6 H 13 )] 2 as precursors.91 Complexes of general formulae In(S 2 CNMeR) 3 (R\ Bu/, n-C 6 H 13 ) are useful air-stable precursors for other materials such as In 2 S 3 .92 The syntheses and X-ray crystal structures of [PPh 4 ][In(SePh) 4 ] and [PPh 4 ]- [In(SePh) 3 (SeH)],93 and of the one-dimensional compound [Ph 4 P][In(P 2 Se 6 )] D have been reported.93 Compound D contains infinite [In(P 2 Se 6 )]n ~ chains with a structure related to that ofK 2 FeP 2 Se 6 .94 Indium tris(alkylthiolate) compounds,95 and the neutral species InM(SCH 2 CH 2 ) 3 NN were synthesized and structurally characterized. 96 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 50The first examples of mixed valence thioindates have been prepared, KIn 5 S 6 and MIn 5 S 7 (M\Na, K), in these indium appears as In`, In3` and covalent pairs of [In 2 ]4` along with S2~ and M`.97 The InII–InII compound M2,6-(Me 2 NCH 2 ) 2 C 6 H 3N(Cl)In–In(Cl)M(2,6-Me 2 NCH 2 ) 2 - C 6 H 3N2 has been prepared and characterised by X-ray crystallography.98a The cyclodiphosph( III)azane complex [M(BuNP)Bu5N2M(BuN)Bu5N2 In] 2 is a dimer of mononuclear indium(II) cages that are connected by an In–In bond.98b The reaction of R 2 In–InR 2 [R\CH(SiMe 3 ) 2 ] E, with Bu5NC or PhNC results in the formation of adducts rather than scission of the In–In bond.The In–In bond length (average 284.8 pm) is only slightly lengthened compared with those for E (282.8 pm).99 KInBr 3 is the first ternary InII bromide.100 In 4 [C(SiMe 3 ) 3 ] 4 abstracts O from o-nitrosotoluene forming the extremely hygroscopic In 4 O 4 [C(SiMe 3 ) 3 ] 4 , the structure exhibits a distorted In 4 O 4 moiety with normal In–O bond lengths, but short intracage In to In and O to O distances.This preparation completes the tetramer series In 4 X 4 R 4 .101 Various cluster compounds have been prepared: [Mo 3 InS 4 (H 2 O) 12 ]5` and the double cube [Mo 6 InS 8 (H 2 O) 18 ]8`;63 as well as Na 2 [W 3 InO 4 (O 2 CEt) 8 ] 2 ;102 Ni[InMC(SiMe 3 ) 3N4 ] is another amazing compound from Uhl’s Oldenburg group, a tetrahedral compound analogous to Ni(CO) 4 but with Ni–In bonds.103 Monomeric InC 6 H 3 (Trip) 2 -2,6 forms an Mn complex [(g5-Cp)(CO) 2 Mn–InC 6 H 3 (Trip) 2 -2,6]; this has a one-coordinate indium in the solid state.104 Organometallics previously mentioned in the gallium section, and with In analogues are [(mes* 2 C 6 H 3 )InCl 2 ] 2 ,70 Bu5 3 SiGaX 2 and (Bu5 3 Si) 2 GaX (X\halide).71 Indium hydride generating reactions have been described.InCl 3 with HSnBu 3 in thf at[78 °C generated HInCl 2 which was stable up to ambient temperature.105 LiInH 4 with NMe 3 ·HCl gave [InH 3 (NMe 3 )] which, whilst it could not be isolated in the solid state, on reaction with the stable carbene :CN(Pr*)C 2 Me 2 N(Pr*) gave [InH 3M:CN(Pr*)C 2 Me 2 N(Pr*)N].Al and Ga analogues were also prepared.106 Either InMe 3 ·Et 2 O or InMe 2 Cl with a large excess of LiH gave [Li(tmen) 2 ]- [Me 3 InH·InMe 3 ].107 Complexes with In–N bonds have been described: Cs[FInMN(SiMe 3 ) 2N3 ];108 indium amides, In(NRR@) 3 (R\Ph, Bu5, R@\SiMe 3 ; R\Bu5, R@\SiHMe 2 ), Li[InMNMe(SiMe 3 )N4 ], Li[In(NPh 2 ) 3 Cl], In(NRR@) 3 (py) (R\R@\Ph; R\Me, R@\SiMe 3 ), In[N(Bu5)(SiHMe 2 )] 3 (p-Me 2 Npy) and In[NMe(SiMe 3 )] 3 (p-Me 2 Npy), X-ray crystallographic measurements were made on many of these compounds;109 [In 2 Cl 4 L 2 (dmf) 2 ]·2dmf [HL\3-(2-pyridyl)pyrazole];110 [Et 2 In(Htmtaa)], [EtIn(tmtaa)], [ClIn(tmtaa)] and [RIn(tmtaa)] [R\Cp, Me, N(SiMe 3 ) 2 or OSiMe 3 ];111 chloro(phthalocyaninato)indium(III) reacted with R@MgBr [R@\p-tri- fluoromethylphenyl, m-trifluoromethylphenyl, p-fluorophenyl, perfluorophenyl] to form r-bonded aryl(phthalocyaninato)indium(III) complexes.112 Reaction in thf of 1,2-bis(halomercurio)tetrafluorobenzene (halide\Cl, Br) with the corresponding indium(I) halide gave spontaneous ring closure with formation of tetrakis(thf) adducts of 9,10-dichloro-9,10-dihydro-9,10-diindaoctafluoroanthracene and 9,10-dibromo- 9,10-dihydro-9,10-diindaoctafluoroanthracene respectively.113 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 515 Thallium The notorious toxicity of thallium compounds is demonstrated by four instances of poisoning: chronic occupational thallium poisoning in a glass factory;114 symptoms involving skin coloration;115 severe sensorimotor neuropathy;116 and retinal damage, 117 this latter was a case of malicious poisoning.Thallium toxicity has also been reviewed.118 A recent substantial review concerns thallium in the environment: the history, production and uses of thallium;119a the aqueous geochemistry of thallium;119b the analysis of thallium in biological samples;119c human thallium toxicity;119d reproductive and developmental toxicity of thallium;119e thallium transport in cellular membranes. 119f The hydrogeochemistry of thallium in natural waters has been reported, 120 and the environmental implications of some revised hydrolysis constants for TlI and TlIII discussed.121 The problems of thallium pollution associated with mining deposits have been discussed.122 In contrast, thallium-201 reinjection imaging and positron emission tomography (SPECT) is finding increasing use in medicine, particularly for cardiac studies.123 Various mixed metal thallium oxides have been studied. In a-Tl 2 Te 2 O 5 there is strong stereochemical activity of both Te and Tl lone pairs.124 The Tl` lone pair is also stereochemically active in Tl 2 CuAsO 4 ,125 and in Tl[CuAsO 4 ] and Tl[CuPO 4 ].126 A new type 2212 phase has been discovered in a Tl–Hg–Ba–Cu–Osuperconducting system.127 The pathway for the formation of the TlBa 2 Ca 2 Cu 3 O 9 (1223) superconductors was studied, the reaction path implies the double-layer Tl–O series, Tl 2 Ba 2 CuO 6 and Tl 2 Ba 2 CaCu 2 O 8 at 800 °C and Tl 2 Ba 2 Ca 2 Cu 3 O 10 at 875 °C.The Tl-1223 phase is formed above 905 °C.128 Enhanced superconductivity was found in the Tl 1~xBixBa 2 Ca 2 Cu 3 O 9 system with increased Bi concentration (T# \110K at x\0.0 to T# \116K at x\0.2).129 Small amounts of fluorine (x) also increase T# in the compounds (Tl 0.5 Pb 0.5 )Sr 1.6 Ba 0.4 Ca 2 Cu 3 O 9~xFx.130 Much work on thallium superconducting materials is now going into improving their preparation,131 fabrication132 and electrical properties.133 The six-coordinate thallium(III) porphyrin triflate [Tl(tpp)(OSO 2 CF 3 )(thf)·thf]134 and a polymeric complex of TlIII containing bis(semiquinone) bridging ligands have been prepared.135 The preparation of four heterometallic porphyrinate dimers containing Rh–Tl r-bonds enabled the magnitudes ofNMRspin–spin coupling constants between thallium and rhodium nuclei to be measured for the first time.136 A new class of oligonuclear direct metal–metal bonded Pt–Tl compounds with the formula [(NC) 5 Pt–Tl(CN)n~1 ](n~1)~ (n\1–4) have been described.The compounds have huge Pt195–Tl205 spin–spin coupling constants, 25–71 kHz, for [(NC) 5 Pt–Tl(CN)] this is 71 060 Hz, and is the largest reported coupling constant ever observed between two di§erent nuclei!137 The X-ray crystal structure of [Tl(OPPh 3 ) 2 ][Au(C 6 F 5 ) 2 ] provides evidence for unsupported Au–Tl bonds forming a polymeric linear chain.138 The double cube compound [Mo 6 TlS 8 (H 2 O) 18 ]8` can be prepared but there was no evidence for the single cube [Mo 3 TlS 4 (H 2 O) 12 ]5`.63 The anions Tl 2 E 2 2~ (E\Se and/or Te) were prepared by extraction of MTlE (M\Na, K; E\Se, Te), in en–liquid NH 3 in the presence of 2,2,2-crypt.139 Several novel thallium(I) compounds have been described.Thus [2,6- (Trip) 2 C 6 H 3 Tl] is a unique monomeric arylthallium(I) compound with a singly coor- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 45–56 52dinated thallium. 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ISSN:0260-1818    

DOI:10.1039/a804877k

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

5 Nitrogen, phosphorus, arsenic, antimony and bismuth K. K. Hiia and T. P. Keeb aDepartment of Chemistry, King’s College London, The Strand, London, UK WC2R 2LS bSchool of Chemistry, University of Leeds, UK LS2 9JT 1 Introduction This report covers important aspects in the development of Group 15 chemistry during the year 1998.1 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 vast areas of nitrogen and phosphorus chemistry, only synthetic work on novel ligand systems, especially asymmetric systems, has been described with concomitant emphasis on applications in asymmetric catalysis. 2 Nitrogen The co-ordination and organometallic chemistry of tris(2-pyridyl) tripod ligands which use nitrogen, phosphorus, arsenic or carbon as the central bridging atoms, including polypyrazolylborate ligands, has been reviewed.2 Chloro– and methyl–aluminium complexes with the tridentate nitrogen ligand (RNHCH 2 CH 2 ) 2 NR@ (R\R@\SiMe 3 ; R\SiMe 3 , R@\Me; R\Pr*, R@\Me) have been reported.Single-crystal X-ray di§raction studies revealed that the tridentate nitrogen donor atoms enforce an approximately trigonal-monopyramidal co-ordination geometry for neutral and cationic four-co-ordinate aluminium complexes.The cationic aluminium derivatives and the neutral aluminium chloride brought about the ring-opening oligomerization of propylene oxide, giving low molecular weight polymers consisting exclusively of head-to-tail linkages.Methyl– and hydrido–aluminium as well as aluminium alkoxide, initiated the polymerization of (D,L)-lactide in benzene at 80 °C to give high molecular weight polymers.3 The interaction of MnII, FeII and CoII with the ligand taci 1 has been studied in the solid state and in aqueous solution.4 Magnetic susceptibility measurements revealed a high-spin electron configuration for the Mn and the Fe complexes.All three structures exhibited distorted octahedral MN 6 co-ordination. The stability constants for the complexes [M(taci)]2` (M\Mn, Fe, Co) and [M(taci) 2 ]2` (M\Fe, Co) in aqueous media have been evaluated by potentiometric titration. Comparison with other Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 57divalent cations showed that the order of stability increases MnII\CoII[FeII\ZnII\CoII\CuII\NiII.A new isomeric form of a bis-taci cobalt(III) complex was formed, where one of the taci ligands co-ordinates the metal cation by one nitrogen and two oxygen atoms. The hexamethylideneimino (hmi) derivative [Co(taci) 2 (hmi)]3` reacts with nitromethane and base and results in the formation of [Co(hebdoc)]`, where the two fragments are fused by two anionicN––CH–C(––NO 2 ~)–CH 2 –NHbridges.5 Two major diastereoisomers were formed from fifteen possibilities which possessed di§erent con- figurations at co-ordinated methylamino groups and were incorporated in a disordered manner in the crystal structure of [Co(hebdoc)] 2 Cl 2 ·3.5H 2 O.In the base-catalyzed reaction of [Co(tmca) 2 ]3` with an appropriate mixture of formaldehyde and acetaldehyde, the condensation process was followed by a coupling reaction.After reduction with NaBH 4 and air oxidation, a cobalt(III) complex with the novel hexadentate ligand N-(q@-amino-8@,10@,11@-trimethoxy-2@,6@-diazabicyclo[5.3.1]undec-4@-ylmethyl)-2,4,6- trimethoxycyclohexane-1,3,5-triamine was formed as the major product.Direct treatment of [Co(taci) 2 (hmi)]3` and [Co(tmca) 2 (hmi)]3` with NaBH 4 resulted in the liberation of the new triamines 1,3,5-trideoxy-1,3,5-tris(methylamino)-cis-inositol and all-cis-2,4,6–trimethoxytris(N-methyl)cyclohexane-1,3,5-triamine. A phenol-based ‘end-o§’ compartmental ligand, 2-[N,N-di(2- pyridylmethyl)aminomethyl]-6-MN-[2-(dimethylamino)ethyl]iminomethylN-4-methylphenol 2 (HL), forms dinuclear nickel complexes [Ni 2 (L)(AcO)(NCS) 2 ], [Ni 2 (L)(AcO) 2 (MeOH)]PF 6 , and [MNi 2 (L)(OH)(MeOH)N2 (CO 3 )](PF 6 ) 2 .The complexes react with urea in ethanol to form the isocyanate complexes [Ni 2 (L)(AcO)(NCS)(NCO)], [Ni 2 (L)(AcO)(NCO)(EtOH)]PF 6 and [MNi 2 (L)- (NCO)(EtOH)N2 (CO 3 )](PF 6 ) 2 , respectively.6 The co-ordination chemistry of the bis(benzimidazolyl) ligands 3 [X\S, O, S(CH 2 ) 3 S, S(CH 2 ) 2 S; R1, R2, R3\H, Me) has been studied for a series of soft-toborderline metal ions such as zinc, mercury, cadmium and silver.7 The ligand bis(2-benzimidazolyl)propane 4 co-ordinates to NiII with chloride as an anion forming a dinuclear compound with the formula [NiCl 2 (tbz) 2 ] 2 ·2EtOH.8 Each NiII ion has a distorted trigonal bipyramidal environment consisting of two asymmetrically bridging chloride anions, two nitrogen atoms of the ligand and a Ni–Ni bond.Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 58This compound appears to be the second example of a five-co-ordinated ferromagnetic dinuclear nickel(II) compound of this type, and its magnetic properties appear to correlate with the ligand structure.Octaethylformylbiliverdin (H 2 OEFB) 5 was found to form low-spin complexes with CuII, NiII and CoII. Both CuII(OEFB) and CoII(OEFB) can be converted to the heme analogues, [CuII(OEOP)]` and [CoII(OEOP)]`, where OEOP is the anion of octaethyl- 5-oxaporphyrin.9 The geometric and electronic structural properties of these complexes of formylbiliverdin were compared to those of analogous compounds of biliverdin and of porphyrins.The (aminoferrocenyl)phosphine 1-diphenylphosphino-2,1@-(1-dimethylaminopropanediyl) ferrocene, 6, was used to synthesize new palladium complexes [Pd(L)(DMFU)] and [Pd(L)(MA)] and the allyl complex [Pd(g3-2-MeC 3 H 4 )(L)] [OTf]. All these compounds exist in solution as mixtures of two diastereoisomers, with either the alkene or the allyl group di§erently oriented with respect to the aminophosphine ligand.Other palladium(II) derivatives of formulae [PdRR@(L)] (R\Cl, R@\Me; R\R@\Me; R\R@\C 6 F 5 ) were also prepared. Pd–N bond rupture in the new complexes was analyzed along with the influence of ferrocenyl aminophosphine and ancillary ligands. The oxidation state of the palladium centre on this process was discussed.10 A simple synthesis has been devised for the tripodal 3,3,4-tetraamine ligand NM(CH 2 ) 3 NH 2N2M(CH 2 ) 4 NH 2N (L).This ligand forms a copper(II) complex, [Cu(HL)Cl 2 ]ClO 4 , the structure of which has been determined by X-ray di§raction. The cation contains a five-co-ordinate copper atom, bonded to two chloride ions, the two propylamine groups and the tertiary nitrogen atom of the ligand adopt a distorted trigonal bipyramidal arrangement in which the two primary amine groups occupy the axial positions.The butylamine group of the ligand does not co-ordinate to copper but is protonated.11 Reaction of the bidentate compound 2-(2-aminophenyl)pyridine with p-toluenesulfonyl chloride a§orded the new bidentate compound HL which contains potentially chelating pyridyl and (protonated) sulfonamide N-donor binding sites.The crystal structure of the latter molecule shows that the sulfonamideNHproton is involved in a hydrogen-bonding interaction with the pyridyl nitrogen atom, resulting in a near co-planar arrangement of the pyridyl and phenyl rings. Reaction of HL with various metal(II) acetates (M\Cu, Co, Pd) a§ords the neutral complexes [ML 2 ] in which the sulfonamide is deprotonated.All of these have been crystallographically characterised; the copper(II) and palladium(II) complexes are planar, whereas the cobalt(II) complex is Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 59pseudo-tetrahedral with the two CoN 2 planes at 85° to one another. Appropriate spectroscopic and electrochemical studies on the complexes were described.12 Reaction of (C 5 H 4 Me) 3 Ln and HTz in THF a§ords the complexes [(C 5 H 4 Me) 2 LnTz] 2 (Ln\Yb, Er).13 An organopalladium complex containing orthometallated (S)-[1- (dimethylamino)ethyl)]naphthalene as a chiral auxiliary has been used successfully to promote the asymmetric [4]2] Diels–Alder reaction between 3,4-dimethyl-1- phenylphosphole and 2-vinylpyridine.14 The pyridyl group in the resulting phosphanorbornene cycloadducts can be located stereospecifically in the exo or endo position by controlling the electronic properties of the organopalladium promoter.In the exo-cycloaddition process, the P–N bidentate ligand ([)-2-M[1-a,2-a-(S),4-a,7(S)]- 5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-en-2-ylNpyridine 7 was produced stereoselectively. However, in the endo-cycloaddition process, a pair of separable diastereomeric palladium template complexes containing the naphthylamine auxiliary and the enantiomeric forms of 2-M[1-a,2-b(R/S),4-a,7(R/S)]-5,6-dimethyl-7- phenyl-7-phosphabicyclo[2.2.1]hept-5-en-2-ylNpyridine 8 were obtained.In these diastereoisomeric complexes, the endo-cycloadducts co-ordinated to palladium as monodentate ligands via only their phosphorus donor atoms.The pyridyl-nitrogen atoms are not involved in metal complexation. The absolute configurations and the co-ordination properties of the exo- and endo-pyridylphosphines have been established by single-crystal X-ray analyses. 