ISSN:0260-1818    

DOI:10.1039/IC99592FX001

出版商:RSC    

年代:1995

数据来源: RSC

ISSN:0260-1818    

DOI:10.1039/IC99592BX003

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

3 Boron By M.A. BECKElT Department of Chemistry University of Wales Bangor Gwynedd LL57 ZUW UK 1 Introduction This report takes a similar format to that used last year’ and reviews the chemistry of boron compounds reported during 1995. The literature has been surveyed by use of Chem. Abstr. vols. 122 and 123 in conjunction with independent searches of BIDS and the principal chemical journals. 2 Reviews The reader is directed specifically to two chapters in the Specialist Periodical Report Organometallic Chemistry (vol. 25) for two reviews complementary to this report. The first review is a comprehensive account of the chemistry of carbaboranes and metallacarbaboranesY2” and the second is a general account of the organometallic chemistry of Group 13 elements.2b Specific review articles have appeared on the following topics “on-spectator behaviour of carborane ligands in icosahedral metallacarborane~’,~~ ‘Transition metal boride clusters at a molecular level’,2d ‘Denud- ing the boron atoms of B-H interactions in transition metal-boron ‘Cluster forming and cage fusion in metallacarborane ~hernistry’,~~ ‘Structural magnetic and conductivity properties of charge transfer salts derived from metallacarborane~’,~~ ‘Recent advances in phosphinoborane chemistry’,2h ‘1,l-organoboration of alkenyl-silicon -germanium -tin and -lead comp~unds’,~~ ‘Palladium-catalysed cross-coupling reactions of organoboron comp~unds’,~j and ‘Versatile a-pinene-based borane reagents for asymmetric ~yntheses’.~~ The authoritative publication ‘Comprehensive Organometallic Chemistry II’ has now appeared and excellent review chapters2’-q covering the literature of the period 1982-1994 are available in the following subject areas ‘Compounds of three- or four-co-ordinate boron emphasizing cyclic systems’ ‘Boron rings ligated to metals’ ‘Polyhedral carbaboranes’ ‘Main group hetero- boranes’ ‘Metallaboranes’ and ‘Transition-metal metallacarboranes’.3 Polyhedral Species Boranes Theoretical ab initio studies have been undertaken on neutral and charged B,H 19 M. A. Beckett Fig. 1 Views of 2,4-(MeCHCH,)B,H8 (top) and 2,4-(trans-MeCHCHMe)B,H8 (bottom) (Reproduced by permission from Inorg. Chem. 1995,34 2841) (n = 3-9) species and aromaticity (three-centre two-electron 71 delocalization) plays an important part in their structure.," The MP2/6-31G* optimized geometries have also been calculated for [B,H,X,] + (X = H F Li) derivatives; [B3(p-Li3)H3]+ is predicted + to be stable in the planar form (D3,Jwhereas [B,(p-H,)X,] (X = H F) are predicted to have non-planar C, symmetry.3b The compounds 2,4-(methylethy1ene)tetra-borane( lo) (MeCHCH,)B4H, and 2,4-( trans-1,2-dimethyle th ylene) te tra borane( lo) (MeCHCHMe)B,H, synthesized from B4HIo and MeCH=CH or trans-MeCH=CHMe respectively have been characterized and their structures determined by gas-phase electron diffraction and ab initio calculations at the MP2/6-3 lG* level (Fig.1); 2-Pr-2,4-(MeCHCH,)B4H and 4-Pr-2,4-(MeCHCHMe)B,H have also been ~haracterized.~' The pentaborane(9) cage structure with a dichloroboryl (BC1,) group substituted for H at the apical boron atom has been confirmed for 1-(BCl,)B,H by electron-diffraction methods supported by theoretical calculation^.^^ The full paper reporting the synthesis isolation and characterization of three linkage isomers of SnPh,(B,H,) has now appeared.,'The first hypho-borane anion [B,H ,I2-has been isolated as its disodium salt in 71% yield from reaction of B,H with Na[BEt,H] in toluene solution at 0°C; the reaction is clean and Na[B,H8] is formed as the co-product in 29% yield.3f The ion-dipole charge-transfer complex M[B,,H 141] [M = NBu", PPh,Me N(PPh,),] is formed upon reaction of MI with BioH14 in the solid phase or in CH,Cl solution.A single-crystal X-ray determination of [PPh3Me][2,4-I,Bl,H,21] shows the Boron 21 unique iodide residing on top of the four bridge hydrogens and 6,g-borons at the opening of the B, basket.3g The low-temperature reaction of B,,H, with pyridine resulted in the asymmetric bis(1igand) adduct 6,6-(py)2BloH12 which was converted to the 6,9-(py)2Bl,H12 isomer upon reflux in ~yridine.~” An improved synthesis of the nido-[Bl,Hl,]2-anion has been reported together with its route of decomposition under various conditions; characterization using high field ’‘B NMR spectroscopy has corrected some earlier literature data.3i Electrospray mass spectrometry has been used to examine M[B,H,] (M = NMe, NBu, Cs) Cs2[BloHl,] and Na,[B,,H,,] where anionic cluster ions of general formula [(Xm+)x(Yn-)y](ng-mx)- (X = cation Y = anion) e.g.[(NMe,),(B,H,)lo]- have been readily observed.,j Metallaboranes For convenience this section is divided into three sub-areas tetrahydroborate complexes metal-rich clusters and boron-rich clusters. As usual there have been a number of publications relating to tetrahydroborate species.4ah The geometries energies and possible arrangements of tetrahydroborate compounds of Cu Ag and Au have been calculated by a variety of methods [MP2 MP4(SDTQ) QCISD(T) and CCSD(T)]; for M = Cu or Ag the bidentate and tridentate [BH,]- structures were of comparable energy but the Au hydrido- (borane)gold species [HAuBH,] was of lowest energy.,” Ab initio calculations on [(BH,)Mn(CO),] and [(BH,)Cu(PH,),] indicated that the q3 mode of co-ordination was preferred and that the mechanism of bridging-terminal hydride exchange presumably occurred via an associative rather than a dissociative mechanism.,’ The helium(1) UV PE spectra of [Zr(BH4)3(cp)] [M(BH,),(cp),] (n = 1 M = Ta; n = 2 M = Zr Hf) and [TaH,(cp),] have been reported but hydroborate ionizations were not discerned.,‘ Monodentate co-ordination of the [BH,] -ligand is observed in trans-[RuH(q’-BH,)L] (L = Me,[16]aneS4 Me,[ 15]aneS,) prepared from cis-[RuCl,(L)] and excess NaBH in EtOH; the structure of trans-[RuH(q’-BH,)(Me,[ 16]aneS,)] was confirmed by a single-crystal X-ray diffraction study.4d The strontium and barium tetrahydroborate complexes [M(BH,),L] [M = Sr Ba; L = 2 O(CH,CH,OMe), 18-crown-61 have been prepared by ligand displacement from the [M(BH4),].2thf solvates; X-ray diffraction data have shown that the [BH,] -ligands in these complexes are tridentate (Fig.2).4eThe reaction of [CrCl,(tmen)] with 2 equivalents of NaBH afforded the thermally unstable [Cr(BH,),(tmen)] complex which was converted by treatment with pyridine to the octahedral monomeric complex [Cr(BH,),(py),]; the reaction proceeded via an intermediate trinuclear complex [(Cr(q2-BH,)-(tmen)(py))2(Cr(q2-BH4)2(py)2}] [p,q1-BH4] which was isolated and characterized by X-ray diffraction.,’-The crystallographically characterized complex [Zr(q-C,H,(SiMe,),)(q3-BH,)(~2-BH,)] has been obtained from the reaction of LiBH with [(ZrC1,[q-C,H,(SiMe3)2]}2].4g Variable-temperature ‘H and “B NMR spectro- scopic data for [M(C5H,(SiMe,-1,3),}(BH,),I (M = Th U) revealed the presence of a fluxional process; the crystal structure of the uranium derivative has been reported and is isostructural with [MBr,(C5H,(SiMe,-1,3)2}].4h Gold-containing boride clusters were unexpectedly formed from reactions of [RhRu,H(cp*)(CO),BH] -with gold(1) phosphine derivatives; crystal Structures of [RhRu,H(cp*)(CO),B(Au(PPh3)),(AuC1)]~CH,Cl and [RhRu,H(cp*)(CO),B- M.A. Beckett Fig. 2 ORTEP diagram of [Ba(BH,),( 18-crown-6)] (Reproduced by permission from Chern. Ber. 1995 128,455) {Au,(dppf)}(AuCl)]~CH2C12have been rep~rted.’~ The reactions of the butterfly cluster [Ru,H(CO),,BH,] with a range of tertiary phosphines and diphosphines and a large excess of P(OMe) have been explored; up to four carbonyl ligands have been displaced per Ru moiety in the 22 derivatives which were ~haracterized.’~ The crystal structure of [RhRu,(cp*)(CO) ,BH,] has been determined and the pentametal structure is best described as a ‘spiked-butterfly’ with the Rh atom occupying the ‘spike’ position.” A full paper concerning the preparation of [Rh,Ru,(CO),,B] -has now appeared together with reactions of this anionic boride cluster with [AuCl(PPh,)] and [AUCl{P(C,H ,),)I; the chemistry has also been extended to [Ir,Ru,(CO),,B] -derivative^.^^ The two new metallaboranes [Co,(CO),B,H,] and [cOs(Co),,(p- CO)B,H] have been prepared in low yield by reaction of [co,(Co),] with BH,*SMe,; both compounds have been characterized spectroscopically and by X-ray diffraction studies and the former compound is isoelectronic with [Fe,(CO),B,H,] and [Co2(CO)6C2H21.Se The crystal structure of the nra~hno-[2-(~~-C,Me,)-2-Cl-2-RuB,H~] cluster has been reported and the endo-chloro conformation was found.,” The gas-phase reaction of B4H1o with [ZnMe,] at ambient temperature resulted in the formation of a dimer [((MeZn),B,H,},] with an unprecedented structure featuring two distinct zinc environments; two {B,H,ZnMe) ligands formally derived from { B,H,) by replace- ment of a p-H by a p-ZnMe group each function in a bis(bidentate) manner linking together two other {ZnMe) centres through pairs of Zn-H-B bridges (Fig.3).6bThe reaction of BH,.thf with [(CrCl(cp*)},] led to the isolation of the nido chromaborane [Cr,(cp*),B,H,] with the chromium atoms occupying the apical vertices and the boron atoms occupying four out of the five equatorial positions of a pentagonal bipyramid; reaction of this dichromaborane with CO cleanly yielded [Cr2(Cp*),(CO)$,H6] which adopted the same cluster core.,‘ The first structurally characterized closo-heterobimetallic heptaborane closo-[{Fe(CO),}{ Ir(CO),- (PPh,))(B,H,)(PPh,)] has been prepared from nido-[{Ir(CO)(PPh,),}B,H,] with [Fe,(CO),] in CH2C1 solution (Fig.4).6dA unique series of iridaosmaborane clusters Boron 23 H(2B Fig. 3 Molecular structure of [{(MeZn),B,H,},] (Reproduced by permission from J. Chem. Soc. Chem. Commun. 1995 1363) Fig. 4 Molecular structure of closo-[{Fe(CO),} {Ir(CO),(PPh,)}(B,H,)(PPh,)] (Reproduced by permission from Angew.Chem. Int. Ed. Engl. 1995,34 1641) containing three four and five boron atoms differing formally by the presence of one BH vertex have been reported and characterized by X-ray diffraction studies nido-[{(cp*)Ir}B,H,{ Os(CO)(PPh,),}] c~oso-[{(cp*)Ir)B,H,{~~(~~)(~l?h~)~}],and pileo-[{(PPh,)(CO)HIr}B5H5{Os(CO)(PPh,),}].6eAn analogous closo rhodium derivative c~oso-[{(cp*)Rh}B,H6{~s(~~)(PPh,),)l and the alkyl substituted nido osmapentaborane [{(PPh,),(CO)Os}B,H,(C,Hg)] have also been identified.6f The related pileo-[{(cp*)Ir},B,H,] cluster has been fully characterized and was formed in low yield from the reaction between [{IrCl,(cp*)},] with Na,[B,H,] in thf.,g The reaction of LiBH with various organometallic derivatives of Mo and W led to B (n = 3 4 5) derivatives; bicapped closo-[(Mo(C,H,Me)},B,H,I closo-[{W(C,H,R)H,},B,H,] (R = Me Pri) nido-[{W(C,H,Pri)H,}B4H8] bicapped closo-[{Mo(C,H,Me)},B5H9] nido-[{Mo(C,H,Me)(PMe,)H}B,H,] nido-[{ W(PMe,),H,}B,H,] and aruchno-[(W(PMe,)H,}B,H,] were reported.6h The conversion of the square-pyramidal { B5) cluster complexes [2-{ Fe(cp)(CO),)B,H,] and [2,4-{ Fe(cp)(CO),},B,H,] into the pentagonal-pyramidal { FeB,) clusters [2-{ Fe(cp)(CO)}B,H,] and [4-{Fe(cp)(CO),}-2-[{Fe(cp)(CO)}B5H7],respectively was readily affected by a photochemical process; the rearrangement of the latter com- M.A. Beckett pound led to the formation of an isomer [3-{ Fe(cp)(CO),}-2-{ F~(C~)(CO)}B,H,].~' The deep green compound nido-[6,9-(q6-p-Pric6H4~e),-6,~-~u2B8~12] was ob-tained in small yield in addition to nido-[6-{(p-PriC,H,Me)Ru}B9Hl J from reaction of [(RU(p-PriC6H4Me)C12}2] with [NEt4][B9Hl,]; the complex has been character- ized crystallographically.6j Heteroboranes The reader is directed to a Royal Society of Chemistry Specialist Periodical Report Organometallic Chemistry for a comprehensive review of the 1995 literature concerning carbaboranes.," Monocarbaboranes will be discussed first.Base-degradation of the arachno nine-vertex ligand adducts exo-6-L-4-CB8Hl resulted in the eight-vertex monoanion closo-[ 1-CB7H,] -;this anion was iodinated with I and afforded [1-CB7H7-7-I]- and [1-CB7H,-7,8-12]-characterized by X-ray diffraction studies as their [PPh,] salts7" + The crystal structure of Cs[CB,,H,,] at 293 K has been determined and is very similar to that of an earlier reported structure of -y-Cs[C,B9H12] at 299K.7b The boron insertion reaction of Me,NBCl with Li2[7-Me,N-nido-7-CBloHlo] gave the new neutral compound 1-Me,N(H)-2-CH2Cl-closo-1-CB, lHlo characterized by X-ray diffraction and NMR spectros~opy.~~ The monocarbaborane anion was regioselective- ly fluorinated by liquid anhydrous HF to [12-CBllH11F]- with the hydrogen atom furthest removed from the carbon replaced by fluorine.7d The first macropolyhedral monocarbaborane species [(NH2Bu')CB17H18(CN)] was isolated as a product of the reaction between Unti-B18H, and Bu'NC in CH2C12 solution; the structure is based on the anti-B,,H, type of macropolyhedral cluster with the amine-substituted carbon occupying the 9-position of one sub-cluster (Fig.5).7e Dicarbaboranes will be considered next. A theoretical study of the reaction of C,H2 with BH, B2H6 and B,H7 has been undertaken with a view to understanding the formation of closo-C,B,H from C2H2 and B4H10; the first step was assumed to be the elimination of BH from B4Hlo with subsequent formation of the addition product of C,H2 and B3H,.7S New dicarbahexaborane(8) derivatives 2,4-Me,-2,3-C,B,H6 5-Et-2,3-C2B4H7 and 2-Et-3,4-Me2-2,3-C2B,H have been prepared from the gas- phase reactions of B4H1o with alkynes; these products have been previously described erroneously as derivatives of tri~arbahexaborane(7).~~ Pentaethyl- 1,5-dicarba-closo- pentaborane(5) prepared by treating diethyl(prop-1-y1)borane with a large excess of tetraethyldiborane(6) has been characterized crystallographically; a substituted 1- carba-arachno-pentaborane(10)derivative was isolated as the reaction intermediate.7h A series of papers addressing steric effects in ortho-C2BloH, derivatives has been p~blished.~"' Thus crystal structures of 1-Ph-2-X-C2BloHlo(X = Me,7i Br,7j SiMe,Bu' 71)have been determined and discussed; for X = SiMe the steric congestion is relieved by mutual 'bend-back' of both the phenyl and trimethylsilyl groups whilst for X = SiMe,Bu' the steric congestion is relieved by elongation of the cage C(l)-C(2) internuclear distance to 1.745(6)8L.Dimethoxyethane has been described as a good solvent for the synthesis of C-monosubstituted o-carbaborane derivatives; thus treatment of o-C2BloH12 with LiBu followed by PPh2Cl in dimethoxyethane led to a high yield synthesis of 1-Ph2P-1,2-C,B,,H 1.7m The crystal structure of this monosubstituted derivative 1-Ph2P-1,2-C2BloH1 1 has been deter- mined at 153 K.7" A procedure for the degradation of 1,2-(PR,),-1,2-C2BloH,o and Boron 25 Fig.5 ORTEP drawing of [(NH,Bu‘)CB,,H,,(CN)] (Reproduced by permission from J. Chem. SOC.,Chem. Commun. 1995 2407) 1-(PR,)-2-R’-1,2-C2BloHlo has been published and nido clusters such as [7-PR2-8- Me-7,8-C,BgH,,]-and [7,8-(PR,),-7,8-C2B,Hlo]- (R = Ph Et Pr’ EtO) have been synthesized; the crystal structure of one such derivative [NMe4][7,8-(PPh,),-7,8- C,BgHlo].EtOH has been determined.7” Hydrated [NBu,]F has been found to be an effective reagent for the conversion of ortho-or meta-R’R”C,B,,H, derivatives into the nido-carbaborane anions [R’R”C,BgH,,] - allowing access to the meta-carba- borane derivatives which are inaccessible using other deboronating reagents.7P Electrophilic iodination of closo-1,2-C,Bl,H, and closo-1,7-C,B,,H1 with 2 equiv- alents of JC1 in the presence of catalytic amounts of AlC1 yielded the corresponding closo-9,12-12- 1,2-C,B1,H and closo-9,10-I,-1,7-C,BloHlo derivatives in excellent ~ield.~q Palladium-mediated cross-coupling reactions of these iodocarbaboranes with Grignard reagents were investigated and the addition of CuI was found to be essential for a successful reacti~n.,~ However iodination reactions of closo-1,12-C,B1,H1 with IC1 in the presence of AlC1 afforded closo-1,12-C2B,,H,,I as a mixture of isomers and the 2,9- 2,3- and 2,7-diiodo derivatives were isolated and characterized.,‘ The reaction of 1,2-dehydro-1,2-C,B,,H1,with acetylenes has been investigated and the synthesis and structure of the carbaborane analogue of benzocyclobutadiene has been reported.7s Two a-amino acids containing the 1,2-dicarba-closo-dodecaborane( 12) cage XCB,,H,,C(CH,)3CH(NH,)C0,H (X = H Me) have been prepared in high enantiomeric purity (> 98%) by asymmetric synthesis; the dextrorotary enantiomers (589 nm MeOH) have the (S)c~nfiguration.~‘ There are a few reports on carbaboranes with more than two carbons in the cage. The first unsubstituted 1 1-vertex tricarbaboranes nido-7,8,9-C3B,H, and nido-[7,8,9- C3B,H 1] -have been successfully prepared by deamination of 7-Me3N-nido-7,8,9- C3B8H The reaction of nido-[6-R-5,6,9-C,B,Hg] -(R = Me PhCH,) with BrBH,.SMe followed by deprotonation using a proton sponge has yielded the 11-vertex tricarbaborane anion nido-[7-R-7,8,10-C3B8Hlo]-.7” The synthesis of 1,6- dihalogeno-2,3,4,5-tetracarba-nido-hexaborane(6) derivatives has been described.’” The crystal structure of the cation of [(cp*)BBr][AlBr,] has a B-C distance (1.68 A) typical of that found in carbaboranes; the methyl groups of the cp* rings are ‘bent-back’ M.A. Beckett towards the apical boron A number of papers have appeared during 1995 concerning non-carbon containing heteroboranes.The Lewis acids RBH or R,BH reacted with the B-B bond of the three-membered ring of Bu'NB(But)BBut to yield 1-aza-nido-tetraboranes;the aminoboranes H,B=NRR' yielded the 2,5-diaza-arachno-pentaboranederivatives N,B,H,BU',RR'.~" The arachno-nonaboranes B9H1 ,(NRH,) (R = p-ClC,H, p-MeC,H, PhCH,) were dehydrogenated at 140 "C to afford nido-RNB,H which was further dehydrogenated at 460°C to closo-RNB'H,; this closo species can be deboronated by NH,Pr' or [NBu,]F to produce the novel anion nido-[RNB,H,] -.,' 1,l-Hydroboration of alkynes (RCCR'; R = H H SiMe,; R' = Me Bu But SiMe,) with 6-aza-nido-decaboranes R"NB,H (R" = H Ph PhCH,) gave corresponding 9-(l-alkenyl)-6-aza-nido-decaboranesRNB,H,,(CH=CRR'); ethenes RCH=CH (R = SiMe, SnMe,) are also hydroborated.8' The crystal structure of the 7-aza-nido- undecaborane derivative (NB2But3H)NBlOHI2 (Fig.6) has confirmed the nido cage structure.8d The aza-ctoso-borane PhNB,,H, was opened by amines NR (R = Me Et) and gave the novel 12-vertex nido derivatives PhNB ,HI 1(NR3); the non-planar open face accommodates the N atom a B-H-B bridge and the base-bound boron atom (Fig. 7)." The reaction of the azadiboriridine Bu'NB(Bu')BBu' with BH,*SPr afforded the thiaaza-urnchno-pentaboranecluster as an addition product.8f The first oxaborane [OB1,H,,]-has been prepared from [B,,H,,]- in aqueous NaOH solution by reaction with dissolved 0,.8g The macropolyhedral oxaborane anion [OB,,H ,]-has been structurally characterized and was formed by the reaction of water with the products of the reaction Of Unti-B,,H, with either Na or NaBH in thf; the structure is based on the Unti-B,,H, type macropolyhedral cluster with the oxygen atom bridging B(8) and B(9).8" 1,2-Dimethyl-1,2-disila-closo-dodecaborane(l2) has been degraded by NaOH in a two-phase Et,O-H,O mixture in the presence of [NMe,]Cl to yield [NMe,][MeSiB,,H,,]; the 11-vertex nido cluster anion structure has been confirmed crystallographically.8i Co-pyrolysis of B,Cl and AsC1 at 333 "C has afforded closo-1,2-As,B4C1 and other perchlorinated arsaboranes As,B,Cl, As,B,Cl, and As,B,,C1,,; at higher temperatures and higher B,CI,-AsCl ratios the 12-vertex species is preferred.,j Metallaheteroboranes A few non-carbon containing metallaheteroboranes have been reported during 1995.The synthesis and solid-state structure ofnido-[{8-(dppe)Rh)-7-SB9Hlo]~2CH2C12 has been reported.'" This 11-vertex { RhSB,} polyhedron shows a gross nido-icosahedral geometry while apparently possessing a cluster count more appropriate to a closo geometry; two one-electron agostic type Rh-H-C interactions are proposed as a source of an additional skeletal electron pair.'" The icosahedral ctoso-{ CuSeB,,} cage has been identified in the structure of [(PPh,),Cu,SeB,,H,,] which has copper and selenium atoms adjacent; the em-cage {Cu(PPh,)} unit is bonded to one triangular {CUB,) face via a Cu-Cu bond and two Cu-H-B interaction^.'^ The crystal structure of [3-(Bu1NC)-3,8-(PMe,Ph),-1,2-As2B,H,] [SbF,] has been determined and contains a cationic polyhedral metallaheteroborane cl~ster.'