3 Phosphorus Abrief review article on the synthetic and structural aspects of dialkyldithiophosphate, alkylenedithiophosphate and dialkyldithiophosphinate derivatives of arsenic, antimony and bismuth and their organometallic moieties has been published.15 Organophosphorus boranes R 3 P·BH 3 (R\Ph, Me, OMe, o-anisyl) react with amine pentacarbonyltungsten complexes under mild conditions to a§ord the corresponding W(CO) 5 (PR 3 ) derivatives in 63–92% yields.The use of piperazine as a diamine tungsten substituent permits a tandem reaction which removes the borane group and leads to the formation of the corresponding organophosphorus tungsten complex. The stereochemistry of pentacarbonyltungsten complex formation from tertiary chiral organophosphorus borane compounds has been shown to proceed with high stereoselectivity and retention of configuration at the chiral phosphorus centre.16 Reaction of the amino acid derivate (S)-N-tolylsulfonylvaline with PhPCl 2 and NEt 3 gives, in [90% yield, a novel chiral phosphorus heterocycle 9 as a [7: 1 mixture of diastereoisomers.The X-ray crystal structure of the major isomer shows that the isopropyl and phenyl groups are mutually cis.The IR spectrum of the W(CO) 5 Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 60adduct of this isomer shows that the N-sulfonyl and carboxylate moieties make it a strongly electron-withdrawing ligand.17 Optical resolution of the asymmetric chelating agent (^)-Ph 2 PCH 2 S(O)Me has been achieved via fractional crystallization of a pair of diastereomeric palladium(II) cationic complexes containing the sulfinyl-substituted ligand and orthometallated (S)-[1-(dimethylamino)ethyl]naphthalene. Optically pure (R)-(])-Ph 2 PCH 2 S(O)Me was displaced from the resolving palladium complex with 1,2-bis(diphenylphosphino) ethane.18 Chelating phosphorus ligands 4,6-bis(diphenylphosphanyl)-2,8-dimethylphenoxathiine 10 (Thixantphos) and 11 with a rigid backbone and a large natural bite angle have been used in the in the nickel-catalysed hydrocyanation of styrene. The para-substituents in the diphenylphosphanyl moiety of the Thixantphos ligands were varied and their electronic e§ects on the activity and selectivity of the catalytic experiments were investigated.19 Recent progress in copper-catalyzed enantioselective Michael additions using new phosphorus ligands have been described.20 A novel enantiomerically pure 2-[2(diphenylphosphino)phenyl]-4,5-(2-deoxy-a-Dglucopyrano) oxazoline ligand 12 has been prepared from glucosamine. The stereodifferentiating potential of the ligand was demonstrated in palladium-catalyzed intermolecular allylic substitutions of symmetrical and asymmetrical substituted allyl acetates which give products in high yields and high enantioselectivity (up to 98% ee).21 A series of novel N,N-disubstituted aminophosphines 13 have been prepared.The new P,N-binaphthyls were utilized as chiral ligands in palladium-catalyzed allylic substitution and enantioselectivities of up to 71–73% ee were achieved at room temperature.22 The sterically demanding binaphthyl backbone has continued to be exploited to make new chiral ligands which have been applied to the copper-catalyzed asymmetric conjugate addition of diethylzinc to cyclic enones with high enantioselectivity.23,24 Cationic allyl palladium complexes of the diasteriomerically pure chiral-at-phos- Annu. Rep.Prog. Chem., Sect. A, 1999, 95, 57–66 61phorus ligand tert-butyl(menthyl-O)phenylphosphinite have been prepared and characterized by X-ray crystallography. Asymmetric co-dimerization of styrene and ethylene was successfully applied.High enantioselectivities of up to 86% ee have been obtained at room temperature. The co-dimer 3-phenylbut-1-ene was formed in high selectivity (up to 96%) with only small amounts of the isomerization products (E)- and Z)-2-phenylbut-2-ene.By addition of various co-ordinating solvents, the catalyst system was e¶ciently stabilized. Variation of the complex counter anion had a significant e§ect on enantioselectivity.23 4 Arsenic and antimony The synthesis of various diorganodithiophosphate (and dialkyldithiophosphinate) derivatives with arsenic, antimony and bismuth and their corresponding organometallic moieties and mixed derivatives as well as their properties and reactions have been described.24 The syntheses of mixed bis(dialkyl dithiocarbamate) dialkyl dithiophosphate complexes of antimony(III) of the type (XCS 2 ) 2 SbS 2 P(OR) 2 (X\NMe 2 , NEt 2 , N(CH 2 ) 4 ; R\Pr/, Pr*, Bu/ and Bu*) have also been described.25 Synthetic routes to arsenic(III) dithiolate [PhAs(HlipS 2 )] and related compounds have been reported.The reactions indicate pathways by which mono- and diorganoarsenic compounds of various arsenic oxidation states (I, III and V) may inhibit enzymes that contain lipoic acid as a co-factor.26 The synthesis and structure of a cyclic polyarsenic ring ligand [MoAs 8 ]2~, which is the first example of a free binary transition metal pnictide ion, have been reported. A preliminary study of its gas phase co-ordination chemistry with alkali metal ions was carried out through negative ion electrospray mass spectroscopy.27 The reaction of Group 15 trichlorides of ECl 3 with the anion [Mo 2 Cp 2 (CO) 4 (l- PH 2 )]~ resulted in the isolation of a complex featuring a hetero l,g2-PE ligand (E\As, Sb).28 Antimony has been found to co-ordinate as a symmetrically bridged ligand in a novel neutral complex [LW–Sb–WL] [L\N(CH 2 CH 2 NCH 2 CMe 3 ) 3 ] 14.29 Reaction of equimolar amounts of the metalloarsaalkene [(g5- C 5 Me 5 )(CO) 2 FeAs––C(NMe 2 ) 2 ] with the carbonyl complexes [Ni(CO) 4 ], [Fe 2 (CO) 9 ] and [M(Z)-C 8 H 14NCr(CO) 5 ] (C 8 H 14 \cyclooctene), respectively, a§ords the adducts [(g5-C 5 Me 5 )(CO) 2 FeAsMM(CO)nN–C(NMe 2 ) 2 ] M[M(CO)n]\[Ni(CO) 3 ], [Fe(CO) 4 ] or [Cr(CO) 5 ]N.These feature g1 co-ordination of the arsaalkene ligand via the arsenic atom.30 (1,2,3,4-Tetraisopropylcyclopenta-2,4-dien-1-yl) arsenic(III) dihalides, TipCpAsX 2 Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 62(X\Br, I), have been prepared by direct metathesis reaction between the corresponding arsenic(III) trihalides with 1 equivalent of TipCpK at low temperature in good yields.The crystal structures were determined by X-ray di§raction methods and the AsX 2 -moiety in both complexes found to occupy an allylic position neighbouring to an isopropyl substituent. The arsenic fragment is r-bound to the cyclopentadienyl ligand, indicating remarkable p interactions with the diene part of the cyclopentadienyl ring.31 The new cyclopentadienylarsanes (CpRAsR 2 ) (CpR\C 5 Me 5 ; R\H, Et, Pr*, Bu5; CpR\C 5 H 2 Me 3 -1,2,4; R\Cl, Et, Pr*) were synthesized via metathesis reactions in satisfactory to good yields.Pyrolysis studies on the cyclopentadienyldialkyls show their potential suitability as precursors in MOCVD processes.32 The photolysis reactions of cyclo-methylarsathiane, cyclo-(MeAsS)n (n\3 or 4) with Group 6 metal carbonyls M(CO) 6 (M\Cr, W) in THF give the complexes [Cr(CO) 5Mg1-cyclo-(MeAsS) 4N], [Cr(CO) 3Mg3-cyclo-(MeAsS) 5N] and [W(CO) 3Mg3- cyclo-(MeAsS) 6N] in which the As–S ring system expands to give metal-stabilized rings of eight, ten and twelve alternating arsenic and sulfur atoms.33 A preference for arsenic over sulfur is shown in all three complexes.Bonding to sulfur occurs only when octahedral symmetry is best accomodated at the metal atom. The main-group ring structures expand as required to fulfil the more demanding electronic and geometrical requirements of the metallic group. The reaction of cyclo-(MeAsO)n (n\2–5) with MCl 3 ·xH 2 Oin acetonitrile at 100 °C a§ords [MCl 2Mcyclo-(MeAsO) 8N] (M\Ru, Os) in which cyclooctamers (MeAsO) 8 are stabilised in a j4As1,As3,As5,As7 As 4 binding mode in the equatorial co-ordination sphere of the Group 8 metals.Octa- or deca-nuclear cagelike platinum complexes [Pt 2Mcyclo-[As(Me)OAsMNC(O)MeNO 2 ] 2N] and [Pt 2M[MMeC(O)NN2 As 5 Me 5 O 4 ] 2N] were also prepared. k5-AsIII atoms in these complexes participate in square-planar PtII co-ordination and themselves exhibit distorted trigonal bipyramidal co-ordination geometries.34 The reaction of Group 15 trichlorides of type ECl 3 with the anion [Mo 2 Cp 2 (CO) 4 (l-PH 2 )]~ has a§orded the first complex featuring a hetero l,g2-PE ligand (E\As, Sb).35 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 63The heterobimetallic antimony(III)–alkali metal complexes [MSb 2 (NC 6 H 11 ) 4N2 Na 4 ] and M[M(C 6 H 11 NH)Sb(l-NC 6 H 11 ) 2N2 Sb]·2thf (M\K or Rb) have been prepared.Comparison of the crystal structures of these species with those of the lithium complexes [MSb 2 (NC 6 H 11 ) 4N2 Li 4 ] and Li[M(C 6 H 11 NH)Sb(l-NC 6 H 11 ) 2N2 Sb] reveals that the geometries of these heterobimetallic cages are fundamentally dictated by the rigidity of the [Sb 2 (NC 6 H 11 ) 4 ]2~ 15 and [M(C 6 H 11 NH)Sb(l-NC 6 H 11 )N2 Sb]~ 16 anions. 36 The synthesis and characterisation of two bis(triphenylantimony)oxo-4-acylpyrazol- 5-ones (4-Me, 4-Ph) and of an analogous derivative of the isomeric ligand 1-acetylpyrazol-5-one have been reported.37 The structure of one compound, [Ph 3 Sb(L)] 2 O (L\1-phenyl-3-methyl-4-benzoylpyrazol-5-one),has been determined and each antimony found to be in a six-co-ordinated Ph 3 SbO 3 environment with a mer-arrangement of the ligand sets.Eleven antimony compounds of the type RSb[(CH 2 ) 3 ] 2 NR@ (R\Cl, I, NCS, OSiPh 3 , Ph; R@\NMe,NCH 2 Ph, NBu*) have been synthesized. The compounds were compared to their arsenic, antimony and bismuth analogues taken from the literature.Evidence was provided for 1,5-chelation of Sb and N via crystal structure determinations, 13C and 29Si NMR chemical shifts, 121Sb and 127I Mo� ssbauer data, cyclic voltammetry, and semi-empiricalMO calculations at the extended Huckel level.38 The reaction of the lithium amide M[2-(6-methyl)pyridyl]trimethylsilylamidoNlithium, with antimony(III) or bismuth(III) trichloride gave the bis-amido antimony(III) or bismuth(III) chloride [M2-(6-Me)C 5 H 3 NNNSiMe 3 ]MCl (M\Sb, Bi).The antimony complex is monomeric in the solid state whereas the bismuth complex is dimeric with bridging chlorides.39 5 Bismuth Synthetic, spectroscopic (IR, Raman, NMR, APCI (atmospheric pressure chemical ionisation)-MS), and X-ray crystallographic studies demonstrate that the highly favorable thiolation of bismuth can be controlled by manipulating stoichiometric conditions for the reactions of BiCl 3 or Bi(NO 3 ) 3 with aminoethanethiolate anions.With this approach, the first homologous series of mono-, bis- and tris-thiolated Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 64bismuth complexes have been isolated and compre-hensively characterized.These include tris(aminoethanethiolato)bismuth(III), bis(aminoethanethiolato)bismuth(III) nitrate, and bis(aminoethanethiolato)bismuth(III) chloride, the corresponding dimethylaminoethanethiolato derivatives and (dimethylaminoethanethiolato)bismuth( III) chloride. The acyclic (dimethylammoniumethanethiolato)bismuth(III) chloride extends the series and represents decoupling of the amine by protonation with the retention of monothiolation.The synthetic guidelines have been postulated to be applicable to other metals and other asymmetric ligands.40 The structure of a very unusual bismuth(III) thioether complex [Bi 4 Cl 12 (MeSCH 2 CH 2 CH 2 SMe) 4 ]·nH 2 O has been reported, where the BiCl 12 (g1- MeSCH 2 CH 2 CH 2 SMe) 4 tetrameric units are linked by bridging dithioether ligands to give a three-dimensional polymeric network; the Bi 4 Cl 4 core is an eight-membered heterocycle which adopts an open cradle conformation.41 The new pentavalent bismuth(V) alkoxide complexes Ph 3 Bi(OR) 2 , Ph3 BiBr(OR) and Ph 4 Bi(OR), (R\C 6 F 5 , C 6 Cl 5 ) have been prepared.42 These compounds were characterized spectroscopically and by single-crystal X-ray di§raction.In the solid state, they possess distorted trigonal bipyramidal co-ordination geometries. The mixed species Ph 3 BiBr(OR) very rapidly redistributes in solution to give equilibrium mixtures of Ph 3 Bi(OR) 2 and Ph 3 BiBr 2 . Trends observed in the values of K%2 correlate with di§erences in the electronegativity of the mixed X species. The thermal stabilities of Ph 3 Bi(OR) 2 have been examined in toluene solution and in the solid state.A number of main group element–transition metal cluster compounds based upon a hexa-capped M 8 cube have been reported in two configurations: empty and with interstitial metal atoms in the center of the cube. Related structures such as [N(PPh 3 ) 2 ] 2 [Bi 4 Co 9 (CO) 16 ]·2thf and [N(PPh 3 ) 2 ] 2 [Bi 8 Co 14 (CO) 20 ]·1.08thf have been characterized by single-crystal X-ray di§raction.A thorough theoretical analysis of these two compounds was undertaken.43 The syntheses and single-crystal X-ray structure determinations have been reported for a number of adducts of bismuth(III) nitrate with the aromatic bidentate base systems 2,2@-bipyridine and 1,10-phenanthroline,44 as well as their halide analogues.45 Vibrational spectroscopic studies of the bismuth(III) halide N,N@-aromatic bidentate base systems were subsequently reported.46 References 1 K.K.Hii and T. P. Kee, Annu. Rep. Prog. Chem., Sect. A, 1998, 94, 99. 2 L.F. Szczepura, L. M. Witham and K. J. Takeuchi, Coord. Chem. Rev., 1998, 174, 5. 3 N. Emig, H. Nguyen, H. Krautscheid, R. Reau, J. B. Cazaux and G.Bertrand, Organometallics, 1998, 17, 3599. 4 M. Ghisletta, L. Hausherr Primo, K. Gajda Schrantz, G. Machula, L. Nagy, H. W. 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Couchman, J. C. Je§ery, K.L. V. Mann, E. Psillakis and M. D. Ward, Inorg. Chim. Acta, 1998, 278, 178. 13 X. G. Zhou, Z. E. Huang, R. F. Cai, L. X. Zhang, X. F. Hou, X. J. Feng and X. Y. Huang, J. Organomet. Chem., 1998, 563, 101. 14 G. S. He, S. K. Loh, J. J. Vittal, K. F. Mok and P. H. Leung, Orgometallics, 1998, 17, 3931. 15 H. P. S. Chauhan, Coord. Chem. Rev., 1998, 173, 1. 16 N. Brodie and S. Juge, Inorg.Chem., 1998, 37, 2438. 17 W.H. Hersh, P. Xu, C. K. Simpson, T. Wood and A. L. Rheingold, Inorg. Chem., 1998, 37, 384. 18 P. H. Leung, G. H. Quek, H. Lang, A. M. Liu, K. F. Mok, A. J. P. White, D. J. Williams, N. H. Rees and W. McFarlane, J. Chem. Soc., Dalton Trans., 1998, 1639. 19 W. Goertz, W. Keim, D. Vogt, U. Englert, M.D. K. Boele, L. A. van der Veen, P. C. J. Kamer and P.W.N. M. van Leeuwen, J. Chem. Soc., Dalton Trans., 1998, 2981. 20 N. Krause, Angew. Chem., Int. Ed., 1998, 37, 283. 21 B. Glaser and H. Kunz, Synlett, 1998, 53. 22 S. Vyskocil, M. Smrcina, V. Hanus, M. 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Rheingold, Organometallics, 1998, 17, 726. 34 I. M. Muller and W. S. Sheldrick, Eur. J. Inorg. Chem., 1998, 1999. 35 J. E. Davies, L. C. Kerr, M.J. Mays, P. R. Raithby, P. K. Tompkin and A. D. Woods, Angew. Chem., Int Ed., 1998, 37, 1428. 36 A. Bashall, M. A. Beswick, C. N. Harmer, A. D. Hopkins, M. McPartlin, M. A. Paver, P. R. Raithby and D. S. Wright, J. Chem. Soc., Dalton Trans., 1998, 1389. 37 M.F. Mahon, K. C. Molloy, B. A. Omotowa and M. A. Mesubi, J. Organomet. Chem., 1998, 560, 95. 38 E. Brau, A. Zickgraf, M. Drager, E. Mocellin, M. Maeda, M. Takahashi, M. Takeda and C. Mealli, Polyhedron, 1998, 17, 2655. 39 C. L. Raston, B.W. Skelton, V. A. Tolhurst and A. H. White, Polyhedron, 1998, 17, 935. 40 G. G. Briand, N. Burford, T. S. Cameron and W. Kwiatkowski, J. Am. Chem. Soc., 1998, 120, 11 374. 41 A. R. J. Genge, W. Levason and G. Reid, Chem. Commun., 1998, 2159. 42 S. Hoppe and K. H. Whitmire, Organometallics, 1998, 17, 1347. 43 B. Zouchoune, F. Ogliaro, J. F. Halet, J. Y. Saillard, J. R. Eveland and K. H. Whitmire, Inorg. Chem., 1998, 37, 865. 44 L. J. Barbour, S. J. Belfield, P. C. Junk and M. K. Smith, Aust. J. Chem., 1998, 51, 337. 45 G. A. Bowmaker, F. M. M. Hannaway, P. C. Junk, A. M. Lee, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 331. 46 G. A. Bowmaker, P. C. Junk, A. M. Lee, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 317; G. A. Bowmaker, F. M. M. Hannaway, P. C. Junk, A. M. Lee, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 325; G. A. Bowmaker, J. M. Harrowfield, P. C. Junk, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 285. Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 66