~ Following on from last year a survey of the more important developments in metallacarbaborane chemistry is included in this section; a comprehensive review of this area is available.," The reaction of 1equivalent of(GaBu'Cl,) with 2 equivalents of Boron 27 Fig.6 Molecular structure of (NB2But3H)NBloH, (Reproduced by permission from Inorg. Chem. 1995 34 5925) Fig. 7 Molecular structure of PhNB,,H,,(NEt,) (Reproduced by permission from Chern. Ber. 1995 128 1225) the disodium compound ~loso-exo-5,6-Na(thf),-l-Na(thf),-2,4-(SiMe~)~-2,4-C~B~H~ gave two products closo-Bu'GaC,(SiMe,),B,H and [GaC,(SiMe,),B,H,] separ-ated by fractional distillation and sublimation; the crystal structure of the digallium- linked system has been determined (Fig.8)."" Reactions of the related dilithiacar- baborane [Li,(thf),C,B,(SiMe,)R] (R = SiMe, Me) with In1,Pr' produced the corresponding closo-indacarbaborane Pr'InC,B,H,(SiMe,)R in yields of 35 and 43%. These closo species reacted with 2,2'-bipyridine 2,2'-bipyrimidine and 2,2' :6',2''-terpyridine in benzene solution at room temperature to form corresponding M.A. Beckett C(321 c12n Fig. 8 Molecular structure of the Ga-Ga linked [GaC,(SiMe,),B,H,] (Reproduced by permission from Angew. Chem. Int. Ed. Engl. 1995 34 332) donor-acceptor complexes with open structures.lob The synthesis characterization and reactivity of a series of Ta Nb and Zr sandwich complexes incorporating small carbaborane or cobaltacarbaborane ligands has been reported thus complexes of the type [(R;C,B,)MCl,(cp’)] [(Et,C,B,H,)-ZrCl(thf)(cp’)] (R’ = Et SiMe,; cp’ = C5H5 or C,Me5) and [(cp*)Co-(Et,C,B,H,)MCl,(cp’)] (M = Ta Nb) have been described.lO‘ The reaction of ZrC1 with closo-exo-Li(thf)-l-Na(thf)-2-SiMe,-3-R-2,3-C2B4H4 (R = SiMe, Me H) in thf-benzene produced [1-C1-1-(thf)-2,2’-(SiMe,),-3,3’-R2-4,4’,5,5’-Li(th~-1,1’-commo-Zr(2,3-C2B,H,),] in moderate yields; their reactions with Me,SiCH,MgCl have been investigated.”” A systematic synthesis of a novel mixed (2,3-C,B,) and (2,4-C2B,} erbium(rr1) carbaborane bent-sandwich complex has been described demonstrating a possible general route to mixed carbaborane-metal complexes.loe The reaction of RuCI,.3H20 or [RuCl,(dmso),] with [NMe4][7-PPh,-8-Me-7,8- C2B,H,,] afforded [RU(~-PP~,-~-M~-~,~-C,B~H~,)~] in which each carbaborane ligand is tridentate with one Ru-P bond and two B-H-B bridge bonds.’Of The synthesis and structural characterization of the first pentacarbametallacarbaborane complex [nidu-2-(cp)Fe-7-Me-7,8,9,10,12-C5B,Hlo] prepared from reaction of arachnu-[6-CH,COCH,-5,6,7-C,B,Hl 1] -tricarbaborane monoanion with [FeI(CO),(cp)] has been reported.log The alkane elimination of [HfMe,(cp*)] with C,B,Hl leads to the metallacarba- borane complex of stoichiometry [((cp*)(C,B9H ,)HfMe),] the structure of which has now been shown to be an unusual unsymmetric dimer composed of [(cp*)(C,B,H ,)Ha + and [(cp*)HfMe,] + bridged by a [C,B,H 1]2-group.’Oh Methane elimination from the reaction between [TiMe,(cp*)] and C,B,H yielded the thermally sensitive titanacarbaborane [(cp*)(C,B,H ,)TiMe] which decomposed Boron 29 at room temperature to the fulvene complex [Ti(q6-C,Me,CH,)(C,B9Hl 1)] and which formed labile adducts with thf and PMe,."' cis Insertion of diphenylacetylene into an em-polyhedral B-H bond has been observed for closo-[3-(PhC2Ph)-3,3-{ P(OMe),),- 3,1,2-MoC,B,H 1] in toluene at 90 OC.loi The three-legged piano-stool structure is adopted by [Zr(NEt,),(NHEt,)(C,B9Hl 1)] which was formed by an amine-elimin- ation reaction of C,B9H13 with [Zr(NEt,),].'Ok The synthesis and crystal structure of + the [PPh,Me] salt of the monoanion [Co(C,B9HllCH,),0] -has been achieved; the ether carbaboranyl anion has been described as a 'Venus flytrap' ligand."' Treatment of [Ni2(p-Br),(q3-C,HS),] with Na,[nido-7,9-R,-7,9-C2BloH (R = H, Me,) in thf afforded anionic clusters [Ni(q3-C3HS)($-7,9-R2-7,9-C2BloHlo] -isolated + as their [NEt,] (R = H, Me,) or [N(PPh,),] + (R = Me,) salts; the latter has been characterized by X-ray crystallography."" Treatment of nido-7,8-C,B,Hl with [Ru,(CO),,] in refluxing heptane resulted in [Ru(C0),(q5-7,8-C,B,Hl 1)] in high yield; reaction of this ruthenacarbaborane with [NEt,]I to form [NEt,]-[RuI(CO),(C,B,H and subsequent reactions of the latter compound have been described."" The crystal structure of the charge-compensated complex [Mn(CO),{qS- 7,8-C,B9Hlo-10-(thf)}] has been isolated from the reaction of nido-C,B,H, with [Mn(CO),Me].'o" The relationship between the molecular structure of [3,3-(PMe2Ph),-closo-3,1,2-PtC2B9H11] and the mechanism of the fluxional behaviour of the {M(PR,),} units in closo-12-vertex metallaheteroboranes has been described.lop Platinum complexes [1-Ph-2-Me-3,3-L,-3,1,2-PtC2B9H9] [L = PMe,Ph PEt, PPh, P(C6H,Me-4),] have been prepared from T1[7-Ph-8-Me-7,8-nido-C2B9H9] and the appropriate [PtCl,(PR,),] species; crystal structures of the PEt and PPh derivatives have been reported."q A kinetic and mechanistic study of 'ring-slippage' in [($-C,B,H ,)Rh(CO),] carbonyl-substitution reactions with phosphines and phosphites has been investigated; the reactions are believed to occur by associative pathways similar to the q5 -+ q3 -+ q5 'ring-slippage'mechanism proposed for CO substitution of [Rh(cp)(CO),].lor The mixed-sandwich ferracarbaborane complex closo-[3-{(cp)Fe}- 1,2-C,B,Hlo-4-SMe,] has been synthesized and characterized by cyclic voltammetry IR and 'H and "B NMR spectroscopy; it forms stable 1 1 charge-transfer salts with 2,3-dichloro-5,6-dicyano-p-benzoquinone and 7,7,8,8-tetracyano-2,3,5,6-tetrafluoro-quinodimethane.loS The tetrathiafulvalenium (ttf) saits [ttf) ,[Fe(C,B,H oC,H,S),] and [ttfJ[Fe(C,B,H,,C,H,S),] have been synthesized in order to study the effect of the thiophene (SC,H,) group on the crystal-packing electrical and magnetic properties of the ttf-metallacarbaborane salts."' The crystal structure of the meso-dias-tereoisomer of the carbaborane sandwich complex commo-[3,3-Fe{ 1,2-C2B,H 10-4- SMe,),] has been determined and the solid-state Raman spectrum of this meso compound is clearly distinguishable from that of the DD/LL isomers."" A number of papers relating to multidecker complexes have appeared in the literature during 1995.New hybrid diboranediyl-tricarbadecaboranyl tripledecker complexes [(c~)CO(~~,~~-M~E~,C,B,)M(M~C,B,H,)I (M = Fe Co Ni) have been prepared from [Co(cp)(MeEt,C,B,)] -and nido-[6-Me-5,6,9-C,B7H9] -with MX,; crystal structures have been reported and the dicobalt derivative is shown in Fig. 9."" A new family of C,B,-bridged tetradecker sandwich complexes having p-cymene rather than cp end rings have been synthesized by reaction of metal ions with derivatives of [nido-(p-Pr'C6H,Me)Ru(Et2C2B3H2-5-X)] (X = Me C1) and examples M.A. Beckett Fig. 9 ORTEP drawing of the dicobalt tripledecker sandwich C(cP)Co(MeEt,C3 B2)Co(MeC3 B 7 H911 (Reproduced by permission from Organometallics 1995 14 191 1) prepared include [{(p-PriC6H,Me)Ru(2,3-Et2c2B3)}2Co] [{(p-PriC6H4Me)-and Ru(2,3-Et,C,B3Me,)},Ni]. lowTreatment of the B(5) halogenated closo complexes [Co(cp*)(2,3-Et2C2B,H,-5-X)] (X = C1 Br I) in thf solution with sodium metal or alkyllithium reagents resulted in dimeric products with either B-B or (cp*)-(cp*) linkages respectively; decapitation of the (cp*Hcp*) linked dimers in wet tmen gave in high yield the corresponding nido complexes [{Co(CH,C Me,)(Et,C2B,H,-5-X)} J. lox Triple- and tetra-decker sandwich com- plexes having planar C2B3 or pyramidal C2B4 carbaborane ligands at one or both ends have been prepared and characterized; representative examples include [(cp*)Co(Et,C,B,H,Me)M(Et2C2B3H2Me)CoH(Et2C2B4H4)] Co Ni).'OY The (M = tripledecker synthon [(c~*)CO(E~~C,B,H~M~)CO(E~~C~B,H,)]~-has been used in the construction of penta- and hexa-decker sandwich complexes by reaction with metal ions and doubledecker anions {e.g.[CO(C~*)(E~~C,B,H,M~)]~-) in cold thf; the crystal structure of the hexadecker complex [{(cp*)Co(Et,C,B,H,Me)-Co(Et,C,B,H,)},H,Co] has been determined."' 4 Heterocycles Containing Boron Tri(tert-butyl)azadiboriridine Bu'NB(Bu')BBu' has been found to 1,l-boroborate isocyanides (RNC) uia the B-B bond to form the four-membered ring Bu'BC(NR)B(BU')NBU'(R = 2,6-Me,C6H,); the azides PhN and PhCH,N are also boroborated to yield the diazadiboretidine four-membered ring Boron 31 Fig.10 Molecular structure of [Rh(cp){(C,Me,)C,(BMe),C,H,}] (Reproduced by permission from Chem. Ber. 1995 128 183) Bu'BN(Bu')B(Bu')NR.''" The boron dihalides BCl,NR (R = Me Et,Pr') and Bu'BF when reacted with the magnesium reagent [Mg(C,H,Ph,)(thfj,] derived from (E,E)-1,4-diphenylbuta-173-diene,.produced the 2,5-dihydro-lH-boroles 2,5--Ph,C,H,BNR and 2,5-Ph2C,H,B Bu' as mixtures of cis and trans isomers.''b Borylation of the potassium pentadienide with BCl(NR,) followed by alcoholysis resulted in ~enta-2~4-dienylboranes C,H,B(NR,) (R = Me Et Pri). Metallation of these Me or Et derivatives in thf by LiNR in the presence of tmen resulted in ring .closure to produce boratabenzene salts [Li(tmen)][C,H,B(NR,)].''c The crystal -structure of [NMe,Ph][C,H,B Me] is also described.' "The first structural character- -ization and initial reactivity studies of 1-Hi-boratabenzene [Li(thf),][C,H,B H] has been described and its structure is very similar to the related [NMe,Ph]- . [C,H,BMe]."d A substituted triboratabenzene ligand [R3B,C3R,I3- has been prepared via 2-isopropylidene-1,3,4,5,6-pentamethy1-l73,5-triboracyclohexane where an q2 interaction of a {(cp)Co} fragment with the exocyclic double bond resulted in a metal-induced hydrogen migration and an q6 complexation of the ring; addition of further {(cp)Co> fragments resulted in a triple-decker complex.' le The synthesis and co-ordination chemistry of 1,4-dimethyl-2,3-bis(isopropylidene)-1,4-dibora-o-pheny-lene has been reported; reaction with [Rh(cp)(C,H,),] led to a complex of a tricyclic ligand via conrotatory [2 + 21 cycloaddition of the isopropylidene groups (Fig.lO)."J Spectroscopic data and molecular orbital calculations have shown that 5-methyl-1 -phenylpyrrole[3,4-d]borepin is a polar aromatic system.' '9 Direct iron-boron bonding interactions in ferrocenylboranes has been observed in the crystal structure of [Fe(C,H,BBr,),] where the C-B bonds are bent towards the iron atom by 10.2"with respect to the planes of their cp rings."" The dynamic behaviour of some boryl-substituted ferrocenes [Fe(cp)(C,H,BRR')] and [Fe(C,H,BRR'),] {RR' = Br, (NMe,), (NMe,)Cl (NMe,)Bu' Bu'Cl 9-bora-bicycloC3.3.llnonane) have been investigated by variable-temperature 'H '3C and "B NMR spectroscopy; three different processes were characterized dependent upon the nature of the substituents. li A series of 1,3-dibora-2-X-[3]ferrocenophanes 32 M. A. Beckett (X = NMe 0,S Se Te) have been prepared and characterized and the crystal structure of [Se((NPr',)BC,H,),Fe] has been reported.''j Ferrocenes bearing a (phosophino)boryl substituent [BR(PPh,)] at each of its cyclopentadienyl rings have been found to establish a novel type of ansa structure through intermolecular head-to-tail donor-acceptor bonding resulting in a B,P bridge; this bridge is non-planar and shows dynamic NMR behaviour with an activation energy of 70 kJ mol-' for the breaking of the P-B donor bond.'lk Reactions of metallocenes [M(cp),] (M = Fe Ru 0s) with excess BBr at reflux temperature have resulted in the formation of [M( l,3-(BBr2),C5H3},] in high yields; MeBBr and PhBBr were less effective borylating reagents and X-ray structural analysis of the tetrakis(dibrom0- boryl) derivatives revealed a weak metal-boron interaction as found in ferrocenyl- carbocations and [Fe(C,H,BBr,),] described above.'" 5 Boryl Complexes and Metal-catalysed Reactions Numerous publications appeared during 1995 concerning metal-catalysed reactions involving boron centres; a brief survey of some of the new developments which would be of interest to inorganic chemists is outlined in this section. A true syndiotactic- specific Ziegler-Natta catalyst for the polymerization of styrene has been based on [Ti(cp*)Me,] activated by B(C,F,)3.'2" Borate substituted di- and tri-anionic cyclopentadienyl ligands [X,B(C,H4)l2- and [X2B(C,H4)l3-(X = C$,) gave anionic Group 4 metallocene derivatives which provided a facile route to zwitterionic 'single-component' alkene polymerization catalysts.'2b Copper and gold complexes with bulky chelating ligands (e.g.[(AuCl)(p-dippe)] [dippe = 1,2-bis(diisopropylphos-phino)ethane]} have been shown to be effective catalysts for the hydroboration of imines or thiazolines by 1,3,2-benzodioxaborole.'2' Reactions of arenes with [M(CO),(B(O,C,H,)}] (M = Mn Re) or [Fe(cp)(CO),(B(O,C,H,))] activated by UV irradiation has led to the selective high yield formation of aryl- and vinyl- boranes.I2" The salt LiBH has been shown to hydroborate alkenes in the presence of UCl, NdC1 or ZrC1,; the reactivity sequence is tetramethylethylene > l-methylcyc-lohexene 9 2-methylpropene or hex-l-ene.',' Methylarenecarboxylates and diaryl- ketones were formed in moderate yield from the [Pd(PPh,),]-catalysed reaction of arylboronic acids with CO at atmospheric pressure in methanol at 24°C.'2J The oxidative addition of HB(O,C,H,) to the iridium(1) cis-phosphine complexes [IrX(CO)(dppe)] [X = Br I H B(O,C,H,)] have been found to proceed stereoselec- tively under kinetic control.'2g The first example of metal-catalysed addition of B-B bonds to C=C bonds has been published; thus B,(O,C,H,) was observed to react with 4-vinylanisole in the presence of a gold(1) complex prepared from the addition of 2 equivalents of (ethane-1,2-diylidene)bis(cyclohexylphosphane)to [AuCl(PEt,)] to yield exclusively the 1,2-bis(boronate) ester.12h The 1:1 and 1 :2 Lewis-base adducts of B,(O,C,H,) have been readily prepared by addition of 1 or 2 equivalents of 4-methylpyridine to B,(O,C,H,),; the molecular structures of [B,(0,C6H,),(NC,H,Me-4)] and [B,(O,C6H4),(NC,H,Me-4),] have been deter- mined by X-ray diffraction studies (Fig. ll).12i The complex cis-[Pt(PPh,),{ B(O,C,H,)),] was cleanly formed as the sole platinum-containing product from the reaction of [Pt(CH,CH,)(PPh,),] with B,(O,C,H,),; however Boron 33 Fig. 11 ORTEP drawings of [B,(0,C6H,),(NC,H,Me-4)] (bottom) and [B2(02C6H4)2(NC.5H4Me-4)21 (top) (Reproduced by permission from Znorg.Chem. 1995 34,4290) tris(bicyclo[2.2.l]heptene)platinum(0) reacted with B,(0,C6H4) to afford diboration of the 01efin.'~' The synthesis and structural characterization of the first dinuclear complex with a bridging boranediyl ligand [{ M~(c~)(CO)~),(~-BNM~,)], has been prepared by reaction of K[Mn(cp)(CO),(SiMePh2)] with B,(NMe,),CI,; the crystal structure is shown in Fig. 12.12k Boron-Pnictogen Species The pulsed-laser ablation matrix isolation technique has been used to study mixtures of argon-ammonia ( < 1%) co-deposited with ablated boron atoms onto a 10 K optical window; IR spectra have shown the formation of HBNH BNBH and B2N.13" The crystal-structure determination of Ph,PN(Me)BH has been undertaken in order to M.A. Beckett Fig. 12 Crystal structure of the boranediyl complex [(Mn(cp)(CO),),(p-BNMe,)] (Reproduced by permission from Angew. Chem. Int. Ed. Engl. 1995,34 825) study the effects of n-bonding between the P and N atoms in Ph,P=NR derivatives as a function of the formal charge on the N atom.13' Amine adducts of (CF,),BH have been described and the crystal structure of (CF,),BH*NMe,CH,Ph has been reported.' 3c The amine adducts of tri~(2~6-dimethoxyphenyl)borane have been investigated; thus 1 1 adducts were formed with NH and some primary amines but not with tertiary amines secondary amines or ~ec-alkylamines.'~~ Biguanide complexes of boron have been investigated as potential exterior grade fixed boron wood preservatives; two biguanide rings around boron were necessary to achieve moderate hydrolytic stability in application to wood and the complexes B[H2NC(=NH)NH2],(OH) and [B{ [H,NC(=NH)NH,],},]Cl have been investigated by "B and 13C NMR spectros- copy and by X-ray crystallography.13e The compound CF,(CI)BNMe, prepared from Cl,BNMe and P(NEt,),-CF,Br in tetrahydrothiophene 1,l-dioxide underwent [2 + 21 cycloaddition reactions with Bu'NCO and Cl,BNMe to yield the four-membered heterocyclic rings CF,(Cl)BN(Me),C(O)N But and CF,(Cl)BN(Me),B(Cl),N Me, respectively.' 31 The diboration of the diazene PhN=NSiMe by diborane(4) derivatives has provided a new synthetic route to N,N'-diborylated hydrazines; products are dependent upon the type of diborane(4) compound used.13g The reactions of the iminoborane C,F,BzNBu' and its isomer BU'BGNC~F with nitriles and isocyanides have been studied and substituted triazadiboracyclohexanes borazines diazaboracyclobutanes azaboracyclobutanes and diazadiboracyclopentenes were reported as products.' 3h The reaction of oxygen sulfur selenium with the P atom of the borane (tmpy)BzNPBu' has been shown readily to lead to the addition product (tmpy)BzNPXBu' (X = S Se) whilst the P-oxide readily dimerized to the eight-membered flat-boat shaped {B,N,P,O,) ring [(tmpy)BN=P(Bu'),O] (Fig.13); also reported were reactions of (tmpy)BrNPBu' with CH,I BBr, 'BH,' and CH2(BC1,),.' Boron 35 C(13 Fig. 13 ORTEP drawing of [(tmpy)BNP(Bu‘),O] (Reproduced by permission from Chem.Ber. 1995 128 205) 7 Boron-Chalcogen Species The preparation of BaNaBO has been reported and its structure is constructed from BO, NaO and BaO groups linked by shared edges vertices and faces.14” The new anhydrous borate CsNbOB,O has been found in the ternary system Cs,O-Nb,O,-B,O and the compound belongs to the already known family AMOB,O (originally reported as AMOB,O,) with A = K Rb Cs T1; M = Nb Ta. 14’ The crystal structure of B(OSnPh,) has revealed an essentially trigonal-planar geometry about boron with the tin atoms located 0.043(5)-0.550(5)A below the BO plane.’& Amine adducts (R,B,O,-L) of (4-MeC,H4),B,0 and (3,5-Me,C6H,),B,O have been prepared and variable-temperature ‘H NMR spectroscopy on selected adducts (L = cyclohexylamine isoquinoline morpholine benzylamine) indicated that a ligand dissociation-recombination process was occurring with AG* of 4349 kJ mol-I; the molecular structure of [(4-MeC,H,),B,0,].C6H ,NH has been determined crystallographically.’4d The stability constants of the neutral 1 1 com--plexes HOBORO ,formed from boric acid (H,BO,) and 1,3-diols have been obtained in aqueous solution and in organic s01vents.l~~ Two potential boronate affinity chromatography ligands (benzene- lY2-diolato)[2-( diethylcarbamoyl)-4-methylphenyl] boron and (benzene-1,2-diolato)[2-(diisopropylcarbamoyl)phenyl]boron were synthesized by direct ortholithiation followed by boronation; X-ray crystallo- graphic analyses have shown that the boron atoms are tetrahedral with a co-ordinated carbonyl-oxygen-to-boron bond.14f The compound (9-H-9-BBN) (BBN = borabicyclo[3.3.llnonane) has been shown to react with monocarboxylic acids and afford (9-RC02-9-BBN) which are dimers in the solid state as shown by the crystal structures of the benzoate and pivalate derivatives; dicarboxylic acids gave more complex reactions. 14g The first stable disulfanylborane LB(SH) (L = 2,4,6-[(Me3Si),HC],C,H,) has been prepared by reaction of the overcrowded lithium hydroborate LBH,Li(thf), with S,; dilithiation followed by reaction with [TiCl,(cp),] resulted in the formation of the M. A. Beckett Fig. 14 ORTEP drawing of [Ti(cp),S,B(C6H,[CH(SiMe,),l-2,4,6)] (Reproduced by permission from Organornetallics 1995 14 4460) four-membered metallocycle 1,3,2,4-dithiaboratitanetane [Ti(cp),S,BL] character-ized by X-ray diffraction (Fig.14).'4h The reaction of Bu',S with RBBr (R = Ph 2-MeC6H4 3-MeC6H4 4-MeC6H, 4-EtC6H4 3,5-Me,C,H,) in refluxing toluene gave the thermally stable moisture-sensitive trithiadiborolane (R2B2S3) derivatives; reaction of the RBBr species with (Me,Si),S in benzene at room temperature readily afforded the corresponding trithiatriborinanes (R,B,S,) and not the expected dithiadiboretanes (R,B,S,) whilst the reaction of S with PhBBr or 4-MeC6H,BBr was reinvestigated by "B and mass spectrometry and RBS species were identified.',' The first organotellurium compounds have been prepared from the reaction of 9-Cl-9-BBN with Na,Te and Na,Te; (9-BBN),Te reacted with water to give elemental tellurium (9-BBN),O and (9-H-9-BBN),.14j 8 Boron-Halide Species The preparation spectra and crystal structure of the archetypal co-ordination compound BCI,.NH has been described; BCl,.NH was prepared in low yield from the reaction of BCI and NH,Cl in toluene solution with trichloroborazine as the principal pr~duct.'~" Thermolysis of BCl,*NH at 450 "C ultimately led to the production of boron nitride.I5" Geometric and electric properties of the donor- acceptor complex BF,*NH have been calculated at the MP2/TZ2P level and are in qualitative agreement with experiment confirming the earlier microwave characteriz- ation of this donor-acceptor complex and providing a physical picture of dative bond formati~n."~ Boron 37 References 1 M.A.Beckett Annu. 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ISSN:0260-1818    