ISSN:0260-1818    

DOI:10.1039/a804881i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

6 Oxygen, sulfur, selenium and tellurium P. F. Kelly Department of Chemistry, Loughborough University, Loughborough, UK LE11 3TU 1 Introduction This review highlights new developments in the chemistry of the Group 16 elements (the chalcogens) reported during 1998. Emphasis has been given to results that demonstrate novelty of product or synthetic approach as their main feature. In addition, the products reported have been limited to those in possession of a discrete molecular structure, thus highlighting the extraordinary ability of sulfur, selenium and tellurium to contribute to novel cluster arrangements. 2 Sulfur, selenium and tellurium As with other years we start by looking at the ability of the heavier chalcogens to form compounds with a vast range of other p-block elements, and do so by working from left to right across the Periodic Table starting with Group 13.It has been revealed that a strong base may transform [B 6 H 5 (ECN)]2~ (E\S or Se) to [B 6 H 5 E]3~.1 The X-ray structure of the doubly protonated derivative of the sulfur species, namely [B 6 H 5 H(SH)]~ confirms the expected monsubstituted B 6 octahedron. A novel selenium- based four-membered boracycle B(tbt)Se 2 SnAr 2 (Ar\Ph or mes) forms when B(tbt)Se 3 SnAr 2 (itself the product of Li[B(tbt)H 3 (thf) 3 ] with [TiSe 5 Cp 2 ] and SnAr 2 Cl 2 ) is deselenated with PPh 3 .2 Intriguingly, thermolysis of these products results in the formation of the selenoxoborane (tbt)BSe which may be trapped from the system with, for example, a diene.A noteworthy 90 reference review of boron–chalcogen species has been published.3 The selenium-bridged aluminium compound trans- [MAl(H)(l-Se)(NMe 3 )N2 ] has been shown to react with (PhE) 2 (E\S, Se or Te) to give colourless products of the type trans-[MAl(l-Se)(PhE)(NMe 3 )N2 ],4 while refluxing [Al(mes*)H 2 ] 2 with S(SiMe 3 ) 2 in toluene produces [Al(mes*)S] 2 .5 The latter exists as a dimer with a planar Al 2 S 2 core; interestingly this is in direct contrast to its oxo analogue which exists as a tetramer.Finally amongst Group 13 species, a detailed investigation into the butterfly-shaped [Tl 2 E 2 ]2~ anions (E\Se, Te or a mixture) has been undertaken using a combination of Raman, 205Tl, 203Tl and 77Se (including Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 67enriched samples) NMR. The elegant solution work shows that lability in en or ammonia solutions increases in the order [Tl 2 Se 2 ]2~\[Tl 2 SeTe 2 ]2~ \[Tl 2 Te 2 ]2~.6 The products of the low temperature reaction of tin dichloride with Na[SiBu53 (thf) 2 ] in turn react with P(E)Et 3 (E\Se or Te) to give (Bu5 3 SiSnE) 4 .7 The products, which are yellow for selenium and red for tellurium, have similar structures wherein the tin atoms occupy the corners of a tetrahedron with the chalcogen atoms lying in a plane bisecting the Sn 4 unit.Still in the area of tin chemistry, only the second example of an X-ray crystallographically characterised planer PS 2 Sn ring has been found in [M(Me 3 Si) 2 NN2 Sn 2 P(S)C 6 H 4 OMe] which forms as a pale yellow crystalline material during the reaction of Lawesson’s reagent with [M(Me 3 Si) 2 NN2 Sn].8 The Ge analogue may also be isolated in a similar manner but in much smaller yield (10% compared to 90%).Lead readily forms Zintl ions and this versatility has been demonstrated yet again by the observation that potassium reduction of PbTe 2 in en results in the formation of silver coloured crystals of K 4 [PbTe 3 ]·2en.9 As the formulation would suggest, they contain the [PbTe 3 ]4~ ion which is trigonal pyramidal with additional capping potassium cations.There has been the usual good deal of interest in the chemistry of chalcogen –nitrogen systems, with perhaps the fundamentally most important result coming with the isolation of [Te 6 N 8 (TeCl 4 ) 4 ].10 This pale yellow, non-explosive material forms when TeCl 4 reacts with N(SiMe 3 ) 3 in thf and exhibits a Te 6 N 8 core, stabilised by coordinating TeCl 4 molecules.The latter explains the lack of explosive nature, a surprise given that this is e§ectively the material formerly characterised as Te 3 N 4 and which itself was originally thought to be Te 4 N 4 (and hence to complete the sequence of explosive chalcogen tetranitrides).It is likely that isolation of this material will spark renewed interest in the chemistry of Te–N systems. Amongst S–N systems, sulfur imides of the type SxN(n-C 8 H 17 ) (x\5 or 6) have been generated (as pale yellow oils) by reaction of [TiMS 2 N(n-C 8 H 17 )S 2NCp 2 ] with SCl 2 or S 2 Cl 2 11 while the first examples of salts of arylsulfurdiimides [RNSN]~ (R\C 6 H 4 F-2 or C 6 H 3 F 2 -2,6) have been isolated.12 The latter show terminal S–Nlengths of ca. 1.45Å which are therefore consistent with the presence of S–– – N triple bonds. A range of new perfluoroalkyl derivatives of the –N(SO 2 F) 2 unit have been studied [thus CF 3 N(SO 2 F) 2 forms from ClN(SO 2 F) 2 and CF 3 I]13 while S(NBu5) 3 has been shown to form via heavy halogen oxidation of [Li 4M(NBu5) 3 SN2 ] (a reaction which progresses through the [Li 3M(NBu5) 3 SN2 ]· radical).14 The ternary heterocycle S 3 N 5 C 4 has been prepared and its redox and magnetic properties studied.Chief amongst structural results is the observation that while at ambient temperatures it exists as ribbons of radicals packed into slipped p-stacks, at low temperature an array of dimers forms.15 The most interesting advance in the coordination chemistry of such species comes with the isolation of the first example of a metal selenonitrosyl.When the terminal nitrido complex [OsNCl 2 Tp] is treated with elemental Se at 80 °C over five days a 28% yield of green [Os(NSe)Cl 2 Tp] is obtained. X-Ray di§raction reveals that the NSe ligand is slightly bent (164.7°) and exhibits an N–Se distance of 1.629Å.16 The coordination chemistry of the sulfimides Ph 2 SNH is currently being developed; recent work has revealed that the homoleptic cobalt complex [Co(Ph 2 SNH) 6 ]Cl 2 possesses an unusual alignment of two sets of three N–H bonds, on either side of the coordination octahedron, forming two H-bonding pockets in which the chloride counter ions Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 68sit.17 Finally, a rare example of aM–NCNE(E\S or Se; andM\Pt) metallocycle is found in [PtMN(H)C(Ph)N(H)EN(dppe)]`, which forms upon decomposition of [PtMENC(Ph)NEN(dppe)].18 It has long been known that introducing phosphorus atoms into chalcogen–nitrogen systems induces interesting chemistry. Further progress in this area has come with the isolation of novel thionylphosphazenes of the type R1OP(R2R3)NS(O)(R@) and of hybrid sulfanuric–phosphazene ring systems of the type Ph 4 P 2 N 4MS(O)RN2 (R1,R2,R3,R@,R\alkyl or aryl).The former can be polymerised to the first examples of polythionylphosphazenes in which the side groups are bound by P–C and S–C bonds (such products also constitute the first examples of inorganic polymers with S, P, and 2N repeat units)19 while the latter consist of eight-membered P 2 N 4 S 2 rings in twisted boat configurations.20 Their thermal stability is such that it rules them out as precursors to polymeric systems.Last year witnessed the usual high level of interest in the chemistry of phosphorus –chalcogen systems. Thus the photochemical selenation of P 4 O 6 with red selenium in CS 2 was shown to generate P 4 O 6 Se 2 (which has two terminal selenium atoms).21 The latter has been characterised by a range of techniques as have the related compounds P 4 O 8 and P 4 O 6 S 2 .22 The concave, cyclic [(NiPS 4 ) 3 ]3~ anion forms from the autofragmentation and rearrangement of one-dimensional [NiPS 4 ]~ in dmf.23 31P NMR has been used to follow this unusual reaction, which does not occur in the analogous Pd case.The same PS ligand is found in [Cr 2 (PS 4 ) 4 ]6~, which happens to be the first discrete transition metal cluster unit to have been isolated from a thiophosphate flux reaction (Cr, P 2 S 5 andK 2 S in the ratio 1: 2: 3 at 600 °C for one week24) and in the bright yellow 1-D chain system [CeP 2 S 8 ]3~.25 The latter forms from the reaction of K 2 S with Ce 2 S 3 , P 2 S 5 and sulfur at 300 °C; within its structure each cerium atom coordinates to nine sulfurs.Many similar selenium systems have been shown to form from high temperature reactions. These may be free salts, such as the orange potassium salt of [P 8 Se 18 ]6~ 1 (from K 2 Se, phosphorus and sulfur at 510 °C),26 coordinated to transition metals (as is the case with the 2-D layered K 2 Cu 2 P 4 Se 10 , which interestingly exhibits the first example of a cyclic [P 4 Se 10 ]4~ group),27 to lanthanides or to other main group elements.Examples of the former include M 3 LnP 2 Se 8 and M 2 LnP 2 Se 7 (M\Rb or Cs; Ln\Ce or Gd)28 while indium reacts with molten [PPh 4 ] 2 [Se 5 ] and P 2 Se 5 at 250 °C to give a yellow salt of formulation [PPh 4 ][In(P 2 Se 6 )].29 While the anion in this case is part of a polymeric array, a discrete anion is found with [In(P 2 Se 6 ) 2 ]5~ 2, formed as an air stable caesium salt by the reaction of the elements in the appropriate ratio.Finally among phosphorus systems, the first examples of complexes of the PSe ligand have been discovered.30 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 69Thus reaction of [MCoCpAN3 (l3 -P) 2 ] with selenium at ambient temperature in toluene for a day results in the formation of [MCoCpAN3 (l3 -P)(l3 -PSe)] and [MCoCpAN3 (l3 - PSe) 2 ]. Both have been characterised by X-ray crystallography; in the mono-PSe case, for example, the P–Se distance is 2.09Å.Se As Se Se Se Se Se Se Se As As Te Au Te Te Te As As Te Te Te Te Se As Se Se In Se en en Se As Se Se Se Se Se Se As Se Se Se Se As Se 2– – 5– 5 6 7 – 4 3 Arsenic–chalcogen systems are also popular for their structural versatility and last year saw a number of interesting developments in this area. A common, and very powerful, technique for isolating new anions of this type involves the extraction of elemental alloys with solvents such as en.In this way anions of the type [As 2 Se 6 ]2~ 3, [AsSe 8 ]~ 4 (both from AsSe 4 ) and [AsSe 6 ]~ 5 (from TlAsSe 4 ) have been generated, together with neutral [InMSeAs(Se)Se 2Nen 2 ]·en 6 (from InAsSe 4 extracted with en and 2.2.2.crypt).31 In a similar manner, extraction of K 2 AuSnAs 3 Te 8 with en and addition of [Et 4 N]I results in the formation of the dark red [AuAs 4 Te 8 ]5~ anion 7.As the diagram shows this is in e§ect two [As 2 Te 4 ]4~ anions coordinating to Au cation leading to a square-planar AuTe 4 unit.32 Somewhat di§erent approaches have led to the related anions [AsSe 6~xSx]~ and [Sb 2 Se 14 ]2~ 8 (by a variety of reactions involving AsCl 2 OPh)33 and to the red crystalline salt of [Pd 7 As 10 S 22 ]4~.34 The latter forms in the hydrothermal reaction of PdCl 2 , K 3 AsS 3 and [PPh 4 ]Br in MeOH at 110 °C leading to a product in which both [As 2 S 5 ]4~ and [As 3 S 6 ]5~ units are present.Hydrothermal techniques also generate interesting antimony species in the shape of the anions [Sb 3 S 25 ]3~ and [Sb 2 S 15 ]2~ 9 which form from the elements in a variety of solvents. While the latter contains discrete anions, the former actually consists of [Sb 2 S 17 ]2~ 10 and [Sb 2 S 16 ]2~ 11 units.35 Finally in this area, a noteworthy 115 reference review of Group 15/16 ligands has been published.36 Moving on to ‘pure’ Group 16 species, we find a number of important results, including the isolation of a new allotrope of sulfur, namely S 14 12.This forms as yellow rods (mp\117 °C) via reaction of [ZnS 6 (tmen)] with S 8 Cl 2 .37 This reaction is important not only for the formation of the product itself but for the fact that it confirms the obvious potential that the recently reported zinc species has as a very versatile synthon, along the lines of the well known and much used [Ti(S 5 )Cp 2 ]. The ability of a range of Co, Cu and Zn halide complexes of 2-methylpyridine N-oxide to fix SO 2 in both the solid state and solution has been investigated (and found to be very much dependent upon the nature of the metal, the halide, the medium and the reaction temperature)38 while a single crystal X-ray study upon the [SeSO 3 ]2~ anion has Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 70S S S Sb S S S S S Sb S S S S S S S S S S S Sb S S Sb S S S S S S S S S S S S S S Sb S S Sb S S S S S S S S S S S Se Se Se Se Sb Se Se Se Sb Se Se Se Se Se Se Se 2– 8 2– 10 9 11 2– 2– S S S S S S S S S S S S S S 12 confirmed the presence of a central sulfur bound to all three oxygen atoms and to selenium (S–Se 2.17Å).39 Studies of chalcogen–halogen systems have proved especially fruitful in 1998.The facile synthesis of the new tellurium halides Te 2 Cl 2 and Te 2 Br 2 was one such important breakthrough. They form when elemental tellurium is reduced by superhydride in the presence of TeX 4 . Both are liquids at room temperature (the chloride being yellow, the bromide orange–red) and were characterised by a combination of NMR and mass spectrometry; additional proof of their nature was provided by their reaction with [Ti(E 5 )Cp 2 ] (E\S or Se) to give 1,2-Te 2 E 5 .40 Novel types of [TeCl 9 ]~ anions (in which octahedral and trigonal bipyramidal Te units are bridged at one edge) are found in [H 5 O 2 ][Te 2 Cl 9 ], the colourless crystalline product of TeCl 4 , 1,4-dioxane and HCl,41 while planar TeCl 4 units occur in the green [Mn(CO) 5 (TeCl 4 )]~ anion.42 Moving away from tellurium, iodine atoms are found to bridge two sulfate units in HIS 2 O 8 , which crystallises from a concentrated solution of iodic acid in oleum.43 The I–O distances, which average 1.975Å, correspond to I–O single bonds while longer bonds link neighbouring units into ribbon arrays.Amongst selenium systems, the synthesis of a range of chloroselenates such as [SeCl 6 ]2~, [Se 2 Cl 9 ]~ and [Se 2 Cl 10 ]2~ has been reported44 while treatment of [Se 4 ][MoOCl 4 ] with SOCl 2 has been shown to produce [SeCl 3 ][MoOCl 4 ].45 Finally, studies upon the halogenation of phosphine chalcogenides have revealed the first crystal structure of a 1: 1 charge transfer type product (that of PPh 3 S·I 2 )46 and of trigonal bipyramidal R 3 PSeBr 2 (R\Me 2 N or C 6 H 11 ).47 As usual there have been a large number of reports of metal reactions generating a variety of metal complexes with chalcogenide ligands.Here we will look at some of these, in increasing order of nuclearity, though we start with one of the more unusual observations. There is still considerable interest in the formation of nanoparticulate CdS and it has now been shown that this forms when a mixture of Na 2 [S 2 O 3 ] and Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 71Cd2` is treated with c radiation. Quite why the thiosulfate ion should act as a sulfide source in the presence of such radiation remains something of a mystery, but the technique obviously has great potential.48 It is worth noting that another important advance in this area came with the deposition of zinc and cadmium chalcogenide nanoparticles through thermolysis of bis[methyl(n-hexyl)dichalcogenocarbamato] complexes.49 The gas phase reactions of lanthanide cations with sulfur in an ion cyclotron resonance mass spectrometer have been studied in detail; results indicate that each lanthanide generates [LnSx]` in which x ranges from 2 to 21 and decreases with time.50 The importance of [Zn(S 6 )(tmen)] as a synthon has been demonstrated earlier; work has also revealed that when the tmen is substituted by tridentate pmdien the product ([Zn(S 4 )(pmdien)]) not only reacts with further sulfur (to give [Zn(S 5 )(pmdien)]) but also with DMAD to give [ZnMS 2 C 2 (CO 2 Me) 2N(pmdien)] and with CS 2 to give [ZnMS 3 C(S)N(pmdien)]. It would appear that in such cases the third amine group of the ligand is responsible for the enhanced nucleophility.51A range of aryloxide substituted analogues of the well known [Ti(S 5 )Cp 2 ] have also been studied,52 as have manganese and rhenium complexes of the type [M(OEF 5 )(CO) 5 ] (E\Se or Te).53 We have already mentioned c irradiation as a technique for the formation of sulfides; another study utilising such radiation has shown that glassy solutions of salts of the d0 chalcogenides [ME 4 ]2~ (M\Cr, Mo or W; E\S or O) results in one electron addition to the anions.In such cases EPR results are consistent with the products ([ME 4 ]3~) having the added electron predominantly located on the metal centre.54 Dimeric [MCu(SCN)(l-SCN)N2 ]2~ anions are present in the colourless product of [N(PPh 3 ) 2 ][CuCl 2 ] and K[SCN] in ethanol55 while violet [Fe 2 (S 2 ) 3 (tacn) 2 ] has provided the first example of a M 2 (S 2 ) 3 core.56 Treatment of [MPtS(dppe)N2 ] with Cu[PF 6 ] 2 in MeOH results in red crystalline [CuMPt 2 (l3 -S) 2 (dppe) 2N2 ]2`57 while [M@(l-S) 2MM(S 2 CNEt 2 )N2 (l-S) 2 ] (M@\Pd or Pt; M\Mo or W) results from [M@(PPh 3 ) 4 ] and [M 2 S 2 (l2 -S) 2 (S 2 CNEt 2 ) 2 ].58 Although a thorough review of tetranuclear (and larger) chalcogenide complexes is beyond the scope of this particular work, the following results provide a flavour of the kind of results reported last year.In the [Fe 4 S 4 Cl 4 ]2~ cluster monoprotonation has been shown to catalyse chloro substitution (though addition of one more proton inhibits it)59 while the first cuboidal cluster with an oxygen centre, namely [Nb 4 OTe 4 (CN) 12 ]6~, has been shown to form in the high temperature reaction of NbTe 4 with KCN.60 The [MVI(S)ReI 3 (CO) 9 (l3 -S) 4 ]~ (M\Moor W) anion is notable for the presence of the very di§erent metal oxidation states;61 other tetranuclear systems include [Pd 4 (l3 -Se) 2 (l-SCH 2 Ph) 2 (l-dppm) 2 Cl 2 ] (which exhibits unusual asymmetric coordination of Pd atoms),62 [MRu(CO)Cp*N2MW(CO) 4N(WS 4 )] (which undergoes both thermal and photolytic isomerisation in benzene)63 and [M 2 Ru 2 (l2 - Se) 2 (CO) 4 (CO) 6 (PPh 3 ) 2 ] (M\Mo or W).64 Pentanuclear systems include [WS 4 Cu 4 (SCN) 2 (py) 6 ] (which exhibits promising optical limiting properties)65 and [MIrCp*N4 M(l3 -S) 4 ]n` (M\Fe, Co or Ni; n\1 or 2) which form in ‘bow-tie’ arrangements.66 A series of hexanuclear products are obtained when main-group elements are incorporated into the [Mo 3 S 4 (H 2 O) 9 ]4` unit; corner shared double cubes of the type [Mo 6 XS 8 (H 2 O) 18 ]2` form in which X may be As,67 Sb68 or In.69 A similar nuclearity is observed for [Yb 6 S 6 (SPh) 6 (py) 10 ] (the first example of a lanthanide cubane structure)70 and for a series of complexes of Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 72the general type [Re 6 S 8 (PEt 3 )nBr 6~n](n~4)` (n\2–6) which form by PEt 3 substitution into [Re 6 S 8 Br 6 ]4~.71 The first discrete CuI 8 cubane encapsulating a selenide has been isolated in the form of [Cu 8 (l8 -Se)MSe 2 P(OPr*) 2N6 ]72 while the same number of metal atoms are found in the mixed-valence, double-cubanoid [Fe 8 S 12 (Bu5NC) 12 ]73 and nine are seen in [MWCu 2 S 3 Cp*N3 S 2 ]~.74 Moving to chalcogenide clusters with ten or more atoms, two zinc-based examples were reported last year, namely [Zn 10 S 7 (py) 9 (SO 4 ) 3 ]·3H 2 O (a new type of Zn sulfide cluster with a three-fold Zn 10 S 7 core75) and the telluride system [Zn 10 Te 4 (TePh) 12 (PPh 3 ) 2 ].76 Larger systems include [Mo 12 S 16 (PEt 3 ) 10 ] (from the reaction of [Mo 6 S 8 (PEt 3 ) 6 ] and NO[BF 4 ]),77 [M 4 Cu 10 S 16 E 2 E@]·H 2 O (M\Mo or W; E\E@\Oor S)78 and a range of clusters isolated from the reaction of Bu5SSiMe 3 and [Fe(HgX) 2 (CO) 4 ] (X\Cl or Br), the largest of which was [Fe 8 Hg 39MFe(CO) 4N18 S 8 (SBu5) 14 Br 28 ].79 Examples of even larger systems include [Cu 72 Se 36 (PPh 3 ) 20 ] [from the reaction of Se(SiMe 3 ) 2 with copper(I) acetate and triphenylphosphine]80 and [Ag 172 Se 40 (SeBu/) 92 (dppe) 4 ].81 3 Oxygen One of the most intriguing papers from this, or indeed any other area last year, hinged around the observation that Cu 2 O acts as a mediator/catalyst in the conversion of stirring energy into the decomposition of water to oxygen and hydrogen.The mechanism for this–which in e§ect converts mechanical energy directly into chemical energy –is as yet unclear but the observation is highly unusual and clearly initiates an area of oxide chemistry that will be intensely studied; it will be intriguing to see what next year’s report has to say on the matter!82 Singlet oxygen remains an important area of study and some results from 1998 reflect this.Thus, for example, a new solid state catalyst for its formation from H 2 O 2 has been developed in the form of molybdate immobilised on a Mg,Al-layered double hydroxide matrix. This set up eliminates the usual requirement for the presence of a soluble base and allows for the gradual release of 1O 2 from a hydrophilic source.83 The yield of 1O 2 from the disproportionation of aqueousH 2 O 2 and sodium tungstate catalysts has been shown to be quantitative (and to proceed via a range of intermediates of which the diperoxo species [W(O 2 ) 2 O 2 ]2~ is the actual singlet oxygen precursor)84 while CaO 2 ·2H 2 O 2 has been implicated as the final precursor when Ca(OH) 2 is used as catalyst.85 Finally, quenching of 1O 2 luminescence by a variety of radicals such as PhS·, PhSO·, PhOO· has been investigated leading to the conclusion that the sulfur-bearing radicals were markedly poorer quenchers than the oxygen-based species.86 Many important results from studies of oxidation reactions were reported last year, including the observation that irradiation of [W 10 O 32 ]4~, alkanes and methylcyanoformate in acetonitrile results in nitriles or iminoesters, depending upon the temperature of reaction. Thus while cyclohexane is converted to C 6 H 11 CN in 78% yield at 90 °C, it is formed in minimal amounts at ambient temperatures [the main product then being C 6 H 11 C(NH)CO 2 Me].87 Manganese substituted polyoxometalates such as Li 12 [Mn 2 ZnWMZnW 9 O 34N2 ] have been shown to catalyse the transformation of alkanes to ketones by ozone in water (via, it appears, a green manganese ozonide intermediate)88 while a new photocatalytic system for the oxidation of cyclo- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 73hexane and cyclohexene by oxygen and sunlight has been developed.89 The latter reactions take place at ambient temperatures and pressures and hinge on the use of iron porphyrins inside a Nafion base.Water soluble palladium(II) complexes of diamine ligands, such as bathophenanthroline disulfonate, have proved to be stable, recyclable catalysts for the selective aerobic oxidation of terminal olefins to alkan-2- ones in biphasic systems.90 Thus a 50% conversion of pent-1-ene is achieved with 99% selectivity with respect to alkanone formation.Addition of sodium acetate to the system appears to be the key to recyclability in this system. Methyltrioxorhenium acts as a catalyst for the conversion of N,N-dimethylhydrazones of aldehydes to nitriles by H 2 O 2 91 while the trans-[Ru(OH) 2 O 3 ]2~/[S 2 O 8 ]2~ system has been shown to catalyse the conversion of a wide range of primary benzylic amines to nitriles at room temperature.92 The latter reactions can be achieved on large scales; thus 6.8 g of p-methoxybenzylamine may be converted to 3.2 g of the corresponding nitrile by treatment with 0.1 g of RuCl 3 ·3H 2 O in 500 ml of 1M KOH containing 10.4 g of K 2 [S 2 O 8 ] over 24 h.Finally, when encapsulated in mesoporous cubic Al-MCM-48, both copper(II) acetate dimer and [Mn(bipy) 2 ]2` show high catalytic activities towards, respectively, the oxidation of phenol to catechol (by O 2 activation) and to the conversion of styrene to styrene oxide (by singlet oxygen).93 The first X-ray confirmation of the presence of ‘true’ peroxocarbonate ion, [H(O 2 )CO 2 ]~ has come in the form of its potasium salt.It is, in e§ect, a hydrogencarbonate ion with the OH group replaced by OOH. As one might suspect, there is also extensive hydrogen-bonding present in the system.94 To continue on the carbon theme, though the chemistry of C 60 is very much beyond the scope of this particular report, two aspects of its oxygen chemistry are noteworthy here.Firstly, it has been demonstrated that ambient air oxidation of C 60 produces C 120 O (in which two C 60 units are linked by an oxygen). The clear implication of this result is that it casts doubt upon reports that C 60 could occur naturally.95 The second result of note comes with the observation that the formation of C 60 O in the reaction of C 60 with singlet oxygen proceeds via a triplet excited state of the former.96 Moving down Group 14, we find that the tin oxo species [MSn(g4-Me 8 taa)(O)N2 ] di§ers from its sulfur and selenium analogues (which exhibit terminal Sn–E bonds) by being dimeric (note the contrast with transition metal systems wherein the O group is more likely to be terminal).97 As is normally the case, NO systems have provided a range of interesting results over the past year.For example, a combination of calculations and mass spectrometry has suggested that ammonia oxide, H 3 NO may be isolable (thus the EI spectrum of aqueous ammonia shows a volatile, hitherto uncharacterised NHO compound that may just fit the bill)98 while the reaction of the NH· radical with O 2 in a xenon matrix has been shown to generate imine peroxide, HNOO.99 The latter material, which was characterised by IR, readily photoisomerises to nitrous acid.A number of studies have looked at the chemistry of the peroxynitrite anion and its parent acid. The use of the latter for the oxidation of organic sulfides has been investigated; it is formed in situ from H 2 O 2 and HNO 2 and under optimum conditions the HNO 2 e§ectively acts as a catalyst for Otransfer from H 2 O 2 to R 2 S.100 Work on the anion has shown that when O 2 NOO~ decomposes in solution ca. 50% of it homolyses into O 2 ·~ and NO 2 ,101 and that decomposition in neutral hydrogencarbonate proceeds via CO 2 catalysed formation of nitrate.102 The molecular structure of the related species CF 3 OONO 2 has been determined for the first time; after preparation by photolysis of CF 3 I, NO 2 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 74and O 2 di§raction studies revealed a skew structure with a very long N–O bond (1.52Å) joining the NO 2 and CF 3 COO units. Calculations indicate that its photolytic half life in the troposphere is of the order of 26 days, suggesting that it may have an important role to play in the transport of NO 2 away from industrial zones.103 Ozonolysis of BrNO generates BrNO 2 which in turn yields a mixture of cis and trans BrONO upon photolysis.104 Amongst metal N–O complexes, reduction of the metal centre in [HB(3,5-Me 2 pz) 3 Fe(ONO)Cl 2 ] has been shown to result in the nitrite ligand changing from O-bound nitrito to chelating nitrito105 while a metal peroxynitrite complex has been implicated in the [Co(NH 3 ) 5 (SO 3 )]` catalysed decomposition of the latter anion in basic solutions.106 Finally among nitrogen species, the first nitrosyl complexes of Nb and Ta have been isolated; the products, both of the type [M(NO)(CO) 2 (trimpsi)] may be isolated as air sensitive purple crystalline solids.107 Reaction of AsCl 3 with As 2 O 3 and [PPh 4 ]Cl in MeCN for 16 h generates the [As 4 O 2 Cl 10 ]2~ anion which in turn reacts with further chloride to give [As 2 OCl 6 ]2~.108 Amongst ‘pure’ oxygen species investigated last year we find the superoxide ion, which has had itsO–Obond distance of 1.34Åaccurately determined for the first time.The key to obtaining this was the use of a large, non-spherical, cation ([1,3- (Me 3 N) 2 C 6 H 4 ]2`) to force order into the anion positions.109 Pure sodium ozonide has been isolated as an intensely red, air sensitive crystalline solid–of the Group 1 ozonides it proves to have both the longest O–O distance (1.35Å) and the tightest O–O–O angle (113°)110–while [O 2 ]` salts have been shown to react with Group 1 fluorides in HF to give solvatedO 2 F.111 Not surprisingly the latter can act as a strong oxidising agent.Amongst work upon ozone performed last year came the observation that it can transfer oxygen to several positive ions (including those of the halogens, with reactivity increasing with halogen size)112 and the first observation of isotopic exchange in ionisedO 3 –O 2 mixtures (via an [O 5 ]` intermediate). The latter may be go some way to explaining the fact that stratospheric O 3 is enriched with 18O.113 A number of studies have focused upon hydrogen-bonding HO cations, including the oxonium crown ether complexes [H 7 O 3 ][AuCl 4 ]·15-crown-5 and [H 5 O 2 ][AuCl 4 ]- (benzo-15-crown-5) 2 .The latter species form when gold is dissolved in aqua regia and the crowns added; while the first cation exhibits an infinite H-bonded chain, the latter has discrete cation/crown units in which a pair of crowns sandwich the oxonium ion.114 [H 5 O 2 ][SbF 6 ] forms from phosphorous acid and HF–SbF 5 at [50 °C115 while [H 3 O 2 ][SbF 6 ] and [H 5 O 4 ][SbF 6 ] are generated in the low temperature reaction of (Me 3 SiO) 2 with HF and SbF 5 .116 Finally, systems in which oxygen is bound to main-group elements we have yet to mention include the [M(MeC 6 H 4 ) 2 TeN2 O]2` cation (formed by the action of either [NO][BF 4 ] or (CF 3 SO 2 ) 2 O and O 2 upon the parent telluride)117 and the chelating [H 2 I 2 O 10 ]4~ groups found in H 11 I 2 InO 14 (the colourless product of the reaction of indium(III) nitrate with H 5 IO 6 at low pH).118 As is usually the case, many metal–oxygen systems were investigated last year, and some brief examples are given here.EPR analysis of the products of the reaction of chromate or dichromate with hydrogen peroxide revealed the presence of known [Cr(O 2 ) 4 ]3~ together with other pH/concentration dependant species such as [Cr(O)(O 2 ) 2 (H 2 O)]~ (such results have potential relevance to the carcinogenic properties of CrVI).119 Electrospray mass spectrometry has revealed the products of the reaction of dioxygen with a range of metal bipyridyl complexes120 while the photo- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 67–78 75catalytic reduction of O 2 to H 2 O 2 by an immobilised ruthenium bipyridyl cation has also been observed.121 Activation ofO 2 by a coordinatively unsaturated manganese(II) thiolate complex bearing a hindered hydrotris(pyrazolyl)borate ligand has been noted (a reaction which proceeds via a manganese superoxo complex)122 while it has now been shown that bridging O atoms in Bi–O clusters can participate in catalytic oxidations.123 The first example of an unsupported Au–O–Au bridge is found in the [Au 2MN 2 C 10 H 7 (CMe 2 C 6 H 4 )-N,N@,CN2 (l-O)]2` cation (Au–O 1.97Å, Au– O–Au 121.3°)124 while X-ray studies have revealed that, unusually for solid-state oxides, FeVMoO 7 and CrVMoO 7 contain Mo––O double bonds (thus making them good models for the surface O-coordination of molybdate catalysts).125 Metal–oxo cluster systems developed last year include [V 3 OCl 4 (Hmba) 5 ] (bearing the triangular [V 3 (l3 -O)]7` core,126 [MRe 6 S 5 OCl 7N2 O]4~ (intriguingly described as an oxo-bridged ‘Siamese twin cluster’)127 and the super-large [(MoO 3 ) 176 (H 2 O) 63 (CH 3 OH) 17 - Hn](32~n)~ 128 and [(MoO 3 ) 176 (H 2 O) 80 H 32 ], the latter being a ring with a 2.3nm cavity.129 References 1 B.Steuer, S. 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ISSN:0260-1818    