DOI:10.1039/IC9959200019

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

4 Aluminium Gallium Indium and Thallium By J.P. MAHER School of Chemistry University of Bristol Bristol BS8 i TS UK 1 Introduction During 1995 the total number of references to Group 13 increased yet again so that some four and a half thousand have been found by computer search! The proportion of references for each element remains essentially identical to that found last year aluminium 70% gallium 15%,indium lo% thallium 5% but only a small proportion of these are reported here. 2 Aluminium J. Organomet. Chem. celebrates its 500th volume with various reviews of Group 13 organometallic chemistry. Thus Professor John J. Eisch presents a personal perspec- tive showing how his understanding of Group 13 organometallic mechanistic chemistry has changed from the viewpoint prevailing in the 1950s of these organometallics as potential carbanionic nucleophiles to treating these reagents as organometallic electrophiles.The syntheses structures and equilibria which occur for Group 13-16 organometallic compounds have been reviewed. In a survey of recent work on organoaluminium and organogallium hydrides Cowley’s group describe how the first base-free aluminium and gallium monohydrides and gallium dihydride have been stabilized by employing the bulky 2,4,6-tris(tert-butyl)phenyl ligand.3 In this context an intramolecularly base-stabilized monomeric organoaluminium dihydride [A1H2{C,H,(CH,NMe,),-2,6}] was recently characterized by means of its X-ray crystal structure. Eight-fold co-ordination is observed for the compound [Ph,MeP]- [Al(BH,),].Four BH units form eight apparent three-centre two-electron Al-H-B bonds with the A13+ centre. This is the first molecular structure of an aluminium compound which contains an eight-co-ordinate aluminium atom. The four BH units are arranged in a distorted-tetrahedral fashion around the aluminium atom and each BH unit contributes two hydrogen bridges to the aluminium. The eight bridging hydrogens thus form a slightly distorted dodecahedra1 co-ordination geometry around the aluminium centre.’ Infrared studies have shown that the major constituent of labile gas-phase equilibria in mixtures of AlMe and AlHMe is the heteroleptic pentamethyldialane Me,Al(p H)(p-Me)AlMe, in this compound there is evidence for a significant strengthening of 41 J.P. Maher the Al-H-A1 bridging bond lending support for a ligand-exchange mechanism involving singly bridged species. Just what constitutes a normal A1-0 bond has been discussed in the light of the observed structural and spectroscopic parameters for the monomeric four-co-ordinate aluminium aryloxide compounds [AIR,(OR'),-xX,] (x = 0 1,2;n = 0 1; R = Et Me Bu'; R' = C,F, C6H2BU',). Experimental evidence for the presence of short A1-0 bond distances the low reactivity of residual aluminium-alkyl groups the electron- rich nature of the aluminium centre and the weakening of the Al-X bonding by the aryloxide ligand were presented. On this basis models for the A1-0 bond were discussed involving steric effects highly ionic bonding d,-p interactions and n bonding via donation into Al-X b-antibonding orbitals.' Aluminium(1) compounds can be readily characterized in the gas phase thus gas-phase electron-diffraction data of [Al(cp*)] show that the gas consists of monomeric Al(q5-C5Me,) units.A model with C, symmetry yields the bond distances A1-C = 2.388(7) C-C(endocyclicf = = 1.414(5) and C-C(exocyclic) 1.529(5)a and a perpen- dicular metal-to-ring distance of 2.063(9)A.* Perfluorinated organoalanes are not often reported but reaction of AlClMe with Li(C,F,) leads to the formation of Al(C,F,),.thf the compound was characterized by X-ray diffra~tion.~ The first example of an aluminium-phosphorus-arsenic mixed-pnictogen ring compound has been prepared and characterized by an X-ray crystal-structure determination namely [Et,AlP(SiMe,),AlEt,As(SiMe,),l.This is the first structurally characterized compound to contain a four-membered ring with two aluminium centres bridged by two different heavier Group 15 atoms." Several new Group 13 chalcogen compounds have been described. In order to investigate the possible occurrence of n bonding in Al-S and Ga-S bonds and the determination of the steric requirements for the isolation of monomeric heavier Group 13 thiolates several sterically crowded aluminium and gallium thiolates have been synthesized and characterized. The following were characterized by X-ray crystallo- graphy and/or by NMR and IR spectroscopy [A1R(SC6H2But3-2,4,6),] (R = Bun (R = Me, But) [G~(SR~C,,H,BU',-~,~,~)~] Ph) [GaBun(SC6H,Bu',-2,4,6)~] [{AIBut,(SC6H,Pr',-2,4,6)) ,] and CAI( thf)(SC H ,Pr',-2,4,6),].The study shows that the M-S pp n-bonding is weak and has an upper limit of 32-38 kJmol-I.'' The reaction of diorganodichalcogens (ER, E = Se or Te) with trimethylamine adducts of alane or gallane yield four-co-ordinate monomeric trimethylamine adducts of the tris(seleno1ato)-or tris(telluro1ato)-metal(Ir1) species [M(NMe,)(ER),] (M = Al Ga; E = Se Te; R = Et Ph CH,Ph).12 The synthesis and molecular structures of selenolates of aluminium and gallium [{ Al(p-SeMe)(mes),),] [{ Ga(p-SeMe)Ph,),] and [AlMe,(SePh)]-PPh have also been described.' A cyclic trimeric alkylaluminium 'propeller' complex [{ Al(p PhNCH,CH,NH)Me),] was prepared by the reaction of AlMe with N-phenylethylenediamine in toluene in this compound all three methyl groups on the aluminium centres occupy the cis-axial positions of a chair conformation.l4 The structure of [{ AlMe(NC,F,)),] displays an almost perfect cube with alternating aluminium and nitrogen atoms. In contrast [Ga{ G~(~~s)),(~,-NC~F~)~(NHC~F,)] consists of a distorted cube and is the first example of an amino-substituted iminogallane containing a heterocubane structure. Aluminium Gallium Indium and Thallium 43 Insertion of trimethylsilyl azide into an Al-A1 bond is observed for tetra-kis[bis(trimethylsilyl)methyl]dialuminium [((Me,Si),CH),Al-Al(CH(SiMe,),),]. The NMR spectra and crystal structure shows the product to contain three- and four-co-ordinated A1 atoms due to the co-ordination of the a-nitrogen atom of the azide group to one of the A1 atoms.An electronically delocalized N system is formed with a N-N bond length of 1.320A and a bond order of 1.5 for both N-N bonds.16 Multifrequency NMR spectroscopy provides a useful window on many forms of aluminium(~~~) complexes. In an elegant (and text-book example) study of alumin- ium(Ir1) isothiocyanate complexes in water-acetone mixtures at temperatures low enough to slow proton and ligand exchange separate resonance signals are observed for co-ordinated and bulk water ('H) and for NCS- (13C 15N) and for the A13+(27Al) from each complex. The 'H NMR spectra show six sets of signals for the complexes [A1(H20)6]3+ through to [A1(H,O)(NCS)J2- including isomers for three of the species.Measurements of the signal areas show a decrease in the A13+ hydration number with increasing NCS- concentration as the NCS- replaces water in the solvation shell. In the 27Al NMR spectra of these systems signals from seven complexes [A1(H20),13 through to [A1(NcS),-j3- are observed with chemical shifts + increasing by about 6 ppm with each additional NCS-. Although broadened somewhat by the 27Al quadrupole the 13C and 15N NMR spectra also show co-ordinated NCS -signals for the complexes including spin-spin coupling J(27A1-13C) for the thiocyanate moiety in [Al(NCS)6]3-. Area measurements of the 15N NMR signals provide an excellent complement to the 'H hydration-number data.17 Since aluminium is potentially toxic possibly since it can be absorbed alongside iron(m) it is important to be able to characterize its speciation in solution so the above kind of study has important implications for bioinorganic chemistry.NMR is a good spectroscopic probe as it overcomes the two major difficulties for speciation studies in aluminium(Ir1) solution chemistry namely the existence of a large number of equilibrium processes and ready hydrolysis. Comparative X-ray and 27Al NMR spectroscopic studies of the speciation of aluminium in aqueous systems of aluminium(II1) complexes of N(CH,CO,H),(CH,CH,OH) (H,L) have been carried out. In this system two components are directly analogous to the iron(Ir1) compounds dinuclear [(A1(L)(H20)),]-2H20 and tri(decanuc1ear) [All,(~~3-OH)6(~-OH)12L6-(H20)6] +.* Complexation of Al"' by the chelates catechol and disodium 4,5-dihydroxybenzene- 1,3-disulfonate (tiron) has been studied by 27Al 13C and 'H NMR spectroscopy. Aluminium(u1) forms 1 :1,l 2 and 1 :3 chelates with both catechol and tiron depending on the pH and ligand concentration. Disproportionation of the 1 :1 chelate with tiron at pH = 7 gave a mixture of 1 :2 and 1:3 chelates leaving a major amount of aluminium in an uncomplexed form. Both the mer andfac isomers of [AIL,]'- (Na2H,L = tiron) were characterized. Hydrolysis of the 1 1 Al-L4-chelate leading to the formation of [Al(OH),] -occurs via the formation of the tetrahedral chelate intermediate [AlL(OH),] -. In the aluminium-catechol system three complex species coexist with [Al(OH),]-in a 1:2 mixture at pH = 12.5.Unlike in the Al-tiron system a tetrahedral 1:2 aluminium<atechol chelate is also formed during hydrolysis of the octahedral 1 :2 aluminium-catechol complex. l9 Complexation studies on aluminium(II1) complexes of DL-myo-inOSitOl 1,4,5- trisphosphate and D-myo-inositol 172,6-trisphosphate by potentiometry show that J. P. Maher both ligands form Al(HL) AIL and Al(0H)L species whereas the inositol 1,2,6- trisphosphate ligand forms in addition an A1,L complex and the inositol 1,4,5- trisphosphate an Al(OH),L species. In an attempt to assess the biological significance of the AI"' binding to DL-rnyo-inositol1,4,5-trisphosphate, the results were compared to the All1'-adenosine 5'-triphosphate complexes that have been found in similar solution conditions.Considering the relative stability of the complexes of both systems it appears likely that the intracellular second messenger system involving DL-~JW-inositol 1,4,5-trisphosphate may be disturbed by the presence of A11''.20 A novel layered aluminium phosphate [Co(en),A1,P,0,,]~3H2~ assembled about a chiral metal complex [Co(en),] [OH], and using hydrothermal synthesis has the chirality of the complex imprinted into the Al-PO layers.21 The synthesis also by hydrothermal methods and structural analysis of a novel open-framework aluminium methylphosphonate has been described. The remarkable feature is the presence of one-dimensional channels parallel to the c axis almost completely lined with methyl groups., The synthesis and structure of a novel layered aluminophosphate [Al P,O ,(C9H2,N3)] containing a twelve-membered ring using a cyclic organic diamine has been reported.In this material the effective pore size of the ring is modified from 6.6 to 3.38L by the pore-blocking action of the intercalated template ion., The novel open-framework gallium phosphate [Me,NH(CH,),NHMe,]-[Ga,P,O,OH].H,O is the first gallium phosphate to be prepared with Ga P ratio of 4 5. The structure is unique and contains large pores in which the tmen cations and water molecules reside., The aloxane [A~,Bu',(~~-O),(~-OH)~] and the largest galloxane hydroxide [Ga,,Bu',,(p3-0),(p-0),(p-0H),] have been reported. In the galloxane each gallium atom and bridging oxygen atoms Ga-0-Ga lie on a mirror plane.The cage has twelve fused six-membered rings with each gallium co-ordinated to one carbon and three oxygen atoms.25 There is a continuing interest in aluminium(m) complexes involving various H,salen-type ligands which have the normal C=N bond of salen reduced to CH,NH giving an H,L rather than an H,L ligand co-ordination. A novel feature of one group of these is the co-ordination of two molecules of solvent alcohol (rather than the more normal alkoxide) trans to each other with the ligand occupying the plane in a slightly distorted Al"' octahedral co-ordination. The complexes have potential relevance to Lewis-acid catalysis.26 The dimers [{Al(salpan)Li(thf),),] and [(Al(L)Li(thf),),] [H,L = bis(salicy1idene)-1,2-diamino-4,5-dimethylbenzene] are members of a new class of aluminium anion with metal-ligand stoichiometries of 1 1.In the former complex the dihedral angles for the two AILiO planes with respect to the central AI,N plane are twisted by about f50.0" giving the molecule helical chirality.,' Other members of the H,salan class of tetradentate N,O,-co-ordination-type ligand demonstrate a wide range of chemistry with AlMe,. Thus H,salpan will react with 1 and 2 equivalents of AlMe forming [AlMe(H,salpan)] and [{ Al(AIMe,)(salpan))] respectively. Adding 3 equivalents of AlMe to the ligand gives novel trimetallic derivatives such as [AlMe(AlMe,),(salpan)]. A crystallographic study showed that the molecules are comprised of a central AlMe group co-ordinated in a planar array to the nitrogens and oxygens of the ligand.The two AlMe groups each bridge an oxygen and a nitrogen atom.28 The formation of the first homologous series of ligand-centred aluminium(II1) radical-anion complexes based upon tris(1,3-diphenyltriazenido)aluminium Aluminium Gallium Indium and Thallium 45 [Al(dpt),] have been described. These complexes were studied by cyclic volammetry in thf solution revealing three successive pseudo-reversible one-electron reduction waves (E -1.50 -1.84 and -2.16V). Sodium-metal reduction in thf enabled the + -. isolation of the radical-anion complexes [Na(thf),],[Al(dpt)J (n = 1 3). The com- pounds were characterized by ESR NMR UV/VIS and X-ray photoelectron spectroscopy and by the X-ray structural determination of [N(PPh,),][Al(dpt),].29 Multifrequency ESEEM (electron-spin echo-envelope modulation) and ESR spectros-copies were then employed to study the electronic structure of the monoradical anion [Al(dpt),] -.ESR spectra of the "N-labelled derivatives clearly indicate that the radical-anion complex is ligand-centred with strong hyperfine couplings to the nitrogen nuclei of a single triazenide ligand. A very weak coupling to the aluminium centre is demonstrated by the ESEEM spectra providing further support for the ligand-centred nature of the radical-anion c~mplex.~' Finally we note the observation of an aluminium peroxide species with the nominal composition AlO, very likely an aluminium peroxide oxide which is formed at the interface between platinum and an cr-Al,O diffusion-bonded surface in a reducing atmosphere at 1200 OC.,' 3 Gallium Organogallium chemistry has provided an interesting crop of unusual compounds this year.Thus the formation of a carbaborane-substituted gallane in which a GaBu' moiety is $-co-ordinated to a C2B3 carbaborane face and the related material where two of the gallium units are co-ordinated through a very short (2.340A) Ga-Ga bond must head the list., In the paramagnetic tetraalkyldigallane radical anion [((Me,Si),CH),Ga-Ga{ CH(SiMe,),),]'-there is a long single-electron n bond (2.401A) which is 0.14A shorter than in the neutral compound.33 The first cyclogallane Na,[Ga( C,H,(mes),)] has been claimed as a 'metallic system with aromatic character'. In the structure the Ga equilateral-triangular core is planar with very short Ga-Ga bonds (2.441 A).The two sodium atoms donate one electron each to the unoccupied p orbitals of the sp3-hybridized gallium atoms so providing 271 electrons for delocalization and making the core isoelectronic with the triphenylcyclo- propenium cation.34 The digallium compound based upon diazabutadiene with two GaC,N rings linked by a 2.333(1)A Ga-Ga bond does not contain a 6n-electron ring system with the gallium atoms involved in any form of delocalization rather the p systems are localized into the C,N parts of the rings.The GaC,N rings are at right angles to each other with sp2 gallium hybridi~ation.,~ The first gallafluorene a benzannelated heterocycle with a GaC ring has been prepared by salt-elimination using [GaCl,(C6H,Bu',-2,4,6)].The analogous inda- fluorene was also prepared. The Ga-C bond lengths in the ring and to the C,H,Bu' group are all characteristic of single Ga-C bonds and are between 1.949 and 1.969A.36 A rare T-shaped three-co-ordinate molecule bis(2,6-dimesitylphenyl)gallium chlor-ide [GaCl{C,H,(rnes),},] has been prepared and its crystal structure determined. The Ga-C1 bond distance is 2.177(5)& while the Ga-C distances are 1.956(16) and 2.000(6)A. The steric demands associated with the two bulky 2,6-dimesitylphenyl 46 J.P.Maher ligands are responsible for the distortion in the co-ordination about the gallium atom. 37 The intramolecular1y base-s tabilized arylgallium(I1I) diazide [Ga(N,) { C,H ,-(CH2NMe,),-2,6)] was prepared by a metathetical reaction of the corresponding arylgallium dichloride with NaN,.It was found not only to be air stable but also to survive vapour-phase heating at 400 "C or UV irradiation at 254 nrn!,* The chlorogal- lanes [GaC1,H3 -"{ P(C,H ,),>] (n = 1 2) are also described as 'thermally robust'. Trimeric [{GaH,[p-P(c,H 1)2]3)3] crystallizes in a twist-boat conf~rmation.~~ Treating GaBu' with P4S10 forms novel Ga-S ring systems; [(GaBu',PS,),] is a trimer containing a (PS) hexamer ring with three GaBu',S groups co-ordinated to give the first example of a gallium phosphino dithiolate; heating the trimer causes a reaction to form a 3 x 4-membered [(GaBu'),{S,P(=S)Bu'},] ring compound with linked S-Ga-S-P Ga-S-Ga-S S-Ga-S-P rings.,' Interest in transition-metal gallium compounds continues largely due to possible applications in MOCVD (metal-organic chemical vapour deposition) technology.The synthesis and spectroscopy of trans-[(Ph,P)(0C),Co-Ga((CH2),NEt2}R](R = C1 Me) and [(q5-C,H5)(OC),Fe-GaCl2(NMe,)] were studied low-pressure MOCVD experiments were performed to give thin films of analytically pure CoGa alloy.41 The carbonyl compounds cis-[Fe(CO),{ GaR[(CH,),NMe,]},] (R = Bu' Ph) are precur- sors for gallium-rich thin Fe-Ga films.42 The new gallium compound [{ Ga(C6H,But3-2,4,6)[Mn(CO),],),] and the new indium compounds [{ In(C,H,Bu',-2,4,6)[C0(C0),],)~] and [{~n(C,H,Bu',-2,4,6)[~n(~~)5]2)4], have been prepared., The crystal structure of a new monomeric tris(arsino)gallane [Ga{ As(SiMe,),},] has been established.The monomeric molecule adopts a trigonal-planar configuration with an average Ga-As bond length 2.421 A.44New crown-ether tellurometalates of gallium and indium have been sunthesized; K[K([ 18]crown-6)],[GaTe3].2MeCN contains the GaTe,,- ion. The [In,Te,]'- anion in [NEt4],[In,Te,]~O.5Et,O has an In,Te cuboidal framework with a missing corner and a Te2- ligand at each of the three In3 + centres giving 'three edge-sharing InTe tetrahedra' a very curious structure. The InTe moiety is also found in Na,InTe,., A novel example of a cyclic gallium(III) porphyrin trimer [(Ga(htpp)},] has been synthesized and characterized with the aid of 'H NMR spectroscopy. The 'H NMR spectra indicated that the complex has a head-to-tail cyclic trimeric structure with the pyrrolic alkoxide groups forming bridges from one macrocycle to the metal in the adjacent macrocycle PGa-0-PGa-0-PGa-0.The three gallium(III) porphyrin subunits were not eq~ivalent.~ Gallium(1rI) binding to ovotransferrin and its half-molecules has been studied using multinuclear 13C 69Ga and ,lGa NMR spectroscopy. When carbonate is the synergistic anion Ga3+ is bound to the two metal-ion binding sites of the protein the metal ion interacts preferentially with the N-site of the intact protein.47 Synthesis and structural characterization of a stereospecific dinuclear gallium triple helix has been described.,* 4 Indium Several In,-containing cubanes have been prepared and characterized; [In,{C(SiMe,),},] has a nearly undistorted In tetrahedron [mean Aluminium Gallium Indium and Thallium In-In = 3.002(1)A] whilst [In,Se,{ C(SiMe,),},] adopts a slightly distorted In,Se heterocubane structure.49 An organometallic In,P heterocubane containing a slightly distorted In,P core with an alternating arrangement of In and P atoms is found in the compound [In,( P(SiMe,)},{ M o(CO),(cp)},].’ The cu bane [In,{ C(SiMe,),} ,] reacts with [Mn2(CO),,] to form a compound in which two carbonyl ligands are replaced by two In[C(SiMe,),] fragments.Thus two Mn(CO) groups are bridged by two monoalkylindium units and a planar Mn,In molecular centre.’ ’ Various indium-Group 16 compounds have been prepared some with a potential for indium chalcogenide synthesis. Reaction of [In(mes),] with various thiols gives [{In(mes),(p-SR)},].A trimeric indium thiolate [{ InMe,(p-SSiPh,)},] was isolated from the reaction of InMe with HSSiPh,.52 Similar selenium compounds have been described also [InMe(p-SePhXSePh)], a spiral chain composed of alternate four- co-ordinate indium atoms and three-co-ordinate selenium atoms.’ The synthesis and molecular structures of the first examples of tellurolate dimers [{ In(mes),(p-TePr”)},] and [{ In(mes),(p-TePh)},] have been reported.’ The compounds Ga[TeSi(SiMe,),] , In[SeC(SiMe,),] , [{ In[SeSi(SiMe,),] ,},(p-dmpe)] and P[SeSiMe,),] have been synthesized and characterized by X-ray diffra~tion.~~ A series of organoindium phosphides including [InPRR’(CH,CMe,),] (R = R’ = Et C6H11; R = C6Hll R‘ = H; R = Me R’ = Ph) and [InP(Me)Ph(CH,SiMe,),] have been prepared and characterized.Dimers and trimers were observed in benzene solution. The dimer [{ InPEt,(CH,CMe,),},] contains a planar In,P core with In-P distances of 2.623(2) and 2.641(2)A and the trimer [{InP(H)(C,H l)(CH,CMe,),},] has an In,P six-membered ring which is in the twist-boat conformation with In-P distances ranging from 2.613(3) to 2.659(2) The novel paramagnetic indium(II1) diphthalocyanine In(pc), isostructural with Sn(pc), has been obtained by the direct reaction of InMg alloy with 1,2-dicyanoben- zene at 2 10 “C. Indium diphthalocyanine contains sandwich-type molecules in which the indium atom is eight-fold co-ordinated by the isoindole nitrogens of two phthalocyanine rings. The distance between the phthalocyanine planes in this sandwich macromolecule is equal to 2.741(7) A.The two phthalocyaninato moieties are rotated about 41.2(4)” with respect to one another.The magnetic susceptibility measurement shows a typical Curie-Weiss behaviour. The effective magnetic moment is 1.67pB and the ESR spectrum exhibits a single strong signal at g = 2.0025.’’ Eight-fold co-ordination is observed for the indium(II1) phthalocyanine tetra(n- bu ty1)ammonium cis-di(ni trito-0,O’)ph thalocyaninatoinda te(II1). This compound has both nitrite anions co-ordinated as chelating nitrito-0,O’ ligands to the indium(m) so that the indium(II1) is eight-co-ordinated within a distorted ‘quadratic’ antiprism and directed towards the pc2- ligand.58 New low-valent indium compounds have been described.The first mixed-valent mixed-metal gold-indium cluster [AU,h,Cl,(dppe),] is composed of a triangle of gold atoms (with one very short edge) penetrated by a perpendicular triangle of indium atoms.” The indium(1) half-sandwich [In(C,H,Ph,)] has been prepared.60 Complexes containing In’[HB(bpz),] have been characterized.61 The In-Fe bond length of 2.463(2)A in [In(HB(dmpz),}Fe(CO),] is the shortest reported to date and [In{HB(drnpz),}W(CO),] is the first complex with an In-W bond [2.783(2)A] to be structurally characterized.62 Tetraphenylphosphonium hexachlorodiindate contains centrosymmetric [In,CI,]*- ions having an In-In bond length of 2.727( 1)A? Investigations performed at the turn of the century into low-valent indium halides 48 J.P. Maher particularly the bromides have been reinvestigated. An excess of indium dissolves in hydrobromic acid In'Br is precipitated and there is evidence for species such as (In,Br)-.64 The bromide In,Br, consisting of (In3f),(In+),(Br-),, has unusual co-ordination numbers for In' of 10 and lL6' In some interesting calculations and on the basis of charge-self-consistent semi-empirical band-structure calculations it was argued that the reduced phases (InBr In,Br and In,Br,) are 'soft' (cf Pearson's hard-soft acid-base concept). Although co-ordination polyhedra around In ions are + highly irregular because of the influence of the indium 5s2 atomic orbital the total In-Br bonding interaction is weak but in none of the cases has there been found a directed electron 'lone-pair' effect for In+.66 The mixed transition-metal indium bromides In,ZrBr6,67 InCdBr,,68 In,Ti,Brg,69 InFeBr and InMnBr,,' have been studied.5 Thallium Whilst the previous section on indium does not contain many surprises thallium again lives up to its reputation first attributed by J. B. A. Dumas as the ornithorhynicus of the elements! Thus the first paramagnetic compound containing thallium(i1) has at last been synthesized and structurally characterized that is [NBu,],[TI(Pt(C,F,),),] prepared by the reaction of [NBu,],[Pt(C,F,),] with [Tl,(p-C1)2(C6F,)4J in dich- loromethane. The structure contains the Pt-T1-Pt linear unit with square-planar Pt(C6F5)4 units at each end and TI-Pt = 2.708(1) 2.698(1)A being shorter than Tl'-Pt" bonds [2.911(2b3.140(1)A].One fluorine from each C6F group has a short [2.839( 10)-3.065( 12).,4] contact distance to the thallium(1r) centre. Evidence for the paramagnetism of the compound comes from its 2 K X-and Q-band ESR spectra and from magnetic measurements. These show 1.1 = 1.82pB <g> = 2.1 (gll = 1.924 g = 2.489) and a quintet hyperfine structure with ,''Tl couplings of All = 33.97 A = 35.88 and "'Pt A ,I = 2.17 A = 2.87 GHz. The Pt-T1-Pt core of the molecule is described as consisting of donor-acceptor interactions with the T1" using sp-hybrid orbitals to accommodate electron density doqated by the Pt atoms of the anionic Pt(C,F,) ligands. This leaves the unpaired electron in a p orbital perpendicular to the Pt-TI-Pt axis which interacts with suitable empty orbitals of the Pt atoms to give a n molecular orbital in which the unpaired electron is shared by all three metal atoms.This picture accords with the hyperfine splitting and the g parameters found.,' The only previously observed thallium atom with a heavy metal bond is [{(Me,Si),Si) ,TI-TI{ Si( Si Me,) 1,]. However another complex described as a 'non-buttressed' metal-metal-bonded complex of platinum and thallium has been characterized in aqueous solution by multinuclear (lg5Pt and 205Tl) NMR spectros- copy [(NC),Pt-Tl(CN)] -.73 This compound has the distinction of having the largest known heterobinuclear spin-spin coupling constant J(195Pt-205T1)57.0(1)kHz. In = the Raman spectrum a peak at ij = 161 cm- is evidence for a strong Ti-Pt bond.Two formal views of this bond are possible either as Pt"-Tl"' or as Pt"'-Tl'' with an electron-pair localized in a CT bond between the metal centres. In the "'Tl NMR spectrum the chemical shift 6 + 1337 is far outside the usual TI' region (6 f200) and is much lower than chemical shifts of other thallium(Ii1) cyano complexes (6 + 2000 to +3000).74 Aluminium Gallium Indium and Thallium Luminescent metal-metal-bonded exciplexes involving tetrakis(p-diphos-phonato)diplatinate(II) and thallium(1) with the species *Pt2Tl and *Pt2Tl have been described. These are two long-lived strongly phosphorescent triplet exciplexes involving the lowest-energy triplet excited state of [Pt2(P2H205)4]4- and T1’ in aqueous solution at room temperat~re.~’ Thallium has a very rich and interesting mineral chemistry many new minerals having been discovered from the Allchar region of Macedonia the latest being Jankovicite T~,S~,(AS,S~),S~~.~~ The crystal structure of this mineral shows it to be very similar to another thallium mineral Rebulite T~,S~,AS,S,,.~~ The crystal structure of the mineral Gillulyite Tl,(As,Sb),S 3 from the mercury-gold deposit of Tooele County Utah has been determined.In the structure the disordering of the position of one of the types of T1’ and the extreme distortion of its co-ordination polyhedron is probably the result of the T1+ 6s2 lone-pair effect.78 One interest in thallium minerals particularly Lorandite T~ASS,,~~,~~ comes with proposals for measuring the low-energy solar-neutrino flux averaged over geologic times using ,05Tl as detector., The thallium sulfarsenites Tl,AsS3 and TlAsS (Lorandite) were synthesized from approximately equimolar mixtures of TlNO and arsenic with an excess of sulfur in aqueous ammonia solution under hydrothermal conditions.The X-ray crystal- structure determinations were reported., The crystal structure of T11n5S6 a new mixed-valence ternary chalcogenide of indium and thallium has been determined. The atomic arrangement can be viewed as T1+(In,4+),(In3+)(S2-)6,with T1+ and In3+ and two distinct In,,’ ‘dumb bells’ with covalent In-In bonding. This is similar to the known indium sulfide In6S7 structure ~n+(~n,, +)(1n3 )3(S2-),.83 + Very low levels of thallium (5 ppb) have been determined spectrophotometrically the method involves preconcentration by extracting the chlorothallate ion-pair complex of a cationic surfactant with toluene.The extract was then treated with a basic dye such as brilliant green., Various crystallographic determinations of T1’ compounds have been described. In the tridymite-related compounds TlBePO and TlBeAsO the oxygen framework shows an unusual distortion again this was attributed to the stereochemically active T1’ 6.5 lone pair.*’ There is a lot of current general interest in pyrazolylborate ligands and the thallium(1) complexes { tris[3-(2-pyridyl)pyrazol-l-yl] borato)thallium(~)~~ and (hydrotris[3,5-bis(trifluoromethyl)pyrazolyl]borato}thallium(1)~~have been crystal- lographically characterized.In the dimeric anion [TI { Se,C=C(CN),),I2 - two TI atoms are co-ordinated by Se atoms of two different ligands forming a distorted orthorhombic bipyramid., The compound Tl[OC,,H,(OH)] derived from 2,2’-dihydroxybiphenyl is a dimer based on a T120 ring. Only one OH of the diol is deprotonated so that there is no chelation and the lattice involves intermolecular TI * * HO bonding.” Simple thallium(1) p-diketonates can give discotic structures via the formation of disc-like dimers by means of T1-T1 bonds reinforced with TI-0 bonds between neighbouring dimers.” Synthesized by electrocrystalhzation [TlAg60,] [ClO,] contains eight-co-ordina- ted thallium(rr1) and shows temperature-independent paramagnetism which appears to be caused by delocalization of unpaired electrons from Ag” into the conduction band.” No new thallium superconductor compounds were reported in 1995 except for J.P.Maher some thallium-based superconducting oxycarbonates with a T up to 70 K.’ Crystal-structure determinations for various organothallium compounds have been reported the heterobimetallic organothallium chelate complex tris[2-(dimethylaminomethyl)ferrocenyl]thallium7g3derivatives of dicyclohexyldithiophos-phinicacid [TlPh,{S2P(C6Hi 1)2}1 CT1Ph{S2P(C6Hi1),)2] and [T1{S2P(C,H,,),}3]* CHCl,’ and an arene-stabilized dimeric thallium(1) tetrachloroaluminate { [Tl(C,H,Me,- 1,3,5),] [A1C1,]},.95 The thallium(1) complex [Tl($ :q5C5 H,PPh,)] has polymeric zigzag chains of alternating thallium ions and cyclopentadienyl rings with the neighbouring chains connected by the weak P-TI atom interaction^.^^ Determination of the structures of species in aqueous solutions is never easy but considerable progress has now been made for thallium(II1) chloride bromide and cyanide complexes.The structures of [T1X,(OH,),](3-”)+ (X = C1 Br CN) were studied by a combination of XAFS large-angle X-ray scattering Raman and far-infrared spectroscopy and using some solid phases with known structures. Octahedral six-co-ordination was observed for [T1(OH2),l3 +,[T1X(OH,),I2 +,trans-[TlX2(OH,),] +,[TlCl,(OH,)]2 -and [TlCl,] 3-and trigonal-bipyramidal five-co- ordination for [TlBr,(OH,),] and possibly [TlCl,(OH,),]. The [TlX,] -complexes + are all tetrahedral. For [TIX(OH,),]2 and [TlX,(OH,),] +,TI-Br = 2.50(2) and 2.49(2)8, respectively TI-Cl = 2.37(2)8 for both complexes.The mean T1-0 bond distances increase slightly approximately by 0.04 8,from that for the [Tl(OH,)6]3 + ion at the formation of the first thallium halide complexes. A further more pronounced lengthening of about 0.1 Aoccurs when the second complex forms and it can be related to the relatively high bond strength in the trans-XT1X entity. In the TlCN complexes the [Tl(CN),]+ complex has a linear structure [TI-C = 2.11(2)8,] whilst the [Tl(CN),] -complex is tetrahedral with the CN- ligands linearly co-ordinated [TI-C = 2.19(2)8,]. A well defined second co-ordination sphere corresponding to at least eight water molecules at a thallium to oxygen distance of approximately4.3 8,was found around the complex which is probably trans-[Tl(CN),(OH,),] +.The complex [T1(CN),(OH2)] is thought to be pseudotetrahedral.” References 1 J.J. Eisch J. Organomet. Chem. 1995 500 101. 2 J. P. Oliver J. Organornet. Chem. 1995 500 269. 3 A.H. Cowley F. P. Gabbai H. S. Isom and A. Decken J. Organornet. Chern. 1995,500 81. 4 L. Contreras A. H. Cowley F. P. Gabbai R. A. Jones C. J. Carrano and M. R. Bond J. Organornet. Chem. 1995 489 C1. 5 D. Dou J. P. Liu J. A. K. Bauer G. T. Jordan and S.G. Shore Inorg. Chem. 1995,33 5443. 6 D.K. Russell T.A. Claxton A. S. Grady R.E. Linney Z. Mahmood and R. D. Maxwell J. Chem. Soc. Faraday Trans. 1995,91 30 15. 7 A. R. Barron Polyhedron 1995 14 3197. 8 A. Haaland K. G. Martinsen S.A. Shlykov H. V.Volden C. Dohrneier and H. Schnockel Organometallics 1995,14 31 16. 9 T. Belgardt J. Storre H. W. 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ISSN:0260-1818    