DOI:10.1039/a804882g

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

7 Halogens and noble gases E. G. Hope Department of Chemistry, University of Leicester, UK LE1 7RH 1 Introduction This chapter reviews the 1998 literature for the elemental halogens and the noble gases and compounds containing these elements in their positive oxidation states only. Publications which involve halide or oxohalide anions as counter ions are not described. 2 Halogens Following the report1 of the observation, by mass spectrometry, of molecular chlorine concentrations at a North American coastal site which cannot be explained using established atmospheric chlorine chemistry, it has been shown, in a controlled laboratory experiment, that chlorine is the product of photolysis of ozone in the presence of aqueous sea-salt particles.2 This has significant implications for marine troposphere chemistry since early-morning photolysis of molecular chlorine may yield su¶ciently high concentrations of chlorine atoms to render the oxidation of common gaseous molecules 100 times faster than the analogous oxidation with hydroxide radicals.Further improvements in procedures to control the extreme reactivity of elemental fluorine have been outlined.The beneficial e§ects of the addition of protic solvents (e.g. trifluoromethanesulfonic acid,3 ethanol4), Lewis acids5 or metal salts (e.g. hydrated copper nitrate6) have been illustrated in the direct fluorination of a range of organic substrates. In comparison with that for tert-butoxide, the chemistry of the tertbutoxylium moiety (Bu5O`) is virtually non-existent. The reaction of fluorine with tert-butyl alcohol, in situ, a§ords tert-butyl hypofluorite which represents a unique source of this novel moiety and which has been used in further synthetic chemistry.7 Fluorination at very low temperatures in solution leads to F 3 SCF 2 CF 2 SF 3 8 and the novel FSCSN 3 species9 which has been characterised by vibrational spectroscopy and the structure investigated by theoretical calculations.At room temperature, NiF 2 is oxidised by sunlight or UV light-irradiated fluorine in anhydrous HF in the presence of alkali metal hydrofluorides to give the corresponding NiF 6 2~ salts.10 In a very interesting series of developments in the quest for highest T# superconductors,11,12 annealing lanthanocuprate or mercurocuprate superconductors in F 2 –N 2 mixtures increases the T# to the maxima (yet reported) in these systems; increases of up to 60K Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 79have been achieved. X-Ray data suggest that, for the fluorination of La 2 CuO 4 thin films, a complex, multistage process occurs, yielding two, distinct, La 2 CuO 4 -type phases. Following the fluorination of the fullerenes and the subsequent application of the products in synthetic chemistry, progress in the bulk synthesis and purification of single-wall carbon nanotubes (SWNTs) has allowed the chemical modification of these species to occur.Between 150 and 325 °C the tube structure is maintained on fluorination with the fluorine atoms covalently attached to the side walls of the SWNTs. These can be cleanly removed by reaction with hydrazine to regenerate the starting material. 13 Chlorine has been used as the oxidant in an improved preparation of SF 5 Cl14 and the oxidation of a series of phosphines with bromine yields [R 3 PBr]`Br~, except for R\C 6 F 5 when the trigonal bipyramidal R 3 PBr 2 is formed.15 Interest in charge-transfer complexes of halogens and donor molecules continues apace.An ab initio study of C 6 H 6 –X 2 (X\F, Cl, Br, I) as model complexes for host–guest interactions has revealed the favoured T-shaped geometries within which the binding energy increases in the order F 2\Cl 2\Br 2\I 2 , and represent shallow minima.16 The reactions of 2,3-dihydroimidazol-2-ylidenes with 1,2-dichloroethane give a series of stable carbene adducts of chlorine (I) which possess unusually reactive Cl–Cl bonds, i.e.in contrast to the established Friedel–Crafts conditions, benzene can be chlorinated with these complexes under extremely mild conditions.17 N N R R Me Me .Cl2 I R = Me, Et, Pri Charge-transfer complexes incorporating iodine include the structurally-characterised [Pd(Et 2 timdt) 2 ] · I 2 ·CHCl 3 ,18 2([15]aneS 5 )·7I 2 , [18]aneS 6 ·I 2 , [18]aneS 6 ·4I 2 , [24]aneS 8 ·I 2 , [24]aneS 8 ·6I 2 ,19 M2,4,6-(MeO) 3 C 6 H 2N3 P·I 2 ,20N,N@-bis(mercaptoethyl)- 1,5-diazacyclooctanenickel(II)–diiodine21and the elusive 1: 1 Ph 3 PS·I 2 adduct,22 all of which contain linear S · · · I–I interactions.The species [18]aneS 6 ·4I 2 and [24]aneS 8 ·6I 2 are the first macrocyclic thioether–iodine charge transfer complexes to show both exo- and endo-diiodine coordination which is thought to arise from the large ring size.19 Theoretical23 and in-depth analyses of the experimental work24 on the pre-reactive intermediates of the halogens with Lewis bases have been published.The experimental and theoretical similarities between the series of B· · ·X 2 and B · · ·HX intermediates were identified o§ering a quantitative scale of gas-phase electrophilicities of the halogens and information on the electron distribution in elemental fluorine. 3 Interhalogen and polyhalide anions The e§ect of relativity on the properties of the interhalogens (ClF, BrF, BrCl, IF, ICl and IBr) has been established from relativistic and non-relativistic calculations of bond lengths, harmonic frequencies and dissociation energies.25 Hybrid Hartree–Fock/den- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 80Fig. 1 Crystal structure of NO`NO 3 ~·IF 5 (reproduced by permission from Z. Anorg. Allg. Chem., 1998, 624, 667). sity functional theory (DFT) calculations of molecular structures, electron a¶nities and dissociation energies of BrFn and BrFn ~ (n\1–7) reveal good agreement with experimental structural data (where available) and the first data (theoretical or experimental) on the electron a¶nities of bromine fluorides.26 Of interest is the prediction of unusually long Br–F!9 bond lengths for the hypothetical BrF 3 ~ and BrF 5 ~ suggesting that the bonding in these anions is di§erent from that in their neutral counterparts.Some thermochemical data on some iodine fluorides and their mono-substituted derivatives have been discussed.27 After an extensive study of a range of solvent systems, iodine pentafluoride has been found to be the only solvent which can be used in the synthesis of nitrosonium nitrate; this unique behaviour of IF 5 has been ascribed to its large dielectric constant and its chemical inertness toN 2 O 4 .The solvateNO`NO 3 ~·IF 5 has been structurally characterised (Fig. 1).28 The interhalogen molecules in the lattice, NO`NO 3 ~ double chains separated by layers of IF 5 , act as a diluent and are virtually unchanged if compared to the structure of the free molecule. However, there are a plethora of short, interchain, contacts from which the role of the IF 5 molecules can be interpreted as a Lewis acid to NO 3 ~ and as a Lewis base to NO`.Iodine penta- and hepta-fluorides have been used as mild fluorinating agents for transition metal oxo-anions29 and the dinitramide anion MN(NO 2 ) 2 ~N has been shown to be superior to the nitrate anion as a reagent for the controlled, stepwise, replacement of fluorine by oxygen for BrF 5 , ClF 5 and IF 7 .30 On reaction with ClF 5 at [13 °C, an equimolar mixture of KClOF 4 and KClF 4 is obtained where the formation of the oxyfluoride anion is remarkable since similar exchange processes give exclusively FClO 2 .With BrF 5 at[45 °C, KBrOF 4 is formed, whilst with IF 7 , deoxygenation of the desired IOF 6 ~ product yields KIF 6 which, in the presence of excess IF 7 , gives the novel KIF 6 ·2IF 7 adduct.Three di§erent reaction pathways are observed when BrF 3 reacts with X–C 6 H 4 SiF 3 .31 When X\H, p-Me or p-MeO, the aryl groups are exclusively oxidised. When X\m- or p-F, oxidation also occurs, but ca. 10% disubstitution at bromine yields [(FC 6 H 4 ) 2 Br][SiF 5 ]; the bromonium salts have been isolated after metathesis with BF 4 ~ or PF 6 ~. When X\m- or p-CF 3 , monosubstitution a§ords CF 3 C 6 H 4 BrF 2 as the first examples of hydrogen-containing phenylbromine difluorides.Iodine monochloride finds diverse applications in organic chemistry as a radical additive to double bonds,32 for iodination33 and chlorination, e.g. in the synthesis of C 70 Cl 10 34 and Cl 4 ARC 59 N35 (Ar\4- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 81Fig. 2 Anionic matrix in [Pd 2 Cl 2 ([18]aneN 2 S 4 )] 1.5 I 5 (I 3 ) 2 (dicationic chains run through vertical channels). Starred atoms identify one I 8 2~ unit (reproduced by permission from Angew. Chem., Int. Ed., 1998, 37, 293). Fig. 3 Primitive cubic lattice of iodide ions bridged by I 2 molecules in (DMFc) 4 (I 26 ) (reproduced by permission from from Z. Anorg. Allg. Chem., 1998, 624, 679).C 6 H 4 X; X\Me, OMe or OPr*) which contains a pyrrole moiety in the fullerene cage. The structurally characterised charge transfer complexes between Ph 3 PS and ICl/IBr consist of discrete molecular units with linear S · · · I–Cl/Br interactions.36 The weak intermolecular complexes between benzene and small molecules has been a fascinating problem for over 50 years.The first theoretical and the first UVPES study of the C 6 H 6 · · · ICl complex indicates, as expected, donation from a p-orbital of benzene to the r*-orbital of ICl in a bond-centred oblique structure.37 Numerous gas-phase pre-reactive intermediates between ClF and Lewis bases have been identified by microwave spectroscopy,38,39 including the related C 6 H 6 · · · ClF adduct.40 Here, the spectra were established to be of the symmetric-top type for which the data were interpreted in terms of a complex in which, at equilibrium, the ClF axis is inclined at ca. 14° to the C 6 axis of benzene, with the two axes intersecting at the centre of mass of the ClF molecule. The ClF axis points towards the centre of the C–C bond, intersecting the plane of the ring ca. 0.24Å inside the ring, and can rotate around the C 6 axis of the benzene molecule. For the furan · · · ClF and thiophene · · · ClF complexes, a similar interaction of the interhalogen with the p-bonding electrons occurs in preference to Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 82that with the heteroatom, non-bonding, lone pairs.39 A theoretical study of the, previously reported, SO 2 · · · ClF pre-reactive intermediate suggests an intermolecular interaction energy of 1.93 kcal mol~1.41 The extensive studies of polyiodide anions and polyiodide anionic networks continue with 30 examples structurally characterised in 1998.As the anionic networks become larger (and it is di¶cult to predict whether discrete anions or extended networks will be produced) the term ‘polyiodide architecture’ has been coined.The formation of these iodine/iodide networks often occurs at complexed metal cations as templates whereby the resulting polyanionic network is dependent, primarily, upon the charge and shape of the cation. This area has been reviewed by one of the leading groups.42 Linear I 3 ~ anions have been identified with the following cations: [Pd 2 Cl 2 (C 12 H 26 N 2 S 4 )]2` in which the cations and anions link into sinusoidal chains,43 [Ni(MeCN) 2 (C 11 H 26 N 4 )]2`,44 [Pd(C 11 H 26 N 4 )]2` where the terminal iodine atoms coordinate to the metal centre and have long interactions with each other to give cations plus pairs of anions in zigzag chains,44 [Co(C 6 H 12 S 3 ) 2 ]2`,45 dimethylferrocinium and decamethylferrocinium,46 [Pr/Me 2 PhN]` and [Pr*Me 2 PhN]`,47 [Ni(NH 3 ) 6 ]2`,48 [(NH 3 ) 3 M(l-OH) 3 M(NH 3 ) 3 ]2` (M\Cr, Co),49 and [Ag([18]- aneS 6 )]`.50 The I 3 ~ and I 4 2~ anions are both present in [Cr(NH 3 ) 6 ](I 3 )(I 4 ).51 Alarger structural diversity is observed for the pentaiodide anions isolated with the following cations: Decamethylferrocenium where the anion is unusually isolated,46 dimethylferrocenium where the anions form chains with alternating planar and helical regions,46 [Pr*Me 2 PhN]` where the anion is a iodide–diiodine zigzag chain with extra I 2 molecules attached to the iodide ion in the trans-position,47 [Ni(NH 3 ) 6 ]2` where the V-shaped anions line up to give a novel pentaiodide chain,48 [Ag([9]aneS 3 ) 2 ]` where charge transfer S · · · I interactions contribute to the extended structure featuring polymeric successions of cations and anions,50 and [BiI 2MOP(NMe 2 ) 3N4 ]` where the central iodine atom is located at an S 4 symmetry site in the crystal.51 This a§ords a very unusual bent anion which is statistically disorded over two sites whence the anion e§ectively forms a three-dimensional network giving an ‘open’ cage structure with the cations occupying the cavities.In [Pd 2 Cl 2 ([18]aneN 2 S 4 )] 1.5 I 5 (I 3 ) 2 , infinite chains of the binuclear cations are embedded in a matrix of the anions (Fig. 2).52 The anionic networks identified for (DMFc) 4 (I 26 )46 and [Ag([18]aneS 6 )](I 7 ),50 despite the signifi- cantly di§erent empirical compositions, are quite similar. For the former, the network may be derived from a primitive cubic lattice of iodide ions with I 2 bridges on all edges by systematically removing 1/12 of the I 2 molecules (Fig.3) whilst for the latter, the iodide ions occupy the lattice points of a primitive rhombohedral lattice with I 2 bridges along all edges.Cations embedded in a three-dimensional polyiodide network of cages of I 5 ~ ions and diiodine molecules are present in [RhCl 2 (C 12 H 24 S 4 )](I 5 )·I 2 .53 In [Pr*Me 2 PhN](I 8 ),47 the anion is best described as I 16 2~ which is present as 14-membered rings, catenated by diiodine molecules and linked into layers with 10-membered and two types of 14-membered rings.Regular anionic shapes are present in the solid-state structures of [(Crypt-2,2,2)H 2 ](I 8 ), [Ni(phen) 3 ](I 8 )·2CHCl 3 and bis(N-methylurotropinium) octaiodide, but that in bis(N-ethylurotropinium) octaiodide represents a new configuration which is somewhere between (I 3 ~·I 2 ·I 3 ~) and broken (I 3 ~, I 5 ~).54 Nonaiodides are very rare, but two, as [Pr*Me 2 PhN]`47 and [K([15]aneO 5 ) 2 ]`52 salts, have been structurally characterised this year. The anion in the former consists of 14-membered rings tied by two iodine bridges into 10-membered Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 83rings, whilst that in the latter is best described as an [I 3 ~·(I 2 ) 3 ] charge-transfer complex.The dodecaiodide dianion in [Ag 2 ([15]aneS 5 ) 2 ](I 12 ) is, again, best represented as a charge-transfer complex [(I~) 2 ·(I 2 ) 5 ] bound to the cation by Ag–I bonds with weak I · · · S interactions combining to build up an extended three-dimensional, spiral, superstructure.50 In marked contrast, the same anion in bis[potassium(dibenzo-18- crown-6)] dodecaiodide is nearly a discrete entity (I 2 ·I 3 ~·I 2 ·I 3 ~·I 2 ).55 A mixture of anions are identified in [Me 3 PNHPMe 3 ] 4 (I 28 ); linear I 3 ~, Z-shaped I 8 2~ and zigzag chains of I 14 4~.56 Unremarkable anionic geometries are reported in [Pd(C 6 H 12 S 3 ) 2 ](IBr 2 ), [Pd(C 10 H 20 S 4 )](IBr 2 )57 and [Cs(18-crown-6)](ICl 2 ).58 Following the preparation of a new IF 2 ~ salt, [NMe 4 ](IF 2 ), from the reaction of tetramethylammonium iodide and XeF 2 in a 1: 1 ratio at[31 °C,59 ab initio calculations on the series of related molecules and ions (XeF 2 , KrF 2 , IF 2 ~, BrF 2 ~ and ClF 2 ~) show that the previous assignments for the vibrational spectra of the IF 2 ~ anion are in error; highly unusually, the antisymmetric stretching modes for both IF 2 ~ and BrF 2 ~ have lower frequencies than their symmetric ones.This is accounted for by mass e§ects and the enhancement of three-centre-four-electron bonding by the antisymmetric stretch.Increasing the XeF 2 :NMe 4 I ratio to 2: 1 gives a route to another new interhalide salt, [NMe 4 ]- (IF 4 );60 the structural characterisation of this anion as the 1,1,3,3,5,5-hexamethylpiperidinium salt was reported in 1997. Addition of NMe 4 F to [NMe 4 ](IF 4 ) in acetonitrile results in the formation of the insoluble [NMe 4 ] 2 (IF 5 ).60 This anion, only the second example of a pentagonal planar AX 5 species, has been characterised by vibrational spectroscopy, ab initio calculations, and by comparison to the isoelectronic XeF 5 ~ anion.Interestingly, this characterisation shows, unequivocally, that the first AX 5 species was prepared 25 years ago, whence Cs 3 IF 6 is actually a 1: 1 mixture of Cs 2 IF 5 and CsF. 4 Halogen oxides and organoiodine oxygen compounds Theoretical studies on chlorine oxides by DFT61,62 correlate well with experimental data (geometries, dissociation energies, vibrational frequencies). Importantly, the C 27 geometry for ClO 4 · is calculated to be the minimum, whereas the hitherto, assumed, C 37 structure is shown to be an energetically higher-lying second-order saddlepoint.Heats of formation of BrO, BrO 2 , BrO 3 , BrONO 2 , BrONO, BrOOH and Cl 2 O 5 have been estimated.63,64 The failure to detect IO in the lower stratosphere (sensitivity^ 0.2 ppt) suggests that the role of iodine in stratospheric ozone depletion is negligible.65 A low-temperature crystal structure determination of Cl 2 O reveals an essentially molecular structure [d(O–Cl)\1.7092(4)Å] with weak secondary interactions [d(O · · · Cl)\2.7986(4)Å] a§ording a distorted tetrahedral coordination around the oxygen atom.66 Vibrational spectroscopic data for BrNO 2 and cis- and trans-BrONO, acquired in a low temperature matrix,67 are in good agreement with earlier theoretical calculations.Vibrational spectroscopic and X-ray structural investigations of the isostructural [Mg(IO 3 ) 2 ·4H 2 O], b-[Ni(IO 3 ) 2 ·4H 2 O] and [Co(IO 3 ) 2 ·4H 2 O] show octahedrally-coordinated metal centres with trans-monodentate iodate ligands and some internal hydrogen bonding.68 The room temperature, ferroelectric phase of Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 84Fig. 4 Polymeric network in HIS 2 O 8 (reproduced by permission from Angew. Chem., Int.Ed., 1998, 37, 1426). [C 5 H 5 NH][IO 4 ] (prepared by the reaction of pyridine with H 5 IO 6 ) contains isolated, non-disordered, tetrahedral periodate anions linked by disordered pyridinium cations. 69 Although polymeric networks of ternary oxides of non-metals are usually regarded as mixed anhydrides of oxoacids and their constitution described in terms of known oxoanions, the structure of HIS 2 O 8 (Fig. 4), for which the iodine atom geometry is most comparable to that in IF 2 `, is based upon an IO 2 structural unit for which neither the free acid nor the free anion are known.70 Whilst the reactions of aluminium or gallium salts with H 5 IO 6 yield [M(H 2 O) 6 ][IO 2 (OH) 4 ] 3 , slow evaporation of an aqueous solution of In(NO 3 ) 3 ·nH 2 OandH 5 IO 6 (1: 3 molar ratio) produces H 11 I 2 InO 14 .A single crystal X-ray study indicates that this represents the first example of a chelating I 2 O 10 unit coordinating via vertices (rather than edge sharing) to give ‘I 2 InO 12 ’ chains.71 OMe OMe OR I OH OTs– R¢OH R¢¢CONH2 V R' = Me, Et, Pri, 2-Adamantyl VI R¢¢ = Et, Pri, But, Ph III R = Me, Et + II OMe I(OAc)2 IV O I HN O R¢¢ O I OR¢ NH2 +OTf– NH2 +OTf– NH I OTf O Significant new studies on organoiodine oxygen/nitrogen compounds, which find widespread application in organic synthesis, have been published.Of note are, a review Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 85of their use in carbohydrate chemistry,72 a cleaner, faster and higher yield, route to diacetoxyiodoarenes using CrO 3 ,73 and the synthesis and structural characterisation of some, relatively rare, chiral hypervalent iodine compounds (II, III); asymmetric oxygenation reactions with up to 53% ee were outlined.74 Compound III shows a strong interaction between the iodine and the methoxy group, allowing its formulation as a salt, whilst II shows no intramolecular interactions.The new benziodazole (IV) reacts with alcohols or amides to give novel 1-alkoxy-3-iminiumbenziodoxoles (V) or 1-amido-3-iminiumbenziodoxoles (VI) for which the isopropyl derivatives have been structurally characterised.Ab initio calculations indicate that the driving force for the novel internal rearrangement is the relative thermodynamic stability of the N- vs. O-protonated species.75 5 Cationic iodine and other organoiodine compounds In the last 20 years, interest in hypervalent iodine compounds has surged.The preparations, properties and applications (in electrophilic alkynylating reactions, Michael-type conjugate additions and Diels–Alder and 1,3-dipolar cycloadditions) of the newest class, the alkynyliodonium salts, has been elegantly reviewed.76 A series of alkynylphenyliodonium salts ([R–C–– – C–I–Ph]`OTf~; R\Me 3 Si, Ph, Bu5, Bu/) have been prepared in high yields from the reactions of the appropriate trimethylsilyl alkyne with diacetoxyiodobenzene in the presence of triflic anhydride.77 The reaction of XCN (X\Br, I) with phosphine gives a mixture of [R 3 P(CN)]X and [R 3 PX]CN20 and a theoretical study confirms the linear structure for the [ICNI]` cation.78 A structural characterisation of CF 3 IF 2 , prepared from the reaction of CF 3 I and CF 3 OCl, con- firms the trigonal bipyramidal structure suggested by earlier NMR studies.79 6 Noble gases Surface structural investigations of silica aerogels,80 AgA zeolite81 and cryptophane-A in organic solution82 using 129Xe NMR have been reported.Polarisation transfer from hyperpolarised 129Xe, the high solubility of xenon in blood and the long T 1 relaxation time of dissolved 129Xe have been exploited in ground-breaking wholebody, thorax, lung and brain MRI studies which open the way for developments using xenon in a wide variety of diagnostic procedures.83,84 The laser polarisation approach, in the gas phase85 and in liquid Xe,86 has also been extended to surface nuclei with low gyromagnetic ratios, e.g.in a 13C NMR study of C 60 and C 70 .85 As postulated in Volume 94 of the Annual Report of the RSC, laser-polarisation in supercritical xenon has now been demostrated which, in view of the particular solvent properties of supercritical fluids, o§ers the extension of laser-polarisation to a wide range of applications. 87 The [Au–Xe]` complex has been examined theoretically as a benchmark for a gold(I) cation a¶nity scale,88 and a theoretical study of XeX (X\F, Cl, Br, I) cations, radicals and anions has indicated weak van der Waals interactions in the radicals and anions, and strong interactions for the cations.89 On annealing difluorovinylidene in a xenon-doped low temperature matrix, additional peaks in the IR spectrum are ob- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 86served which have been ascribed to a Xe · · ·C––CF 2 charge-transfer complex for which theoretical calculations suggest a Xe · · ·C distance of 2.379Å and a Xe–C–C angle of 102°.90 No comparable krypton charge-transfer complex has been observed on annealing difluorovinylidene in a krypton-doped matrix. 7 Noble gas compounds A detailed review of recent advances in noble gas chemistry has been published.91 Following the reports on noble gas–hydride compounds (H–Ng–Y) produced during the photolysis of HY in noble gas matrices, the first examples of xenon–sulfur (in H–Xe–SH)92 and krypton–carbon (in H–Kr–CN)93 bonds have been identified after the photolysis of H 2 S in xenon and HCN in krypton respectively.For HXeSH, only the Xe–H stretch has been observed experimentally which shows a characteristic shift on deuterium labelling and whose position is in good agreement with theoretical calculations which suggest a bent structure with the H–S–Xe angle close to 90°. Extensive theoretical studies on krypton fluorides has revealed, for the first time, that KrF is a bound molecule (in agreement with experiment), that triplet state KrF 2 is bent (71°), and that the Kr · · ·F 2 van der Waals complex has the expected T-shape.94 R R R R R R H F FXeO Me3SiO O O O O O XeF2 FXe+ (1) Xenon difluoride continues to find application as a mild fluorinating agent in organic systems, e.g.in the generation of 18F labelled methionine derivatives for positron emission tomography studies.95 In an interesting paper96 on the modes of reaction of XeF 2 with organic substrates, it is shown that the choice of reaction vessel and solvent are crucial.It is presumed that the acidic surface of the glass promotes the generation of electrophilic XeF` whereas in FEP un-ionized XeF 2 acts as a oneelectron oxidant [eqn. (1)]. The intriguing outcome, occasionally explosive, of the addition of water to a mixture of XeF 2 andUO 2 or U 3 O 8 or ZrO 2 (which do not react at room temperature in the absence of water) has been described.97 Xenon difluoride has been used in the synthesis of a rare example of an organoselenium(VI) species, [SeF 2 (C 12 H 8 ) 2 ],98 and a well ordered Y 2 BaCu 7 O 14 F superconductor (T# \62 K).99 The related Xe(OEF 5 ) 2 (E\Se, Te), have been used in the oxidation of M 2 (CO) 10 (M\Mn, Re).100 A structural characterisation of XeF 2 ·2CrF 4 reveals independent, octahedrally coordinated, chromium atoms where two of the fluorine ligands are provided by di§erent, linear, XeF 2 molecules.101 A new assignment of the vibrational spectra of the [XeF 5 ]~ anion has been made,60 and in the crystal structure of [XeF 5 ]`[CrF 5 ]~, prepared by the reaction of XeF 6 with either CrF 4 or CrF 5 , the cations show three short contacts to terminal fluorine atoms on the cis-bridged anionic chain.101 Cyclic voltametric measurements on pentafluorophenylonium cations (C 6 F 5 X)` Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 87Fig. 5 ORTEP drawing of the two discrete molecules in the unit cell of [C 6 F 5 Xe] [AsF 6 ] (reproduced by permission from Inorg.Chem., 1998, 37, 4884). [X\Xe, N 2 , C 6 F 5 Br, C 6 F 5 I, (C 6 F 5 ) 3 P] reveal that the xenon cation has the lowest reduction potential whence a one-electron reduction a§ords, after loss of xenon, C 6 F 5 ·.102 Metathesis of [C 6 F 5 Xe][(C 6 F 5 ) 2 BF 2 ] with either AsF 5 (g) or AsF 5 ·MeCN a§ords [C 6 F 5 Xe][AsF 6 ] which has been structurally characterised (Fig. 5).103 The Xe–F"3*$'% distance for this complex is less than that in [2,6-C 6 H 3 F 2 Xe][BF 4 ] which, from theoretical calculations, appears to be related to a lower r-charge on xenon in the BF 4 ~ salt. Further work on the reaction of XeF 2 in anhydrous HF with tetra- fluorobenzenes C 6 F 4 HR (R\Xe`Y~; Y~\AsF 6 ~, BF4 ~) has a§orded the first F F F F Xe+Y– H F F F F Xe+Y– H F F F F Xe+Y– F F F F F Xe+Y– F F F F F F F F F Xe+YH F F F F F F F F Xe+YF F F F F (2) XeF2 XeF2 aHF aHF + + + VII VIII IX X Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 79–91 88hydrogen-containing (polyfluorocycloalken-1-yl)xenon(II) salts [eqn. (2)].104 The spectroscopic data indicate close similarity between these hydrogen-containing cations (VII, IX) and their perfluorinated analogues (VIII, X) which precludes the presence of a ‘through space’ or chelate-like stabilization of the xenon–carbon bond as previously supposed.References 1 C.W. Spicer, E. G. Chapman, B. J. FinlaysonPitts, R. A. Plastridge, J. M. Hubbe, J. D. Fast and C.M. Berkowitz, Nature (London), 1998, 394, 353. 2 K.W. Oum, M.J. Lakin, D. O. DeHaan, T. Brauers and B. J. FinlaysonPitts, Science, 1998, 279, 74. 3 P.L. Coe, A. M. Stuart and D. J. 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ISSN:0260-1818    