DOI:10.1039/IC9959200041

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

5 Carbon Silicon Germanium Tin and Lead By D.A. ARMITAGE Department of Chemistry King's College Strand London WCZR 2LS UK This review covers the literature for 1995. Carbon rings with 4n + 2 atoms favour a flattened structure. The cumulenes with a Dfn/2)hstructure have been found in a lower energy than the C(n,2)h structure of the cyclopolyyne for small C rings but the latter becomes more stable as n increases. Thus C, prefers D,, for CI4 D,h and C7h are nearly degenerate while C18 prefers a flattened circular polyyne c9h.I In an attempt to prepare the c180 fullerenyne comprising an icosahedral arrangement of cymantrene ([Mn(CO),(cp)]) residues bridged by 30 butadiynyl units [MnC,(CO),] 12-[C~C-CZC],~,a series of mono- and bis-(trimethylsilylethynyl) cymantrenes have been prepared.Desilylation and Hay coupling leads to oligomeric species up to the heptamer but they are unstable. Calculations have supported a tetracapped tetrahedron with a Tdstructure for the Ti,C, cluster. For the Til,C ,cluster a cube-like arrangement with Ti at the corners and C in the middle (face-centred cubic) is favoured. In the mass spectrometer the gas-phase reactions of V,,C, and V,,C, show sequential addition of eight moles + + of water to give hydrated hydroxides while eight moles of MeCN also adds sequentially. The Nb,C,+ cluster oxidizes to Nb,C,+ and reacts with water to give Nb4C40H+ while a range of NbC,' (n = 15-50) ion clusters occur as monocyclic rings (n < 22) and bicyclic rings graphitic sheets and metallof~llerenes.~ Heating erbium triiodide with erbium metal in the presence of carbon and NaN gives the carbide [Er14(C2)2(N)2]124 in which the tetrameric cation clusters comprise interconnected octahedra and tetrahedra filled with C and N respectively.The C-C bond distances are 144 ~m.~ The structure of tris(piperidino)cyclopropenium perchlor-ate shows short C-C distances of 137-139pm and C-N bonds of 133 pm supporting delocalization. With the bis(amino)chloro derivative [C,(NPr',),Cl] +,however two of the C-C bonds are significantly shorter (133pm) and one longer (143pm). The exocyclic C-N bonds are also shorter (127 and 130 pm).6 The reaction of osmocene and mercury(I1) acetate in I 1-dichloroethane gives the deca(acetoxymercurio) derivative which with CuX (X = C1 Br) and KI gives [Os($-C,X,),].The structure of the decachloro derivative shows the rings eclipsed and is isomorphous with the ruthenium analogue with the 0s-C bonds being very similar in length to the Ru-C bonds of the ruthenium deri~ative.~ + The sequential bond dissociation energies of [Cu(CO),] + and [Ag(CO),] (x = 1-4) increase up to x = 2 then decrease. A comparison with the isoelectronic [Ni(CO),] and [Co(CO),] -provides evidence for the increasing importance of n-back bonding as 53 D.A. Armitage electron density at the metal increases.8 Reducing [UCl(C,Me,H),] followed by carbonylation gives the first isolable carbonyl of an actinide [U(CO)(C,Me,H),]. The low carbonyl stretching frequency at 1900cm-'and short U-CO bond suggests strong back b~nding.~ The first metaloxyketene complexes (1)result through 'double insertion' of carbon monoxide into thorium-silicon bonds.Ketene absorption bands at 2044 and 1244cm-' for the pink complexes support the structure with the ketene angle 174" (Scheme l)." I R3 = (SiMe3)3 or Bu'Ph2 SiR3 lC0 CI Scheme 1 Carbon suboxide does not hydrolyse as readily as ketene in neutral and acid catalysed conditions by three to four orders of magnitude in support of ab initio calculations providing some support for its detection recently in the water-ice of comet Halley.' ' The calculated electronic spectra of polythiene suggest a polytrithiapentalene structure comprising a central carbon chain with sulfur atoms bonding to each carbon and to each other.This structure (2) is more stable than the polythioketone structure (3).' Carbon disulfide irradiated at 313 nm gives a polymeric solid of relative density 1.92 (liquid CS, 1.26) and vibrational data suggest trithiocarbonate groups with extensive S-S cross linking.' Carbon Silicon Germanium Tin and Lead Treating C,S,O (4) with base then [NEt,]Br gives the salt [NEt,],[C,S,] (5) with the planar anion showing extensive n delocalization. It readily complexes with both Ni2+ and Cu2 + to give semiconductors.14 A range of 2-thioxo-1,3-dithiole-4,5-dithiolates of Cu" have been made while [C,S,Se]2 -gives [Re,(C,S,Se),12 -which shows conductivity and has two dithiolate groups half bridging the Re-Re bond and the other three chelating the Re atoms (6) two on one and one on an~ther.'~ Oxidizing Ph,CSH with 4-MeC6H4SO2NSC1 in CS gives the perthiocarbonate Ph,CSSC(S)SCPh,*CS,.The structure shows the CS group to be planar and the S-S bond 201.4 pm.16 Treating Na,[PdCl,] and Na,S with [MeN(C,H,),NMe]I in MeOH at 110 "C gives the [Pd6(c2S6)(s,)6l6- cluster. The centrosymmetric hexa- thioorthooxalate anion c2s66-provides the central group and Pd atoms bridge pairs of sulfur atoms of this anion while S,,-anions bridge pairs of Pd atoms. The carbon atoms of the orthooxalate group are thought to result through demethylation of the amino cation. At 80 "C with PdCl, the [Pd6(C2S,)(S,),(S,),]6- anion res~1ts.l~ Photolysing the acylsilane (7) gives two geometric silene isomers which give PhCECH adducts at 90 "C and isomeric MeOH adducts at 100"C [equation (l)].Extensive heating in an attempt to eliminate (SiMe,),O and form the silyne results in extrusion and formation of (8) which adds PhCGCH and MeOH more readily [equation (2)].18 (7) (ratio 2 :1) R = adamantyl Me R Me Si \si-cP 120% si=c: 3 2,4,6-Pi3H2$ 'R 5d 2.4,6-Pi3H2$ SiMe2(OSiMe3) The ruthenium complex (9) which results from [RuCl(cp*){ P(C6Hl 1)3)] and Ph,C=C(Li)(SiHMe,) supports 1-silaallene co-ordination with the Si-C bond of the silaallene chain 180.5 pm shorter than the two terminal Si-C bonds of 186 and 188 pm and a Si-C-C angle of 128.9".19 D.A. Armitage The recent synthesis of [R~H(cp*)(q~-Me,C,SiSi(SiMe,)~)1 '[BPh,] -represents the preparation of the first $-silole complex.A structure determination indicated a planar structure for the silole ring and delocalization. This is also supported by the $-co-ordination of Li'in Li+ [Si(CH),H] -which increases delocalization and aromaticity relative to the parent anion. It shows 80% of the stabilization energy of Li+[C5H5]- but only 55% if not complexed vsto Li.,' Reducing 1,1-dichloro-2,3,4,5-tetraphenyl-l-silacyclopentadiene with lithium gives the q',q5-dilithiosilole solvated with thf three molecules for ql-Li and two for qs-Li. The Si-C bonds (184 and 185pm) are shorter than single bonds and the Si atom projects just 11 pm out of the plane.,' The germacyclopentadienide anion results from the deprotonation of the substituted germacyclopentadiene with base using either KN(SiMe3),-18-crown-6 or LiBu"-12-crown-4.The structure of the latter derivative (10)shows considerable pyramidalization at Ge with the angle between the GeC plane and Si being 100.1". Also the Ge-C bond length appears a little longer (196 and 201 pm) than those in the parent germane (194.4 and 194.8pm) [equation (3)]. Calculations support less aromaticity in the Ge derivative than in the Si one. This contrasts with the Ru derivative where the Ge-C bonds are 190.0 and 189.9pm.22 . 1 #H . .-I LiBu" 12-crown-A (3) .-.-... . . 'Si(SiMe& 'Si(SiMe3) The two salts [K(C6H6)]+[K{C(SiMe3)2(SiMe2Ph))2]-and [K(OSiMe,),] +-[K(C(SiMe,),[SiMe,(HC=CH,)]),] -result from the trisilylmethane and KMe the structure of the former indicating a Ph-K+-C6H6 sandwich with the potassium of the anion interacting strongly with the tertiary carbon atoms of two trisilylmethyl groups and with six methyl groups of separate silyl groups.23 Calculations suggest that the silylium cations give a 6(29Si)shift in the gas phase of 400 ppm and in non-co-ordinating solvents of 370-400ppm.Values less than this result for solvents with increasing co-ordinating ability. It has been suggested that carbocations disperse the positive charge more effectively so interact less effectively with the solvent.24 In the gas phase it is suggested that [SiR,-arene] complexes exist + as a Q complex although a .n one is not ruled Adding silyl enol ethers to a-asymmetric aldehydes using the supersilylating agent [SIR,] [B(O,SCF,),] as Carbon Silicon Germanium Tin and Lead catalyst indicates a level of Cram-type selectivity that correlates with the steric bulk of the silyl group with the triisopropylsilyl enol ether resulting in unprecedented 1,2-asymmetric induction [equation (4)].26 (97%)Cram (1%) antKram Gaseous SiMe,' interacts with the arylgermanes GeMe,(C,H,X) (X = H Me) to give the arylsilane and extrude the germyl cation.,' The trifluoromethanesulfonates (triflates) [GeMe,][B(O,SCF,),] and [SnEt,][B(O,SCF,),] hydrolyse to give the protonated bis(germy1)- and bis(stanny1)-oxonium salts.The structures indicate that the M-0 bond lengths increase 13 and 16pm respectively from those in (Ph,M),O (M =Ge Sn) with pronounced germylium and stannylium character and with tetrahedral flattening.28 With [SiMe,][B(O,SCF,),] bis[2-(dimethylaminomethyl)phenyl]silane and [(2- dimethylaminomethyl)phenyl]phenylsilane give the amino-co-ordinated silyl triflate.The former exists with a five-co-ordinate isolated cation but that of the latter is a very tight ion pair with the triflate group occupying one axial position around the trigonal-bipyramidal silicon.29 The reaction of !,2-dimethyl-1,2-disila-closo-dodecaborane( 12)Me2Si,Bl,Hl with alkali and then [NMe,]Cl gives [NMe,]+[MeSiB,,H,,]- in which one silicon atom has been removed from the Si,B icosahedral cage. 1,2-Dicarba-closo-dodecaborane( 12) alsc loses boron under strongly basic conditions. It has C symmetry with a protonated ollide-like structure possessing an open B,SiMe ring with two bridging hydrogen atoms.This is supported by the "B NMR spectrum which shows six signals in the ratio 1:2 2 2 2 1. The Si-B bonds are in the range 203.6-206.9 pm.,' The highly hindered disilene R(mes)Si=Si(mes)R {R = C6H,[CH(SiMe,),],-2,4,6) results from the reductive coupling of the dibromide with lithium naphthalenide. The (E) and (2)isomers show a remarkable pyramidalization at silicon and long Si=Si double bonds of 222.8 and 219.5 pm respectively. Both dissociate to the silylene at 70 "C and are air stable but eventually give the 1,3-dioxa-2,4-disiletane after 40d.,l The unsymmetrical disilene (rnes),Si=Si(C,H,Pr',-2,4,6) with rn-chloroperbenzoic acid gives the oxadisilirane while 0 gives the 1,3-dioxa-2,4-disiletane.With (mes),Si=Si(mes) and stilbene oxide the 3-oxa-1,2-disilacyclopropaneis formed together with the 2,4-dioxa- 1,3-disilacyclohexane and cyclodisiloxane.32 Treatment of (mes)(Bu')Si=Si(Bu')(mes) with sulfur gives a mixture of episulfide isomers.33 The disilirane (11) reacts with the dimetallofullerenes La,@C,, La@C8 and Sc,@C, to give the disi!acyclopentane derivative through addition to a C-C bond of the fullerene [equation (5)]. The gadolinium derivative Ga@C, reacts similarly and its ionization potential (6.25 eV) is similar to that of the lanthanum compound and is more reactive than C, which has a higher ionization potential (6.96 eV)., Cyclotetra- silanes and -germanes both add photolytically to c6 to give stable 1 1 adducts [( 12) and (1 3)] which result through rearrangement of the tetrasilane or tetragermane unit [Equation (6)].Photolysing [SiBu',] gives Si,(H)Bu' through disilene formation which dimerizes with loss of isobutene. The four-membered ring is slightly folded with two very long Si-Si bonds of253.8 pm. This ring also results from SiCl,Bu' and The highly D.A. Armitage branched decasilane (Me,Si),SiSiMe,SiMe,Si(SiMe,) results as crystals from Li(thf),Si(SiMe,) and shows Si-Si bonds of 234-237 pm while photolysis with CCl leads to cleavage of the central Si-Si bond.37 Condensing MM’Bu‘ (M = Si M’ = Na; M = Ge M’ = Li) with GeCl,*dioxane in thf gives the novel cyclotrigermene ring (14) with an isosceles structure with Ge=Ge 223.9pm7 some 28pm shorter than the other two ring bonds.The exocyclic Ge-Si bonds are 244.8 (Si-Ge=Ge) and 262.9 pm (Si-Ge-Ge much greater hindrance). It does not react with EtOH or CH,N but is oxidized by tcne at 100°C to Si(H)Bu‘ and But3 SiS iB u‘,. 4,8-Dihalogenooctakis( 1,1,2- trimethylpropyl)tetracyclo[3.3.O.O2~7.03~6]octasilanes (15)(X=Cl Br I) can be reductively dehalogenated with sodium to give red crystals of the octasilacubane together with the colourless dihydride (15) (X = H) with Si-Si 234.2-246.1 pm.,’ A higher isotactic polysilane results on reducing dichloro(methylpheny1)silanewith graphite-potassium C8K rather than an alkali metal. The molecular weight ap- proaches 100 OO0.40 The first reported tetraaryldistannene results from SnC1 and the Grignard reagent Carbon Silicon Germanium Tin and Lead 2-Bu'-4,5,6-Me3C,HMgBr.It is the monomeric stannylene in solution but dimerizes on crystallization with a long Sn-Sn bond of 291.0pmY a trans bent structure and fold angles of 21.4 and 64.4".,' The barium europium silicide Ba,Eu,Si comprises infinite chains of C3.3.3)baralene units comprising Si ,units (16) with elongated Si-Si bonds (241-244pm).* The nido lead cluster completes the series Pbg4- and is formed as a K+(K(cryptand- 222)') derivative with C, symmetry in the presence of a stoichiometric deficiency of cryptand 222. An excess of the cryptand gives Pb,[K(cryptand 222)] with a C, structure.43 Heating lead dioxide and potassium gives the basic hydroxide K,,Pb,O,(OH) which contains Pb,4- tetrahedra (Pb-Pb 310-31 1pm) which are also present in K4Pb4.44 The germylene :Ge[N(SiMe,),] displaces CO from the oxalate complex [Pt(C,O,)(PEt,),] in refluxing benzene to give the metal germylene derivative with planar geometry at Pt and Ge and a short Pt-Ge bond.45 With :Ge[CH(SiMe,),J addition to ethylene gives the unstable germirane which adds further germylene to give the 1,2-digerma~yclobutane.~~ Reducing this germylene and the analogous stannylene with sodium gives the radical anions the ESR spectra supportinglittle s character with the n radical^.^' The stannylene :Sn(C6H,Bu',-2,4,6) rearranges in solution to reduce crowding and gives :Sn(C,H,B~',-2,4,6)(~~,~~e,~~~~Bu~,-3,~).This reacts with [W(CO),(thf)] to give the Sn=W complex with trigonal-planar tin.With selenium the Sn,Se ring results.48 Treating :Pb[N(SiMe,),j' with KSi(SiMe,) gives black crystals of :Pb[Si(Si- Me,),],. The structure shows Pb-Si bonds of 270 pm and a SiPbSi angle of 114". The tin analogue can be prepared similarly but crystallizes as the distannene with a trans bent conformation and a Sn-Sn bond of 282pm in the single bond range.49 The stannocenes :Sn(C,H,Pr',-1,2,4) and :Sn(C,HPri4-1,2,3,4) result from the cyclopentadienylpotassium derivatives and SnCl in thf. The former is an air-sensitive oil and the latter an air-stable solid possessing a bent metallocene geometry like the calcium derivative." The lead derivatives :Pb(C,H,Bu',-1,2,4) (17) :Pb(C,HPr',-1,2,3,4) and Pb(C,Pr',) can be similarly prepared from the lithium cyclopentadienide while (17) also results remarkably from Pbg4- and [BiC1(C,H,Bu'3-1,2,4)2].51 With [Pb(cp),] and [Li(cp)] in 12-crown-4 a mixture of anionic sandwich complexes result in the formation of [Pb,(~p),]-[Pb~(cp)~]- [Li(12-crown-4)J2+.The polydecker sandwiches in the anions comprise Pb atoms trigonally bonded to three cp residues. By way of contrast [Sn(cp),] and [Li(cp)] give a paddle-wheel anion [Sn(cp),] -[Li(l2- crown4),] .52 + The first monoorganolead(I1) derivative [{Pb(p-Cl)[C(SiMe,Ph),]},] results from [Li(thf),{C(SiMe,Ph),}] and PbC1 as a yellow-orange solid with a centrosymmetric molecule with chloride bridges of 272.9 and 296.2pm and a stereochemically active lone pair., The Si-H addition to transition-metal complexes has long been known and that of trichlorosilane to [Cr($-arene)(CO),] occurs photolytically to give the Cr'" derivative (18) [equation (7)].There is no evidence to support either q2-HSiC1 or q2-H,bonding. Codepositing iron atoms and an excess of arene followed by addition of HSiCl gives the [Fe($-arene)(H),(SiCl,),] with J(29Si-1H) coupling constants of 15 Hz compared with 370 Hz for HSiCl, and supporting a Fe" complex with no q2-co-ordination.54 hv [Cr(q6-arene)(CO),] HSICI,-[Cr($-arene)(C0)2(SiC1&] + [Cr(q6-arene)H2(SiCI&] (7) (18) D.A. Armitage Trifluorosilane reacts similarly to give the first trifluorosilyl hydrido transition- metal complex [Fe(rf-C H Me)(H),(SiF,),] with the 'H NMR spectrum showing a septet with ,J(H-F) 9.2 &z.'~ The first transition-metal complex with silane SiH bonded q2 results from [Mo(CO)(R2PC2H,PR2),] (R = Ph Bu') and SiH,.The q2 bonding is supported by J(Si-H) 50 and 31 Hz and the structure of the Bu' derivative while in solution both the Bu' and Et derivatives show an equilibrium in which the q2 species and the seven-co-ordinate silyl hydride derivative is present [equation (8)].56 I SiH3 \SiH 0SiH2 Reaction of [{RuH,(cp*)),] with SiH2But2 leads to the three-membered Ru,Si ring in which the Si-H bonds act predominantly as an v2-ligand to the metal since J(Si-H) is 75 Hz. While an excess of SiH,Bu' does not react because of size less hindered silanes give a second bridge and q2 bonding from each Si-H bond.57 1,2-Disilylbenzene reacts with [Pt(PEt,),] at 80°C to give the first PtIvSi,P2 species (19) with octahedrally arranged substituents and cis phosphines.It reacts with more [Pt(PEt,)J to give the mixed-valence Pt"-Pt"' derivative (20) [equation (9)].58 Heating silicon diimide with alkaline-earth metals at about 1600 "C gives the nitrido silicates M2Si5N8 (M = Ca Sr Ba) in which the anion comprises a three-dimensional lattice of interconnected SIN tetrahedra in which the nitrogen atoms interact with either two or three silicon atoms in equal proportions. Lanthanide metals react similarly to give both LnSi,N and Ln,Si,N the SIN tetrahedra giving a zeolite-like lattice." Two tris(amin0)silanes RSi(NH,) have been prepared from the hindered trichlor- ides RSiCl (R = 2,6-Pri2C6H,NSiMe or 2,4,6-Bu',C6H20) using ammonia.While both have Si-N bond lengths in the range 169-172pm the NSiN angles vary from 101 to 123°.60 The tris(ptolysily1)amine is planar with Si-N bond lengths 172.8-1 73.6 ~m.~' 1,4,7,10-Tetraazacyclododecanereacts with MeSiC1 in the presence of NEtPr' to precipitate two moles of the base HC1 and gives the five-co-ordinate salt (21) which with an excess of LiBu" gives (22) which can be alkylated stepwise to give both mono- and 1,7-di-substituted macrocycles on hydrolysis [equation ( The compound [Si(NHSiMe,Bu'>,F(Ph)] reacts with LiBu' to give Carbon Silicon,Germanium Tin and Lead [Si(NLiSiMe,Bu'),F(Ph)]. Lithium fluoride loss in the presence of thf gives the silaamidide which is isolated as the cyclodisilazane anion (23) m.p.290°C. The endocyclic bonds (171-177pm) are much longer than the exocyclic ones (165.0 and 165.6pm) and the Si,N ring is not planar [equation (ll)].63 -+ I - CI- 3LiBu" (r) R'x __F (ir)R"X; (iii)H30+ 1- The amido germanates K,[GeO,NH,] and K,[GeO,NH,].K[NH,] result from GeO and KNH in supercritical ammonia at 450 "C in high-pressure autoclaves for days. The former contains tetrahedral GeO,NH,,- anions which are connected in chains by N-H.. * 0 bridges (218-240pm) while the latter contains GeO,NH,,- and NH,-ions with N-H...N hydrogen bonds (241-261 The hindered aminogermane (mes),Ge(Br)-NH(C6H,F,-2,4,6) on lithiation and heating eliminates LiBr to give the cyclodigermazane and the germaimine which adds chloroform across the Ge=N double bond and the nitrone (24) to give the five- membered heterocycle (25) (Scheme 2).65 R IN'CHPh -phCH=N(O)BU' (2-\O.~~~t LiBu" (mes)2Ge(Br)-NHR (me~)~Ge=NFi ycct3 (25) R = CeH2F3-2,4,6 Scheme 2 Condensing Sn(NMe,) with primary amines RNH provides a convenient route to imidotin(1r) tetramers [Sn(NR)] with cubane-like structures.66 The triorganotin fluoride hydrates [N(CH,CH,CH,),]SnF*H,O and [MeN(CH,CH,CH,),]-SnF(Me).H,O result from exchange of an Sn-Me group with SnFPr",.The former is a tetramer with intermolecular Sn -F interactions and hydrogen bonding and is the first intermolecular six-co-ordinate triorganotin fluoride. The metallotranes SnXN(CH,CH,CH,) (X = C1 Br I) show Sn.*.N interactions of about 238~rn.~' The first lanthanide tris(phosphid0) complexes [M(thf),{P(SiMe,),),] (M = Tm Nd) show trigonal-pyramidal co-ordination with the phosphido groups equatorial.68 62 D.A.Armitage With P(SiMe,), [Mo(CO),(cp)InCl,] gives the tetrameric cluster [{ Mo(CO),(cp)),In,(P(SiMe,)),] with a heterocubane-like In,P structure and Si-P bonds of 223.5 to 225.4~m.~' The first structurally characterized Si-P and Si-As multiple bonds (26) result from [SiF,Bu'(C6H,Pr',-2,4,6)] on reaction with [Li(EH,)(dme)] (E = P As) (Scheme 3). The disilaphosphene shows silicon-phosphorus bonds of 206.2 and 225.5 pm and the arsene analogue has silicon-arsenic bonds of 216.4 and 236.3 pm. The tellurium adduct of the arsene has Si-As 235.4 (endocyclic) and 239.6pm (exocyclic) and Si-Te 249.1 E = PIAS;R = C~H2Pj3-2~4~6 (26) E=As Te I Scheme 3 A range of thermally stable phosphine- and arsine-substituted carbene analogues result from the silyl-phosphides and -arsenides with Ge Sn or Pb dihalides and are either green or yellow-brown [equation (1211.Calculations indicate the carbene to be increasingly preferred to the double-bonded isomer as the atomic weight of M increases [equation (1 3)]. Reaction of the disilazane derivatives M[N(SiMe,),] (M = Ca Sr) with AsH(SiMe,) gives the alkaline-earth arsenides solvated with four moles of thf. The structures have octahedral co-ordination with trans arsenide ligands. The As-M-As unit is almost linear but in the Sr case one arsenic is trigonal planar and the other pyramidal.72 Condensing (2,4,6-Bu',C,H2)COC1 with Li[Sb(SiMe,),(dme)] gives the acylstibine which isomerizes through silyl migration then loses Si,Me6 to give the siloxy- substituted 2,3-distibabutadiene (27) [equation (14)].' Condensing SnCl,Me with K,[Bu'P(PBu'),PBu'] or K2[Bu'PPBuL] gives the SnP and Sn(P,),Sn rings the latter with a boat conformation showing Sn-P bonds 250-253 pm.74 The first accurate silyl cyanate structure has been determined for (Me,Si),(PhMe,Si)CSiMe,OCN.The Si-0 bond of 173.8pm is long and the SiOC bond angle is 126.7" with NCO almost linear (176.5"). This contrasts with the isocyanate (PhMe,Si),CSiMe,NCO in which Si-N is 173.9 pm and SiNC and NCO 155.7 and 175.9".75 While [Si(thf),](cat) and Li,[Si(cat),(dme),].O.Sdme show octahedral co-ordina- tion at Si the former with trans thf ligands the ethane-1,2-diol derivative [NaSi(C,H,0,),(C,H502)] shows one ligand monodentate and Si five-co-ordinate.The unbound OH group hydrogen bonds to adjacent oxygen atoms to give a tetrameric unit. Germanium is similarly five-co-ordinate in the complex Carbon Silicon Germanium Tin and Lead 63 R3Si\ MX2 ELi(thf)2 -[M{E(SiR'3)SiR3}2] (12) R;Si' E = P M = Ge Sn Pb; E = As M = Sn H H\ ,M=P\ H2P H R -Si,M+ RC(0)Sb(SiMe3)2 -RC(OSiMe3)= Sb(SiMe3) -(Me3Si)OC.r (14) Sb-Sb\\ R = C6H2BUt3-2,4,6 ,C(OSiMe3) R Na[Ge(OH)(C,H ,02),].3MeOH formed from GeO, pinacol and MeOH. The equatorial Ge-OH bond is shorter than the other two equatorial Ge-0 bonds.76 Oxidizing [(cp*)(OC),(Me3P)MSiH3] (M = Mo W) with dimethyldioxirane gives the metallosilanetriol which condenses with Me,Si(H)Cl to give branched siloxanes functionally substituted by Si-H.The silane diol [(C~*)(OC),(M~,P)MOS~M~(OH)~] crystallizes as a centrosymmetric hydrogen-bonded dimer the six-membered Si,O ring having a chair conformation with 0 -* 0 distances of 284 pm.77 The hindered germylene :Ge(C,H,Pri,-2,4,6)(C6H2[CH(SiMe3)2]3-2,4,6} can be oxidized to the germanone with (PhCH,),N+O. It adds to mesitonitrile oxide and slowly decomposes in solution to give isomeric intramolecular cycloaddition products [equation (15)].78 O(SiMe3) I HC(SiMe3) Both Sn" and Pb" form hydroxide clusters with [Sn3(OH),][NO3] possessing a six-membered ring structure (28) with the nitrate groups completing the SnO octahedra.With [Pb,(OH),][NO,] the four lead atoms are arranged in a tetrahedron with the OH groups bridging faces.79 With [Sn(OBu'),] and [Sn(OAc),] in refluxing toluene the hexagonal tub-like derivative [Sn,O,(OBU'),(O,CMe),] results. In pyridine however the exchange products [S~(OBU'),(OAC),-~] (x = 1,2,3) result. Using [Pb(OAc),] gives [PbSn,(p3- O)(OBu'),(OAc),] in toluene with structure (29) showing SnlV and Pb". In pyridine only [Sn(OBu'),(OAc)(py)] and [Pb(OAc),(OBu')] result. Transalcoholysis of [Sn(OBu'),] with an excess of Bu'OH gives [(Sn(OBui),(HOBui)},] quantitatively. D.A. Armitage H 12+ The ecige-bridged bioctahedral Sn unit is centrosymmetric and comprises a pair of intramolecular hydrogen bridges between apical co-ordinated alcohol and apical a1 koxide.meso-Oxolane-3,4-diolate gives a monohydrate with Pb" which is a one-dimensional polymer with Pb,O bridges formed from the diolate groups with water also co-ordinating to Pb".81 A structure determination of a diastereomer of AgLa,GeS shows a chain of AgS units co-ordinating to La in La,GeS cubane-like sub-units interconnected through Ge-S bonds.82 Heating freshly precipitated GeS and NEt,+HCO -with copper(I1) acetate gives crystals of [NEt,][CuGe,S,] comprising Ge,SIo4- clusters.83 With [PPh,][SnCl,] Na,S gives the Sn" derivative Sn(S,),,-with an octahedral structure while (Sn,S,)(NHMe,) consists of sheets with 24-membered rings compris- ing six Sn,S units interconnected through sulfide bridges at each tin atom to compose a two-dimensional network with each tin atom being fi~e-co-ordinate.~ The selenide and telluride Rb,GeX (X =Se Te) result from Rb,CO, Ge and the chalcogen on heating.The selenium derivative comprises chains of GeSe tetrahedra connected through Se-Se bonds with terminal (227-230 pm) and bridging (242-243.7pm) Ge-Se bonds. In addition Rb,Ge,Se,,.MeOH is formed and has an adamantane-like structure with terminal Ge-Se bonds of 225pm and cage ones of 234-239~m.~~ Reducing the alloy Bi,Sn,Se with potassium in the presence of [PPh,]Br gives [PPh,],[Sn,Se,Ph,]. The anion has a square-planar Sn,Se ring with trans phenyl groups and trans exo selenium atoms.86 Oxidative addition of SiH,Ph to [Rh(SR)(PMe,),] (R =aryl) gives the complex mer-[RhH(SiHPh,)(SR)(PMe,),] which isomerizes through SR transfer to Si to give the complex ~~c-[R~H,(S~P~,SR)(PM~,),].~~ The first 2,4,5~trithia-1,3-disilabicyclo[ 1.1.llpentaneresults from the desulfurization of the tetrathia[2.l.l]hexane itself resulting as the major product of the pyrolysis of (Me,Si),CSiH with an excess of sulfur in decahydronaphthalene.The Si * -Si distance of 240.5pm is within the range of Si-Si single bonds. The germanium-selenium analogue can be prepared similarly and shows the bridgehead Ge **-Ge bond slightly longer than the single bond value.88 Sulfur reacts with [GeH,(mes)(R)] {R =C,H,[CH(SiMe,),],-2,4,6} at 160 "C to give the tetrathiagermolene. With Ph,CN, the heterocycles (30k(32) result [equation (16)].89 The stannylene :SnR(R') (R =C,H,Pr',-2,4,6) and selenium form monomeric Se=SnR(R') which gives heterocycles with PhNCS R"CN-+O (R" =aryl) and styrene Carbon Silicon Germanium Tin and Lead oxide the former giving the dithia- and diselena-stannetanes (33) and (34) and not the mixed derivative.With CS, the 1 1 adduct results and with an excess of CS, gives the unsymmetric olefin (35) which thermolyses to the symmetric olefin (36) through CS loss while olefins add to the 1 1 adduct to give cyclic products (37) (Scheme 4).” The plumbylene :PbR(R’) and sulfur give the tetrathiapl~mbolane.’~ The novel gaseous cation F,SiXe+ results from the displacement of HF from protonated SiF in the gas phase with Xe and has C, symmetry and a Si-Xe bond length of 254.1 Reacting SiPh,OH with HF and NBu”,F gives the salt [NBu”,][SiF,Ph,].This readily fluorinates alkyl halides and p-toluenesulfonates. Similarly 4,4’-[(EtO),Et- Si],biphenyl gives the trifluorosiliconate with HF-NBu”,F or HF-KF-18-cr0wn-6.~~ The salts M+[SiF,(C,F,)]- result from MF (M = K Cs NMe,) and SiF,(C,F,) in PhNCS R R ,Se -Sn/’>NPh + Sn PNPh RI’ \Se R” \s Scheme 4 D. A. Armitage MeCN or bis(2-methoxyethyl) ether and react readily with electrophiles with cleavage of the aryl-Si bond.' The intramolecular fluoride donor-acceptor system involving m-and [p-(difluorophenylsilyl)phenyl]trifluorophenyl silicate undergoes bimolecular exchange through a cyclophane-like transition state on the basis of the 13C NMR spec tr um.The tetrahedral [(Al(cp*)},] reacts with two moles of SiF,Ph to give fluoride addition across four of the Al-A1 bonds and SiPh insertion into the other two. The resulting eight-membered A14F4 ring is therefore bridged by two SiPh groups with A1-Si bonds 245.1 pm [equation (17)].96 The chelating halide-ion acceptors Ph,XSn(CH,),SnXPh (X = F C1 Br I; n = 1,2 3) all chelate a single halide ion fluoride preferentially while for n = 1 an excess of fluoride gives the dianions [Ph2F2SnCH,SnF,Ph2]2-.97The SnF,- anion crystal- lizes as a discrete trigonal pyramid in [SnF,],[Ni(H,O),] with Sn-F 204-206 ~m.'~ Lead@) iodide reacts with NaI and NBu",PF to give the complex iodide-bridged anion Pb,& with D, symmetry in which each lead atom is octahedrally co-ordinated to six iodine atoms.These octahedra are connected through layers comprising 1,4,8,4 and 1 lead atoms respectively in a Chinese-puzzle type of arrangement." 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ISSN:0260-1818    