DOI:10.1039/a804883e

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

8 Zinc, cadmium and mercury John Malito Department of Chemistry, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland 1 Introduction This review highlights the 1998 literature for the zinc triad. Emphasis is placed on co-ordination and organometallic chemistry. For the purposes of this review, cluster complexes are defined as those which contain at least three transition metal atoms, connected by metal–metal bonds and/or bridging ligands. 2 Co-ordination chemistry A review of some zinc-fluorophores developed since 1996 has been published,1 in which basic principles, properties and limitations are discussed with extension to real and potential biological and environmental applications. An extensive summary of solution- and solid-state chemistry for triakylsilyl-substituted dimeric phosphanides of the alkaline earth metals has included discussion of zinc compounds.2 Linear polymeric chlorocadamates(II) have been reviewed,3 and a review of solid-state 199Hg NMR spectrometry, relevant to the present review, appeared late in 1997.4 Group 15 donor ligands The X-ray crystal structure for [ZnCl 2 (quin-N 2 ] reveals a tetrahedral geometry with identical Zn–Cl bond lengths [2.241(1) and 2.244(1) Å] but significantly di§erent Zn–N bond lengths [2.050(3) and 2.074(3) Å].5 The complex, [Zn(4,4@- bipy)(H 2 O)(SO 4 )]·0.5H 2 O, exists in the solid state as a pseudo-three-dimensional co-ordination polymer,6 while the related compound, [Zn(4,4@-bipy)(H 2 O) 3 (ClO 4 )]- (ClO 4 )·(4,4@-bipy) 1.5 ·H 2 O, is composed of extended linear polymeric chains held through H-bond crosslinkages to form a two-dimensional rhombic network.7 Heating of a suspension of zinc dust in 1-methylimidazole under a carbon dioxide atmosphere a§ords [Zn(1-Me-2-Im) 2 (1-MeIm)].The crystal structure reveals bonding to the metal through both N and O atoms.8 Synthesis and detailed characterisation, including 113Cd NMR, for forty-five new Zn and Cd compounds of N-substituted Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 93imidazoles have been reported.9 The new ligand bimOH has been reported along with the X-ray crystal structure for [Zn(bimOH) 2 ][BF 4 ] 2 .10 Crystal structures have also been reported for [Zn(L)Cl](ClO 4 ) (L\a-Metpa, a-Mebqpa or a-Phtpa).11 The structure for [ZnCl 2 (4,2@-6@,4A-terpy)] shows an overall network of non-interacting chains in which the Zn atom is in a highly distorted tetrahedral environment.12 In the monomeric complex of the tetradentate (N 4 ) ligand, tris(benzimidazolylmethyl)amine, [Zn(N 4 )(PhCO 2 )](BF 4 )·MeOH, the zinc is in a close to trigonal bipyramidal environment, with the benzoate acting as a monodentate ligand.13 Structures have also been determined for the diphenylamido complexes, [MZn(NPh 2 ) 2N2 ] and [Zn(NPh 2 ) 2 - (thf) 2 ].14 In [ZnLCl 2 ], the ligand, L\phenyl 2-pyridylketoneazine 1, acts as a tridentate chelate, leading to a trigonal bipyramidal geometry.15 The crystal structure for [Zn(tepa)](ClO 4 ) 2 reveals that the zinc is tetra-co-ordinated rather than penta-co-ordinated as is observed with similar tripodal ligands, including tmpa.This is ascribed to weak co-ordination of the perchlorate ligands, but also to di§ering sizes of the ligand–metal chelate rings.16 Zinc compounds of two new tripodal N,O ligands, bis(2-pyridylmethyl)(o-hydroxybenzyl)amine and bis(2-pyridylmethyl)( 2-carboxymethyl)amine, have also been synthesised.17 X-Ray crystallography has verified that the zinc centre is penta-co-ordinated in the complex [ZnS 4 (pmdeta)] prepared from [ZnS 6 (tmeda)].This new complex reacts with elemental sulfur to produce [ZnS 5 (pmdeta)], and shows enhanced nucleophilicity in simple reactions with CS 2 , C 2 (S 2 CO) 2 and with dmad.18 Schi§-base complexes of the type [ZnL] and [Zn(HL@)2] have been prepared by reactions of [Zn(O 2 CMe) 2 ] with azomethines obtained from p-phenylenediamine and 3-methoxy-4-hydroxybenzaldehyde (H 2 L) or 3-hydroxybenzaldehyde (H 2 L@).19 A triple-helical structure, as a result of a spontaneous self-assembly process, was proposed for dinuclear Zn(II) and Cd(II) complexes of the chiragen ligand 2.20 X-Ray crystal structures have been reported for mixed Zn(II)–Cr(III) chloride complexes with urea described as [Cr(CON 2 H 4 ) 6 ][ZnCl 4 ]Cl·H 2 O and [Cr(CON 2 H 4 ) 6 ]- [ZnCl 4 ][ZnCl 3 (CON 2 H 4 )].21 Other X-ray crystal structures reported include those for [Zn(NCS) 2 (dien)] which shows trigonal bipyramidal geometry with Zn–N bond lengths in the range 1.984(7)–2.252(8)Å,22 [ZnCl 2 (N 6 C 8 H 14 )] [N 6 C 8 H 14 \3(5)- amino-5(3) methylpyrazole],23 the 4-pyridone complex [ZnCl 2 (C 5 H 5 NO) 2 ]24 and the zinc dicyanamide, [ZnMN(CN) 2N2 ].25 The structural properties of self-assembled poly[bis(quinolato)zinc] have also been investigated.26 Extensive thermal and structural studies have been carried out for some bis(pyridyl) cadmium(II) iodide complexes.27 Thermal studies have also been reported [Cd(medien)X 2 ] (X\Cl, Br, I, NCS or NO 3 )28 and the molecular structure deter- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 942 Me Me Me Me N N N N mined for the X\NO 3 complex reveals hepta-co-ordination with the cadmium bound to three nitrogen atoms of the medien moiety and four oxygen atoms of the two bidentate nitro groups.29 The complexes [Cd(NCO) 2 L 2 (H 2 O)] 2 , [Cd(NCS) 2 L 2 ], [CdCl 2 L 2 ], [Cd(SO 4 )L 2 ]·H 2 O, and [Cd(O 2 CMe) 2 L 3 ]·H 2 O for L\3-amino-5- methylpyrazole have been synthesised and then subjected to thermal analyses.30 The crystal structure has been reported for [Cd(aepn)(NCS) 2 ].31 Mercury-199 NMR spectra and X-ray crystal structure determinations have been reported for the mercury complexes, [Hg(bmpa) 2 ](ClO 4 ) 2 and [Hg(bmpa)(NCMe)]- (ClO 4 ) 2 .These have distorted trigonal prismatic and distorted square planar structures respectively, owing to the close associations to the perchlorate moieties.32 Reactions of HgCl 2 with the potentially tetradentate ligand, tla, lead to the penta-coordinate compounds [Hg(tla)Cl 2 ] and [Hg(tla)Cl] 2 (Hg 2 Cl 6 ). In the crystal state, however, the ligand does act as a tetradentate chelate for dimer-like orientations.33 X-Ray crystallography has revealed a rutile-like three-dimensional structure for [Cd(tcm)(hmt)(H 2 O)](tcm).34 Other structures determined include the complexes, Li 4 [Hg 2 (edta) 2 ]·8H 2 O and Ba 2 [Hg 2 (teta) 2 ]·9H 2 O,35 [Me 2 NH 2 HgBr 3 ],36 and [HgCl 2 (dppf)]·MeOH for which the central mercury atom is in a tetrahedral environment. 37 Stable complexes of mercuriophosphaalkenes from the addition of organomercury halides to the Ru–P bond in [Ru(P––CH––Bu5)Cl(CA)(PPh 3 ) 2 ] (A\Oor S) have been reported with the crystal structure determined for the species shown as 3.38 P Ru Cl Cl OC PPh3 Ph3P But Hg (C5H4)Fe(C5H5) HC 3 Group 16 donor ligands As part of a continuing study of zinc carboxylates, vibrational spectra measured for anhydrous zinc acetate and zinc stearate led to the observation that stearate can also behave as a bridging bidentate ligand.39 A monomeric complex formed with 5- aminoprotic acid, [Zn(H 3 L) 2 (H 2 O) 4 ], and its related polymeric compound, Annu. Rep.Prog. Chem., Sect. A, 1999, 95, 93–104 95MZn(H 2 L)(H 2 O) 2Nn (H 4 L\5-amino-2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid), have been reported.This potentially bis(bidentate) ligand can act as both a nitrogen- and oxygen-donor ligand. Slow crystallisation from dmso solution of either the monomeric or polymeric species, however, a§ords the isolable complex [Zn(H 3 L) 2 (dmso) 2 (H 2 O) 2 ] for which the ligand bonds to the metal through one carboxylate oxygen atom exclusively.40 Each of the four ligands in the distorted tetrahedral complex, [Zn(dips) 2 (dmso) 2 ], acts in a monodentate fashion binding to the metal centre through an oxygen atom.This complex proves to be more e§ective than the free dips ligand as an anti-convulsant and/or inhibitor of seizures.41 Syntheses, spectral studies and structural characterisations have been reported for [ZnL 2 (MeIm) 2 ] (L\2-quinolinecarboxylate),42 and the first zinc(II) ferrocenedicarboxylate, [Zn(1,1@-ferdc)(MeIm) 2 ] 2 .43 Some new metal chelated species, including those of zinc, with salicyladoxime (salo) have been synthesised and characterised by absorption spectroscopy.The salo ligand is bidentate, bonding through both the phenolic oxygen and the oxime nitrogen atoms.44 Crystal structures have been determined for the aryloxide compounds, Na[Zn(OC 6 H 3 Ph 2 -2,6) 3 (H 2 O)] and Na[Zn 2 (OC 6 H 3 Pr* 2 -2,6) 4 Cl]·3thf.45 Solution and solid-state structural studies have been reported for phosphine adducts of monomeric zinc bis(phenoxides) of the type, ZnQ 2 L (HQ\2,6-di-tert-butylphenol; L\PMePh 2 , PCy 3 ).46 The synthesis and structure have been reported for pseudo-octahedral Na 2 [Zn(ida) 2 ]·7H 2 Oand pseudobicapped octahedral Na 4 [Hg(nta) 2 ]·7H 2 O complexes.47 The dimeric dithiolate complex, [MZn(bme-daco)N2 ], and its cadmium analogue have been studied as models for the active site of zinc-dependent methylation proteins. 48 The new ligand, 2,6-(Ph 2 PCH 2 CH 2 SCH 2 ) 2 C 5 H 3 N, has been prepared and the complexes [ML(O 3 SCF 3 ) 2 ] (M\Zn or Cd) obtained.Details of the X-ray crystal structure have been given for the CD species which shows an unusual distorted pentagonal-bipyramidal geometry, in which the cadmium centre bonds to all five donor atoms of the ligand as well as to oxygen atoms of the two monodentate CF 3 SO 3 ~ anions.49 The thiolate complexes, (Me 4 N) 2 [M 4 (o-SC 6 H 4 Me) 10 ] (M\Zn or Cd), have been synthesised, characterised by various methods, and observed to have selectively scavenging e§ects on hydroxyl radicals.50 Zinc thiolate compounds of the type [Zn(bima)(SR)][X] (R\Ph or CH 2 Ph; X\BPh 4 or ClO 4 ), have also been prepared.X-Ray crystallography shows that the zinc centre is in a pseudo-tetrahedral environment.51 Some novel dimeric carbamato species of cadmium, [CdL 2 (O 2 CNEt 2 )] 2 [L\Me 2 N(CH 2 ) 2 NMe 2 , py or (MeNCH 2 ) 3 ] as well as the monomeric complex [Cd(O 2 CNEt 2 ) 2 ] have been reported.52 A family of monomeric cadmium(II) bis(phenoxides) of general formula, [Cd(OC 6 H 3 R 2 -2,6) 2 ](base) 2–3 (R\Ph, Bu5 or Me; base\thf, tht, py or propylene carbonate), have been synthesised.Their reactivities with the small molecules CO 2 , COS and CS 2 have been studied.No reaction was observed with carbon dioxide but the others do undergo insertion reactions. It was found that the parent compounds show reduced activity for the copolymerisation of CO 2 with epoxides, a reaction for which the analogous zinc(II) bis(phenoxides) are highly active.53 The X-ray crystal structure for [CdCl 2 (imt) 2 ] has been re-determined.The Cd–S bonds [2.525(2) and 2.535(2)Å] are appreciably longer than those measured for the analogous gold(I) and copper(II) complexes while the intraligand C–S bonds are the Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 96same.54 Crystal structures have also been reported for the bis(thiourea) cadmium halide complexes, [CdX 2MSC(NH 2 ) 2N2 ] (X\Cl, Br or I).These pseudo-tetrahedral complexes are isostructural although the iodide complex crystallises in a di§erent space group.55 Thiosulfate acts as a polydentate ligand in the complex, [Cd(S 2 O 3 )(phen)(H 2 O)]·H 2 O, for which the crystal structure reveals a polymeric chain structure with each cadmium atom sitting in a distorted octahedral environment. 56 The complexes [CdHL(pn) 2 ]`and [CdL(pn) 2 ] for H 2 L\2-thiouracil or 6-methyl-2-thiouracil have been reported.57 Polytopal isomerism of the thiobenzoate complex (PPh 4 )[CdMS(O)CPhN3 ] has been revealed by an X-ray crystallographic study.58 The X-ray crystal structure has also been reported for the analogous triethylammonium salt.59 Multinuclear NMR (13C, 113Cd and 199Hg) and X-ray crystallographic studies for the related species (Ph 4 As) 2 [MCl 4 HgMS(O)CPhN2 ] (M\Cd or Hg), formed from Ph 4 AsCl·H 2 O, [HgMS(O)CPhN2 ] and MCl 2 (M\Cd or Hg), have also been reported.60 The complex [CdMCy 2 P(Se)C(S)NPhN2 ] has been synthesised and characterised by X-ray crystallography which shows the CdSe 2 S 2 core to be in a tetrahedral arrangement. 61 The selenato complexes, containing a chelating oxazoline ligand, [MMSe(ox@)N2 ] (M\Zn, Cd or Hg) each have a helical structure in the solid state that is maintained in solution.62 Solid- and solution-state 113Cd and 77Se NMR spectra have been reported for complexes of the general formula, [Cd(SeR) 2 L 2 ] (L\N-donor ligand), and the X-ray crystal structure was determined for the complex, [Cd(SeC 6 H 2 Pr* 3 -2,4,6) 2 (bipy)].These complexes serve as models for biologically occurring species of general formula, [M(S-Cys) 2 (His) 2 ].63 Another study found that cysteine and histidine both behave as bidentate ligands with Zn.64 Addition of E–– C––NR (E\S, R\Bu5; E\Se, R\Cy) to [CdMN(SiMe 3 ) 2N2 ] in the presence of tetramethylethylenediamine yields [Cd(ESiMe 3 )] or (tmeda)[CdMN(SiMe 3 ) 2N(SiSiMe 3 )]n.Upon protolysis, the latter complex yields MCd[XR](SiSiMe 3 )Nn (X\Oor S, R\SiPh 3 ; X\O, R\2,6-di-tert-butyl-4-methylphenyl). 65 Lewis acid adduct formation of [PhHgS(S)POGO] [G\–CH 2 CH(Me)–, –(CH 2 ) 5 – or –CMe 2 CMe 2 –) with mercury(II), cadmium(II) and silver(I) salts gave 24 bimetallic derivatives, generally formed through co-ordination of the thiono sulfur to the soft metal centre.66 The thioethereal complexes, [HgMN(CH 2 CH 2 SCHMe 2 ) 3N] 2 - [Hg 2 X 6 ] (X\Cl, Br) were prepared directly by reaction of the appropriate mercuric halide with ligand.The crystal structure is reported for the chloro-species.67 X-Ray crystallography shows [Hg(dmit)(phosphine)] (phosphine\dppe, dppf) to be a onedimensional co-ordination polymer held together by bridging diphosphine ligands.This structure is ascribed to the marked preference of the Hg to be in a tetrahedral configuration.68 The synthesis and structure for the first heavy metal complex of an x-thiocaprolactam, [HgCl 2 (C 6 H 11 NS-S) 2 ] 4 (C 6 H 11 NS\1-azacycloheptane-2-thione), has been reported. Bonding distances are 2.480(2) and 2.613(2)Å for Hg–Cl, and 2.496(2)Å for Hg–S.69 The dimeric complexes, [MHg(C 5 H 4 S 5 )X 2N2 ] (X\Cl or Br) for C 5 H 4 S 5 \4,5-ethylenedithio-1,3-dithiole-2-thione, have been characterised, including an X-ray structure determination for the chloro species.70 The crystal structure, with corroborating spectroscopic data, has been reported for a mercury dimer, [MHgCl 2 LN2 ] 5 formed from HgCl 2 and benzothiazole. The resulting 2-aminoben- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 97N N S Hg Cl S Cl H H 4 zenethiol ligand (L) exists in the zwitterionic form. Significant bond distances include Hg–Cl 2.383(1), Hg–S 2.340(2), Hg–l-Cl 2.720(1) and 2.976(1)Å.71 +NH3 S Hg Cl – Cl – Cl Hg Cl S +NH3 5 Halide and pseudo-halide donor ligands A novel blue luminescent complex, [Zn(Hdpa)(CN) 2 ], shows potential as a material for blue-light emitting diodes.Self-assembly is observed for this compound in the crystal state via intermolecular hydrogen bonding [N–H· · ·NC 2.965(7)Å], and faceto- face p–p aromatic stacking to form two-dimensional sheets.72 A detailed lowtemperature multinuclear (13C, 15N, 113Cd)NMRstudy of the complexing of divalent zinc and cadmium with isothiocyanates in solution has been reported.73 Formation of the layered co-ordination polymer, (4-cyanopyridine)cadmium iodide diiodine is assisted by two types of iodide bonding, involving co-ordinated iodine atoms of the layers and iodine molecules that bridge adjacent layers.74 The use of methyl acetate as the guest molecule has provided a novel mineralomimetic Cd(CN) 2 framework, and the novel clathrate species, [Cd(CN) 2 ]·MeCO 2 Me.The X-ray structure was reported for the latter material.75 Solid state NMR studies have been reported for the series, [Hg(X)(O 2 CMe)] (X\Cl, Br, I, CN or SCN), and the X-ray crystal structure of the cyano species has been determined.76 The 199Hg MAS NMR spectra were also measured for [Hg(SCN) 2 ], [Hg(SeCN) 2 ], M[Hg(SCN) 3 ], M 2 [Hg(SCN) 4 ] (M\K or Cs) and K 2 [Hg 3 (NCO) 8 ], along with the crystal structure for the selenocyanato species.77 In the course of an investigation, employing Raman spectroscopy and factor analysis, into the equilibria displayed by Hg(SCN) 2 /NaSCN in dmf solution, the following species were tentatively assigned, [Hg(SCN)]`, [Hg(SCN) 2 ], [Hg(SCN) 3 ]~ and [Hg(SCN) 4 ]2~.78 Other ligands Phase transition studies by the DSC method for crystalline [M(H 2 O) 6 ][ClO 4 ] 2 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 98(M\Zn, Cd or Hg) have been reported.79 The complex [Zn 2 L 2 (OH) 2 ] for L\N- [(benzoylamino)thioxomethyl]glycine proves to be an e§ective anti-oxidant because it demonstrates scavenging e§ects on dioxygen radicals.80 The synthesis, 11B NMR spectra and X-ray crystal structure have been reported for [NBu/ 4 ] 2 [Cd(g3-B 6 H 6 ) 2 ]· 2CH 2 Cl 2 .81 The amine-carboxylate adduct, bis(morpholine borane carboxylate)zinc(II) dihydrate has been shown to have antitumor activity.82 Insertion of CO 2 into one the B–H bonds of the bis(pyrazolyl)hydroborato ligand in [ZnCl(HBp5.B6,*.P3)] yields the complex, [ZnClMg3-(HCO 2 )Bp5.B6,*.P3N]ZnCl, characterised by single crystal X-ray di§raction.83 The trigonal fragment, [Au(dpnapy) 3 ]`, acts as a metalloligand with a strong a¶nity for Cd(II) in [AuCd(dpnapy) 3 ][ClO 4 ] 3 .84 The synthesis and X-ray crystal structure of the fulleride, [Cd(NH 3 ) 6 ]C 60 ·6NH 3 , have been reported.85 3 Macrocyclic compounds The structure for [ZnCl(Me 3 [12]aneN 3 )](PF 6 ) has been assessed as a model for zinc-containing active sites on hydrolytic metalloenzymes such as carbonic anhydrase.The parent ligand, [12]aneN 3 , has previously been found to be an appropriate ligand for this purpose.86 Crystal structures have been reported for [ZnCl([15]aneN 4 )] (ClO 4 )87 and for the zinc complex of the new ligand, 5,10,15,20-tetra[4(n-butylphenyl) ethynyl]porphyrin.88 Both 1D and 2D 1H NMR were used to study the dinuclear complex [Zn(TTP-m-O(CH 2 ))] 2 (CH 2 ).In solution, this compound axially co-ordinates both pyrazine and pyrimidine. The crystal structure for the former species shows a 1:1 adduct formation but with the pyrazine acting as a bridging ligand.89 A zinc porphyrin bound to fullerene has shown some interesting luminescence and photophysical properties,90 and the opto-electronic properties for several other conjugated porphyrin oligomers have also been studied.91 The preparation and X-ray crystal structure have been reported for a unique 2: 1 complex of mercuric chloride with 5-oxa-2,8-dithiabicyclo[7.4.1]tetradeca-9,11,13- trien-14-one.92 Cadmium and mercury complexes of the semi-rigid diimine ligand, OpyNpy 2 6, were prepared from a [1]2] Schi§ base condensation of 2,6-bis(2- aminophenoxymethyl)pyridine and 2-pyridinecarbaldehyde in the presence of MX 2 (M\Cd or Hg; X\NO 3 or ClO 4 ). X-Ray di§raction revealed a mono-helical structure for the Cd complex, [Cd(OpyNpy 2 )](NO 3 ) 2 ·2H 2 O.93 4 Cluster chemistry The crystal structure has been reported for [Zn 3 (bdc) 3 ]·6MeOH,94 and the cluster [Zn 8 L 4 (OH) 2 ](ClO 4 ) [H3 L\1,3-bis(salicylamino)propan-2-ol] which has been shown to have a unique cage structure composed of eight zinc atoms, four alkoxo O atoms and eight ligand phenoxoObridges.95 The synthesis and molecular structure of a new type of zinc sulfide cluster, [Zn 10 S 7 (py) 9 (SO 4 ) 3 ]·3H 2 O, has been reported,96 and also for the zinc selenide and telluride clusters, [NEt 4 ] 2 [ZnCl 4 (SePh) 6 ], [NEt 4 ] 2 - [Zn 8 Cl 4 Se(SePh) 12 ], [Zn 8 Se(SePh) 14 (PPr/ 3 ) 2 ], [HPPr/ 2 R] 2 [Zn 8 Cl 4 Te(TePh) 12 ] (R\Pr/ or Ph), and [Zn 10 Te 4 (TePh) 12 (PR 3 ) 4 ] (R\Pr/ or Ph).97 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 996 N N N O O N N In the solid state, [Cd 7 (tren) 12 ][ClO 4 ] 14 is made up of flat star-shaped disks composed of Cd(tren) moieties linked by other tren ligands.98 Other crystal structure determinations have included those for [Cd 3 (py) 8 (O 2 CMe) 4 ](ClO 4 ) 2 ,99 [Cd 10 Se 4 (SePh) 12 (PPh 3 ) 4 ] and [Cd 16 (SePh) 32 (PPh 3 ) 2 ],100 and the tri-heteropolymetallic species, [(dppf)Pt(l-L) 2 CdX 2 ] (X\Cl, Br or I) and [M(dppf)Pt(l- L) 2N2 Cd][X] 2 (X\BF 4 or ClO 4 ) for HL\Hpz, Hdmpz or Mepz.101 The crystal structure for [Hg 3 (H 2 pdm) 2 (Hpdm)(l-Cl) 2 Cl 3 ] shows that the metal environment is pseudo-octahedral for the central Hg atom but distorted squarepyramidal for the two end Hg atoms.102 Synthesis and crystal structures have been reported for [Hg 6 (SePh) 12 (PBu5 3 ) 2 ] and (HPBu5 3 ) 2 [Hg 6 (SePh) 14 ],103 the three new Hg–Fe cluster complexes: [Hg 7MFe(CO) 4N5 (SBu5) 3 Cl], [Hg 14 Fe 12MFe(CO) 4N6 - S 6 (SBu5) 8 Br 18 ] and [Hg 39 Fe 8MFe(CO) 4N18 S 8 (SBu5) 14 Br 28 ],104 as well as for several related phosphinido-and phosphinidene-bridged cluster complexes: [Hg 3MFe(CO) 4N2 - X 2 ] (X\Cl, Br), [Hg 10MFe(CO) 4N4 (PBu5) 4 Cl 4 ], [Hg 14MFe(CO) 4N5 (PBu5) 8 Cl 2 ], [SiMe 3 OPPr* 3 ][Hg 12MFe(CO) 4N7 (PBu5) 4 (PBu5SiMe 3 )Br 2 ], [Hg 5MFe(CO) 4N3 (PBu5) 2 - Br 2 ], [Hg 8MFe(CO) 4N4 (P 2 Ph 2 ) 2 (PPr/ 3 )Cl 4 ], [Hg 8MFe(CO) 4N4 (P 2 Ph 2 ) 2 (PEtPh 2 )Cl 4 ], and [Hg 10MFe(CO) 4N6 (P 2 Ph 2 ) 2 (PPr/ 3 )Br 4 ].105 The synthesis of the first polymetallic mesocycle containing the first example of an attractive Hg–Cu interaction has been reported, and the molecular structure 7 for this compound has been determined by X-ray crystallography.The observed Cu–Hg separation of 2.689(2)Å is only slightly longer than the sum of the Pauling covalent radii (2.61Å).106 5 Organometallic chemistry IR and Raman spectroscopic studies for both solution and solid-state samples indicate that in solution zincocene has the slip-sandwich structure, [Zn(g5-C 5 H 5 )(g1-C 5 - H 5 )].107 The synthesis and the crystal structure determination have been reported for [Zn(C 6 F 5 ) 2 ].108 The homoleptic organometallic species [MMRN2 ] or [MR 2 ] (M\Zn, Cd or Hg) have been prepared for a series of ligands derived from LiC 6 H 4 (CH 2 NEt 2 )-2, LiC 6 H 3 (CH 2 NMe 2 )-2,6, LiC 6 H 3 (CH 2 NEt 2 ) 2 -2,6, Li(CH 2 ) 3 NC 5 H 10 and [Li(CH 2 ) 3 ] 2 NMe.Whether the dimer or monomer forms depends upon the nature of R.109 The X-ray crystal structure was determined for [Li(tmeda) 2 ][Zn(C 6 H 2 Pr* 3 -2,4,6)].110 Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 93–104 100A boron–zinc transmetallation methodology has been employed to prepare [ZnCH 2 CHRCH 2 ZnCH 2 CHRCH 2 ] and [Zn(CH 2 ) 3 Hg(CH 2 ) 3 ] (R\H or Bu).Based on NMR spectra, the structures have been assigned as eight-membered rings. Under appropriate conditions these species are reactive with electrophiles such as allyl bromides or propargyl bromide and benzoyl chloride.111 The compound [(Z)- PhCH 2 CH 2 CH––CMeHgBr], prepared from the Grignard reaction of (Z)-2-bromo-5- phenylpent-2-ene with HgBr 2 in thf,112 reacts with silver acetate in thf to give [(Z)- PhCH 2 CH––CMeHg(O 2 CMe)]113 or can undergo an SnCl 2 -mediated coupling in the presence of NaOH in either ethanol or water to give [(PhCH 2 CH 2 CH––CMe) 2 Hg].114 The bifunctional ligand Hdpb and its oxide, dpbo, react with mercury to form [HgMe(L)] (L\dpb or dpbo).The X-ray crystal structures have been reported.115 Organometallic pyrimidine derivatives of the type [RHgL] (R\o-, p-HOC 6 H 4 ; L\uracil or thymine) have been synthesised.116 The cationic species [HgR]` (R\Me, Et, Pr, Pr*, Ph, C 6 H 4 Me-p, CH 2 Ph, 5-methylthienyl or ferrocenyl) have been reacted to form complexes with hydridotris(3,5-diphenyl-1H-pyrazol-1-yl)borato and hydridotris(4-bromo-1H-pyrazol-1-yl)borato ligands.The former appears to be the better donor ligand.117 Reactions of [Hg(O 2 CR) 2 ] (R\Et, Pr, Pr* or Bu) with methylphenylacetylene in appropriate acidic solvents yield mixtures of cis and trans 8 Me O O O O O Hg Br Annu.Rep. 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ISSN:0260-1818    