DOI:10.1039/IC9959200053

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

6 Nitrogen Phosphorus Arsenic Antimony and Bismuth By K.K. HI1 Dyson Perrins Laboratory South Parks Road Oxford OX1 3QY UK and T.P. KEE School of Chemistry University of Leeds Leeds LS2 9JK UK 1 Introduction This report covers important aspects in the development of Group 15 chemistry during the year 1995. A comprehensive review is unfortunately beyond the remit of this article and attention has therefore been focused on the areas of metalloorganic and co-ordination chemistry. In the field of phosphine chemistry where more than 1000 articles were published during 1995 according to the Chemical Abstracts Service only synthetic work on novel asymmetric phosphines is described with particular emphasis on applications in asymmetric catalysis. For a description of this area covering the 1994 literature the interested reader is directed to a previous review.' 2 Nitrogen The organometallic chemistry of aryldiazenido arylazo complexes of transition metals has been reviewed.* Hydrazido(2-) complexes (2) trans-[MX(NNH,)(dppe),]+ (M = Mo W; X = F C1) and cis,rner-[WX,(NNH,)(PMe,Ph),] (X = C1 Br) which are readily derived from trans-[M(N,),(dppe),] and c~~-[W(N,)~(PM~,P~),] (1)have been found to react with 71 K.K.Hii and T.P. Kee 2,5-dimethoxytetrahydrofuran to give pyrrol- 1-ylimido complexes (3) trans-+ [MX(NNCH=CHCH=C H)(dppe),I3 and cis,mer-[WX,(NNCH=CHCH=C H)-(PMe,Ph),] respectively. Electrophilic substitution reactions at the pyrrole rings occur selectively at the P-position to give the pyrrolylimido complexes trans-+ [MX{NNCH=C(E)CH=C H}(dppe),] (E = Br CN SO, COR) which are reduced by LiAlH to liberate pyrrole and N-aminopyrrole in high yield^.^ The chemistry of bis(2-pyridy1)phosphides and bis(2-pyridy1)arsenides with Group 13 metals has been in~estigated.~ Single-crystal X-ray diffraction analyses revealed no contact between the metal centre and the central phosphorus or arsenic atoms of the ligand.The [E(py),]- ions (E = P As) bind to the metal exclusively through both pyridyl nitrogen atoms (4). The reaction of [RuCl,(terpy)] with potentially cyclometallating 2,2’ 6,4”-ter- pyridine results in the formation of the complex ions [RuCl(terpy-N,N,N)(terpy-+ N,N,C)]+ and [R~(terpy-N,N,N)(terpy-N,N,C)]~ in which the cyclometallated ligand is protonated on the non-co-ordinating nitrogen atom.If ethane-1,2-diol is used as the solvent the latter complex is the major product while use of glacial acetic acid as solvent favours the former. The electron-withdrawing pyridinium functionality significantly affects the properties of this complex. Both complexes have been fully characterized and studied by cyclic voltammetry and electronic spectro~copy.~ New monocyclopentadienyl complexes of titanium(1v) with linked pyrrolidine and piperidine functions have been synthesized. The first X-ray crystal-structure determi- nation of a titanium complex stabilized through an intramolecular nitrogen donor has been reported.6 The complexes [Re(CO)3(NH,R),(C(NHPh)(NHR))]+Br-(e.g. 5 R = Ph) were synthesized from [ReBr(CO),(CNPh)] by successive reactions of rhenium isocyanide complexes with nitrogen-containing ligands and a crystal structure has been de~cribed.~ But But CI-+p\ IN\ Te\ J’e=NBut ButN=Te Te=NBut BlifClN’ N \N’ ” ..I.But But But Nitrogen Phosphorus Arsenic Antimony and Bismuth Rings containing tellurium-nitrogen double bonds [Te,(NBu'),(NHBu')]Cl (6) [(T~(~-NBU')(NBU'))~] (7)and [{Te(NBu')),] (8) have been reported for the first time.* (9) n Q NH HN rNH HN-\ 60H Hob OOH HOa The class of tetradentate N,O compounds (9),(lo) (1 l) (12) and (13) have revealed a wide range of chemistry with AlMe to produce complexes of the form AlMe(H,L) and [AI(AIMe,)L] respectively. The novel trimetallic complexes (AlMe)(AlMe,),L have also been synthesized and characterized via single-crystal X-ray diffra~tion.~ The reaction of [RU(C,H,M~-~,~-P~')(O,SCF~)~]X with a series of indoles has led to the synthesis of new ruthenium(r1) indole complexes of formula [RuL(C,H,Me- 1,4- Pri)][03SCF3] (14) (L = indole 1-methylindole 2,3-dimethylindole 2-methylin- dole).The indole nitrogen can be deprotonated to form the corresponding monoca- tions. Aqueous pK values for the indole ligands have been determined by titration. Reaction of the cations with palladium complexes affords heteronuclear compounds." A variety of 8-amino-and 8-amido-substituted quinolines (15) react with [IrH,(PPh,),(OCMe,),]SbF to give a series of complexes in which the amine or K.K.Hii and T.P. Kee R = H COBu' SiMe2Bu',COMe amide nitrogen atom binds to the metal. Definitive evidence for a lone-pair bound structure was obtained from natural-abundance I5N heteronuclear multiple-quantum coherence spectroscopy and proton nuclear Overhauser effect data. The amine or amide N therefore rehybridizes to sp3 on binding a previously unreported complexa- tion mode for undeprotonated amides.' ' The 4-ethylpyridyl functionalized compound (16) has been prepared its protonation and complexation properties toward copper(1r) ions have been studied in aqueous solution and binding constants have been determined. The resulting complex contains a free pyridine unit capable of co-ordinating to a second metal centre such as a cis-[PtCl,] unit. The resulting species represent the first example of a supramolecular compound which contains exchangeable peripheral transition-metal cations.A new potentially pentadentate (ONNNO donor) compound 6,6"-bis(2-hy-droxypheny1)-2,2' 6',2"-terpyridine (17 H2L) reacted with Cu" to give [Cu(HL),]- [PF6I2,the crystal structure of which has been rep~rted.'~ The copper ion was found to be co-ordinated by one phenolate oxygen and three pyridyl nitrogen atoms of HL with the remaining phenol group protonated and not co-ordinated but involved in hydrogen bonding with [PF,] -ions or lattice MeCN molecule^.'^ Synthesis and co-ordination chemistry of new asymmetric multidentate ligands designed for modelling co-ordination number asymmetry at metal sites in binuclear metalloproteins is described.A binuclear copper complex of compound (18 HL) [Cu2L(OAc)][C10,] has been prepared. A single-crystal structure determination revealed that the copper atoms are bridged by the acetate anion and the alkoxide oxygen of the ligand. As a result of the inherent asymmetry of the ligand one copper ion is five-co-ordinate while the other is four-co-ordinate. The vacant co-ordination site at the latter atom demonstrated site-directed reactivity towards azide ions. This was Nitrogen Phosphorus Arsenic Antimony and Bismuth Ye Me &OH Ho~ Me thought to be the first example of a binuclear copper complex to exhibit both co-ordination number asymmetry and directed reactivity at one metal centre by virtue of ligand design.' A comparative study of a series of nickel(1r) complexes with structurally related tetradentate 14-membered hexaaza macrocycles (19 20 and 21) has shown that the non-co-ordinating (remote) nitrogen atoms in the macrocyclic backbones drastically influence the solution equilibria between the four- and six-co-ordinated forms of the complexes.The phenomenon was interpreted in terms of the formation of intramolecu- lar along with co-ordinative hydrogen bonds between the axial ligand and remote nitrogen. High differentiating effect for hydrogensulfate uersus hydrogenphosphate has been established.I5 3 Phosphorus Phosphazanes and phosphazenes The molecular structures of four cyclic (phosphorany1idene)aminophosphazenes(22 23 24 and 25) have been determined by single-crystal X-ray diffraction; gem-N,P,Cl,[NP(OPh) J2 N,P,(OPh),[NP(OPh),] 2 N,P,(OPh),NP(OPh) and N,P,(NHPr),NP(NHPr),-HCl.l6 A series of cyclic tri- and tetra-meric phosphazenes [NP(OR),] (n = 3 or 4) N,P,(OR)Cl and N,P,(OR),Cl has been prepared with 1-or 2-naphthyloxy 1-naphthylmethyloxy 1-naphthylethyloxy 9-anthryloxy and K.K. Hii and T.P. Kee I1 I CI-P ?P,CI ROyP ?P,OR CI' N CI RO OR RO /N=P(OR) NRPb I1 I 0HCI I1 7 RO-;P 9P,-OR R'HNTP,~,P~NHR' RO OR R'HN NHR' 9-phenanthryloxy side groups OR.17 These syntheses are model processes for the preparation of the corresponding phosphazene polymers. The versatile chemistry and potential applications of phosphazenes have been described.'* Hexasubstituted products N,P,(OC,H4N-2) and N,P3(OC,H4N-4) have been prepared from hexachlorocyclotriphosphazene [N,P,CI,].The crystal structures of both these compounds have been determined. The hexacationic complex [N,P,{(OC,H4N)Mn(CO)3(bipy)}6][c~04]6 was prepared by reaction with fac-[Mn(OCIO,)(CO),(bipy)].lg The reaction of cyclotriphosphazenes N,P,(OC,H,R- 4),(OC6H4CN-4) (where R = H Bu') N3P,(OC,H4CN-4) and nitrile-containing phosphazene polymers with manganese carbonyl complexes were also studied.20 ,F The cyclophosphazene [(Me2N)3S]2[(P,N,F,)NPF2NPF2NPF5]2 (26) was pre- pared from the reaction between [(Me,N),S] +[Me,SiF,] -and P,N,F and exam- ined by single-crystal X-ray diffraction2' The phosphazane (27) was found to undergo aza-Wittig reactions with aldehydes followed by 1,5-electrocyclic ring closure of the resulting aldimines to give imidazo[3,4-dlpyridines.The phosphazane also undergoes pyridine annelation by reaction with diethyl ketomalonate to give the corresponding isoquinoline derivative.22 The complexes (28) (n = 1-5) have been prepared in high yields.23 The structure of lithiated P-diphenyl(methy1HN-pheny1)phosphazenehas been determined. The crystal structure of the lithiated ligand consists of monomeric units containing a four- Nitrogen Phosphorus Arsenic Antimony and Bismuth membered ring with the lithium bonded to the nitrogen and methylene carbon atoms of the phosphazetane (29).24 Bicyclic metallaphosphazenes with four- and six-membered rings containing Fe and Pt have been synthesized and all were characterized by their 'H 31P,I3C NMR IR Raman and mass spectros~opies.~~ Phosphines Monodentate phosphines ( +/ -)-chloro(phenyl)isopropylphosphine26 and tert-b~tyl(pheny1)methylphosphine~~ have been resolved using N-chiral orthopalladated resolving agents.The absolute configurations of the complexes were determined by X-ray crystallography. The new P-chiral bis(phosphine) (S,S)-1,2-bis{(o-ethyl- pheny1)phenylphosphino)ethane has been prepared via optically active phosphine- boranes. Asymmetric hydrogenation of a-(acry1amino)acrylic acids by a rhodium complex with this ligand affords the products in 86-93% e.e.28 The preparation of a range of diphosphine-ruthenium complexes with different diphosphine precursors has been de~cribed.~' The products of general formula [Ru(acac)(P-P)R] (P-P = diphosphine ligand R = allyl) can be converted into catalytically active species by reaction with trimethylsilyl trifluoromethanesulfonate.Catalysis of the hydrogenation of a range of alkenes and direct comparisons with related rhodium complexes have been described. Syntheses of novel chiral phosphines containing the ferrocenyl moiety e.g. (30),30 (31),31 (32),32 (33)33 and (34),34 have been reported along with their application as ligands in asymmetric catalytic reactions. In particular a range of trans-chelating chiral diphosphine ligands bearing aromatic P substituents 2,2"-bis[l-(diarylphos-phino)ethyl]-1,l"-biferrocenes (35) were reported.35 Transition-metal complexes of K.K.Hii and T.P.Kee such compounds were tested in a range of asymmetric catalytic reactions such as rhodium-mediated hydr~genation.'~ Chiral phosphines have also been synthesized from the chiral pool e.g. (36)37and (37).38New rhodium complexes with the disugar phosphines (38) were also synthesized and tested as catalysts in asymmetric hydr~genation.~~ R=H,Me Nitrogen Phosphorus Arsenic Antimony and Bismuth New chiral phosphine complexes with an additional chelating group containing tricarbonyl($-arene)chromium (39 40) have been prepared. Catalytic asymmetric allylic alkylation mediated through the complexes proceeded to 94% e.e.40 (39) (40) R = Ph cyclohexyl Syntheses and chemistry of new chiral P-N (41)41 and P-0 (42)” compounds have been described.A variety of amphiphilic phosphines comprising PRPh (R = 3-hydroxyphenyl 4-carboxyphenyl) PR’,-,,Ph, (R’ = CH,C6H4X-4; X = NEt, NMePh NPh,; n = 1-2) and PR”,-,Ph (R = 3- 4-pyridyl; n = 1,2) have been s~nthesized.~~ In the rhodium-catalysed hydroformylation of higher alkenes such as oct- 1-ene the ligands were found to be comparable with triphenylphosphine. A catalytic amount of the copper iodide complex of the chiral phosphine (43) was found to catalyse the conjugate addition of organomagnesium chlorides to cyclic ketones and pent-4-en-5-olide to give the product in 9472% e.e.44 A dramatic reversal in enantiofacial differentiation was observed with the same phosphine using organo- K.K. Hii and T.P. Kee cuprate reagents; S and R products in up to 98%e.e.were obtained by using magnesium and lithium cuprate re~pectively.~~ R= Ph NMePh But,NMe2 (43) Phosphites and phosphinites Chiral phosphites such (44),(45)46 and (46)47have been synthesized and used in asymmetric hydroformylation reactions. Rhodium complexes of (44),(45)"* and (47)49 were also used as catalytic precursors for asymmetric hydrogenation catalysts. CH3 (45) (46) Line-shape analysis of 31P NMR spectra of catalyst substrate complexes of seven-membered ring rhodium(1) bis(phosphinites) containing the compounds (48),(49) and (SO) indicated for the first time a quantifiable preference of the intramolecular major-minor isomerization of both diastereoisomeric chelates of dimethyl methyl- enebutanoate over the slow intermolecular intercon~ersion.~' Phospholes and phosphiranes Correlations between 31PNMR chemical shifts and Hammett o-substituent constants are reported for a total of 22 anti-and syn-phosphiranes obtained from the reactions of the carbene-like phosphinidene complexes [W(CO),(PPh)] and [W(CO),(PMe)] Nitrogen Phosphorus Arsenic Antimony and Bismuth .OPPh Ph (49) with various pnrn-substituted styrenes. The origins of these four sets of correlations with respect to electronic and electrostatic interactions are disc~ssed.~ A homochiral diphosphine bearing PPh and menthylphosphetane moieties has been prepared from the corresponding phosphetane oxide through a stereoselective phosphorylation reaction. Monometallic and bimetallic ‘A-frame’ rhodium complexes (51) have been synthesized and characterized by single-crystal X-ray diffra~tion.~~ (51) R = menthyl The synthesis application and crystal structures of two enantiomerically pure dihydrobenzazaphosphole-borane complexes (52 53)53 has been described.These ligands have been used as precursors for highly enantioselective palladium catalysed allylic substitution reactions. A set of novel bidentate ligands (54) (55) and (56) which have two axially chiral binaphthylphospholyl substituents connecting through carbon chains of different lengths have been synthesized. Atropisomerization was observed for the free diphos- pholes in solution54 and platinum(I1) complexes derived from these compounds were found to be active in the hydroformylation of styrene.55 Thermal extrusion of nitrogen from 3-alkylidene-4,5-dihydro-3H-1,2,4-diaza-phospholes (57) to alkenyl phosphines (58) and alkylidenephosphiranes (59)was reported.56 K.K.Hii and T.P. Kee "oocOS~P~ - + p%Ph 8' osipri R (57) (59) Phosphorus macrocycles and cryptands The properties of metallocrown ethers with cis-co-ordinated phosphines has been reviewed by Gray.' The byproducts of thermal ring-opening polymerization of a six-membered N,P,S ring were identified as 12- 18- 24- 30- and 36-membered sulfur(v1)-nitrogen- phosphorus macrocycles. The 24-membered macrocycle is the largest inorganic ring system that has yet been characterized by X-ray crystallography.'* The reaction of new phosphorus dialdehydes PhP(O)[(CH,),CH=CHC,H,CHO] with PhP(S)[NMeNH,] yields macrocyclic compounds (60) and (61) arising from cyclocondensation of 1 2 or 3 equivalents of each reagent.59 The first examples of mixed phosphorus-ferrocenyl macrocycles (62) (X = 0,S)have been prepared.Reduction with LiAlH affords [Fe{ C,H,CH,N(H)N( Me)- P(S)PhN(Me)N(H)CH,C,H,),Fe]. This was found to be a novel type of a receptor capable of recognizing H2P0,- HS0,-and C1- anions electrochemically.60 Nitrogen Phosphorus Arsenic Antimony and Bismuth Phosphorus dialdehydes RP(OC6H4CHO) (R = Ph NMe,) react with phosphonic hydrazides PhP(Y)(NMeNH,) (Y = S 0) to give macrocycles arising from cyclocondensation reactions. Treatment of the phosphonic hydrazone PhP(S)[OC6H4C H=NN( Me)H] with dichlor o(pheny1)phosphine affords a macr0-cycle possessing three- and four-co-ordinated phosphorus atoms.Clean desulfuriz- ation of thiophosphorus macrocycles give rise selectively to new three-co-ordinated phosphorus-containing macrocycles.61 K.K.Hii and T.P. Kee The zinc complex [ZnCl,{PhP(S)(NMeNH,),)I (63) is a good reagent for the production of polymetallic compounds by condensation reactions with aldehydes. The zinc-iron phosphonic hydrazone complex [ZnCl,{ PhP(S)[NMeN= CHC,H,- Fe(cp)],)] (64) has also been synthesized and its structure determined by X-ray crystallography.62 The reaction of functionalized phosphonic hydrazides RP(X)(NMeNH,) (R = C1 N3) with organic or phosphorus dialdehydes leads to the synthesis of di- or tetra-functionalized phosphorus macrocycles in good yield.Macrocycles containing PN were obtained by reaction with sodium azide. All compounds are useful precursors of cryptands and multimacrocyclic species.63 The meso-tetrakis[4-(diphenylphosphino)phenyl]porphyrin (65)64 and a water-soluble octakis(phosphonium salt) phosphyrin double-decker with a cage structure has been reported. Nitrogen Phosphorus Arsenic Antimony and Bismuth 85 4 Arsenic Metal-free arsenic compounds The single-crystal X-ray structure of the novel hydrido cluster [As,HI2- was reported and the reactivity features of this cluster anion probed by pyrolysis photolysis and pr~tonation.,~ Primary unsaturated arsines vinylarsines prop- 1-enylarsine and ethynylarsine were prepared by a chemoselective reduction of the corresponding dichloroarsines and examined by photoelectron spectroscopy.Base-induced rearrangements in the pres- ence of solid K,CO in gas-solid reactions under vacuum conditions leads to ethylidenearsine propylidenearsine and ethylidynearsine respectively. This is the first time the electronic structures of these compounds have been probed and compared with possible phosphorus analogues., Reactions of 172-propadiene- 1,3-dione C,O, with a series of stabilized triphenylar- soranes Ph,As=CHX [X = CN CO,Me C(O)Me C(O)Ph C(0)C6H40Me-4] have yielded two different kinds of compounds. When X = CN C0,Me the reaction proceeds in a 2 1 ratio yielding the open-chain compounds XC(=AsPh,)- C(O)CH,C(O)C@sPh,)X whereas in the cases of X = C(O)Me C(O)Ph C(O)C,H,OMe-4 only 1:1 cyclic zwitterionic compounds are obtained.,’ Metal-containing arsenic compounds Osmium complexes of the form trans-[OsI,(L-L),] [L-L = Ph,AsCH,CH,AsPh or C,H,(AsMe,),-2,6] trans-[OsI,(L-L),]BF, tr~ns-[OsI,(C,H,(AsMe,),-2,6)~]-[ClO,], trans-[OsI,(AsPh,),] trans-[OsI,(AsMe,),] and trans-[OsI,(AsMe,)]BF have been described.68 The compound [(Cr(cp)(CO),},(q2-As,)] reacts with 2 mol equivalents of [M(CO),(thf)] to give the adducts [((cp)Cr(CO),),(q’-As,)( M(CO),),] (M = Cr W) in 55-60% isolated yield.The crystal structure of the chromium adduct has been determined. Reaction of either Li,PPh or Li,AsPh with the diborane derivative B,(NMe,),Br affords the compounds [PhP(BNMe,),] or [PhAs(BNMe,),] in good yield.Both have cyclic structures featuring non-planar six-membered rings P2B4 or As,B, which possess chair conformations. Although all four boron atoms in each ring have planar co-ordination the two phosphorus or arsenic centres have different degrees of p yramidaliza tion. 5 Antimony Metal-free antimony compounds Exchange reactions of R,Sb (R = 2- 3- 4-MeC6H,) with SbCl in a 1 2 molar ratio afford RSbC1,. Silylstibanes RSb(SiMe,) were obtained by reaction of RSbC1 and Me,SiCl with Mg in thf. Slow aerobic oxidation of solutions of RSb(SiMe,) afforded crystals of composition (RSb),. Structures were determined by X-ray crystallography for the R = 2- 3-MeC6H derivatives and reveal stacks of (RSb) rings with chair conformations and substituents in equatorial positions.Solutions of these compounds 86 K.K. Hii and T.P. Kee analysed by 'H NMR spectroscopy were found to contain (RSb) and (RSb) rings in dynamic equilibrium. Raman spectra and I3C CP-MAS NMR data of these com- pounds were also rep~rted.~ Nitrile complexes with antimony&) fluoride in cryogenic matrices have been studied by FT-IR spectro~copy.~~ A large increase in CsN stretching frequency induced by complexation with SbF was observed in all investigated nitriles. Current interpreta- tions of this nitrile effect in terms of rehybridization of the nitrogen atom or partial antibonding character of the CN G bond were discussed on the basis of both the IR spectra and high level ab initio calculations.The adduct CF,OCl*SbX has been obtained by the reaction of CF,OCl with SbX (X = F C1) at 195 K. At 213 K it forms SbCl,F C1 and OCF, while CF,OCl*SbF slowly decomposes giving ClF OCF and mixed antimony(v) halides.73 Metal-containing antimony compounds Reaction of RSbCl and cobaltocenein thf or C6D6 leads to the polymer (RSb) and the salt [Co(cp),] [RSbCl,] the structure of which has been determined by single- crystal X-ray diffraction. The ditellurostibane RSb[Te(C6H4Me-4)] has been ob- tained in quantitative yield through a complete reaction between (RSb) and [Te(C6H4Me-4)],. 74 The synthesis and structure of a trimetallic complex [{ LiN(C,H ,)},Sb,(Bu'OK),- (C,H,Me),] has been reported." 6 Bismuth Addition of bismuth(1rr) chloride and the triaza macrocyclic ligand Me3[9]aneN gave a 1 :1 adduct.The X-ray diffraction structure showed a half-sandwich arrangement in which the tridentate N-donor macrocycle and the three chlorine atoms occupy opposite faces of an octahedral bismuth(1rr) ion.76 Differential pulse polarography has been used to determine the formation constants of Bi3+ at an ionic strength of 0.5 and 25 "C with the compounds (66) (1 4 7-triazaheptane) (67) (1 4 7 10 13-pentaazatridecane) (68) [2-(aminomethy1)py-ridine] (69) [bis(2-pyridyl)amine] and (70) [N,N,N',N'-tetrakis(2-hydroxypropyl)-1,2-diamin~ethane].~~ Formation constants were obtained and a good linear free energy + relationship between log K-values for Bi3 and log K-for analogous complexes of the isoelectronic Pb2+ ion was found.Two trifunctional compounds (71) and (72) have been prepared under Michaelis-Arbuzov conditions and characterized by spectroscopic and X-ray struc- tural analysis. Their co-ordination chemistry with Bi(NO,) was studied. The ligands bind in a tridentate fashion to Bi3+ and the nitrate ions remain in the inner co-ordination sphere.78 Structural features of the bound and unbound ligand were discussed. Thereaction ofPh,BiCl with the dinuclear Group 6 anions [M2(CO),,]2- (M = Cr Mo W) produced the isostructural mixed organo-metal complexes [Ph,Bi,]. The [N(PPh,),] salts of these three clusters were characterized both spectroscopically + Nitrogen Phosphorus Arsenic Antimony and Bismuth nn nnnn H2N N NH2 H2N N N N NH2 H HHH (66) (67) and structurally.The analogous reaction of Ph,BiCl with [Fe,(C0),I2 -yields [Ph,Bi,],. This complex can also be prepared from the reaction of [Ph,BiFe(CO),]-with [Fe,(CO),]. Similarly the reaction of [Cr(CO),(thf)] generates the heterometallic cluster [Ph,Bi(Fe(CO),}(Cr(CO)5}]2- the [NEt,] salt of which has been studied by single-crystal X-ray diffraction. Comparison of the structural parameters in these and other related compounds indicates that the hybridization of the bismuth atom is dependent on its co-ordination en~ironment.~' References 1 K.K. Hii and T. P. Kee Annu. Rep. Progr. Chem. Sect. A 1994 91 67. 2 R. B. King J. Organomet. Chem. 1995 500 187. 3 H. Seino Y. Ishii T. Sasagawa and M. Hidai J. Am. Chem. SOC.,1995,117 12 181.4 A. Steiner and D. Stalke Organometallics 1995 14 2422. 5 E.C. Constable A. M. W. Cargill Thompson J. Cherryman and T. Liddiment Inorg. Chim. Acta 1995,235 165. 6 W. A. Herrman M. J. A. Morawietz T. Priermeier and K. Mashima J. Organornet. Chem. 1995,486,291. 7 J. S. Fan J.T. Lin C. C. Chang S.J. Chou and K. L. Lu Organometallics 1995 14 925. 8 T. Chivers X. L. Gao and M. Parvez J. Am. Chem. SOC. 1995 117,2359. 9 D.A. Atwood J. A. Jegier K. J. Martin and D. Rutherford Organometallics 1995 14 1453. 10 S. Chen V. Carperos B. Noll R. J. Swope and M.R. Dubois Organometallics 1995 14 1221. 11 J. C. Lee B. Muller P. Pregosin G.P.A. Yap A. L. Reingold and R. H. Crabtree Inorg. Chem. 1995,34 6295. 12 G. Desantis L. Fabbrizzi A. M. M. Lanfredi P. Pallavicini A.Perotti F. Ugozzoli and M. Zema Inorg. Chem. 1995,34 4529. 13 J. C. Jeffery J. P. Maher C.A. Otter P. Thornton and M. D. Ward J. Chem.Soc.,Dalton Trans. 1995,819. 14 J. H. Satcher M. W. Droege T.J. R. Weakley and R.T. Taylor Inorg. Chem. 1995,34 3317. 15 L.V. Tsymbal S. V. Rosokha and Y.D. Lampeka J. Chem. SOC.,Dalton Trans. 1995 2633. 88 K.K. Hii and T.P. Kee 16 H. R. Allcock S. E. Kuharcik K. B. Visscher and D.C. Ngo J. Chem. Soc. Dalton Trans. 1995 2785. 17 H. R. Allock S. Alshali D.C. Ngo K. B. Visscher and M. Parvez J. Chem. Soc. Dalton Trans. 1995,3521. 18 W. Schnick Comments Inorg. Chem. 1995 17 189. 19 G. A. Carreido P. G. Elipe F. J. G. Alonso L. Fernandezcatuxo M. R. Diaz and S. G. Granda,J. Organomet. Chem. 1995 498 207. 20 G.A.Carreido L. Fernandezcatuxo and F. J. G. Gomezelipe J. Organomet. Chem. 1995 503 59. 21 E. Lock P.G. Watson and R. Mews J. Chem. Soc. Chem. Cornmun. 1995 1717. 22 F. Palacios C. Alfonso and G. Rubiales Tetrahedron 1995 51 3683. 23 A. Bader Y. B. Kang M. Pabel D. D. Pathak A. C. Willis and S. B. Wild Organometallics 1995 14 1434. 24 F. Lopezortiz E. Pelaezarango B. Tejerina E. Perezcarreno and S. Garciagranda J. Am. Chem. Soc. 1995 117,9972. 25 J. Ellermann P. Gabold C. Schelle F. A. Knoch M. Moll and W. Bauer Z. Anorg. Allg. Chem. 1995,621 1832. 26 M. Pabel A.C. Willis and S. B. Wild Tetrahedron Asymmetry 1995 6 2369. 27 V. V. Dunina and E. B. Golovan Tetrahedron Asymmetry 1995 6 2747. 28 T. Imamoto H. Tsuruta Y. Wada H. Masuda and K. Yamaguchi Tetrahedron Lett.1995 36 8271. 29 J. M. Brown M. Rose F.I. Knight and A. Wienand Recl. Troc. Chim. Pny-Bas. 1995 114 242 30 P. Barbaro and A. Togni Organometallics 1995 14 3570. 31 C. J. Richards D. E. Hibbs and M. B. Hursthouse Tetrahedron Lett. 1995,36 3745. 32 Y. Nishibayashi K. Segawa K. Ohe and S. Uemura Organometallics 1995 14 5486. 33 U. Burckhardt L. Hintermann A. Schnyder and A. Togni Orgnnometallics 1995,14 5415. 34 I. R. Butler W. R. Cullen S. J. Rettig and A. S.C. White J. Organomet. Chem. 1995 492 157. 35 M. Sawamura H. Hamashima M. Sugawara R. Kuwano and Y. Ito Organometallics 1995 14 4549. 36 M. Sawamura R. Kuwano and Y. Ito J. Am. Chem. Soc. 1995 117 9602. 37 A. Borner A. Kless R. Kempe D. Heller J. Holz and W. Baumann Chem. Ber. 1995 128 767.38 G. Knuhl P. Sennhenn and G. Helmchen J. Chem. Soc. Chem. Coniniun. 1995 1845. 39 S. R. Gilbertson and C. W.T. Chang J. Org. Chem. 1995 60 6226. 40 Y. Hayashi H. Sakai N. Kaneta and M. Uemura J. Organomet. Chern. 1995 503 143. 41 J. M. Valk T. D. W. Claridge J. M. Brown D. Hibbs and M. B. Hursthouse Tetrnhedron Asymmetry 1995 6 2597. 42 T. Minami Y. Okada T. Otaguro S.Tawaraya T. Furuichi and T. Okauchi Tetrahedron Asymmetry 1995 6 2469. 43 A. Buhling P.C. J. Kamer and P. W.N. M. van Leeuwen J. Mol. Cntal. 1995 98 69. 44 M. Kanai and K. Tomioka Tetrahedron Lett. 1995 36 4275. 45 M. Kanai and K. Tomioka Tetrahedron Lett. 1995,36,4273. 46 S. Naili J. F. Carpentier F. Agbossou A. Mortreux G. Nowogrocki and J. P. Wignacourt Organometallics 1995 14 401.47 G. J.H. Buisman M.E. Martin E. J. Vos A. Klootwijk P.C. J. Kamer and P. W.N. M. van Leeuwen Tetrahedron Asymmetry 1995 6 7 19. 48 F. Agbossou J.F. Carpentier C. Hatat N. Kokel A. Mortreux P. Betz R. Goddard and C. Kruger Organometallics 1995 14 2480. 49 C. Dobler U. Schmidt H. W. Krause H. J. Kreuzfeld and M. Michalik Tetrcihedron Asymmetry 1995,6 385. 50 R. Kadyrov T. Freier D. Heller M. Michalik and R. Selke J. Chern. Soc. Chem. Commun. 1995 1745. 51 J.T. Hunt and K. Lammertsma J. Organomet. Chem. 1995,489 1. 52 A. Marinetti C. Lemenn and L. Ricard Organometallics 1995 14 4983. 53 G. Brenchley M. FedoulofT M. F. Mahon K.C. Molloy and M. Wills Tetrahedron 1995,51 10581. 54 S. Gladiali D. Fabbri and L. Kollar J. Organomet. Chem. 1995,491 91.55 C. Bergounhou D. Neibecker and R. Reau Bull. SOC.Chim. Fr. 1995 132,815. 56 B. Manz and G. Maas J. Chem. SOC.,Chem. Commun. 1995 25. 57 G.M. Gray Comments Inorg. Chem. 1995,117 95. 58 N. I. Yz,A. J. Lough A. L. Rheingold and I. Manners Angew. Chem. Int. Ed. Engl. 1995 34 998. 59 C. Galliot A. M. Caminade J. P. Majoral M. Kuznikowski M. Zablocka and M. Pietrusiewicz Chem. Ber. 1995 128 443. 60 B. Delavaux-Nicot Y. Guari B. Douziech and R. Methieu J. Chern. Soc. Chem. Comrnun. 1995 585. 61 D. Prevote C. Galliot A.M. Caminade and J. P. Majoral Heteront. Chem. 1995 6 313. 62 B. Delavaux-Nicot B. Douziech R. Mathieu and G. Lavigne Inorg. Chem. 1995,34,4256. 63 J. Mitjaville A. M. Caminade and J. P. Majoral Synthesis 1995 952. 64 G. Mark] M. Reiss P.Kreitmeier and H. Noth Angew. Chem. Int. Ed. Engl. 1995 34 2230. 65 R.E. Bachman S.K. Miller and K.H. Whitmire Organometallics 1995 14 796. 66 V. Metail A. Senio L. Lassalle J. C. Guillemin and G. Pfisterguillouzo Orgonometallics 1995 14 4732. 67 L. Pandolfo R. Bertani G. Facchin L. Zanotto P. Ganis G. Valle and R. Seraglia Inorg. Chim. Am 1995 237 27. 68 N. R. Champness C.S. Frampton. W. Levason and S. R. Preece Inorg. Chim. Actu 1995 233 43. Nitrogen Phosphorus Arsenic Antimony and Bismuth 69 L.Y. Goh W. Chen and R.C. S. Wong J. Organomet. Chem. 1995,503,47. 70 A. Moezzi M.M. Olmstead D.C. Pestana and P. P. Power Z. Anorg. Allg. Chem. 1995,621 1933. 71 H.J. Breunig K.H. Ebert S. Gulec and J. Probst Chem. Ber. 1995,128 599. 72 R. Hoti Z. Mihalic and H.Vancik Croat. Chem. Acta 1995 68 359. 73 R. Minkwitz and D. Konikowski Z. Naturforsch. Teil B 1995,50 1277. 74 A. Silvestru H. J. Breunig K.H. Ebert and R. Kaller J. Organomet. Chem. 1995 501 117. 75 D. Barr A. J. Edwards M.A. Paver P. R. Raithby M. A. Rennie C. A. Russell and D.S.Wright Angew. Chem. In?. Ed. Engl. 1995,34 1012. 76 G. R. Willey L.T. Daly M.D. Rudd and M.G. B. Drew Polyhedron 1995 14 315. 77 R.D. Hancock I. 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ISSN:0260-1818    

DOI:10.1039/IC9959200071

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

7 Oxygen Sulfur Selenium and Tellurium By P.F. KELLY Department of Chemistry Loughborough University Loughborough LE17 3TU UK 1 Introduction This review highlights the new developments in the chemistry of the Group 16elements (the chalcogens) reported during 1995.Since by definition such a brief must preclude a comprehensive survey results that demonstrate the novelty of the product or the synthetic approach as their main feature have been emphasized. In addition the reported products have been limited to those which possess a discrete molecular structure so as to highlight the extraordinary ability of these elements (sulfur selenium and tellurium in particular) to contribute to novel cluster arrangements. Structures (1H11)illustrate how such products can exhibit a fascinating range of structural features and for this reason the earlier and greater part of the review is devoted to the heavier chalcogens.2 Sulfur Selenium and Tellurium One of the most important aspects of the chemistry of the heavier chalcogens is their ability to exist in a variety of allotropicforms. Of these structural types undoubtedly the most widely known is the crown structure associated with S, Se and mixed species such as 1,2-Se2S {the latter having been shown to form in high yield when [Zn(tmen)(S,)] (see below) is treated with Se,Cl,}.' Though the tellurium analogue of such crowns Te, is unknown as a free species it has now been reported to form as an isolated unit in the product of the reaction of Cs,CO with As,Te in superheated methanol.Within this compound of overall stoichiometry Cs,Te,, the crowns exist in the co-ordination sphere of the Cs atoms a likely factor in their stability with the rest of the tellurium in the system being present as layered anions. Interestingly this result parallels the observation that an Se, ring the hitherto unobserved selenium analogue of well known S12 exists embedded in the lattice of ammonium and [Mo,-(S l,72)(Se,,,,)]2- ions present in the product of the reaction between [NH,][MoS,] and Na,[S,Se,].3 Here it appears that the new ring is stabilized by the metal cluster unit via interchalcogen interactions. These results would strongly suggest that many more new structural types await discovery through this technique of serendipitous formation/stabilization.It has been known for some time that oxidation of the heavy chalcogens may result in 91 P.F. Kelly cationic species that exhibit a wide range of often unique structures. An interesting development in this area has been the increasing use of transition-metal halides as the oxidizing agents. A key feature of such reactions is that they are carried out in the vapour phase with the resulting ions being deposited upon condensation. The volatile nature of early-transition-metal halides makes them ideal reagents in such an environment. In some cases the resulting cations are well known; thus selenium and [MoCl,O] react in a sealed ampoule at 190 "C to give the square [Se,] 'cation. The same species and its Te congener also forms from the reaction of the element with HfCl,.' Of more interest however are reactions which produce novel cations.A good example of one such reaction is that of selenium with WCl,. At 350°C this mixture generates dark red crystals of [Se,,][WCl,] which contain the novel [Se,,I2+ cation consisting of two Se rings joined by an Se chain. Novel tellurium cations are also amenable to this technique. Reaction of the element with [WCl,O] leads to a salt of the [Te,],' cation (l).,The latter often predicted but never before seen consists of a six-membered Te ring in a boat configuration. In contrast the analogous reaction with [VCI,O] leads to a totally different species [Te,],' (2).* It is suggested that the formation of this new cation present in the salt [Te,][VCl,O], is favoured by the presence of the rigid framework provided by the polymeric [VC1,0]2- anions.Finally it is worth noting that this technique also provides access to new tellurium-halogen cations. Thus reaction of WCl with iodine and tellurium results in the formation of the [Te,I,]2+ cation (3). The use of transition-metal complexes as precursors to new chalcogen-containing systems is an area of great interest and potential. Probably the best known such complex is the titanium species [Ti(S,)(cp),] which acts as a source of the S unit. Thus two moles of CISCCl react {via production of [TiCl,(cp),]) to generate S,(CC1,),.9 The latter a colourless low melting point crystalline solid consists of nine-atom helical C-S,-C chains which disrupt to a mixture of species of the type S,(CCl,) (n = 4-12) upon thermolysis.As mentioned earlier a unique source of the s6 fragment has been found with [Zn(tmen)(S,)] a complex which results from the reaction of zinc powder with a solution of sulfur in tmen (a reaction performed as the authors put it 'sans explosion' highlighting the contrast with the classic zinc-sulfur reaction). lo In addition to the aforementioned Se,Cl reaction this species has also been shown to act as a source of cubic ZnS by either pyrolysis or treatment with tertiary phosphines. In the above examples the metal complexes are acting as sources of fragments consisting solely of chalcogens; sources of mixed systems are however also possible. A good example comes with complexes of the type [Ti(S,NR)(cp),] (where R = H Me) which result from the reaction of S,NH (or its methyl derivative) with [Ti(CO),(cp),] Oxygen Sulfur Selenium and Tellurium and which react with sulfur halides to generate novel imide systems." An interesting feature of these two complexes is that the nitrogen occupies a different position in the nine-membered metallocycle depending upon the nature of its substituent.Another interesting example is the binuclear species [Ti,(C,S,)(cp),] {prepared by treating [Ti(CO),(cp),] with CS,) in which a C=C unit is bound to the two titanium atoms uia four bridging sulfurs. It has been shown to react with COC1 to give mononuclear [Ti(S,C,S,CO)(cp),] and with C6H,(SCl) to give the bis(tetrasu1fane) (C6H,S,C),.'2 Mononuclear complexes of many more chalcogenide ligands are known.The bidentate [E4]'- ion for example is a commonly observed reaction product; it has recently been reported in the [Ir(Se4),l3-anionI3 and in the tellurometalates [M(Te,),12 -(where M = Hg Cd Zn).' An intriguing development in this area comes with the preparation of heterochalcogen analogues by utilizing the ability of TePEt to substitute tellurium for selenium as in Equation (l).I5 [M(Se,),]'-+ nP(Te)Et -+[M(Se,-,,Te,)I2-+ nP(Se)Et (1) A key feature of this reaction is that ring-bound selenium atoms are invariably substituted before metal-bound ones. Elegant multinuclear NMR observations also indicate that when only 2 equivalents of triethylphosphinetelluride are used the two tellurium atoms substitute into opposite rings.A reaction mechanism based upon the insertion of a Te atom into the Se-Se bond followed by loss of P(Se)Et has been proposed. On the subject of mixed chalcogen ligands the lone sulfur atom present in [Ti(SSe,)(cp),] has now been shown by X-ray crystallography to be metal bound.I6 Mononuclear complexes containing smaller chalcogenide fragments as ligands are well known. Thus treatment of the elements with [Zr(CO),(cp*),] at 80 "C results in the formation of [Zr(CO)(q'-E,)(cp*),] which in turn reacts with further chalcogen to give [Zr(q2-E,)(~p*)2].'7 Bidentate [S,]'- ligands are also present in the niobium complex [Nb(0)(S,)2(SH)]2- which may be converted into [Nb(SH)(S),12- by the action of triethylphosphine; the latter complex displays three terminal metal-sulfide bonds.I8 On the subject of terminal chalcogenide ligands examples of terminal telluride complexes of molybdenum and tungsten trans-[M(PMe,),(Te),] have been reported as the ultimate products of the reaction of [MHJPMe,),] with tell~rium.'~ The conversion of the intermediates in this reaction i.e.species of the type [MH,(PMe,),(q2-Te,)] to the final products clearly involves an unusual case of oxidative cleavage of the ditelluro ligand. The use of laser ablation techniques to prepare mononuclear metal-sulfur cluster cations has proved increasingly fruitful. When the metal (typically a first-row transition eIement or an alkaline-earth metal) is ablated in the ion trap of a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer in the presence of a small back- ground pressure of sulfur vapour a variety of species ensue.Typically these are of the type [MS,]' where y = 2-16.20 Across a range of metals the y = 4 species appear ubiquitous although calcium appears to be an exception. In this case the y = 3 cluster forms initially with the y = 11 species becoming the dominant product with time.,' It is suggested that the most stable isomer of the latter consists of a [Ca(q2-S,)(q4-1,3,5,7- cyclo-S,)] structure. Clearly this technique has great potential for the preparation of novel structural arrangements (albeit on a small scale!). The ability of mixed-chalcogen compounds to form polynuclear complexes with transition metals is well illustrated by the intriguing products formed when tellu- P.F.Kelly rium-sulfur anions (or their precursors) are treated with simple gold or silver species. Reaction of [S,Te]’-with [AuCN] in dmf generates the [Au,(S,Te),12- anion (4) whilst a mixture of AgNO, K,Te sulfur and [N(PPh,),]Cl results in a salt of [Ag,Te(S,Te),12-(S)., Binuclear species also result from the reactions of either H,S2 or selenium24 with the palladium(1)dimer [Pd,Cl,(p-dppm),]; ‘A-frame’ adducts of the type [Pd,Cl,(p-E)(dpprn),] are formed in which the chalcogen bridges the palladium atoms. Treatment of the sulfur complex with free dppm regenerates the starting material via loss of the phosphine sulfide. A detailed discussion of all the metal cluster complexes involving chalcogen- containing species is beyond the scope of this work.However a number are worthy of a brief note (and are dealt with in order of ascending nuclearity). The trinuclear sulfide clusters [{Ir(~p*)}~(p~-S),]”+ have been shown to catalyse and [{C~(cp’)}~(p~-S),]’+ oxalate generation from electrochemical reduction of C02,25 while Cs,. [Mo3( CN),(,u,-Te)(p-Te,),] I,. 5*3H,O constitutes the first example of a M ,Te cluster core.26 Tetranuclear anions of the type [M4(Co)8(Te,)2(Te),(TeMe)2]2-form during the hydrothermal reaction of the iron or ruthenium carbonyls M,(CO),, with Na,Te in methanol,” while two different sulfur bridging modes are found in the mixed-valence cluster [Ru,(p-H),{P(OMe),}8(p-S)2(p4-S)2]28and in the raft-type tetratungsten cluster [W,(PMe2Ph),(~,-s)2(p-S)4(SH)2].29 Sodium telluride is again the tellurium source for the pentanuclear mixed-metal system [Fe,W,(CO),2Te8(TeMe)]3-.30 The conversion of W6CI, into [W6(py)$g] is performed by the action of NaSH and Na(0Bu”) in refluxing pyridine,,’ while the iron cluster [Fe6(CO),&12 -forms from the reaction of aqueous K,[SeO,] with Fe(CO) and KOH in methanol., Finally the octanuclear species [Fe8(CO),,Te6]2- may be prepared from Fe(CO) using a variety of tellurium sources K,[TeO,] TeCl or ~~0,.33 Main-group chalcogenide anions continue to exhibit an amazing range of structural types.Thioborate anions result from a range of reactions and form with a variety of stoichiometries and structures; e.g. reaction of equimolar amounts of Cs,S boron and sulfur at 600°C results in CS,[B,S,].~~ The larger [B,S,]’- anion results when either lithium or sodium sulfide is used in a similar manner (in the presence of excess sulfur),35 while the six-membered ring system [B,S,I3- (6) is formed from a mixture of Li,S Bas boron and sulfur in the molar ratio 1:2:6:9 at 750°C.36 This last reaction is however very sensitive to the reagent stoichiometries; with the starting materials present in the ratio 1:2 2 3 the trithioborate(rI1) ion [BS,]” is produced.The telluroplumbate [Pb,Te,12- (7) results from the reduction of the binary Oxygen Sulfur Selenium and Tellurium telluride PbTe with potassium-liquid ammonia in the presence of cryptand 222.37 This reaction system is extremely effective at producing novel anionic products; for example a similar reaction involving CdTe generates the intriguing [Cd,Te,,I4- anion (8).Examples of arsenic-antimony species reported last year include [As,S,] 2-(9) (which results from reaction between Na,[AsS,] and [PPh4]C1)38 and the antimony species [Sb,&]2- (10) and [Sb4S612- (II) which form when Sb,S5 is reduced with either [BH,] -or [FeH(CO),] -re~pectively.~’ The co-ordination chemistry of such systems is also receiving increased attention with the preparation of complexes such as [Fe(CO)(As,Se,),12- [Mn(CO),(As,Se5)12-and [Fe,(CO),-(AsTe,),] -.,’ A good example of the ability of acyclic chalcogenoethers to exhibit new co-ordination modes comes with work involving the formation of silver(1) complexes. While MeSe(CH,),SeMe generates the expected mononuclear [Ag{ MeSe(CH,),- SeMe),] the longer chain PhSe(CH,),SePh produces a complex exhibiting an infinite array of tetrahedral silver atoms co-ordinated by one selenium atom.42 The sulfur analogue of the latter possesses a similar structure while use of MeS(CH,),SMe results in a chain polymer.Clearly many more variations upon such arrangements await discovery. Other Group 14 systems reported recently include the selenagermane [(SiMe,),C],- Ge,Se,, and the organotin selenide anion [PhSnSe,],’ - which results from potassium reduction of a Bi,Sn,Se alloy in the presence of [PPh,]Br.44 Similar chalcogen-bridged tin species [(S~(,U-E)[N(S~M~,),]~)~], result from the sonification of a mixture of any of the elements with [Sn(N(SiMe,),),] in thf.45 Though not novel these products are formed in substantially higher yields (~90%)~ and at a much faster rate than in previous methods.Bimetallic tin-germanium products may also be produced by this method. Chalcogen-nitrogen chemistry continues to be an area of intense interest. Although the emphasis in such work is shifting somewhat from sulfur to the heavier elements interesting work is still being performed on S-N systems. For example the preparation of S,N,(OMe) (by methanolysis of S4N4C12),46 [{NS(O)F),{ NS(O)F,}] -{by addition of fluoride to [NS(0)F],}47 and the cation [Bu’CPSNS] + (from [NSN] + and P. F. Kelly Bu‘CP)~~ all represent important developments in the chemistry of cyclic species. The use of the NPMe fragment to stabilize Sv’in [S(NPMe3)4]2+,49 the preparation of a variety of SNO species from Me,SiNPPh,’O and the isolation of [UC~,{NH(SP~,))(C~*)~],~~ a rare example of a complex of diphenylsulfimide attest to the continued interest generated by acyclic systems.Two other S-N systems that have been the subject of particularly fruitful study are the P-N-S cage 1,5-Ph,P2N,S and the cyclothionylazaphosphorine [(NPCl,),(NSOCl)]. The former is a versatile ligand; it reacts directly with ruthenium carbonyls to give dimeric complexes52 and in the form of a sodium salt readily produces complexes of zirconium hafnium5 and rhodium.’ Substituted derivatives of the type Ph,P,N,(SR)(SR’) have also been the subject of recent study.” Pyrolysis of the aforementioned thionylazaphosphorine results in a number of new cyclic species including the fascinating 24-membered [(NPCl,),NS(O)Cl], the largest inorganic heterocycle yet characterized by X-ray ~rystallography.~~ The observation that explosive Se,N reacts with simple palladium halide dimers to give the first examples of adducts of neutral Se,N, hints that a route to the much sought-after polymer (SeN) may yet be a viable prop~sition.’~ Other Se-N species reported include HC(NH,)(NSePh) [the product of the reaction of HCN,(SiMe,) with PhSeC1],58 SeO(NPPh,) (from the action of SeO upon Me,SiNPPh,)” and [(Me,Si),N],Se (x = 2-4).60 Although the organic chemistry for which it was used is outside the direct scope of this report it is worth noting the observation that in the presence of NH,R and NEt, the selenyl chloride PhS0,SeCl acts as a source of the transient R-N=Se unit.This has clear potential within an inorganic reaction framework. Finally on the subject of chalcogen-nitrogen systems a number of important inroads into the chemistry of tellurium systems have been reported including the first preparation of a Te-N-X (X = halogen)cation [Te4N2Cl8I2 +.62 The latter consists of a planar Te,N ring bound to chlorine atoms at Te and to TeCl units at N. A Te,N ring is also found in [Te,(NHBu‘)(NBu‘),]Cl which results from the reaction of TeCl with LiCNHBu‘] and which contains the first genuine example of a Te=N double bond (1.84&.63 This reaction is a useful source of new material as it also produces [{Te(NBu‘),},] the first example of a tellurium diimide and [(TeNBu‘),] the first cyclic tellurium imide.The former reacts with further LiCNHBu‘] to give [{TeLi,(NBu‘),},] which effectively contains the first structurally characterized tris(imido)tellurate(Iv) ion [Te(NR),]2-.64 Other Te-N systems reported include the cation [Te(F)SeS,N,]+ (which shows a cage structure similar to that of S,N,),65 the cyclic Te,N,S,Cl (from the reaction of TeCl with Me3SiNS0),65 the azide compound [{ Ph,(N,)Te},0],66 and the bicyclo halogen species Te,N,SeX6.67 Development of the chemistry of Te(NSO), a potentially important synthon in this area is also underway.68 Interest in the chemistry and properties of the phosphorus chalcogenides continues unabated. Briefly the main thrust of current work in this area appears to centre on the synthetic applications of P,S,I (in for example the preparation of P,S,O from PhHgOH-NEt,),69 the formation ofmixed 0x0-chalcogen systems (such as P,O,Se)” and analysis of the NMR parameters of mixed systems.71 In addition interest continues to be shown in mixed P-N-E (E = chalcogen) systems in particular the bis(dipheny1phosphino)aminechalcogenides and their co-ordination properties (which Oxygen Sulfur Selenium and Tellurium have been the subject of a 157 reference review).72 Recent examples of such work include the preparation of rhodium palladium and platinum complexes,73 a number of main-group complexes (for example polymeric [(Me,Sn(SPPh2NPPh,S))n])74and the unexpected observation that in the salt [N(PPh3),][N(SPPh2),] the anion exhibits an absolutely linear P-N-P fragment.75 The related anions [R,P(E)NR'] -have been studied both for their structural parameters76 and for their ability to co-ordinate to metals,77 while the pyramidal cations [E(NPR,),] +,result from a variety of reactions involving chalcogen halides.78 Finally work on the chemistry of [R,PS,]- ligands continues.Results include the preparation of [TePh,(S,PPh2),]79 and the report of an unusual synthetic route to a metal complex via UV activation of a diphosphine disulfide.80 This area has also been the subject of a review.8' 3 Oxygen Investigations into two different aspects of alkane oxidation have produced interesting results. In one case it has been shown that in the presence of the supported catalyst Sr0-La20,-SA5205 the energy-efficient (and safe) conversion of ethane to ethylene by steam and oxygen occurs.82 This is made possible by the simultaneous exothermic oxidative dehydrogenation and endothermic cracking of the ethane; the energetics of the coupled reactions mean that the process requires minimal energy input.The other study focussed on the oxidation of methane. Although it has long been known that the high-pressure gas-phase radical reaction of methane with 0 results in methanol it has now been shown that this may occur at pressures as low as a few atmo~pheres.'~ Thus in a quartz reactor at 425490 "Ca methanol selectivity of >30% results via a series of radical species such as [MeO]'.A variety of studies of oxidation of main-group systems have been reported. For instance the oxidation of nitric oxide to [NO,]- by dioxygen has been shown to proceed via a weakly bound complex of the type N0...02.84 It then progresses through species such as ONOONO and [NO,].; the latter radical has been also identified as a reactive intermediate in some oxidations involving the oxoperoxo- nitrate(I1r) anion.85 An elegant method has been utilized to study the analogous oxidation of NO with superoxide [OJ. Following the observation that NO forms from the pulse-radiolysis-induced reduction of nitrite Kobayashi et a!. applied this technique to oxygen saturated nitrite solutions.86 In such a situation both the NO and the superoxide form in situ then react; the oxoperoxonitrate(II1) ion [NO(O,)] -,is the result.The superoxide ion has been found to form during the interaction of dioxygen with metaphosphate melts at elevated temperatures and there is evidence that when transition-metal cations are present in the system they show some degree of interaction (i.e.electron-density sharing) with these anions." Work on the 0,-[HSO,] -system (prompted by its important environmental consequences relating to acid rain etc.)has shown that chain initiation occurs through the reaction of [HSOJ-with [HSO,]- resulting in the [SO,]'- and [SO,]'-radical anions.88 Finally a rather different form of oxidation occurs during the use of [O,] ion bombardment to leach carbon from + aryloxides a technique recently studied using X-ray photoelectron spectros~opy.~~ Hydrogen peroxide in the presence of various catalysts is an effective oxidizing P.F.Kelly agent towards a number of substrates. For example in the presence of the + phase-transfer cation [N(C,H,,),] the tungsten species “Me,],-[(WO(02)2)2(WO(02)2(H20))(PhP03)] cleanly catalyses its epoxidation of a variety of cyclic and linear alkene~.~’ By way of illustration cyclooctene is taken to 1,2-epoxycyclooctane by biphasic 15%H202-benzene with a 95% yield and turnover ratio of 183. Another report in this area studied the abilities of 21 polyoxometalates to act as such catalysts and found only [W,20,0P]3- and [W,,039P]7- to be effective; both of these readily form the epoxidation agent [{ W(0)(02)2),P0,]3 -.” Activation of H202 towards epoxidation can also be achieved using [ReMe0,].92 The first step in such reactions involves the binding of peroxide to Re; the mechanism of the latter has been studied and results suggest that it involves nucleophilic attack with transfer of two H atoms from the H20 to one of the rhenium-bound oxygens forming an q2-peroxo ligand and a weakly bound water.Such an intermediate also plays a part in the catalytic oxidation of YR (Y = P As Sb).93 Finally the ability of molybdate ions to catalyse the production of singlet oxygen from H202 has been investigated using 95MoNMR. Four intermediates are shown to form of which one [Mo0(O2),l2- is the main precursor of the Many main-group 0x0 systems were the subject of interest in 1995.These include FC(O)OF which has now been ascertained to be more stable than previously suggested [instability in samples being due to the presence of FC(0)OOF impurity]. It may be stored for a number of hours in the (pure) gas form and its cis-trans isomerism studied by NMR and IR/Raman.” Although the related compound bis(trifluor0-methyl)trioxide CF,O,CF, has been known for over 30 years its molecular structure has only now been determined.’6 In the crystalline state it appears as a twisted chain with trans CF groups and 0-0 distances of 1.44A(i.e. shorter than in H202 longer than in ozone). A unique reaction of P,O has been shown to occur with organic a~ides.~~ Rather than resulting in the degradation of the cage as seen with amines or aldehydes for example these reactions defy conventional wisdom and retain a cage structure via an 0-N redistribution.The products P,O,NR contain the NR group in place of one of the original oxygens with the latter now involved in a terminal P=O bond. Two such bonds are present in the novel bifunctional tridentate ligand SeC(Ph,PO) which intriguingly forms when the initial product of the reaction between CuCl and CH,(Ph,PSe) is exposed to air.98 The new ligand is formed uia replacement of the chalcogens on the phosphorus atoms and selenium transfer from the P=Se unit to the methylene carbon. The product thus formed may be formulated as [Cu”(Cu’Cl,[p-SeC(Ph,PO),]),] with the ligands binding to one copper atom by both oxygen atoms and to another via the methaneselone n bond.An unusual product also results when MoO(02)*(H,0) is treated with Me2NC6H,P(0)Ph and H20,. Instead of the expected P(O),N chelate a complex of Me(O)NC,H,P(O)Ph (the first example of a phosphorus-nitrogen dioxo ligand) is produced.” A number of studies on heavy-chalcogen-oxo systems have been reported including the equilibrium reaction between elemental selenium and aqueous sulfite to give [SeS0,I2-(for which k = 0.43 at 20 oC).’oo Interestingly the isomeric [SSe0J2- does not result from sulfur plus trioxoselenate(Iv) nor may selenotrioxoselenate(1v) be prepared from Se and [SeO,]’-. A combination of low temperature Raman and X-ray crystallography has been applied to solid Se02F2 and has revealed the existence of two Oxygen Sulfur Selenium and Tellurium 99 crystal modifications differing from each other in terms of the intermolecular Se-0 Se contact present."' The oxidation of pentafluoroethylseleninic acid by permanganate has been shown to generate the [C,F,SeO,] -ion; the presence of three oxygens on the selenium atom has been confirmed by the crystal structure of the tetraphenylarsonium salt.A chalcogen in oxidation state VI is also found in [Te(C,F,),O,] which is formed when [Te(C,F,),] is treated with concentrated nitric acid followed by H,O2.'O2 Finally the reaction of [Te(OTeF,),] with free [OTeFJ-has been shown to generate [Te(OTeF,),]- and a small amount of [TeF(OTeF,),] -.Io3 Oxygen-containing ligands have been reported in a wide variety of transition-metal systems; a selection are highlighted here.An interesting development in the co- ordination chemistry of dioxygen comes with the report of an unprecedented Co,(O,) unit [present in a substituted tris(pyrazoly1borate)cobalt complex] in which the dioxygens link the cobalt atoms in a trans-p-q' q' fashion.'04 The resulting Co,O ring adopts a chair configuration. The reaction of [(NbCl(C,H,SiMe,),),] with dioxygen has been shown to progress through q2-peroxide p-0x0 and peroxide bridged species on the way to the final product [Nb(0)C1(C,H,SiMe,),],'os while an unusual example of a tungsten-0x0-nitrosyl complex has also been reported.'06 One result of the combination of ligand types in the latter (i.e.the strongly n donating 0,-and the 71 acceptor NO) is the unusually low frequency of the N-0 stretch (1433 cm-') in the IR spectrum.The potential of polynuclear complexes with 0x0 ligands to model biologically important systems has been noted for complexes of copper (containing in this case a [Cu,(p-0),l2+ core),'07 chromium ([Cr,(p-O),]* core)Io8 and ruthenium (a + binuclear analogue of important iron systems).'0g Other cluster systems reported include [PbSn,(p,-0)(0Bu'),(OA~)~] [prepared via ester elimination from Sn(OBu') and Pb(OAc),] 'lo and the octanuclear [MO,C1,0,(~,-OXOH),(p(-OH),(p-' OE t),( HOE t),] . References 1 A. K. Verma and T. B. 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ISSN:0260-1818    