DOI:10.1039/a808998a

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

9 Titanium, zirconium and hafnium S. A. Cotton Uppingham School, Uppingham, Rutland, UK LE15 9QE 1 Introduction This report follows the pattern of recent years in being selective, particularly in the area of organometallic chemistry. It covers the available 1998 literature, together with some late 1997 papers. An important account1 of bent metallocenes covers aspects of their structure and bonding as well as certain reactions including Ziegler–Natta polymerisation catalysed by [ZrRCp 2 ]` systems.A review of zirconium and hafnium fluoro complexes systematises their structural chemistry on the basis of the F: Zr(Hf) ratio.2 Alkene and alkyne complexes of zirconium formed by thermolysis of [ZrR 2 Cp 2 ] (R\alkyl) have been reviewed3 as have titanocene and zirconocene olefin polymerisation catalysts.4 An account of dicatechol ligands includes several examples of their application to produce helicate complexes of titanium.5 A review of organically pillared micro- and meso-porous materials is relevant.6 A review of fluorenyl complexes of zirconium and hafnium as catalysts for olefin polymerisation covers their preparations and structures as well as their catalytic activity.7 Another review concerned with olefin polymerisation catalysts treats Group 4 ansa-cyclopentadienyl –amide complexes.8 The McMurry reaction for the coupling of ketones and aldehydes to a§ord alkenes, most usually with titanium catalysts, has been reviewed.9 The co-ordination chemistry of titanium for the year 1994 has been reviewed.10 2 Metallacarbohedranes Areview of metal–carbon cage compounds includes metcars11 whilst an overall review of metcars has been published.12 Ab initio SCF calculations of [Ti 8 C 12 (H 2 O) 8 ] and [Ti 8 C 12 (C 2 H 4 ) 4 ] indicate that in the former electron transfer occurs from water to the cluster whilst in the ethene adduct the transfer is in the opposite direction.13 New prominent clusters including [Ti 3 C 8 ]~, [Ti 4 C 8 ]~, [Ti 6 C 13 ]~, [Ti 7 C 13 ]~, [Ti 9 C 15 ]~ and [Ti 13 C 22 ]~ have been observed in negative ion mass spectra.14 3 Halides and their complexes Reaction of TiCl 4 with hexamethyldisilane a§ords an active form of TiCl 3 in high Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 105–115 105yield.15 Raman studies of liquid and gaseous ZrCl 4 establish the presence of dimeric species in equilibrium with monomeric ZrCl 4 in the vapour; and monomeric ZrCl 4 in equilibrium with polymeric [ZrCl 4 ]n in the liquid.16 Study of melts of ZrCl 4 with CsCl establishes the existence of Cs 2 ZrCl 6 and CsZr 2 Cl 9 .HfCl 4 catalyses the intramolecular allylsilylation of alkynes.17 LiCs 4 [Zr 3 F 17 ]·HF has individual [Zr 3 F 17 ]5~ ions, involving seven- and eight-co-ordinate zirconium.18 An NMR spectroscopic study of the reaction of TiCl 4 with HF in MeCN establishes the formation of [TiCl 4~xFx(NCMe) 2 ] (x\1–4).19 In the presence of [PPh 4 ]Cl, partial hydrolysis of TiCl 3 and TiCl 4 gives a variety of complexes.20 Hydrolysis of TiCl 4 in CH 2 Cl 2 gives the heptanuclear mixed-valence compound [PPh 4 ] 3 [Ti 7 Cl 10 O 3 ].In acetone, hydrolysis of TiCl 3 leads to [PPh 4 ] 2 - [Ti 2 Cl 7 (H 2 O)(OH)(OCMe 2 )] and [TiCl 3 (H 2 O) 3 ] as the products whereas hydrolysis of TiCl 4 gives polymeric M[PPh 4 ][Ti 2 Cl 6 X(O)]N (X\OH, Cl) and [PPh 4 ]- [TiCl 5 (H 2 O)] as well as the simple complex [PPh 4 ] 2 [TiCl 6 ]. Reduction of TiCl 4 by HSnBu 3 a§ords a brown solid which reacts with Cl~ forming a precursor for facesharing Ti(III) complexes, including [Ti 2 Cl 7 (PEt 3 ) 2 ]~, [Ti 2 Cl 9 ]3~ and [Ti 3 Cl 12 ]3~, though pyridine cleaves bridges to form trans-[TiCl 4 (py) 2 ]~.A number of complexes, [TiCl 4 (SHR) 2 ] and [TiCl 4 (SR 2 ) 2 ], have been synthesised as possible precursors for titanium sulfide films and the structure of cis-[TiCl 4 (tht) 2 ] determined, along with that of [(TiCl 4 ) 2 (MeSSMe)] which has a Ti 2 Cl 8 core together with a bridging disulfide ligand.21 TiCl 4 reacts with Me 2 Se 2 and Et 2 Se 2 forming [(TiCl 4 ) 2 (Se 2 Me 2 )] and [(TiCl 4 ) 2 (Se 2 Et 2 )] respectively;22 the former is unstable, decomposing to [TiCl 4 (SeMe 2 ) 2 ] and Se, which, like [TiCl 4 (SeEt 2 ) 2 ], can be prepared directly from TiCl 4 and R 2 Se (R\Me, Et).[TiCl 4 (SeEt 2 ) 2 ] gives (moisture-sensitive) TiSe 2 films at 500–600 °C. [MZrF 4 (dmso) 2N2 ] has seven-co-ordinate zirconium with two bridging fluorides;23 other complexes [ZrF 4 L] (L\dmf, dmso, dimethylacetamide, tetramethylurea) have been synthesised. A range of PMe 3 complexes have been reported and structurally characterised,24 [ZrI 4 (PMe 3 ) 3 ] (capped trigonal antiprism) and [HfI 4 (PMe 3 ) 2.5 ] Ma mixture of [HfI 4 (PMe 3 ) 3 ] and [HfI 4 (PMe 3 ) 2 ]N; the bioctahedral M(III) compounds [Ti 2 I 6 (PMe 3 ) 4 ], [Hf 2 I 6 (PMe 3 ) 4 ], [Zr 2 Br 6 (PMe 3 ) 4 ]; and the M(II) species [Hf 2 I 4 (PMe 3 ) 4 (l-g6: g6-C 6 H 6 ].Serendipitously prepared [TiCl 4 (dmpe) 2 ] is the first eight-co-ordinate titanium phosphine complex.25 Monomeric [TiCl 4MMe 2 Si(NPEt 3 ) 2N] has distorted octahedral co-ordination of titanium.The dimer [MTiCl 3 (NPEt 3 )N2 ] has asymmetric Ti 2 N 2 bridges; in the thf adduct [TiCl 3 (NPEt 3 )(thf) 2 ] the thf trans to the phosphoraneiminato ligand has a much longer Ti–O bond (238.0 pm) than that trans to Cl (213.7 pm).26 A trimeric species [Ti 3 Cl 9 (NPEt 3 ) 3 ] is a cluster [Ti 3 Cl 8 (NPEt 3 ) 3 ]Cl in which two nitrogens act as l3 -bridges, the remaining nitrogen and two chlorides acting as l-bridging atoms.27 ABr (A\Na–Cs), Zr, ZrBr 4 and an interstitial element Z (Z\B, Be, H, Mn) react in Ta containers at 850 °C to form two series of quaternary phases that contain A 4 Br3` ions.28 Various cubic [A 4 Br] 2 [Zr 6 XBr 18 ] (A\Na–Cs; X\Be, B, H, Mn) exist.[K 4 Br] 2 [Zr 6 BBr 18 ] has the inverse fluorite structure. [Cs 4 Br] 2 [Zr 6 BBr 18 ] has puckered Zr 6 Br 16 layers with Cs 4 Br3` in tunnels normal to the layers. Neutron and X-ray di§raction studies29 on [PPh 4 ] 3 [Zr 6 Cl 18 H 5 ] show that the hydrogens (which undergo rapid movement at room temperature) occupy the triangular faces of the Zr 6 octahedron with an average Zr–H distance of 1.92Å.Deprotonation by amines yields the new tetrahydride clusters [PPh 4 ] 4 [Zr 6 Cl 18 H 4 ] and [NH 3 Et] 4 [Zr 6 Cl 18 H 4 ]. The Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 105–115 106mixed-halide cluster Na[Zr 6 Cl 10.94 I 3.06 B] has a di§erent cluster connectivity to other zirconium cluster halides.30 Ligand-exchange and solvolysis reactions of the [Zr 6 BCl 12 ]` cluster have been studied by NMR spectroscopy.31 Spectra were observed for [Zr 6 BCl 12 Cl 6~xLx]x~5` (L\MeCN, MeOH, py) as well as for others species such as [Zr 6 BCl 12 (PR 3 ) 6 ]` and [Zr 6 BCl 12 (OPR 3 ) 6~xLx]`.Structures were reported for [Zr 6 BCl 12 Cl(py) 5 ] and [Hpy]cis-[Zr 6 BCl 12 Cl 2 (py) 4 ]. Mo� ssbauer spectra of [Zr 6 Cl 14 Fe], Li[Zr 6 Cl 15 Fe],and Rb[Zr 6 Cl 15 Fe] show extremely negative isomer shifts.32 4 Oxides and other binary and related compounds Among its many useful properties, TiO 2 absorbs UV light and is potentially a very useful photocatalyst for decomposing organic compounds and bacteria; TiO 2 -coated surfaces become hydrophilic and thus resist fogging.33 Sunlight-irradiation of a TiO 2 suspension in MeCN containing maleic anhydride and 4- methoxybenzyl(trimethyl)silane causes a C–C bond-forming reaction leading to benzylated succinic acid in good yield.34 A rapid solid-state route for the synthesis of TiC and ZrC from reaction of the metal halides with CaC 2 or Al 4 C 3 has been reported.35 TiN reacts with Sr 2 N forming SrTiN 2 , a rare ternary nitride of Ti (SP titanium).36 Zr/Ti reacts with BaSe/SrSe and Se in a flux forming columnar compounds Ba 15 Zr 14 Se 42 and Sr 21 Zr 19 Se 57 with mean oxidation states of ]3.86 and ]3.79 respectively.37 The solubility product of Zr(OH) 4 has been determined; logK4 \[55.26.38 Cs 2 ZrSe 3 contains complex anionic chains 1 = [ZrSe 3 ]2~ built up of quadratic ZrSe 5 pyramids sharing oppositeasal edges.39 5 Alkoxides, thiolates, amides and imides FT-IR and polarised FT-Raman spectra of [Ti(OPr*) 4 ], both neat and in solution, have been investigated and assigned.40 EXAFS studies of [Zr(OPr/) 4 ] and [Zr(OBu/) 4 ] indicate the presence of oligomers with six-co-ordinate zirconium; studies of mixed zirconium–titanium species are interpreted in terms of hetero species.41 [Ti(OPr*) 4 ] and PPh 3 mediate a reductive olefination reaction which has been applied to the one-pot synthesis of perfluorinated trans-allylic alcohols.42 The mixed alkyl –aryloxide [Ti(OPr*) 3 (OC 6 H 2 Me 3 -2,4,6)] is dimeric [(2,4,6-Me 3 C 6 H 2 O)(Pr*O) 2 - Ti(l-OPr*) 2 Ti(OC 6 H 2 Me 3 -2,4,6)(OPr*) 2 ].43 Hydrolysis of [Ti(OPr*) 4 ] in the presence of acetylacetone gives [Ti 4 (l3 -O) 2 (l-OPr*) 2 (OPri) 8 (acac) 2 ].44 Controlled addition of water to [MMOSi(OBu5) 3N4 ] results in the isolation of aqua complexes [MMOSi(OBu5) 3N4 (H 2 O)x] (M\Zr, Hf; x\1,2) which are stable indefinitely in the solid state and for weeks in solution.Hydrolysis occurs by an associative mechanism involving a seven-co-ordinate intermediate, postulated to be [MMOSi(OBu5) 3N4 (H 2 O) 3 ].45 [Ti(OPr*) 3 (OCH 2 CH 2 NMe 2 ] and [Ti(OPr*) 2 (OCH 2 - CH 2 NMe 2 ) 2 ] have been synthesized as MOCVD precursors for TiO 2 thin films.46 [Ti(OR) 4 ] (R\Et, Pr*) react with R@CO 2 H forming [Ti 6 (l3 -O) 6 (l-O 2 CR@) 6 (OR) 6 ], confirmed by X-ray di§raction on [Ti 6 (l3 -O) 6 (l-O 2 CC 6 H 4 OPh) 6 (OEt) 6 ].47 With one mole of formic acid, [Ti(OPr*) 4 ] gives [Ti 4 (l4 -O)(l-O)(O 2 CH) 2 (l-OPr*) 4 (OPr*) 6 ], Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 105–115 107which decomposes in solution by transesterification; with two moles of formic acid, the stable [Ti 6 (l3 -O) 6 (l-O 2 CH) 6 (OPr*) 6 ] is formed.48 [Ti(OPr*) 4 ] substitutes protons in the pinacolate complex [Zr 2 (OCMe 2 CMe 2 O) 2 (OCMe 2 CMe 2 OH) 4 ] forming first [Zr 2 (OCMe 2 CMe 2 O) 4 (OCMe 2 CMe 2 OH) 2 Ti(OPr*) 2 ] then [Zr 2 (OCMe 2 CMe 2 O) 6 - MTi(OPr*) 2N2 ].49 In the solid state, [MTi(OR) 3 (acac)N2 ] (R\Me, Et, Pr*) and [MTi(OR) 3 (tmhd)N2 ] (R\Me, Pr/, Pr*) are centrosymmetric dimers with alkoxide bridges; in solution they undergo ligand redistribution reactions to a§ord mixtures of [MTi(OR) 3 (acac)N2 ], [Ti(OR) 2 (acac) 2 ] and [Ti(OR) 4 ].50 Thin films of ZrO 2 have been obtained by liquid injection MOCVD from the mixed ligand precursor [Zr 2 (OPr*) 6 (tmhd) 2 ].51 Several Group 2 heterometallic alkoxides have been reported, including [SrTi 4 (OEt) 18 ], which has a bow-tie Ti 2 SrTi 2 core with strontium bound to two face sharing Ti 2 (OEt) 9 bioctahedra, and [Sr 2 Ti(OPr*) 8 (Pr*OH) 3 ]·2Pr*OH, with a triangular Sr 2 Ti core bridged by three l-Pr*O ligands and capped by two l3 -Pr*O groups.52 Ba(OMe) 2 reacts with Ti(OMe) 4 forming a number of mixed alkoxides53 including BaTi 4 (OMe) 18 (possibly with a similar structure to that of the strontium compound described above), Ba 2 Ti(OMe) 8 and BaTiO(OMe) 4 .[Ti(OPr*) 4 ] reacts with [Pb(O 2 CR) 2 ] to produce heterometallic compounds54 such as [Pb 2 Ti 2 (O)(O 2 CR) 2 (OPr*) 8 ] (R\C 3 F 7 , Bu5) and [Pb 2 Ti 4 (O) 2 (O 2 CR) 2 (OPr*) 14 ] (R\Pr*). Three zirconium alkoxide species share a common Zr 3 (l-OR) 3 (l3 -OR) 2 core: [Zr 3 O(OCH 2 CMe 3 ) 9 Cl], [Zr 3 O(OCMe 3 ) 9 (OH)] and [Na 4 Zr 6 O 2 (OEt) 24 ], the last formed from Zr(OEt) 4 and NaOSiMe 3 .55 [TiCl 3 (thf) 3 ] reacts with LiNPh 2 forming [Ti(NPh 2 ) 4 ], which has distorted tetrahedral co-ordination; partial hydrolysis a§ords the symmetric dimer [(Ph 2 N) 3 Ti(l-O)Ti(NPh 2 ) 3 ].56 [MMN(SiMe 3 ) 2N3 Me] (M\Zr, Hf) react with B(C 6 F 5 ) 3 forming the salt [MMN(SiMe 3 ) 2N3 ][BMe(C 6 F 5 ) 3 )] ; unlike the starting material, the product displays M–Si–C multicentre interactions.57 [MMN(Ph)SiMe 3N3 Cl] and [MMN(Ph)SiMe 3N3 Me] were also reported.The bulky lithium amide LiL·OEt 2 ML\3,5–Me 2 C 6 H 3 N(Ad)N reacts with [ZrCl 4 (thf) 2 ] forming [ZrClL 3 ]; the remaining chloride can be substituted to a§ord [ZrMeL 3 ] and [Zr(BH 4 )L 3 ].58 TBPY complexes of a tridentate diamido amine [MX 2MRC(C 5 H 4 N)(CH 2 NSiMe 3 ) 2N] (M\Ti, Zr; X\Cl, Br; R\H, Me) have been synthesised59 and used as a synthon for mono- and di-alkyls such as [TiXR@MMeC(C 5 H 4 N)(CH 2 NSiMe 3 ) 2N] and [TiR 2MMeC(C 5 H 4 N)(CH 2 NSiMe 3 ) 2N] (R@\PhCH 2 , Me3 SiCH 2 , Me3 SiC 2 ).Compounds of a tridentate diamide ligand (H 2 L\Bu5NHSiMe 2 NHCH 2 CH 2 NMe 2 ) have been made, including [ZrL(NMe 2 ) 2 ] and [ZrLCl 2 ].60 A wide range of Ti-(II), -(III) and -(IV) benzamidinates includes61 a binuclear dinitrogen complex 1.Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 105–115 108Chiral imine(alkoxy) complexes such as 2 have been synthesised.62 Titanium imide complexes of macrocycles include [Ti(NBu5)(ttp)] and [Ti(NBu5)(acen)].63 Heteroallylic imide complexes synthesised64 include [Ti(NCCMe 3 )Cl(py) 2MPhC(NSiMe 3 ) 2N], [Ti(NCCMe 3 )Cl(py) 2MMeOC 6 H 4 C(NSi-Me 3 ) 2N], [Ti(NCCMe 3 )Cl(py)MPh 2 P(NSiMe 3 ) 2N], [Ti(NCCMe 3 )MPh 2 P(NSiMe 3 ) 2N2 ] and [Ti(NCCMe 3 )(py)MPhC(NPr*) 2N]. 6 Complexes of macrocycles ZrCl 4 reacts with 1,2–dicyanobenzene under a stream of I 2 forming [Zr(pc)I 2 (NCC 6 H 4 CN)].65 This contains seven-co-ordinate zirconium; the dicyanobenzene molecule is bound through one nitrogen. The alkyne in [Ti(ttp)(g2- RC–– – CR)] (R\Et, Ph) is displaced by PhN––NPh forming the azobenzene adduct [Ti(ttp)(g2-PhN––NPh)]; at high temperatures this reacts with [Ti(ttp)(g2-RC–– – CR)] forming the phenylimide [Ti(ttp)(–– NPh)].66 Reduction of [Ti(ttp)Cl] a§ords trans- [Ti(ttp)(thf) 2 ], the thf of which can be displaced by Bu5NC giving [Ti(ttp)(NCBu5) 2 ].A ligand binding order of py[methylpyridine[Bu5NC[PhC–– – CPh[ EtC–– – CEt[thf was deduced.67 The structure of [MTi 2 (l3 -O)Cl 2 LN2 ] (L\p-tertbutylcalix[ 4]arene) is based68 on a four-runged Ti 4 O 4 planar ladder; each calixarene is bound to three titanium atoms. 7 Phosphates and phosphonates Dehydration of c-titanium phosphate, c-[Ti(H 2 PO 4 )(PO 4 )]·2H 2 O proceeds via a number of steps, through the anhydrous compound then the layered pyrophosphate [Ti(PO 4 )(H 2 P 2 O 7 ) 0.5 ] and finally the anhydrous pyrophosphate [TiP 2 O 7 ].69 a,/- Alkyldiamines have been intercalated as monolayers into g-titanium phosphate affording compounds with the maximum composition g-[Ti(H 2 PO 4 )(PO 4 )]· 0.67NH 2 CnH 2nNH 2 ·H 2 O (n\2–9).70 a-Zr(HPO 4 ) 2 ·H 2 O (a-ZrP) can be made by decomposing zirconium fluoride complexes in the presence of phosphoric acid.71 a- Zirconium phosphonate can in turn be made from a-ZrP by reaction with molten phenylphosphonic acid.72 The interlayer distance in pillared derivatives of c-zirconium phosphate, ZrPO 4 [O 2 P(OH) 2 ] 1~x[O 2 P(OH)(CH 2 )nHOPO 2 ]x@2 ·mH 2 O (n\4, 6, 8, 10, 12, 16; for example x\0.098,m\2.60; x\0.22,m\2.50; x\0.47,m\2.05), can be modulated by varying the length of the alkyl group.73 A new method of preparing Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 105–115 109colloidal suspensions of a-ZrP, involving the use of a phase swelled with npropylamine vapours, was applied to the synthesis of chromia-pillared materials.74 Intercalation and exfoliation of a-ZrP have been studied microscopically; the ratedetermining step in intercalation is the opening of the interlamellar galleries.75 Hydrothermal reaction76 of [Zr(OPr/) 4 ] with phosphoric acid in the presence of en and HF yields the one-dimensional [H 2 en][Zr(HPO 4 ) 3 ], the two-dimensional [H 2 en] 0.5 [Zr(PO 4 )(HPO 4 )] and the three-dimensional open-framework compound [H 2 en] 0.5 [Zr 2 (PO 4 ) 2 (HPO 4 F)]·H 2 O.The synthesis and structure of a new phase of zirconium phosphate, s-Zr(HPO 4 ) 2 , has been reported.77 The vapour-phase intercalation of amines by a-HfP has been studied.78 Compounds [Hf(HPO 4 ) 2 ]·yamine·H 2 O have been obtained (y\1, amine\piperidine, pyridine; y\2, amine\aniline, benzylamine, cyclohexylamine); when y\1, the amines form a monomolecular layer and for y\2 the arrangement is bimolecular.a-HfP also intercalates the isomeric methylpiperidines. 79 [NH 4 ]Zr[F 2 ][H 3MO 3 PCH 2 NH(CH 2 CO 2 ) 2N2 ]·3H 2 O has a linear chain of zirconiums linked by phosphonate bridges.80 A new layered phosphonate, [Zr(O 3 PCH 2 C 6 H 4 NH 2 )x(O 3 PCH 3 ) 2~x], has been prepared in an intercalated hydrochloride form, [Zr(O 3 PCH 2 C 6 H 4 NH 3 Cl)x(O 3 PCH 3 ) 2~x].81 8 Other complexes Ab initio calculations indicate that the [Ti(H 2 O) 7 ]2` ion could be implicated in water-exchange reactions of the titanium(II) aqua ion.82 EPR studies of g-irradiated titanium in mesoporous molecular sieves have been interpreted in terms of Ti3` at both tetrahedral and octahedral sites.83 EXAFS has been used to detect two di§erent framework Ti sites in a Ti silicalite.84 [ZrCl(PhCOCHCOPh) 3 ] has capped octahedral co-ordination of zirconium.85 In the dimeric anion [MZr(OH)(CO 3 ) 3N2 ]6~ each zirconium is bound to three chelating carbonates and two bridging OH groups in a dodecahedral environment,86 a similar arrangement being found in M[Zr(OH)(C 2 O 4 ) 3 ] 2N6~.A new cluster, [Zr 6 (OH) 8 (OMe) 4 (O 2 CCHPh 2 ) 12 ]·2MeCN, contains an octahedron of zirconiums with bridging carboxylates and l3 -OH bridges.87 [Zr(O 2 CNEt 2 ) 4 ] has a dodecahedral co-ordination at the zirconium atom.88 [TiCl 2 Cp 2 ] reacts with Na 2 H 2 edta forming [Ti(edta)(H 2 O)] which has sevenco- ordinate titanium.89 H 5 O 2 [Hf(dtpa)]·H 2 O is isomorphous with the Sn analogue, having square antiprismatic co-ordination of hafnium.90 TiCl 4 reacts with [ZnS 6 (tmen)] forming a material analysing as TiSx (x[1.9) which is soluble in donor solvents a§ording isolable complexes [TiS 4 L 2 ] (L\py, 4–butylpyridine) and [TiS 4 (Meim) 3 ], the latter containing two g2-S 2 ligands 3.On oxidation, it forms [Ti 2 S 6 (Meim) 4 ], which is [(g2-S 2 )(Meim) 2 Ti(l-g2:g2-S 2 )Ti(g2-S 2 )(Meim) 2 ] with a bridging disulfide ligand.91 Annu. Rep. Prog. Chem., Sect.A, 1999, 95, 105–115 110A range of halide titanium(IV) Schi§ base complexes such as [Ti(H 2 salen)F 4 ], [Ti(salen)Cl 2 ], [Ti(salen)Br 2 ] and [MTiI(salen)N2 (l-O)], in addition to the seven-coordinate [Ti(salen)Cl 2 (thf)], are reported.92 The range of titanium(IV) Schi§ base complexes has been broadened with the synthesis93 of phenolates 4; R\H; R@\Ph, C 6 H 4 Bu5-4; R\Bu5; R@\C 6 H 4 Bu5-4) and triflates (R\CF 3 SO 2 ) as well as unsymmetrically substituted compounds of the type [Ti(salen)Cl(OPr*)].Some titanium imide Schi§ base complexes of the type [Ti(salen)NR] (R\C 6 H 3 Me-2,6) have been made.94 9 Organometallics A highlight is the synthesis and structure of the first ‘titanocene’, [TiMg- C 5 H 4 (SiMe 2 Bu5)N2 ], which has parallel Cp rings in a staggered arrangement.95 A postscript to the recent synthesis of [TiL 2 ] (L\pentalene) is provided by DFT calculations which indicate that only nine of the ten ligand p-orbitals interact with the metal, so that it really is an 18–electron compound.96 Gas-phase electron-di§raction of [TiCl 3 Et] gives no indication of any agostic Ti .. .H–Cb interaction or unusual ethyl geometry, unlike the situation in solid [Ti(dmpe)Cl 3 Et], where b-agostic interactions exist.97 The solid-state structure of [ZrCl(CH 2 CMe 3 ) 3 ] contains linear polymeric chains 5.98 Improved syntheses of [Ti(CH 2 EMe 3 ) 4 ] (E\C, Si) have also been reported.When [Zr(CH 2 CMe 3 ) 4 ] is treated with a partly dehydroxylated silica–alumina, binding to surface silanol groups gives a surface species Zr(–– – SiO)(CH 2 CMe 3 ) 3 which forms a hydride formulated as Zr(–– – SiO)H on hydrogenation at 150 °C.This catalyses the hydrogenation of polythene and polypropene to ‘diesel’ and lighter fraction alkanes under mild conditions.99 [Ti(g3-C 3 H 5 )(C 5 Me 4 CH 2 )Cp*] isomerises to the propenyl [Ti(C 5 Me 4 CH 2 )(g1-CH––CHCH 3 )Cp*] in a series of reversible firstorder steps.100 Zirconium attached to a calixarene binds butadiene ligands in a p2, g4 fashion.101 High-yield syntheses of [MCp 4 ] (M\Ti, Zr, Hf) use the reaction between [MCl 2 Cp 2 ] and NaCp in toluene.102 [ZrCp 4 ] reacts with CF 3 SO 3 Hforming [Zr(CF 3 SO 3 ) 2 Cp 3 ]; with water this gives [MZr(CF 3 SO 3 )Cp 3N2 (l-O)]. Cyclopentadienyl arylkoxides such as [Ti(OC 6 H 3 Pr* 2 -2,6) 3 Cp] have been characterised.103 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 105–115 111[M(O 2 CNEt 2 ) 4 ] (M\Zr, Hf) reacts with MgCp 2 forming [M(O 2 CNEt 2 ) 3 Cp] which can be grafted onto silica as a [M(O 2 CNEt 2 ) 2 Cp] fragment.104 A series of luminescent zirconium thiolates [Zr(SR) 2 Cp* 2 ] (R\Bu/, C 6 H 4 Bu5-p, C 6 H 4 Cl-p or Ph) and one selenium analogue [Zr(SeR) 2 Cp* 2 ] (R\Ph) have been prepared; the structure of [Zr(SBu/) 2 Cp* 2 ] was determined.105 Fenske–Hall MO calculations imply a thiolate-based HOMO and a LUMO with largely Zr d character.The structure of [ZrPh 2 Cp 2 ] is reported.106 [Zr(thf)(CF 3 SO 3 ) 2 Cp 2 ] reacts with 2,2@-biquinoline (L) forming bright yellow [Zr(L)Cp 2 ]2`, whose lowest energy electronic transition is a Cp~]biquinoline ligand-to-ligand charge-transfer transition.107 [TiMe 2 Cp 2 ] reacts with SiH 4 in the presence of PMe 3 forming paramagnetic [Ti(PMe 3 )(SiH 3 )Cp 2 ].108 In a most detailed study of the e§ect of cation–anion structure upon metallocenecatalysed polymerisation, various cationic species have been characterised.[MMe 3 Cp*] (M\Zr, Hf) reacts with ppb to form the base-free [MMe 2 Cp*]- [pbbMe]. Similar reaction with [CPh 3 ][pba] a§ords [MMe 2 Cp*][pba].Some basefree dimeric species have also been synthesised, such as [(ZrMeCp 2 ) 2 (l-Me)][pbbMe] an e¶cient catalyst for the polymerisation of methylmethacrylate to form syndiotactic poly(methylmethacrylate).109 Tris(b-perfluoronaphthyl)borane (pnb) has been evaluated as a strong organo–Lewis cocatalyst by using it to activate a range of Group 4 metallocenes producing Ziegler–Natta alkene polymerisation catalysts.110 Thus it reacts with [ZrMe 2 Cp* 2 ] forming [ZrMeCp* 2 ][pnbMe], with rac- [ZrMe 2MMe 2 Si(ind) 2N] and [MMe 2 (cgc)] (M\Ti, Zr) to form rac- [ZrMeMMe 2 Si(ind) 2N][pnbMe], and [MMe(cgc)][pnbMe].Binuclear complexes such as [MTiMe(cgc)N2 (l-Me)][pnbMe] and [Ti 2 (l-Me)Cp 2 )][pnbMe] have also been synthesised.These compounds have catalytic activities at least as high as the corresponding B(C 6 F 5 ) derivatives. 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ISSN:0260-1818    