DOI:10.1039/IC9959200091

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

8 The Halogens and Noble Gases By E.G. HOPE Department of Chemistry University of Leicester Leicester LEI 7RH UK 1 Introduction This chapter reviews the 1995literature for the elemental halogens and noble gases and compounds containing these elements in their positive oxidation states only. Publica- tions which only involve halide or oxohalide anions as counter ions are not described. Two issues of J. Fluorine Chem. carry the collected abstracts of meetings in San Diego,' in honour of George H. Cady and Kyoto2 which review key developments in fluorine chemistry. Review articles on the halogenation of fullerenes have also been p~blished.~ 2 The Halogens The most common reactions of the halogens are oxidations. Those involving elemental fluorine have been considered previously to be too vigorous and too difficult to control without specialist equipment.However a number of papers indicate that fluorination of organic substrates can be accomplished in a controlled manner in solution; e.g. fluorination of 1,3-dicarbonyl c~mpounds,~ p-fluorocarboxylic acids,' diaryl- 1,3- dithiolanes,6 pho~phanes,~ chloro- and aryl-substituted ethersg polyf~rmaldehydes,~ F I I F (X-=BF4; PF6; FSO,; CF,Sq-) (11 and the synthesis of the bis(N-fluoro) compound (1).lo Similarly F,-anhydrous HF offers a convenient medium for the oxidation of chromium metal" and silver(]) salts.12 Fluorine gas has also been used in a one-pot laboratory scale safe preparation of [AuF,]13 and in the fluorination of c60-and C,,-f~llerene.'~ Gaseous fluorine has also been used in the first general method for the preparation of non-terminal geminal bis(fluoroxy) compo~nds'~ and in a very rapid fluorodestannylation reaction which as a consequence of this rapidity may be important in [18F]-positron emitting tomography studies.16 103 104 E.G.Hope Me I Ph ,P=N I Ph" 'Ph (3) Direct iodination ofaromatic compounds is difficult; the use of elemental fluorine as a co-oxidant in solution represents an elegant new approach.I7 Oxidation of (2) with iodine affords (3) [equation (l)] which represents a trapped cation-anion complex and may be regarded as a model of an intermediate in the polar-oxidation reactions of iodine where instead of co-ordination of the second iodine atom stabilization is achieved by co-ordination of the pendant N-atom of the ligand.l* Three papers describe the addition of bromine iodine or IBr to triorganyl Group 15 element~;'~ the shapes either trigonal bipyramidal or four-co-ordinate molecular 'spoke' adopted by the R,EX (E = P As Sb; X = F, Cl, Br, I, IBr) compounds are summarized.The charge-transfer complexes of iodine with hexamethylbenzene have been studied using femtosecond transient-absorption studies in a series of non-complexing solvents illustrating the value of ultrafast polarization measurements in investigations of solution-phase systems.20 A theoretical paper has considered the inclusion of the halogens into caesium fluoride and predicted a unique phenomenon in intercalation science where the incoming halogen molecules transform the cubic lattice into a layered structure and intercalate between the ionically bound layers of CsF.,l In a series of papers Legon and co-workers22 have continued to describe the formation and characterization in the gas phase by ground-state rotational spectros- copy pre-reactive intermediates of halogens (and interhalogens see below) with a series of Lewis bases; n-type complexes of ethene and ethyne with chlorine and o-type complexes of H,S with chlorine and of ammonia with bromine and fluorine.The H,N - F species which is the first pre-reactive complex of elemental fluorine has C, symmetry a N...F distance of 2.708(7)A and K (intermolecular force con-stant) = 4.69(3)Nm-'.22 Some of the work has been highlighted2 and ab initio calculations on the H,N -* X (X = F C1) complexes are in good agreement with the experimental data.24 The identification by UV/VIS and NMR spectroscopies in solution of a Mulliken 'outer'-type product a n complex of bromine with an alkene has been reported from the reaction of bromine with a sterically congested silbene.,' 3 Interhalogen Compounds and Poiyhalide Anions The oxidations of iodine and bromine to IF and BrF using CF,OCl have been outlined.26 Chlorine monofluoride has been used as an oxidizing agent in a new The Halogens and Noble Gases high-yield route to difluorocarbimides (Rf),NN=CF2,27 and in the synthesis of F,C(OF)(OCl) the first example of a compound containing both the OF and OC1 functional groups.28 Iodine monochloride forms a 1:1donor-acceptor complex with Me,SiNPMe which contains a linear N-I-Cl unit whilst 12C16 reacts in dichloro- methane to give Ph,PN(Cl).ICl (which also contains a linear N-I-C unit) or in carbon tetrachloride to give [Me,PN(H)PMe,][ICl,] (in which one IC1 -anion is hydrogen bonded to the cation).,' The gas-phase pre-reactive intermediates between CIF and H,S (CJ CO (Cmv), ethene and ethyne (C,,),' and between BrCl and NH (C3Jand HCN (C,J3' have been identified and characterized by Legon; as expected the Lewis base co-ordinates to the more electropositive halogen.Twenty-three years since its first preparation a single-crystal X-ray structure determination of CF,IF (at 172 K) has confirmed the expected square-pyramidal geometry.The structure is held together by three long I F intermolecular interactions with three adjacent molecules.32 A comparable molecular structure has been observed for C6F,IF4 prepared by the nucleophilic fluorine-aryl substitution reaction of IF with Bi(C,F,), except that in this structure there are two types of iodine atoms one with two intermolecular interactions the other with three., Previously the F,-anion has been the subject of numerous calculations which suggest that it is thermodynamically more stable by ca. 110 kJmol-' than (F + F-) comparable to those for C13- Br,- and I,-. However elemental fluorine does not form a stable [NMeJF salt with [NMe,]F which may be attributed to the high solvation enthalpy of fluoride in highly polar solven ts.j4 Polyiodides continue to provide a rich area for investigation offering various degrees of catenation and a wide variety of geometrical arrangements.In a series of papers Tebbe and co-workers3' have described a range of polyiodide anions with a variety of N- and P-based cations e.g. [MePh,P),I, (4) (the anion consisting of two 'L'-shaped I,- units bridged by an I A I iodine molecule and completed by two end-on 1,-groups),36 and a new type of complex [SEt,][Hg2I,]+-3I, the first polyiodo complex.37 In two closely related papers new types of 1,-anions have been obtained using oxonium-crown38 or metal-macrocyclic thioether The I -anions comprise I- and I units instead of discrete I and I,-units linked uia a strong intermolecular interaction in one direction to give an infinite sawhorse polymeric array (5),38or via strong intermolecu- lar interactions in all three dimensions giving effectively a cubic structure in which I- 106 E.G.Hope anions occupy the lattice points of a rhombohedra1 lattice with one I molecule along each edge bridging two iodide ions.,' Schroder and co-workers3' have also described a related I -complex which together with the earlier characterized I,-complex offers the complete series of one- two- and three-dimensional adducts of I-with one two or three iodine molecules respectively. In contrast to the other binary halogen fluorides little is known about the chemical properties of BrF or IF. The synthesis of [NEt,][IF,] (the anion is linear from vibrational data) has confirmed that IF can act as a fluoride-ion acceptor4' and a species which reacts with alkenes (as BrF would be expected to react) has been obtained by mixing HF and an electrophilic source of br~mine.~' New work on the [BrF,]- anion synthesized as the 1,1,3,3,5,5-hexamethylpiperidiniumsalt (one of a new series of cations for high oxidation-state systems) has confirmed the strict octahedral ligand arrangement and a stereochemically inactive lone pair.The authors conclude that by comparison with the structures for the [SeF,I2- and [IF,] -anions the non-bonding electron pair will only play a directional steric role if the size of the central atom allows it. The observation for [BrF6]- of a different "F NMR chemical shift but the same 'J("Br-F) and 'J("Br-F) coupling constants to those reported for the [BrF,] + cation suggests very similar s-orbital characteristics in the Br-F bonds in these ions., Further studies and reviews of covalent halogen azides have been published., 4 Halogen Oxides and Organoiodine Oxygen Compounds Many publications have described kinetic studies and ab initio calculations on halogen oxides (Cl,O C10 BrO C10,) which are believed to play a crucial role in ozone depleti~n.,~ Ofparticular interest are reactions believed to take place on the surface of ice particles in the atmosphere which suggest new heterogeneous catalytic cycles leading to ozone Dichlorine trioxide Cl,O, generated in the reaction of C10 with ClO, has a relatively short lifetime and is not expected to be an important reservoir for C10,.46 The gas phase UV/VIS spectrum of Br,O formed by the reaction of Br with HgO has been reported for the first time.,' Iodine monoxide has been detected and rate coefficients for the reactions of iodine with ozone and I0 with NO have been measured following speculation that catalytic reactions of the I0 radical may also play a role in ozone depletion.48 Exploring the field of binary halogen oxides has always been a task of particular intricacy since except for I,O, all oxides of the halogens are thermodynamically unstable.However Jansen remains preeminent in this area describing an improved synthesis (the reaction of HJO with H2S04)and crystallographic characterization of 10 (6).,' The structure consists of I,O, units (two 10 octahedra sharing an edge and two pyramidal 10,groups sharing two vertices with the double octahedron) linked through I -0bridges and may be considered to be the mixed anhydride of H,IO and HIO,.Trifluoromethyliodine dinitrate CF,I(ONO,), prepared according to equa- tion (2) has also been crystallographically characterized. The central iodine atom has a distorted planar geometry as a result of an intermolecular I * 0 ~ontact.~' CF,I + ClONO +CF,I(Cl)(ONO,) 'IoNo2+ CF,I(ON0,)2 (2) In halogen oxoanion chemistry NaCBrO,] (with NaCHSO,]) is reported to be an The Halogens and Noble Gases efficient oxidizing agent of primary alcohols to esters in aqueous media,” Li[IO,] Li[BrO,]*H,O and Ba[H,IO,] have been structurally characterized5 and free energies of hydration for [IOJ- and [IO,]- in the gas phase have been reported as part of a general paper on hydration enthalpies of some main-group compounds.53 Periodate groups are strongly co-ordinating towards transition-metal ions producing stable complexes containing unusually high oxidation states of the metal; e.g.[Ru0,(bipy){I0,(OH),}]*1.5H20 and [OsO,(L-L){IO,(OH),)] (L-L = bipy phen 2,2’-dipyridylamine) which may be complexes of interest as catalysts for organic oxidation^.'^ A seriesof iron complexes formed according to equation (3),including the crys tallograp hicall y characterized K,Na [Fe,I ,O,,H 7]0 14H 0,have Anderson- type polyanions with a central FeO octahedron surrounded by distorted FeO and 10 groups.” Fe(N0,),-9H20 + NaIO,% [Fe,1302,H,,] 3M,[Fe,I,O,,H~, -,J (3) Iodosobenzene in the presence of iron porphyrins as catalysts continues to be used as a convenient oxidizing agent in organic systems.56 Supporting the metallopor- phyrins on silica results in a 10-fold decrease in reaction rate compared to the homogenous ~atalysis.’~ Iodosobenzene has also been used in the preparation of a series of Pt,Re 0x0 clusters58 and [Ru(q2-O=S0,)(PMe,),(cp*)]PF6which represents the first complex between a transition metal and The related iminoiodinanes (R,H,C,)IN(SO,C,H,Me-4) (R = H, Me,-2,4,6) have been crystallographically characterized.The essentially monomeric iminoiodinane units are bridged by I -0 N or I -0. O interactions.,’ 5 Cationic Iodine and Other Organoiodine Compounds A convenient two-step method for the conversion of alcohols to fluorides involves the treatment of 5-methyl dithiocarbonates (xanthates) with 4-methyl(difluoroiodo)ben-zene.,l The lower degree of intermolecular association in sterically encumbered molecules has been illustrated by structural studies on 2,4,6-Pri,C6H21C1260 and 2,6-(3,5-C1,-2,4,6-Me3~6)~6H~I~~262 in which the electrophilic ‘T’-shaped iodine(II1) moieties weakly associated by intermolecular C1-..I interactions are held in protective pockets.It should be noted that the C-I and I-C1 bond lengths are longer than those observed for PhICl (7) for which the crystallographic data has been re-evaluated in terms of a polymeric structure.62 Iodobenzene dichloride has been used in the synthesis of 1,3,6-[W,C15(PMe,),] the first structurally characterized example of a W25+ 108 E.G.Hope Phenyliodine(II1) bis(trifluoroacetate) has been suggested as a radical-cation-generating reagent of comparable oxidizing potential to that of [T1(02CCF,),]64 whilst the related bis(acetate) salt has been used in the synthesis of phenylco- (trimethylsilyl)phenyl]iodonium trifluoromethanesulfonate (triflate) which is a con- venient reagent for the generation of benzyne under mild/neutral conditions since although it can be stored easily for extended periods reaction with [NBu,]F at room temperature gives ben~yne.~' Stang and co-workers66 have described the fascinating syntheses of hybrid iodonium-transition metal cationic tetranuclear macrocyclic squares (8).The interac- tion of bis[4-(4'-pyridyl)phenyl]iodonium triflate or bis(4-pyridy1)iodonium triflate with cis-[M(OSO,CF,),L,] (L = PEt,; L = dpp; M = Pd Pt) generate the squares by self-assembly. Crystallographic characterization of one of the derivatives indicates a rhomboid-like geometry rather than a perfect square and three-dimensional channels which may be a source of other useful molecular interactions and potential host-guest chemistry.66 Bis(2,6-difluorophenyl)iodine(111) triflate has been synthesized by anion exchange from the BF -salt,67 and vinyl(pheny1)iodonium salts [e.g. (9) prepared using iodosylbenzene] offer a remarkable nucleofuge the phenyliodio group which is lo6times more reactive than triflate.68 A range of iodonium cations including [I([14]- aneN,)(NCMe)]PF, [I([ 14]aneN,)]I and [I(SMe2),]UF6 have been prepared either by displacement of acetonitrile from [I(NCMe),] + or by direct reaction between iodine and the macr~cycle.~~ Laser flash photolysis of PhCH(I)CH,CH,CH,CH(I)Ph leads to (lo) a cyclic hypervalent iodine radical as a transient intermediate.70 The Halogens and Noble Gases 109 6 The Noble Gases Theoretical and experimental work (29Siand 12'Xe NMR and ESR spectroscopy and powder XRD) on the structural order and textural uniformity of xeolites and doped/exchanged xeolites using the noble gases have been extensively de~cribed.~ ' Xenon-129 NMR spectroscopy has also been used in the study of clathrate formation where small and large clathrate cages have been observed using optically enhanced NMR technique^.,^ The technique has also been used to study intermolecular assemblies of acetyleneureas and shown them to assemble into dimeric capsules by xenon binding.73 High pressure and high temperature 3He labelling used previously to investigate 0-and C,,-fullerenes has been applied to a study of a mixture of isomers of c76-9 c78-and C,,-fullerenes by 3He NMR spectroscopy.This has revealed that since each isomer gives a single resonance due to an endohedral complex five isomers for C,,-fullerene and eight isomers for C,,-fullerene exist not three for each as suggested previo~sly.~~ Other endohedral noble gas-fullerene complexes have been described. A review article extols the virtues of supercritical xenon in particular as a useful spectroscopically transparent solvent for chemistry and supercritical fluid chromatog- raphy with FTIR detection of the analyte~.~ This is elegantly demonstrated by the characterization for the first time by IR spectroscopy of carbonyllithium and acyllithium (species postulated as intermediates in organolithium chemistry) and the corresponding isocyanide products in supercritical xenon.77 Furthermore although it is generally established that photodissociation of a ligand from a transition-metal complex results in the formation of a solvent-stabilized metal centre the free 16-electron complex [Co(CO)(cp)] is observed on UV irradiation of [Co(CO),(cp)] in liquefied krypton or xenon., One of the aims of cluster science is that of determining how large a chunk of matter must be before it can be called macroscopic.Using IR spectroscopy of molecular beams of the noble gases seeded with SF it has been shown that for argon and krypton the f.c.c. lattice appears at 2000 200 atoms7' 7 Noble Gas Compounds A range of metal-atom noble gas complexes including van der Waals complexes such as CuKrY8' and electrostatic complexes such as [CaAr] +,81 have been spectroscopi- cally or theoretically investigated and a review article in this area has been published.82 The spectroscopic confirmation of the hydrogen-noble gas bond has been described. The UV irradiation of HX (X = C1 Br I) in noble gas (Kr Xe)matrices yields the linear + + [Kr-H-Kr] and [Xe-H-Xe] centrosymmetric cations.Annealing the matrices results in the production ofstrong absorptions in the 1700-1000cm- 'region which are assigned to [H-KrlX and [H-Xe]X.83 Additional absorptions in xenon matrices which show a strong hydrogen dependence but no halogen dependence are assigned to XeH (the deuterio analogue is also described) in which the bonding is explained in terms of ionic HXe'H- and H-Xe+H which are analogous to the valence-bond descriptions of XeF2.84 Ab initio calculation^^^ are in good agreement with the 110 E.G. Hope observed spectra (v2 = 701; v3 = 1166 1181 an-'). It is unlikely that XeH will be stable in the solid state. Xenon difluoride continues to find application in transition-metal and main-group fluorine chemistry.Controlled oxidation of [Ir4(CO),,] in anhydrous HF affords fac-[IrF,(CO),] which contains predominately a-bonded carbonyl ligands with high CO stretching frequencies.86 The mechanism of the XeF oxidation of low-valent metal complexes has been elucidated in reactions with [M(CO),(PPh,),] (M = Ru 0s) which proceed via XeF+ oxidation to give a monofluorinated cation subsequent F-attack at co-ordinated CO and CO elimination gives finally [MF,(CO),(PPh,),].87 Xenon difluoride has also been used in a study on the Lewis-acid behaviour of [Te(OTeF,),] toward [OTeF,] -[(equation (4)].88 The hyperfluorination of c60-fullerene by KrF gives complexes ranging from C60F44 to C,,F7 as determined by mass spectrometry and in comparison with other fluorination methods the concentra- tion of oxygenated derivatives is 2[Te(OTeF,),] -+ XeF =fl2LTeF(OTeF5),] -+ Xe(OTeF,) (4) Thirty years after the first description of the [XeOF,] -anion two publications have described a re-investigation of this ion with different cations.A single-crystal structural investigation of the NO + salt indicates a pentagonal-pyramidal structure for the anion (oxygen apical) in which xenon is co-ordinatively unsaturated and forms two weak intermolecular Xe * * F interactions with adjacent anions.g0 An analogous structure (C,,) has been proposed for the "Me4]+ salt on the basis of vibrational data and theoretical cal~ulations.~~ The most recent theoretical study on XeF uses a much larger data set and predicts the C, structure to have the lowest energy; the alternative C, and 0 structures are transition states with imaginary vibrational frequencies which lead to the C, structure.The calculated properties agree well with previous experimental data.92 Further work on the vibrational spectra of salts containing the [XeF,]+ and [Xe,F,,]+ cations has been reportedg3 and the xenon(v1) salts of [NiF,],-react with Lewis acids in anhydrous HF to give [NiF,] which is stable to -60 OC.' The reduction potentials of a series of arylxenon(I1) tetrafluoroborate salts have been measured by cyclic v~ltammetry.~~ These complexes are less strong oxidizers than the comparable aryliodonium salts. Anion exchange of [Xe(C,H,F,-2,6)]BF4 with trimethylsilyltriflate gives the comparable triflate salt.67 As part of a systematic study of organoxenon(I1) compounds the reactions of [Xe(C,F,)]ASF with (i) halide ions in acetonitrile giving aromatic and coupled-aromatic moleculesg6 and with (ii) pyridines of different basicities where co-ordination weakens the Xe-C bond and promotes C6F radical formation have been outlined; the adduct [Xe(C6F,)(NC,H,F,-2,6)]AsF has been crys tallographicall y characterized.References 1 American Chemical Society George H. Cady Memorial Symposium J. Fluorine Chern. 1995 71 155. 2 International Conference on Fluorine Chemistry J. Fluorine Chern. 1995 72 157. 3 J. H. Holloway and E. G. Hope in The Chemistry of Fullerenes ed. R. Taylor World Scientific Singapore 1995 p. 109; R. Taylor in The Chemistry of Fullerenes ed. R. Taylor World Scientific Singapore 1995 p.123. The Halogens and Noble Gases 4 R.D. Chambers M. P. Greenhall and J. Hutchinson J. Chem. SOC.,Chem. Commun. 1995,21. 5 R.D. Chambers C. J. Skinner J. Thomson and J. Hutchinson J. Chem. Soc. Chem. Commun. 1995 17. 6 R.D. Chambers G. Sandford and M. Atherton J. Chem. SOC.,Chem. Commun. 1995 177. 7 J.L. Kampa J. W. Nail and R. J. Lagow Angew. Chem. Int. Ed. Engl. 1995,34 1241. 8 K. Sung and R. J. Lagow J. Am. Chem. SOC. 1995,117,4276. 9 T. Ono K. Yamanouchi R.E. Fernandez and K.V. Scherer,jun. J. Fluorine Chem. 1995,75 197. 10 R.E. Banks and M.K. Beshecsh J. Fluorine Chem. 1995,74 165. 11 0.Kramer and B.G. Miiller 2. Anorg. Allg. Chem. 1995 621 1969. 12 G. Lucier J. Miinzenberg W. J. Casteel jun. and N.Bartlett lnorg. Chem. 1995 34 2692. 13 I. C. Tornieporth-Oetting and T. M. Klapotke Chem. Ber. 1995,128 957. 14 R. Taylor G. J. Langley J. H. Holloway E. G. Hope A. K. Brisdon H. W. Kroto and D. R. M. Walton J. Chem. SOC.,Perkin Trans. 2 1995 181. 15 A. Zedda and D.D. Desmarteau Inorg. Chem. 1995,34 5686. 16 M. Namavari N. Satyamurthy and J. R. Barrio J. Fluorine Chem. 1995 74 113. 17 R.D. Chambers C. J. Skinner M. Atherton and J. S. Moilliet J. Chem. SOC. Chem. Commun. 1995 19. 18 P. Imhoff J. H. Giilpen K. Vrieze W. J.J. Smeets A. L. Spek and C.J. Elsevier Inorg. Chim. Acta 1995,235 77. 19 L. J. Baker C. E. F. Rickard and M. J. Taylor J. Chem.SOC.,Dalton Trans. 1995,2895;N. Bricklebank S. M. Godfrey H. P. Lane C.A. McAuliffe R. G. Pritchard and J.M. Moreno J. Chem. Soc. Dalton Trans. 1995 2421,3873. 20 L.A. Walker 11 S. Pulen B. Donovan and R. J. Senison Chem. Phys. Lett. 1995 242 177. 21 E. Ruiz and S. Alvarez J. Am. Chem. SOC.,1995 117 2877. 22 See for example H. I. Bloemink K. Hinds J. H. Holloway and A. C. Legon Chem.Phys. Lett. 1995,245,598; H. I. Bloemink S.J. Dolling K. Hinds and A.C. Legon J. Chem.Soc. Faraday Trans. 1995,91,2059and refs. therein. 23 R. Herges Angew. Chem. Int. Ed. Engl. 1995 34 51. 24 H. Tachikawa and E. Komatsu Inorg. Chem. 1995 34 6546. 25 G. Bellucci C. Chiappe R. Bianchini D. Lenoir and R. Herges J. Am. Chem. SOC.,1995 117 12001. 26 R. Minkwitz and D. Konkowski Z. Naturforsch. Teil B 1995,50 1277. 27 B. Krumm R. L. Kirchmeier and J. M. Schreeve Inorg. Chem. 1995 34 5049.28 A. Russo and D. D. Desmarteau Inorg. Chem. 1995 34 6221. 29 J. Grebe K. Harms F. Weller and K. Dehnicke 2. Anorg. Allg. Chem. 1995 621 1489. 30 H.I. Bloemink K. Hinds A. C. Legon and J. H. Holloway J. Chem. SOC.,Chem. Commun. 1995,1833 and refs. therein. 31 A.C. Legon J. Chern. Soc. Faraday Trans. 1995 91 1881 and refs. therein. 32 R. Minkwitz R. Briichler and H. Prent Z. Anorg. Allg. Chem. 1995 621 1247. 33 H.J. Frohn S. Gorg G. Henkel and M. Lage Z. Anorg. Allg. Chem. 1995,621 1251. 34 K.O. Christe J. Fluorine Chem. 1995 71 149. 35 K.-F.Tebbe and M. Bittner,Z. Anorg. Allg. Chem. 1995,621,218;H. Stegemann,A. Oprea and K.-F. Tebbe Z. Anorg. Allg. Chem. 1995,621,871;K.-F. Tebbe and K. Nagel,Z. Anorg. Allg. Chem. 1995,621,225;K.-F. Tebbe M.El Essawi and S.A. El Khalik Z. Naturforsch. Teil B 1995 50 1429. 36 K.-F. Tebbe and T. Farida Z. Naturforsch. Teil B 1995 50 1440 1685. 37 H. Stegemann K.-F. Tebbe and L.A. Bengtsson Z. Anorg. Allg. Chem. 1995,621 165. 38 P. C. Junk L. R. MacGillivray M.T. May K. D. Robinson and J. L. Atwood Inorg. Chem. 1995,34,5395. 39 A. J. Blake R. 0.Gould S. Parsons C. Radek and M. Schroder Angew. Chem.,Int. Ed Engl. 1995,34,2374. 40 D. Naumann and A. Meurer J. Fluorine Chem. 1995 70 83. 41 D.Y. Chi P.J. Lidstrom Y.S. Choe T.A. Bonasera M. J. Welch and J.A. Katrzenellenbogen J. Fluorine Chem. 1995 71 143. 42 A.R. Mahjoub X. Zhang and K. Seppelt Chem. Eur. J. 1995 1 261. 43 I. C. Tornieporth-Oetting and T. M. Klapotke Angew. Chern.,Int. Ed. Engl. 1995,34 51 I; A. Schultz I.C. Tornieporth-Oetting and T. M. Klapotke Inorg. Chem. 1995 34 4343. 44 See for example U. Rockland H. Baumgartel E. Ruhl 0. Losking H.S. P. Miiller and H. Willner Ber. Bunsenges. Phys. Chem. 1995,99,969; 0.V. Rattigan R. A. Cox and R.L. Jones J. Chem. SOC.,Faraday Trans. 1995 91 4189. 45 See for example H. W. E. Mereand and A. W. Castleman,jun. J.Phys. Chem. 199S,99 15 678; C. J. Pursell J. Conyers P. Alapat and R. Parveen J. Phys. Chern. 1995 99 10433. 46 M. H. Harwood D. M. Rowley R.A. Freshwater R.A. Cox and R. L. Jones J. Chem. Soc. Faraday Trans. 1995,91 3027. 47 J. J. Orlando and J. B. Burkholder J. Phys. Chrm. 1995 99 1143. 48 A. A. Turnipseed M. K. Gilles J. B. Burkholder and A. R. Ravishankara Chem. Phys. Lett. 1995,242,427. 49 T.Kraft and M. Jansen J. Am. Chem. Soc. 1995 117 6795. SO R. Minkwitz T. Hertel and H. Preut Z. Anor-g. Allg. Chern. 1995 621 1552. 51 K. Takase H. Masuda 0.Kai Y. Nishiyama S. Sakaguchi and Y. Ishii Chem. Lett. 1995 871. 52 T. Kraft and M. Jansen Z. Anorg. Allg. Chern. 1995 621 484; A. C. Blackburn and R. E. Gerkin Acta 112 E.G. Hope Crystallogr. Sect. C 1995,51,3; M. Sasaki T. Yarita and S. Sato Acta Crystallogr. Sect. C 1995,51,1968. 53 A.T. Blades J.S. Klassen and P. Kebarle J. Am. Chem. Soc. 1995 117 10563. 54 A.J. Bailey W. P. Grieth and P.D. Savage J. Chem. SOC.,Dalton Trans. 1995 3537. 55 E. M. Jones W. Levason R. D. Oldroyd M. Webster M. Thomas and J. Hutchings J. Chem. Soc. Dalton Trans. 1995 3367. 56 G.J. Harden and M. M. Coombs J.Chem. SOC.,Perkin Trans. 1 1995,3037; G. J. Harden J. Chem. SOC. Perkin Trans. 2 1995 1883; J. W. Sam X.-J. Tang R. S. Magliozzo and J. Peisach J. Am. Chem. SOC.,1995 117 1012. 57 C. Gilmartin and J. R. L. Smith J. Chem. SOC.,Perkin Trans. 2 1995 243. 58 J. Xiao J. Hao R. J. Puddephatt L. Manojlovic-Muir and K. W. Muir J. Am. Chem.SOC.,1995 117,6316. 59 E. Dombrowski and W.A. Schenk Angew. Chem. Int. Ed. Engl. 199534 1008. 60 A.K. Mishra M.M. Oldstead J. J. Ellison and P.P. Power lnorg. Chem. 1995,34 3210. 61 M. J. Koen F.L. Guyader and W.B. Motherwell J. Chem. SOC.,Chem. Commun. 1995 1241. 62 J. D. Protasiewicz J. Chem. Soc. Chem. Commun.,1995 11 15. 63 F.A. Cotton and E.V. Dikarev lnorg. Chem. 1995,34 3809. 64 L. Eberson M. P. Hartshorn and 0. Persson Acta Chem.Scand. 1995,49,640. 65 T. Kitamura and M. Yamane J. Chem. SOC.,Chem. Commun. 1995,983. 66 P. J. Stang and K.Chen,J. Am. Chem. SOC.,1995,117,1667; P. J. Stang K. Chen and A. M. Arif J.Am. Chem. SOC.,1995 117 8793. 67 D. Naumann R. Gnann V. Padelidakis and W. Tyrra J. Fluorine Chem. 1995 72 79. 68 T. Okuyama T. Takino T. Sueda and M. Ochiai J. Am. Chem. SOC.,1995 117 3360. 69 W. Shi Hua S.I. Ajiboye G. Haining L. McGhee R.D. Peacock G. Peattie R. M. Siddique and J.M. Winfield J. Chem. Soc. Dalton Trans. 1995 3837. 70 J. T. Banks H. Garcia M. A. Miranda J. Perez-Prieto and J. C. Sciano J. Am. Chem. SOC.,1995 117 5049. 71 See for example R. Ryoo and J. M. Kim J. Chem. SOC.,Chem. Commun. 1995,711; C. I. Ratclime and J.A. Ripmeester J. Am. Chem. SOC.,1995,117,1445; R.H. Jones P. Lightfoot and R. M. Ormerod J.Chem. SOC. Chem. Commun. 1995 783. 72 T. Pietrass J.C. Gaede A. Bifone A. Pines and J. A. Ripmeester J. Am. Chem. SOC. 1995 117 7520. 73 N. Brauda R.M. Grotzfeld C. Valdes and J. Rebek jun, J. Am. Chem. SOC.,1995 117 85. 74 M. Saunders H. A. Jimenez-Vazquez R. J. Cross W. E. Billups C. Gesenberg A. Gonzalez W. Luo R. C. Haddon F. Diederich and A. Herrmann J. Am. Chem. Soc. 1995 117 9305. 75 M.-S. Son and Y. K. Sung Chem. Phys. Lett. 1995,245,113; C.G.Joshin C. G. Cray and S.Goldman Chem. Phys. Lett. 1995 244; 93; T. Braun and H. Rausch Chem. Phys. Lett. 1995 237 443. 76 M. PoliakofT S. M.Howdle and S.G. Kazarian Angew. Chrm. lnt. Ed. Engl. 1995 34 1275. 77 M. Tacke Chem. Ber. 1995 128 1051.78 A.A. Bengali R.G. Bergman and C. B. Moore J. Am. Chem. SOC. 1995 117 3879. 79 S. Goval D. L. Shutt and G. Scoles J. Chem. Phys. 1995 102 2302. 80 L. R. Brock and M. A. Duncan Chem. Phys. Lett. 1995 247 18. 81 T. Buthelezi D. Bellert V. Lewis and P.J. Brucat Chem. Phys. Lett. 1995 246 145; 242 627. 82 W. H. Breckenridge C. Jouret and B. Soep in Adcancrs in Metal and Semiconductor Clusters ed. M. A. Duncan JAI Press Greenwich 1995 vol. 111. 83 M. Pettersson J. Lundell and M. Rasanen J. Chem. Phys. 1995 102 6423. 84 M.Pettersson J. Lundell and M.Rasanen J. Chem. Phys. 1995 103 205. 85 N. Runeberrg M. Seth and P. Pyykko Chem. Phys. Lett. 1995 246 239. 86 S. A. Brewer A. K. Brisdon J. H. Holloway E. G. Hope L. A. Peck and P.G. Watson J. Chem. SOC.,Dalton Trans.1995 2943. 87 S. A. Brewer K. S. Coleman J. Fawcett J. H. Holloway E.G. Hope D. R. Russell and P.G. Watson J. Chern. SOC.,Dalton Trans. 1995 1073. 88 H. P. A. Mercier J.C. P. Sanders and G.J. Schrobilgen lnorg. Chern. 1995,34 5261. 89 O.V. Boltlina A.K. Abdul-Sada and R. Taylor J. Chem. Soc. Perkin Trans. 2 1995 981. 90 A. Eltern and K. Seppelt Angew. Chem. lnt. Ed. Engl. 1995 34 1586. 91 K.O. Christe D.A. Dixon J.C. P. Sanders G. J. Schrobilgen S.S. Tsai and W. W. Wilson lnorg. Chem. 1995,34 1868. 92 T.D. Crawford K. W. Springer and H. F. Schaefer Ill J. Chem. Phys. 1995,102 3307. 93 S. Milicev Vih.Spectrosc. 1995,8,309 (Chem. Abstr. 1995 122 1 17753); Sh. Sh. Nabiev Zh. Neorg. Khim. 1995,40,2016 (Chem. Ahstr. 1995 124,070177). 94 B. iemva K.Lutar L. Chacon M. Fele-Beuermann J. Allman C. Shen and N. Bartlett J. Am. Chem. Soc. 1995,117 10025. 95 D. Naumann R. Gnann N. Ignat’ev and S. Datsenko Z. Anorg. Allg. Chem. 1995,621 851. 96 H. J. Frohn A. Klose V.V. Bardin A. J. Kruppa and T. V. Leshina J. Fluorine Chem. 1995,70 147. 97 H. J. Frohn T. Schroer and G. Henkel Z. Naturforsch. Teil B 1995 50 1799.