DOI:10.1039/a804890h

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

10 Vanadium, niobium and tantalum John Malito Department of Chemistry, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland 1 Introduction This review highlights the literature for 1998, but o§ers only few specifics for the very active area of bio-vanadium chemistry. Fortunately, however, several reviews in this particular area did appear during 1998. Spectroscopic, electrochemical, electron transfer, X-ray crystallographic and catalytic properties of vanadium-containing chloroperoxidase enzymes have been reviewed, along with the first X-ray di§raction study for a vanadium-containing protein.1 The related bromo-peroxidase system has also been reviewed.2,3 Several vanadium4–6 and vanadyl7,8 compounds have been studied for their insulin-mimetic properties. Other reviews of various aspects of vanadium bioactivity have appeared in Volumes 30 and 31 of Advances in Environmental Science and Technology.The preparation, characteristics and properties of radio-frequency sputtered thin films of VO 2 9 and VOx 10 for application in electro- and thermo-chromic devices have been reviewed. The history, occurrence, production and various other issues (metallurgical, therapeutic, pigmentary, catalytic, etc.) for vanadium11 and spectroscopic methods for the characterisation of V(III, IV, V) complexes have also been reviewed.12 All other relevant review articles are noted within the appropriate sections that follow. 2 Co-ordination chemistry Vanadium The first V(III) and oxovanadium complexes containing dipeptides have been structurally characterised13 while potentiometric and 51V NMR spectroscopic studies of vanadate–dipeptide and related systems have been reviewed.14 The structure has been determined for the dimer, [MVO(ma)(l-OMe)N2 ], prepared from the monomeric maltolate species, [VO(ma) 2 ], a potential insulin mimic.15 EPR, UV-VIS, ESCA and X-ray data all support a ferromagnetically coupled dimeric structure for K 4 [MVO(cit)N2 ]·6H 2 O.16 A new method for the production of the highly reduced species [V(CO) 6 ]~ and [V(PF 3 ) 6 ]~ proceeds via anthracenide-mediated reductions of [VCl 3 (thf) 3 ].17 Reac- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 117tion of [VCl 3 (thf) 3 ] with chloride salts leads to [NEt 4 ] 3 [V 2 Cl 9 ], and with Na 2 (mba) in the presence of [PPh 4 ]Cl to [PPh 4 ] 2 [V 3 OCl 4 (Hmba) 5 ], while reaction of [NEt 4 ] 2 - [VOCl 4 ] with H 2 (mba) and LiS 2 gives [NEt 4 ] 4 [V 2 Li 4 O 2 Cl 4 (mba) 4 ].Crystal structures are reported for each of these new complexes.18 Kinetic and thermodynamic parameters measured for twelve penta-co-ordinate V(V) complexes containing polydentate amino alcohols, with diethanolamine as the parent ligand, provide information useful towards future design of vanadium complexes with specific properties.19 The first vanadyl(IV) complexes of a new unsymmetrical and polyfunctional N,O-donor hexadentate ligand, H 2 bbpeten, [VO(Hbbpeten)]- [PF 6 ], have been prepared.20 The complexes, [VO(noq) 2 ] and [VO(noq) 2 (OH)], have also been prepared and characterised.21 N N HO N HO N H2bbpeten N O N N OH N V O [VO(Hbbpeten)] + + The 2: 1 reaction between Li(dctp) and [VCl 2 (tmen) 2 ] yields [V(tmen)(dctp) 2 ] which reacts with azobenzene to give the imido-containing complex, [V(tmen)(dctp) 2 (NPh)].Crystal structures are reported for both products.22 Structures have also been reported for [V 2 O 2 (OH) 2 (SO 4 )(bipy) 2 ], which has a chain structure,23 the methyl lactato complex, [NBu 4 ] 2 [VO 2 (C 4 H 6 O 3 )] 2 ·2H 2 O,24 the distorted octahedral complex, [PPh 4 ] 2 [(VO) 2 (C 2 O 4 ) 3 (H 2 O) 2 ]·8H 2 O,25 in which all three oxalato groups are bidentate and one is bridging, [AsPh 4 ] 2 [V 2 O 3 (NO 3 ) 2 X 4 ] (X\Cl, NO 3 ),26 and [VOCl 2 (OC 2 H 5 )(Hpheca)].27 X-Ray, spectroscopic28 and magnetic susceptibility studies29 have been reported for the inorganic ester-like complex, oxoethoxobis(5,7-dichloro- 8-hydroxyquinolinato)vanadium(IV), constituting the first direct evidence of the formation of · · ·V––O · · ·V––O ·· ·V–– O· · · ferromagnetic chains in oxovanadium complexes.Oxidation of [VO(btap)] with peroxides, iodosylbenzene and oxaziridines results in the sequential formation of mono- and di-sulfenate complexes.The mono-sulfenates can be prepared in an optically active form by using chiral oxaziridines, and act as reversible oxo-tranfer agents. Structural and 51V NMR spectroscopic analyses for the disulfenate indicate a unique g2 side-on bonding to the vanadium.30 Reactions of the p-tolyimido complex [V(Ntol)Cl 3 ] with Na[S 2 CNR 2 ] yield the homologous series of complexes, [V(Ntol)(S 2 CNR 2 )nCl 3~n] (R\Me, Et; n\1–3).31 Syntheses and crystal structures have been reported for the heterobimetallic complexes, [VOL1Cu(l-OAc)(MeOH)][ClO 4 ], [VOL1M(l-OAc)(H 2 O)][ClO 4 ]·H 2 O (M\Ni, Co, Fe, Mn) and [VOL2CuII(l-OAc)(H 2 O)][ClO 4 ].Variable temperature magnetic susceptibility measurements and spin exchange coupling in these complexes are also discussed.32 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 118n ] [ Me OH HN NH HN NH OH Me H2L1 ( n = 1) H2L2 ( n = 0) Niobium and tantalum Reduction reactions of [NbCl 4 (thf) 2 ] to give [Nb(CO) 6 ]~, [Nb(CO) 5 ]3~ and [Nb(PF 3 ) 6 ]~ have been reported, along with the synthesis of [Nb(CO) 5 H], [Nb(CO) 5 Y]~ (Y\NH 3 and CNBu5) and [Nb(CO) 5 (SnPh 3 )]2~. Previously, the PF 3 complex was accessible only photochemically.33 Crystal structures have been reported for the trichloroacetonitrile complex, [NbCl 5 (NCCl 3 )],34 the propionitrile complex, [NbOCl 3 (NCEt)]35 and for [NBu 4 ][NbCl 6 ].36 Intramolecular C–H· · · Cl hydrogen bonding to the isopropyl or cyclohexyl group hydrogen atoms is observed for the ligand in [NbCl 3 L(thf)] [L\bis(isopropyl)glyoxaldiimine or bis(cyclohexyl)glyoxaldiimine]. 37 Potassium and lithium salts of bis(2-pyridyl)amine and diphenylamine react with [(tmen) 2 Nb 2 Cl 5 Li(tmen)] in thf to form the two very di§erent products, [M(C 5 H 4 N) 2 NN2 Nb] 2 (l-C 5 H 4 N)[l-N(C 5 H 4 N)][Li(thf) 2 ]·(thf) 2 ·[Li 2 Cl 2 (thf) 4 ] and M[(Ph 2 N) 2 Nb] 2 [l-NPh(l-g1:g2-C 6 H 4 )](l-H)NMLi(tmen) 2N·C 6 H 5 Me, arising from either C–H or C–N bond cleavage of the amide.38,39 Crystal structures for [Nb 2 L 4 ] (L\hpp or azin) reveal triple bonds between the two niobium centres.40 EPR and X-ray studies for solid solutions of [Nb(hfacac) 4 ] and for [Nb(O 2 CNEt 2 ) 4 ] confirm the presence of non-interacting paramagnetic centres.41 The complex, [NBu/ 4 ] 2 [MNb(OMe) 3 (O 3 PPh)N2 (l-O)], prepared from [NBu/ 4 ]- [PhPO 3 H] and [Nb(OMe) 5 ], was characterised by X-ray crystallography.42 The dinuclear alkoxide complexes, [MNbCl 3 (OR) 2N2 ] (R\Me, Et) react with KTp@ to give [NbTp@OCl(OR)] which in turn react with Me 3 SiCl or PCl 3 to give [NbTp@OCl 2 ], or can be hydrolysed to give [MNbTp@OClN2 (l-O)].43 The first nitrosyl complexes of Nb and Ta, [M(NO)(CO) 2 (trimpsi)], have been prepared via a four-step synthesis beginning with [NEt 4 ][M(CO) 6 ] (M\Nb, Ta).44 Synthesis and structures have been reported for [PPh 4 ] 2 [Cl 2 (S 2 )M(l-O)(l- S 2 )M(S 2 )Cl 2 ] (M\Nb, Ta).45 A DFT study of the geometric and electronic structures for the 17-electron radicals, [Ta(CO) 6 ] and [Ta(CO) 4 (dppe)], and their corresponding dimers, indicates that the dimers are bound by linear semi-bridging carbonyl groups which support a weak Ta–Ta interaction.46 Each of the Ta(II) complexes [Ta 2 Cl 6MPh 2 P(CH 2 )nPPh 2N] (n\1–6) and [Ta 2 Cl 6 (Ph 2 PCH––CHPPh 2 )] was prepared by direct reaction of TaCl 5 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 119with the appropriate diphosphine ligand.47 The crystal structure has been determined for the first reported dinuclear compound containing a bridgingBH 3 group with direct Ta–B bonds, [Ta 2 (l-BH 3 )(l-dmpm) 3 (g2-BH 4 ) 2 ].48 Schi§-base ligands Potentially tri-, tetra- and penta-dentate alkoxo-rich Schi§ bases and their derivatives have been prepared and reacted with oxovanadium to give four new complexes characterised by NMR, FTIR, UV-VIS, cyclic voltammetry, conductivity and X-ray crystallography.The ligands appear to bond only in the tri- and tetra-dentate modes.49 Some new vanadium(IV) and oxovanadium(IV) complexes of ligands derived from b-diketones and ethanolamine or o-aminophenol exhibit promising catalytic activity towards aerobic oxidation of p-phenylenediamine. A correlation is observed between activity and vanadium ion Lewis acidity as a function of the donor properties of the ligand.50 51VNMRspectroscopic data have been reported for [VO(Asal)L] (L\Hpd, H 2 gl) formed by stoichiometric reaction in MeOH of [VO(Asal)(H 2 O)] with H 2 pd or H 3 gl (H 2 Asal\salicylaldimine of glycine, alanine, L-valine or L-phenylamine).Crystal structures have also been reported for the glycine-derived complexes.51 For H 2 L\hydroxyphenylmethylene hydrazone of 4-hydroxy-4-phenylbut-3-en-2-one, salicylaldehyde or 2-hydroxynaphthaldehyde, the compounds [VOLL@] (L@\H 2 gl or Hpd) are formed upon reaction with [VO(acac) 2 ] in the presence of excess glycerol and MeO–acetone respectively, and have been characterised by 51V NMR spectroscopy and X-ray di§raction.52 The 14-membered macrocyclic complexes, [VOL]SO 4 , have been reported for L\1,4,8,11-tetraazacyclotradeca-2,3,9,10-tetrathio-5,7,12,14-R,R@-4,6,11,13- tetraene (R, R@\Me, Ph).53 Crystal structures have been reported for [VOL3(bz)] and [VOL4(bz)]·MeOH [H 2 L3\N-salcylideneglycine, H 2 L4\N-(2-carboxyphenyl) salicylidenamine].54 The Schi§-bases amben, ambpn and ambtn, prepared from 2-aminobenzaldehyde with 1,2-diaminoethane, 1,2-diaminopropane and 1,3-diaminopropane respectively, react with VO(SO 4 ) to give ionic species in dmso solution.55 The reaction between [VOX 3 ] and functionalised enamine Schi§ bases (enam) leads to oxovanadium complexes of the types, [VOCl(enam)] (X\Cl) and [VO(OPr*)(HOPr*)(enam)] (X\OPr*).56 3 Organometallics Vanadium Vanadocene and its derivatives have been treated as a new class of human spermicides. 57–59 The pyrolysis behaviour of vanadocene60 and some bis(arene) vanadium compounds61 as precursors for the chemical vapour deposition of vanadium carbide has been studied. Vanadocene-containing polyesters have been prepared from reaction of the dichloride with adipic, sebacic, isophthalic or terephthalic dicarboxylic acid.62 The synthesis and structure of the unique 17-electron paramagnetic species, Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 120[V(CNAr) 6 ] (Ar\2,6-dimethylphenyl) have been reported. Reduction and oxidation reactions lead to the expected 18- and 16-electron species respectively.63 A redox reaction between [VCl 2 (tmen) 2 ] and benzil yields [V(tmen)MPh(O)C––C(O)PhN2 ]·thf, the first structurally characterised vanadium–endiolate complex.64 The trimer [MV(l- Cl) 2 Cp*N3 ] is formed from the reaction of [VCl 3 (thf) 3 ] with Bu 3 SnCp*, and is oxidised to [VOCl 2 Cp*].65 Reaction of [V(CO) 4 Cp] with SOCl 2 a§ords the oxodichloride species [VOCl 2 Cp] via oxidative decarbonylation; X-ray crystallography confirms a piano-stool configuration.66 Monomeric V(II) acrylates have been prepared and induced to undergo polymerisation. 67 The species, [V(amidinate) 2 Cl] and [V(amidinate)Cl 2 (thf) 2 ], prepared for two di§erent amidinate ligands [PhC(NSiMe 3 ) 2 ]~ and [Bu5C(NPr*) 2 ]~, served as precursors in the formation, via substitution, of [V(amidinate) 3~nRn] (R\alkyl or allyl; n\1 or 2). The allyl ligand is g3-bound.68 Insertions into the V–C bonds of V–R linkages (R\Me, CH 2 Ph, p-MeC 6 H 4 ) anchored to a quasi-planar O 4 matrix in [Mp-Bu5-calix[4](OMe) 2 (O) 2NVR] have been studied.With CO and Bu5NC, the new anchored functionalities are V(g2-COR) and VMg2-C(NBu5)RN respectively.69 Niobium and tantalum X-Ray crystallographic measurements for Li[M(Me) 6 ] (M\Nb, Ta) reveal an almost ideal trigonal prismatic geometry, ascribed to a fairly strong contact between the lithium cation and one of the methyl groups,70 and a DFT study for [M(Me) 6 ]~ (M\V, Nb, Ta) has rationalised this observed preference for a non-octahedral geometry.71 The synthesis and reactivity of [NbOXCp* 2 ] (X\H, OMe, Cl), and the crystal structures of two derivatives, [Nb(OH)FCp* 2 ][BF 4 ] and [NbOMOC(O)HNCp* 2 ] have been reported.72 An equilibrium between a- and b-agostic interactions is observed in [NbTp@Cl(CHMe 2 )(PhCCMe)] while only a-agostic interactions are observed for the analogous ethyl complex.This di§erence is ascribed to steric e§ects.73 The synthesis and reactivity of niobium compounds containing r-bonded a-thienyl groups and their application for the preparation of niobocene derivatives have been reviewed.74 Reactions of [NbCl 4 Cp] with arenedithiolates yield the complexes [Nb(1,2-S 2 C 6 H 3 R-4) 2 Cp] (R\H, Me).Similar tantalum derivatives were much less tractable.75 The preparation of a series of chlorosilyl-substituted monocyclopentadienyl niobium chloro, imido chloro, and benzyl complexes has been reported. The crystal structure was determined for the oxo species [M(NbCl 2 ) 2 (l-O)(l-Cl) 2NMg5- C 5 H 4 ) 2 (Me 2 SiOSiMe 2 )N].76 The synthesis and reactivity of [Nb(NC 6 H 3 Pr* 2 -2,6)Cl(CH 2 Ph)Cp] and [Nb(NC 6 H 3 Pr* 2 -2,6)(CH 2 Ph) 2 Cp*],77 and the new half-sandwich and ansa-niobocenes, [Nb(g5-C 5 H 4 R)(NMe 2 ) 2 (––NC 6 H 3 Pr* 2 -2,6)] (R\CMe 2 C 9 H 7 ) and [Nb(NMe 2 )(––NC 6 H 3 Pr* 2 -2,6)Mg5:g1-(C 5 H 4 )C(CH 3 ) 2 (C 9 H 6 )N] respectively have been reported.78 The synthesis, characterisation and aspects of reactivity have also been reported for some isocyanato, amido and imido derivatives of [MNbCl(g5- C 5 H 4 SiMe 3 ) 2N2 ].79 Oxidations of [NbCl 2 (g5-C 5 H 4 Bu5) 2 ] by CuCl 2 or AgBF 4 produce [NbCl 2 (g5-C 5 H 4 Bu5) 2 ][CuCl 2 ] or [NbClF(g5-C 5 H 4 Bu5) 2 ][BF 4 ] respectively.Crystal structures are reported for both products.80 The first niobocene germyl complexes, [NbH 2 (GeR 3 )(g5-C 5 H 4 SiMe 3 ) 2 ], were pre- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 121pared by thermal treatment of [NbH 3 (g5-C 5 H 4 SiMe 3 ) 2 ] with HGeR 3 [GeR 3 \GePh 3 , GePh 2 H, GeEt 3 , Ge(C 6 H 13 ) 3 , Ge(C 6 H 13 ) 2 Cl, Ge(C 6 H 13 ) 2 H, GeAm* 3 , GeAm* 2 Cl, GeAm* 2 H]. Crystal structures are reported for the GePh 3 complex and the analogous SnPh 3 complex prepared in a similar manner.81 The sulfido species [NbSClCp 2 ] and [Cp 2 NbCl(l-S)SnPh 3 Cl] have been prepared.The latter is hydrolysed to the corresponding oxo-species, [Cp 2 NbCl(l-O)SnPh 3 Cl].82 The complexes, [MNbE 2 (C 5 Me 4 R) 2N2 ]M (R\Me, Et; E\S, Se;M\Cr, Mo), have also been prepared.83 Improved preparative routes for [M(CO) 4 (g5-C 5 H 4 R)] (M\Nb, Ta) have been developed,84 and new 1,3-dimetallabenzene derivatives have been prepared by the stoichiometric insertion reaction of an alkyne into one of the alkylidyne-bridges of [(cb) 2 M(l-CSiMe 3 ) 2 M(cb) 2 ] (M\Nb, Ta).85 X-Ray studies for the latter reveal nonplanar six-membered dimetallacycles which are electronically delocalised.N Ta O O O 1 Pri Pri Pri Pri But But Reaction between [Li 2 (thf) 4 ][C(NPh) 3 ] and [TaMe 2 (Cl)(OSO 3 CF 3 )Cp*] yields [TaMe 2MC(NPh) 3NCp*] in which the triazamethylenemethane ligand is g2-bound.86 As part of a model study of hydrodenitrogenation catalysis, the preparation, reactivity and structure of the stable metallapyridine 1 were reported.87 Studies of [TaCl 2 (NC 6 H 3 Me 2 -2,6)Cp*] include the crystal structure for [TaCl(NC 6 H 3 Me 2 -2,6)Cp*Cp@].88 The mechanism for addition of dihydrogen to benzyne hydride tantalocene to give the trihydride, [TaH 3 Cp*], via an intermediate dihydride, [TaH 2 Cp*], has been studied.89 The air-stable tantalaborane [TaCl 2 (B 4 H 8 )Cp*] has been viewed as both the first example of an unsaturated cluster containing a single metal atom, and as a chiral 16-electron organometallic complex, isoelectronic with both [TaCl 2 (C 2 B 9 H 11 )Cp] and [TaCl 2M(Me 3 Si) 2 C 2 B 4 H 4NCp].90 The carborane complex, [TaCl 2 (Et 2 C 2 B 4 H 4 )Cp], is reduced to [MTaH(Et 2 C 2 B 4 H 4 )CpN(l-Cl) 2 ] which undergoes alkyne insertion with p-MeC 6 H 4 CCH to give trans-[TaCl(p- MeC 6 H 4 CHCH)(Et 2 C 2 B 4 H 4 )Cp], and with PhCCPh or MeCCPh to give hydrido tantalum alkyne complexes, the first examples of alkyne p-co-ordination to a formal d0 metal centre.91 The analogous complex, [TaMe 2 (Et 2 C 2 B 4 H 4 )Cp] undergoes very clean photochemical insertion reactions with alkenes to produce vinyl tantalum species.Alkyne insertion reactions were also observed.92 The complex [TaCl 3MC 4 H 4 BN(CHMe 2 ) 2N] provides a versatile entry into tantalum borollide complexes.For example, methylation of this species using MeMgCl leads to the tripledecker complex, [MC 4 H 4 BN(CHMe 2 ) 2NMe 2 TaMl-C 4 H 4 BN(CHMe 2 ) 2NTaMe 4 ], whereas a more controlled alkylation using LiCH(SiMe 3 ) 2 gives Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 122[TaCl 2MC 4 H 4 BN(CHMe 2 ) 2NCH(SiMe 3 ) 2 ].93 The trigonal prismatic complex, [MLi(Bu5 3 SiCC) 3NTa(CCSiBu5 3 ) 3 ] undergoes metathesis with potassium triflate to give K[Ta(CCSiBu5 3 ) 6 ].94 Various products were prepared from the S 8 , Te, CS 2 and COS insertion reactions of [TaH(CO)(g- C 5 H 4 Me) 2 ].95 The complex [TaH(g2-C 60 )Cp 2 ] has been prepared and characterised. 96 4 Clusters and metalates The structure, changes with heating, and lithium insertion properties have been reviewed for vanadium oxide.97 Co-crystallisation of tetramethylammonium vanadate and cryptand (C22n) in tetramethoxysilane gel at pH 5.5 has yielded [C22n(H`) 2 ] 2 - [H 2 V 10 O 28 ] (n\1,2).Crystal structures were determined for both species.98 Crystal structures have been reported for a series of monomers and clusters assembled in stepwise fashion from [VO(acac)], [V 2 O 2 (l-OCH 3 ) 2 (acac) 2 (OCH 3 ) 2 ], [V 4 O 4 (l- O) 2 (l-OCH 3 ) 2 (l3 -OCH 3 ) 2 (acac) 2 (OCH 3 ) 2 ]·2MeCN, [V 4 O 4 (l-O) 2 (l-OCH 3 ) 2 (l3 - OCH 3 ) 2 (acac) 2 (OCH 3 ) 2 ], [V 3 O 3Ml,l-(OCH 2 ) 3 CCH 3N2 (acac) 2 (OR)] (R\Me, Et) and cis-[VO(OCHMe 2 )(acac) 2 ].99 The following polyoxoalkoxyvanadate clusters, [CN 3 H 6 ] 4 Na 2 [H 4 VIV 6 P 4 O 30M(CH 2 ) 3 CCH 2 OHN2 ]·14H 2 O, Na 6 [H 4 VIV 6 P 4 O 30 - M(CH 2 ) 3 CCH 2 OHN2 ]·18H 2 O, [NH 4 ] 7 [H 7 VIV 12 VV 7 O 50M(CH 2 ) 3 CCH 2 OHN]· 11.5H 2 O, [CN 3 H 6 ] 4 [VIV 3 VV 4 O 19 FM(CH 2 ) 3 CCH 2 OHN]·5.25H 2 O, Na 6 [VIV 10 VV 2 - O 30 F 2M(CH 2 ) 3 CCH 2 OH 2 OHN2 ]·22H 2 O, [CN 3 H 6 ] 4 [VIV 2 VV 8 O 28 F 2M(CH 2 ) 3 CCH 2 - OHN2 ]·4H 2 O, are formed by induced self-assembly in the presence of pentaerythritol, C(CH 2 OH) 4 , for aqueous vanadate solutions.It is assumed that MV 3 O 13N and MV 3 O 12 FN act as nucleation centres.100 After five days at 170 °C, the 1: 1: 1: 35 reaction mixture of BPO 4 , NaVO 3 , en and H 2 O produces [H 3 O] 12 [(VO) 12MB 16 O 32 (OH) 4N2 ]·28H 2 O, the structure of which is an intricate H-bonded network of [V 12 B 32 O 76 (OH) 8 ]12~ 12-membered rings consisting of trans-edge-sharing VO 5 square pyramids capped on either side by the squareshaped polyborate unit, [B 16 O 32 (OH) 4 ]20~. Eight of the vanadium atoms have oxidation state 4] while the other four are 5].101 The 3-D organically-templated vanadium phosphate, [H 3 NCH 2 CH 2 NH 3 ][(VO) 3 (H 2 O) 2 (PO 4 ) 2 (HPO 4 )], has a structure consisting of binuclear units of corner-sharing [VO 6 ] octahedra and square pyramidal [VO 5 ] units linked by phosphate tetrahedra.102 Structural and magnetic susceptibility measurements, and valence sum calculations for the polyoxovanadium borate cluster, Rb 4 [(VO) 6MB 10 O 16 (OH) 6N2 ]·0.5H 2 O indicate that all six vanadium atoms are present in the 4] oxidation state.103 Crystal structures have been reported for [Fe 2 V(l3 -O)(l-O 2 CCH 3 ) 6 (thf) 3 ]Cl·3H 2 O104 and the antiferromagnetic cluster, [MV(l-Cl) 2 Cp*N3 ], which has a layered structure.105 Amphiphilic organoruthenium oxovanadium clusters of types, [(g6-p- MeC 6 H 4 Pr*) 4 Ru 4 V 6 O 19 ] and [(g6-C 6 Me 6 ) 4 Ru 4 V 6 O 19 ],106 and vanadium–C 60 clusters formed in the gas phase by a two-laser vapourisation method107 have been reported.For reactions of Nbn ~ (n\3–28) clusters with C 6 H 6 , investigated under single collision conditions in an FT ion-cyclotron-resonance mass spectrometer, the observed reactivity patterns are more a function of cluster shape and geometry than of Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 123the details of the electronic structure.108 X-Ray crystallography combined with solution- and solid-state NMR spectroscopy have shown that the structure of [Nb 4 O 4 (OAc) 4 (OPr*) 8 ] is fully preserved in solution.109 The heterobimetallic derivatives, [MM[Nb(OPr*) 5 Cl](l-Cl)N2 ] and [MMNb(OPr*) 5 ClN2 ] [M\Be(II), Mg(II), Zn(II) or Sn(II], were prepared by 1: 1 and 1: 2 reactions of MCl 2 and [Nb(OPr*) 5 ] in benzene respectively.110 The clusters [M 6 X 12 (EtOH) 6 ]X 2 react with dmf to give [M 6 X 12 (C 3 H 7 NO) 6 ]X 2 (M\Nb, Ta; X\Cl, Br).111 Substitution and redox chemistry reported for [NBu 4 ] 2 - [Ta 6 Cl 12 (OSO 2 CF 3 ) 6 ] includes the crystal structure of [NBu 4 ] 3 [Ta 6 Cl 12 (NCS) 6 ]· CH 2 Cl 2 .112 Reduction of [TaCl 2 (O 2 CNEt 2 ) 3 ] gives either [Ta(O 2 CNEt 2 ) 3 ] or [Ta 8 (l-O) 12 (O 2 CNEt 2 ) 16 ], depending on the reducing agent and reduction conditions employed.The crystal structure is reported for the cluster.113 5 Catalysis Heterogeneous The preparation, characterisation and catalytic activity of VOx/ZrO 2 catalysts for the abatement of NO with NH 3 have been reviewed.114 There has been an investigative review into the apparent contradictions in propane and propene ammoxidations over vanadium–antimony catalyst.For example, propene on its own is converted much faster than is propane to acrylonitrile, but the propene-to-acrylonitrile step in propane conversion is slower than the propene-to-propane step.115 The active site of vanadium phosphate catalysts (VPA, VPO, VPD) for the oxidation of butane to maleic anhydride comprises a V4`/V5` couple that is well dispersed on the catalyst surface.116 Proposals have been made for the design of V-centred active sites in micro- and meso-porous silica-based catalysts for the selective oxidation of alkanes and other hydrocarbons, and for epoxidation of alkenes.117 Photooxidation reactions of light alkanes over alkali-ion-modified vanadium catalysts have been reviewed,118 and the synthesis, characterisation and photocatalytic activity of niobia mesoporous molecular sieves have been reported.119 A new EPR spectroscopic method for identifying the incorporation of transition metals into the framework of zeolite molecular sieves has been developed, and demonstrated for a novel hydrothermically prepared Nb silicate molecular sieve of MFI topology.120 Homogeneous A correlation has been observed between 51V NMR chemical shifts and activity of oxovanadium(V) catalysts like [VO(CH 2 SiMe 3 ) 3 ] for ethylene polymerisation.The latter is quantified in terms of DFT-derived barriers to the rate-determining step of ethylene insertion into the V–C bond.The data indicate that the catalyst activity may be increased in the presence of Lewis acid co-catalysts stronger than Al(CH 2 SiMe 3 ) 3 . The results also suggest that suitable co-catalysts can be screened by 51V NMR spectroscopic measurements for the complexes formed initially with the oxovanadium complexes. Those which are most de-shielded should be the most active.121 The reaction between hexacyanomanganate(IV) and H 2 O 2 in acidic media is stongly Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 117–128 124catalysed by vanadium present in either the 4] or 5] oxidation states. The kinetics for this system have been studied.122 The oxidation of methane by air–H 2 O 2 is catalysed, at 25–50 °C, in acetonitrile solution containing vanadate anion as the tetrabutylammonium salt and pyrazine-2-carboxylic acid.The products are MeOH, CO, formaldehyde, formic acid and CO 2 . In solutions containing the sodium salt, methyl hydroperoxide is formed selectively in the temperature range 40–70 °C.123 The same systems have been used for the oxidation of both cyclohexene and decalin.124 Carboxylation of methane at moderate temperatures by either CO or CO 2 in aqueous solution in the presence of oxygen is catalysed by NaVO 3 , or in the presence of H 2 O 2 by NaVO 3 -pyrazine-2-carboxylic acid , to give predominantly acetic acid along with some methanol and formaldehyde.125 The addition of catalytic amounts of vanadium promoters results in faster reaction and purer products in the hydrogenation of nitroarenes.Accumulation of the hydroxylamine intermediate is reduced by up to 40%.126 Ethylene polymerisation is catalysed by the half-metallocene complexes, [MR 2 LCp*] (M\Nb or Ta, R\Cl, L\o-xylene; M\Ta, R\Cl, CH 2 Ph, L\anthracene). Comparisons with earlier work for L\buta-1,3-diene indicate that the catalytic activity decreases as L\oxylene [butadieneqanthracene.127 The alkali and alkaline earth tantalates, YTaO 3 (Y\Li, Na, K) and YTa 2 O 6 (Y\Mg, Ba), show catalytic activity for the decomposition of water into H 2 and O 2 , without co-catalysts.The species BaTa 2 O 6 is the most e§ective, and among the transition metal tantalates, NiTa 2 O 6 is also active.128 There has been a detailed study of the control of stereoselectivity in the ring-opening metathesis polymerisation of norbornene by the auxiliary ligands, butadiene and o-xylylene in well-defined Cp*Ta–carbene complexes.129 Tertiary cyclopropanal systems undergo ring-cleavage in the presence of a catalytic amount of [VO(acac) 2 ] under O 2 to give b-hydroxyketones and b-diketones.130 The species, [Ta(OAr) 2 XMg2-NC 5 Bu5 3 H 2 -N,CN] (Ar\C 6 H 3 Pr* 2 -2,6; X\Br, OBu5, SBu5) were studied as structural models for the substrate–catalyst adduct in hydrodenitrogenation reactions.131 There is a severe interruption of aromaticity within the heterocycles, and comparisons with earlier work suggest that the ancillary ligand p-donor ability decreases as OBu5[OAr[SBu5[Cl, Br[Et, even though SBu5 does seem to be a better overall r]p donor than either OAr or OBu5.References 1 A. 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ISSN:0260-1818    

DOI:10.1039/a804892d

出版商:RSC    

年代:1999

数据来源: RSC