ISSN:0260-1818    

DOI:10.1039/IC9959200103

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

9 Zinc Cadmium and Mercury By I.6. GORRELL School of Chemistry and Molecular Sciences University of Sussex Falmer Brighton BNlgQJ UK 1 Introduction This chapter summarizes results published in the literature during 1995. Porphyrins and phthalocyanines are not included. Zinc cadmium and mercury have been covered in reviews on intermolecular co-ordination in organometallic compounds,' developments in the chemistry of derivatives containing NC,H,(CH(SiMe,)}-2 NC,H,(C(SiMe,),)-2 and related ligands, and precursor chemistry for the deposition of 11-VI semiconductor^.^ A major reference work which covers the organometallic chemistry of these elements has also appeared. 2 Zinc X-Ray diffraction studies of nearly 40 organozinc compounds have been re~iewed.~ The co-ordination geometry of divalent zinc cations has been investigated using the crystal structures of small molecules containing this cation found in the Cambridge Structural Database and by ab initio calculations on [Zn(H,0),]2'*rnH,0 (n = 1-6 rn = 0-2).The results were compared to those obtained for beryllium and magnesium.6 Carbon-donor ligands A 13C solid-state NMR study of I3CO in zeolite Zn-Y and on ZnO led to the observation of a zinc carbonyl species.' Electrolysis of CF,Br in dmf using zinc or cadmium anodes yielded MBr(CF,) and M(CF,) (M = Zn Cd); the mechanism of these reactions was discussed.8 Matrix-isolated MH(Me) (M = Zn Cd Hg) obtained in reactions of excited metal atoms with methane have been studied using IR ~pectroscopy.~ Density-functional methods and force-field calculations have indicated regular helical structures for a series of gaseous cyanide anions [M,(CN),,+ '1-(M = Zn Cd; x = 1-27) formed by laser ablation of M(CN),." An ab initio study of the mechanism of the aminoalcohol-promoted reaction of dialkylzinc compounds with aldehydes has appeared.' Nitrogen- and phosphorus-donor ligands A series of monomeric four-co-ordinate zinc complexes [ZnR(HB(bpz),)] and 113 114 I.B. GorrelI Fig. 1 Crystal structure of K[ZnMe(Bu'NCH=CHNBu')]-thf (Reproduced by permission from J. Chem. Soc. Chem. Commun. 1995 1839) [ZnR( HB(dmpz),)] (R = Me Et) has been prepared from thallium hydroborates and ZnR,. The three-co-ordinate derivatives [ZnR{ H,B(bpz),)] (R = Me Et But) and the hydride [ZnH( HB(bpz),)] were similarly prepared.Reactivity studies led to the isolation of [ZnX{HB(bpz),)] (X = O,CH O,CMe C,Ph SH OSiMe, CN N, NCS C1 Br I) C(zn(~-oH)CH2B(bpz>,l),l CZn(?2-0,CMe)(H,B(bpz)2)] and [ZnR(HB(OR')(bpz),)] (R' = Me Et Pri). Several compounds including [Zn(HB(dmpz),),] were crystallographically characterized.' The reaction of [MeZn(Bu'N=CHCH(NBu')CH(NBu')CH=NBu')ZnMe]with potassium in thf afforded K[ZnMe(Bu'NCH=CHNBu')]*thf a linear polymer of alternating cations and anions (Fig. l).' A series of phosphaallyl complexes [M(RNPNR'),] (M = Zn Cd; R = SiMe, R' = C6H2BU',-2,4,6; M = Zn R = R' = C6H,Pri,-2,6 Bu'; R = C6H4Pri-4 R' = C6H,Bu',-2,4,6; R = c6H,Bu',-2,4,6 R' = Bu' adamantyl) and [in((2,4,6-Bu',C6H,)NPPj(C,H,But3-2,4,6))Me] have been prepared and character- ized.' A mixture of CuI and ZnI in pyridine gave crystals of [Cuo~,,Zno~081,(py),]~2py which contained a square-planar arrangement of pyridines with axial iodides.' A quasi-octahedral co-ordination sphere of two trans imidazolium nitrogen atoms and four square-planar water molecules has been found in a zinc complex of 3-(imidazol-5- yl)prop-2-enoic acid molecules were linked by hydrogen bonding.I6 The structure of [Zn(bipy),][ClO,] has been determined.17 A distorted-tetrahedral environment was found for the metal centres in [MCl,L,] (M = Zn Cd; L = creatinine;18 M = Zn L = anta~oline'~), [ZnCl,(C,H,N,),] in which the zinc centres were bonded to N(7) of the purine ligands,,' and [Zn(C,,H 1N20,),(NH3)2]~0.5H,0 zinc being co- ordinated to two deprotonated diphenylimidazolidine-2,4-dionatoligands and two ammines.,' The preparations of ZnX,L [L = N,N'-ethylenebis(pyrrolidin-2-one); Zinc Cadmium and Mercury X = NO, C1 Br I] ZnX,L (X = ClO, BF,) Cd2(N03),L3 and Cd(NO,),L,-H,O have been reported and several were characterized by X-ray crystallography.22 A series of zinc complexes containing the dithiosquarate ligand and a bidentate nitrogen base have been prepared and characterized and some photophysical properties reported., Reaction of Zn(NO,) with (EtO,C),CC(SK) (K,L) and en gave [Zn(L)en] which has been studied using spectroscopic conductivity and magnetic measurement~.~~ A polymeric chain was present in [Zn(C,H,NCO,),] in which trans L-prolinato ligands bonded through nitrogen and one carboxylate oxygen with a fifth site occupied by the other oxygen of a neighbouring molecule.25 Reaction of lY2,4-1H-triazole (HL) with ZnC1 in EtOH gave [ZnCl(L)] in which each metal ion was surrounded by three nitrogen atoms from different ligands and a chloride.Each ligand was simultaneously bonded to three different zinc atoms through its three nitrogen atoms leading to the formation of polymeric chains.26 Reaction of K[Zn(CN),] ZnC1 and py in aqueous solution yielded [Zn(py),][Zn(CN),] with a polymeric structure of alternate arrays of tetrahedrally and octahedrally co-ordinated zinc atoms bridged by cyanide ligand~.,~ A quartz-like net structure was observed for [ZnAu,(CN),] in which each silicon atom was replaced by zinc and each Si-0-Si link by Zn-NC-Au-CN-Zn.28 The crystal structure of [Zn(4,4'-bipy),(SiF6)]n*xdmfshowed squares with zinc at the corners and 4,4'-bipy along the sides.These two-dimensional networks were connected along the c axis by bridging anions.29 The crystal structure of [Zn(CN)(NO,)L,,,] [L = 2,4,6-tris(4-pyridyl)-1,3,5-triazine] revealed two identical interpenetrating three-dimen-sional nets each composed of cages made up from six [Zn(CN)(NO,)] squares linked by eight L units.30 The reaction of [M{N(SiMe,),},] (M = Zn Cd) with Bu',P(E)NHR (E = Se Te; R = Pri C6Hl1) gave the monomeric and sublimable complexes [M{ Bu',P(E)NR),]; the mixed-ligand compounds [Zn{ N(SiMe,),}(Bu',P(E)NR}] were also prepared.,' Metallation of Ph,PH with ZnEt (5:3) in thf produced [{Zn(p-PPh,)(Et)},(HPPh,),(thf)] which contained a Zn,P ring.32 The 1:1 reaction of ZnR (R = Me Et Pri Bun Bu' CH,SiMe,) with (Me,Si),PH yielded [ZnR{P(SiMe,),}].The compounds were dimeric or trimeric depending upon the size of R in the solid state and in solution; [Zn{ C(SiMe,),}{ P(SiMe,),}] was monomeric.33 Likewise reaction of ZnR (R = Me Et CH,SiMe,) with AsH(SiMe,) yielded [ZnR{ As(SiMe,),}] which crystallized as dimers or trimers again depending upon the size of R., Reaction of ZnC1 with Ph,PSiMe and PR'R2 (R' = Ph R2 = Et; R' = Me R2 = Pr"; R' = R2 = Bun) gave [Zn,Cl,(PPh,),(PR'R2,),] and of ZnC1 with PhP(SiMe,) or Bu',PSiMe in thf yielded [Zn,Cl,(PhPSiMe,),(thf),l or [{ZnCl(PBu',)},] respectively. All were crystallographically characterized.35 Oxygen-donor ligands Electrochemical oxidation of zinc in a solution of 1-methylimidazoline-2-thione(HL) in MeCN gave [Zn,OL,] containing a central oxygen bonded to a tetrahedral array of zinc atoms with six bridging thionato ligand~.,~ The alkyl carbamates [M,R,(0,CNEt,)6] (M = Zn R = Me Et; M = Cd R = Me) have been prepared and characterized. The crystal structure of [Zn,Me,(O,CNEt,),] [Fig. 2(a)] revealed a planar array of zinc atoms whereas [Zn,Me,(O,CNEt,),] [Fig. 2(b)] formed by its reaction with ZnMe, contained a tetrahedral arrangement of zinc atoms.37 The magnetic and spectroscopic properties of a series of complexes [M3L6(H20)6]- 116 I.B. Gorrell t Fig. 2 Crystal structures of (a)[Zn,Me,(O,CNEt,),] and (b)[Zn,Me,(O,CNEt,),] (Reproduced by permission from J.Chem. SOC. Dalton Trans. 1995 1043) X,*xH,O (L = 3-methyl-4-phenyl-l,2,4-triazole, X = CIO, M = Zn x = 0; M = Cd x = 5; X = BF, M = Zn Cd x = 0) have been in~estigated.~~ The zinc centres were trigonal bipyramidal in the dimer [Zn2(C3H50,),(C6H6N20),] with two bidentate bridging and one monoden tate propionate ligands and two apical nicotinamide ligand~.~' The crystal structure of [Zn(C,0,)(OH,),(dmso)2] revealed extended chains of zinc squarate linked by hydrogen bonds to form a layer structure. At 25-100 "C in aqueous solution conversion to the known three-dimensional cage network Zn(C,O,)(OH,) o~curred.~'An X-ray crystallographic study has shown that the pyridone oxygen atom bridges pairs of zinc atoms to form Zn,O units which in turn Zinc,Cadmium and Mercury are linked by N,N’-p-phenylenebis(rnethylenepyridin-4-one)(L) bridges forming com- plex arrays of 34- and 38-membered rings in [Zn,L4][BF,]4-4H,0.41 The crystal structure of NaA,[Zn,{ H(CO,),)(CO,),(H,O),] (A = K Rb) revealed two-dimen- sional Zn,(H(C0,),}(C03),(H20)2 layers with zinc in a distorted trigonal-bi-pyramidal geometry.42 The syntheses and structures of two new carbamates of zinc [Zn(O,CNEt,),(tmen)] and [Zn,Me(O,CNEt,),(py)] have been reported.43 The 4-cyanopyridine complex of zinc crotonate was dimeric with square-pyramidal zinc whereas the vinylpyridine complex was polymeric with five-co-ordinate zinc.44 The zinc centres in [Zn(PhCO,),(tu),] and [Zn(OAc),(OC(NH,),),] adopted a distorted tetrahedral ge~metry.~’.~~ The crystal structure4’ of the nitroacetophenonato com- plex [Zn{(ON(0)CHC(Ph)O},(py)2] and the synthesis48 of [ZnCl (EtO2CCH,N(H)CH,CO2}(H20)]have been reported.Aerosil (colloidal silica) has been shown to react with ZnMe to give Zn(0Si)Me and SiMe surface structure^.,^ The geometrical structures of Zn(NO,) aqueous solutions over a wide range of concentrations have been determined using EXAFS spectros- copyso and hydrolysis of Zn” in OSm~ldm-~ NaX (X = NO, C1 ClO,) gave [Zn(OH)] in all three media but Zn(OH),(aq.) only in perchlorate solution^.'^ + Sulfur-and selenium-donor ligands A severely distorted square-pyramidal geometry was adopted by the zinc centre in [{ Zn(c,H,S,)(bipym)),].One sulfur atom of the benzenedithiolate ligand bridged the metals while the second was terminally bound.’ The organic conductors Let],- [MM’(SCN),] (M = K Rb Cs; M’ = Co Zn Cd) have been prepared and some crystallographically characterized. Resistivities were also rep~rted.’~ Reaction of KCS with Zn(acac) or CdC1 followed by addition of [PPh,]Cl gave [PPh4]- [M(CS,),] (M = Zn Cd).54 The crystal structures of [Zn(SPh),( 1-mim),] and “Me,] -[Zn(SPh),(l-mim)] and their reactivity with (MeO),PO has been reported. The relevance of these results to the DNA methylphosphotriester repair site in Escherichia coli Ada was disc~ssed.~~ The structures of [(Zn(SBu‘)Me),] and its py and tmta adducts have been reported and their potential as precursors to ZnS disc~ssed.’~ The use of ZnMe and propylene sulfide to grow ZnS layers has been reported.57 Zinc powder was found to react with sulfur in donor solvents solv to give [ZnS,(solv),] [solv = tmen lmim 4-(dimethylamino)pyridine].The structure and reactivity of the tmen complex were rep~rted;’~ ZnS,-tmen has been used as a polysulfide-transfer reagent in the preparation of 1,2-Se,S,.59 The reaction of [Zn(N(SiMe,),),] with 2,6-(2,4,6-Me,H,C6),c6H,seH in hexane yielded the diselenolate with a linear geometry at zinc; recrystallization from thf gave the adduct which contained planar three-co-ordinate zinc.,’ Treating [Zn-{N(SiMe,),) ,] with [TeH(C,H Me,-2,4,6)] yielded [{ Zn[Te(C,H Me,-2,4,6)] )n] which on reaction with 1 equivalent of PMe gave the 1 1 adduct while an excess of Lewis base (PMe, 1-mim py dmpe) gave tetrahedral adducts.Heating these complexes led to the formation of cubic ZnTe.6’ Reactions of [MSe,12- with TePEt to give [MTe,Se,-,]’- (M = Zn Cd Hg; n = 0-4) have been investigated using 77Se and 125Te NMR and the crystal structure of [PPh,][Hg(Te,Se,),] has been deter- mined.62 The syntheses crystal structures and 125Te NMR spectra of [PPh,] [M(Te4)J (M = Zn Cd Hg) have been reported.63 A variety of bi- tetra- penta- and hexa-metallic compounds of general formula LnM(SePh),L (Ln = Eu Sm Yb; 118 I.B. Gorrell M = Zn Hg; L = py thf; x = 4 10 12; y = 3 4 6 7) have been prepared and structurally characteri~ed.~ Halogen-donor ligands Energies geometries force constants vibrational frequencies and dipole moments have been calculated for the free molecules MX MX and M,X and the solids M,X (M = Zn Cd Hg; X = F C1 Br I)using relativisticdensity-functional methods.65 The crystal structure66 of [NMe,][NEt,][ZnCl,] and the synthesis and structural chara~terization~~ of [H2L] [ZnCl,]*H,O (HL = 4,6-dimethyl-2-sulfanylpyrimidine) have been reported.Thermal decomposition of the latter yielded [ZnCl,(HL),] and [ZnL,]. The structure of [H,L][ZnBr,] (L = 4,6-diamino-2-methylsulfanyl-pyrimidine) showed anion tetrahedra hydrogen bonded to the cations.68 An X-ray powder diffraction and IR spectroscopic study of the hydrogen bonding in [Zn(NH,),]X (X = Br I) has been published6’ and reaction of PhP(S)(NMeNH,) with ZnC1 yielded the 1 1 adduct which gave polymetallic compounds on condensa- tion with aldehydes.70 3 Cadmium Carbon-donor ligands The zeolite-mimetic host clathrate [NMe,.xG][Cd,(CN),] showed highest inclusion selectivity for ethylbenzene from mixtures of ethylbenzene and xylene isomer^.^ The polymorphic behaviour of a series of Cd(CN) host clathrates has been discussed in terms of the geometry and functionality of the guest molecules.72 The clathrate Cd(CN),CCl has been studied using extended-Huckel tight-binding calculation^.^^ Donor-free Cd(CF,), which can act as a source of difluorocarbene has been obtained from CdEt and CF,I at -40°C.74 The crystal structures of [Cd(cp),L] (L = tmen pmdien) showed that the hapticity of the cyclopentadienyl ligand changed from q2 in the tmen complex to q1 in the pmdien complex.75 Nitrogen- and phosphorus-donor ligands X-Ray analysis of [CdMe,(dabco)] revealed a polymeric structure with cadmium in a distorted-tetrahedra1 en~ironment.~~A crystallographic study of [Cd(C,H,NO,S),(NH,),] revealed octahedral cadmium centres with square-planar ammines and axial saccharinato groups bonded through nitrogen.77 X-Ray crystallo- graphy showed that [Cd(en),][Ni(CN),] contained discrete ions whereas [CdNi(CN),].2H2N(CH,),NH,.rnH,O (n= 2-7 9; rn = 0-2) was constructed by catenation of ammine or [Ni(CN),] -units or both linking octahedral cadmium atoms.78 The [Ni(CN),12 -anions in [Cd(Hdabco)][Ni(CN),],-4NH2Ph acted as bidentate ligands between the cations along the a and c axes to form a two-dimensional network.Two monodentate (Hdabco) groups were axially co-ordinated to cadmium and the aniline molecules were hydrogen bonded to give an inclusion c~mpound.~’ Reaction of [Cd {N(SiMe,),) ,] with LiPPh yielded [Li( thf),] ,[Cd,(PPh,) J a crystallographic study of which showed an adamantane-like anion.80 Oxygen-donor ligands Reaction of Cd(BH,) with MOR (M = Li R = Et Bu‘ Ph mes; M = Na R = Bu‘) Zinc Cadmium and Mercury led to the formation of either addition products [Cd(BH,),(OR)] or ligand exchange to give [Cd(BH,)(OR)]. The model compound [CdMe(OBu')] was tetrameric in the solid state. With [Cd(OC6H,Me,-2,4,6),] Cd(BH,) gave [Cd(BH,)(OC,H,Me,- 2,4,6)].81 Reaction of Riecke cadmium with benzoquinone in thf yielded [Cd(C6H4O2'-)(thf),][C6H,O2'-] or ([Cd(C,H,O,'-)(thf),] + [C6H402'-]}.The radical anion was either symmetrically or asymmetrically co-ordinated to the The cadmium centres were pentagonal bipyramidal in [Cd(C,H,NCO,),(H,O)] which formed a polymeric network in which each nicotinate anion acted as a bidentate chelating carboxylate ligand to one cadmium and also bonded through nitrogen to a second cadmium.83 The crystal structure of polymeric tetraaquabis(ma1onato)di-cadmium showed six- and eight-co-ordinate cadmium atoms which were correlated with 'I3Cd NMR chemical shifts at 6 18 and -107 respe~tively.~~ Pyrazolylborate cadmium carboxylates were found to form 1 1 complexes with epoxides and subse- quent epoxide-carboxylate coupling provided epoxide oligomers with terminal ester groups.85 Cadmium complexes containing the betaine ligand triphenylphosphonio- propionate [{Cd[Ph,P(CH2)2C02],X}2]Y2 (X = NO, Y = NO, ClO,; X = C1 Y = ClO,) have been prepared and shown to possess a centrosymmetric tetrakis(p carboxylato-0,O')dimetal core.86 Sulfur- and selenium-donor ligands A new three-dimensional structure for a cadmium thiolate [Cd{ SCH,CH(OH)CH,OH},] has been publisheds7 and the structures of [Cd{ S,P(C,H 1)2}2]2CHC13 and its PBu' adduct and [{ Cd[S,P(OC,H ,),],),] have been determined.88.89 The preparation characterization and thermolysis of Cd(SR) (R = Pr' Bu' CH,Ph) Cd(SPr'),*l-mim and [(Cd(SCH,Ph),},].l-mim have been reported," as has a double-layer superlattice structure built up of [Cd3,S,,{SCH,CH(OH)CH3}36]~4H20 cl~sters.'~Layers of CdS have been grown from CdMe and propylene s~lfide.'~ Irradiation of CdS powder suspended in ethereal solutions of organolithium compounds LiR yielded cadmium and R via a radical mechanism.' Halogen-donor ligands The anions in 4,4-oxydianiliniumg4 and 4-nitroaniliniumg5 tetrachlorocadmates contained corner-sharing octahedra.The structure of 2-methylpentane-1,5-di-ammonium tetrachlorocadmate revealed layers of CdCl corner-sharing octahedra in a perovskite-like structure. Electronic and thermal properties were also reported.96 The crystal structures of [CuCl([ 14]aneN4)],[CdC1,] and [Cu([14]aneN4)]-[CdCl,(H,O),]Cl have been determined.97 The structures of [H2L][Cd,C1,(H,O),] and [HL'] [Cd3Cl,,(H,0)] (L = N,N'-dimethylpiperazine L' = N-methylpiperazine) both contained anion chains with cadmium atoms six-co-ordinate in the former and five- and six-co-ordinate in the latter.98 Reaction of 4,6-dimethyl-2-sulfanylpyrimidine (HL) with CdC1 yielded [CdL(OH)] and { [H,L][CdCl,]},; the latter contained face- sharing CdC1 ~ctahedra.~' The crystal structure of [C ,H7N,0][CdBr,].2H,0 indicated that the water was hydrogen bonded between the ions.'00 The structures of the tetramethylpyrazinium salts [C,H,,N,][CdI,]~nH,O (n = 0 3) revealed hydro- gen bonding involving either anions and cations (n = 0) or cations only (n = 3).'01 120 I.B. Gorrell 4 Mercury A theoretical study of mercury-photosensitized reactions has suggested the initial formation of exciplexes followed by insertion of Hg* into a reactive X-H bond (X = H CH, C,H, SiH,) giving ultimately X radicals and H atoms.'02 Carbon-donor ligands The structural data on more than 320 organomercury compounds has been reviewed.lo3 Weak Lewis acid-base interactions exist between the mercury centres and the halogen atoms in dimeric [{HgPh(CBrCl,)),].The angle at mercury is 179".'04 Reaction of HgC1 with o-lithio-(S)-( -)-dimethyl( 1-phenylethy1)amine gave (S)-[HgCl(C ,H,CH(Me)NMe,)] which contained a non-planar metal stereocentre. The bromide and iodide were isostructural. lo' The ylide Ph,PCHCOPh with HgX (X = C1 I) in MeOH yielded the centrosymmetric dimer [{HgX,[PhOCCHPPh,]},] (chloride as MeOH solvate). '06 The synthesis and thermal transformations of complexes of [Hg(Ge(CF,),},] with o-quinones have been reported."' A crystal structure revealed Hg-C 0 bonds in Hg(C,H,Bu',-1,2,4) prepared by sodium- amalgam reduction of the [BiC1(C5H,Bu',-1,2,4)] analogue.'" The formation of an exciplex 3[Hg(q2-C,H,)] has been proposed on the basis of experimental and theoretical studies to account for the unusual products in the mercury-photosensitized dehydrodimerization of a series of aromatic substrates.'09 The geometries and electronic structures of the complexes formed between halide anions and cyclic trimeric perfluoro-o-phenylenemercury and some of its analogues have been modelled using the MIND0 (modified intermediate neglect of differential overlap) method.' lo Nitrogen-donor ligands Both metal centres are approximately tetrahedral in [HgL,] [Hg(CF,CO,),]* 0.7CH2CI (L = 4-benzyl-1,7-diphenyl-2,4,6-triazahepta-2,5-diene).''' The crystal structure of [HgL2][CI0,],.6CI,HCCHC12[L = 2,4,6-tris(4-pyridyl)- 1,3,5-triazene] revealed a new three-dimensional framework. '' N-Acetylpyrrole and N-phenylsul- fonylpyrrole were each selectively mercurated in the 2-position with HgC1 and the products converted to the diorganomercury derivatives with sodium iodide. These compounds transferred the ligands to ruthenium and osmium.' l3 The crystal structure of [Hg(cryptand 222)][(Hg(SCN),},] showed a polymeric array of Hg-SCN-Hg chains with each mercury also linked to two terminal SCN ligands.' l4The structures of [HgI,(dabco)] and [Hg(SCN),(dabco)] revealed HgI units linked by dabco in a chain structure with tetrahedrally co-ordinated mercury and chains of Hg(SCN) units linked by dabco in a layer structure with octahedrally co-ordinated mercury atoms."' Polymeric chains were found in the structure of [HgI,(hmta)].' " Oxygen- and sulfur-donor ligands The Crystal structure of the betaine derivative [Hg,Cl,(C,H 18N202)2]revealed a centrosymmetric 16-membered ring fused with two six-membered rings and mercury in a distorted-tetrahedra1 environment.'" The structure of two two-dimensional double-betaine complexes [(2Hg,C16(L')*Hg2C14(L')),1 and [(Hg,CI,(L2)},] Zinc Cadmium and Mercury [O,CCH(NR,)CH,CH,CH(NR,)CO,; NR = NMe L1 py L2] have been re-ported.'" Mercury@) complexes containing flexible double betaines and chloride lkands C{ Hg2(L1)C14) "1 9 C( Hg,(L2)C1 )"I and [{ Hg,(L3)Cl >"I-[-O,CCH,N+Me,(CH,),N+Me,CH,CO,-; n = 2 L1 3 L2,4 L3] have been shown to possess similar polymeric structures by X-ray diffraction."' An octahedral HgO core was found in [Hg(dmso),][CF,S0,] which may be of use as a solid-state "'Hg NMR standard.',' A series of complexes has been obtained by electrochemical oxidation of mercury in an acetonitrile solution of neutral heterocyclic thione,I2' and a new structure of Hg(SEt) has appeared.122 The structures of [2H,-et],[Hg,C1,(SCN)4] and C2H,- et],[HgBr(SCN),] revealed a packing arrangement in the chlorine compound different from that in the proton ana10gue.I~~ N,N'-Dicyclohexyldithiooxamide(H,L) upon reaction with HgX (X = C1 SCN) formed [HgCl,(H,L)] [Hg(H,L)(SCN),J and [{ HgCl,(H,L)),]*EtOH; crystal structures of the latter two compounds were ob- tained.Halogen-donor ligands The first full crystallographic characterizations of the [Hg,C1812- anion have appeared and interestingly two different structures were observed; both contained a central mercury atom with a distorted-tetrahedral geometry. However in the NEt,' salt'25 the central HgCl unit bridged through two chlorine atoms to two trigonal- planar mercury centres whereas in the [(Bu'N),Mn(p-NBu'),Mn(NHBu')(NBu')] + salt', the HgCl unit bridged through all of its chlorine atoms to two mercurycentres each with a highly distorted-tetrahedral geometry. The structure of the ditetrahedral [Hg,CI6l2 -anion has been determined in the N-phenylpipera~inium'~' and [{ Mn(NBu'),(p-NBu'),),Mn] salts.Reaction of HgI with cryptand 222 gave + [Hg(cryptand 222)][Hg,I,] the structure of which provided the first example of a discrete [Hg,I,I2- anion (Fig. 3) and can be regarded as being built up from three [HgI,] tetrahedra sharing two common edges as well as one corner common to all three tetrahedra.', The crystal structures of [R,S][HgI,] (R = Me Et)showed chains of trigonal HgI units (R = Me) or Hg,I dimers (R = Et). The triiodide predominated in melts and in solutions and this was rationalized using ab initio calculation^.'^^ The crystal structure of [Et,S],[Hg2I,]*6I, prepared from HgI and Et,SiI, revealed centrosymmetric anions linked by iodine molecules.' ,' Mercury-transition-metal complexes Reactions of [M(cp),(SnPh,)]-(M = Mo W) with HgX (X = Br I) gave [M(cp),(SnPh,)][HgX] or [M(cp),(SnPh,)],Hg depending on the reactant ratio.Treatment of [M(cp),SnPh,)]- with ZnBr or CdCl gave only the trinuclear product.13' The carbanions derived from [M(CO),(dppm)] (M = Cr Mo W) on reaction with [HgCl(R)] [R = Me Et Ph Fe(C,H,)(C,H,)] gave [M(CO),{ Ph,PCH(HgR)PPh,)].' 32 The pentanuclear complexes C{ Rh(aet),),(HgCl,),I and C( M(aet),),Hg,(NO,),I"O,l (M = co Rh) have been prepared. X-Ray crystallography showed the mercury centre to be in a highly distorted-tetrahedral ge~metry.'~ The thiolatefac-(S)-[M(aet),] (M = Co Rh) upon addition of HgO in water produced the T-cage-type octanuclear complexes [{ M(aet),),Hg,016 +;spectroscopic properties were reported.' 34 Complexes of gen- 122 I.B. GorrelI Fig. 3 Crystal structure of the [Hg3I8I2- anion (Reproduced by permission from J. Chem. SOC.,Chem. Cornmun. 1995,451) era1 formula [Pt(HgR)(H,O)(dmphen)(Z-R'02CCH=CHC02R')]BF4 (R = R' = Me; R = Me R' = Bu'; R = Bu' R' = Me) have been i~olated.'~' The structure of [Hg,Pt(CH,P(S)Ph,},]X (X = BPh, PF,) has been determined and reactivity with halogen compounds investigated. Fenske-Hall calculations showed the HOMO to be ~*(pt-S).'~~ Reaction with mercury converted the 16-electron clusters [M(Au(PPh,)},]"+ (M = Pt Pd n = 2; M = Au n = 3) into the 20-electron clusters + + [H~,M(AU(PP~,)),]~(M = Pt Pd) and [H~,Au(Au(PP~,)},]~ whereas reaction with HgZ2+ salts gave the 18-electron clusters [H~(NO,),M(AU(PP~,)}~]~ + (M = Pt Pd).'37 With Hg,I [Pt,(p-CO),(PMe,Ph),] yielded the bicapped cluster [Pt4(p- CO),(PMe,Ph),(p3-HgI)2].'38 Reaction of HgTf, AgTf dppm and Hg yielded a cluster cation based on an AgHg triangle with dppm lying along each edge.139 In thf Eu-Hg and Ph,S gave a product which crystallized from pyridine as [(~y)~Eu(p- SPh),(p3-SPh)Hg(SPh)],*2pyand which upon treatment with cadmium in pyridine yielded the cadmium analogue and with zinc in thf gave the zinc(thf) anal~gue.'~' References 1 G.-J.M. Gruter G. P. M. van Klink O.S. Akkerman and F. Bickelhaupt Chem. Rev. 1995,95 2405. 2 T. R. van den Ancker and C. L. Raston J. Organomet. 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ISSN:0260-1818    

DOI:10.1039/IC9959200113

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

I0 Inorganic and Organometallic Polymers By 1. MANNERS Department of Chemistry University of Toronto 80 St. George St. Toronto M5S 1A1 Ontario Canada 1 Introduction Inorganic polymeric materials possess many interesting and unusual properties and have actual or potential applications as speciality materials. 1-4 This review focuses on developments in inorganic and organometallic polymer science published in 1995 and has the same format as and follows on from the three previous articles in the series which cover the years 1991-1994.5-8 The first sections of the review cover new developments concerning the well established inorganic polymer systems namely the polysiloxanes polyphosphazenes and polysilanes. 1-3 A brief introduction to each of these classes of inorganic polymer systems was included in the appropriate sections of the first article of this series.' Following these sections recent developments concerning other polymers based on main-group elements and transition metals are disc~ssed.~ As with previous articles in this series'-8 the main emphasis is placed on polymers with inorganicelements within the main chain rather than in the side group structure.A very recent review which focuses mainly on the new inorganic polymer systems prepared in the past ten years or so may also be of interest to reader^.^ 2 Polysiloxanes (Silicones) Polysiloxanes continue to be the focus of considerable attention particularly their liquid crystalline properties. Poly(diphenylsi1oxane) has been reported to form a mesophase above its melting temperature of 260 "C.The isotropitization temperature for this material is believed to be above 500°C. In addition the polymer is intractable below 160°C. In order to circumvent these problems Harkness et UI.'~reported the synthesis and study of well defined oligomers with the aim of lowering the transition temperatures to facilitate detailed studies. The synthetic methodology used to prepare the oligomers (1) involved treating hexaphenylcyclotrisiloxanewith the polymerization initiator derived from the reaction of (Me,SiO) with LiBu" followed by capping with an Si-H group via reaction of the living polymer with Me,SiHCl (Scheme 1). An oligomer with M 3600 relative to polystyrene showed three distinct melt 127 128 I.Manners Ph ,Ph 0 Ph I ph/Si. 0' 'Ph Initiatingsegment f \ Me Me Ph Me Bu-~i-9t~i-O~~i-O$-ki-H I ni Me Me Ph Me (11 Scheme 1 (i) LiBu" + (Me,SiO) (1:l) in Ph,O 160"C thf promoter; (ii) Me,SiHCl transitions at 198,208 and 214 "C. On increasing the molecular weight of the oligomers the melting temperature increases and the lower temperature transition gradually disappears and the two others merge. The sample with M 3600 showed an isotropitization temperature at 330 "C. The X-ray diffraction pattern for the oligo(diphenylsi1oxane) at 220 "C and the high molecular weight poly(dipheny1- siloxane) at 300 "Cwere found to be very similar with a sharp peak at d ca. 8" (ca. 11A) and a broad reflection between 15 and 25".This may imply that the mesophase formed by each possesses a similar structure. In addition studies show that a critical degree of polymerization of approximately 12 diphenylsiloxane units is needed for the me- sophase to be formed. This is significantly less than that needed for poly(diethy1- siloxane) or poly(di-n-propylsiloxane) to form a mesophase. Examination of the microscopic texture that appears on cooling the material from the isotropic melt indicated that the mesophase is one where the chains occupy positions within a three-dimensional crystalline structure. In late 1995 full details of this work were also reported.' In addition studies of poly(dipheny1siloxane) by molecular mechanics and WAXS have indicated the presence of a quasi-planar array rather than a helical structure." Moller and co-~orkers'~ have investigated the mesophase formation in random copoly(di-n-alkylsiloxane/di-n-hexylsiloxane) containing either diethylsiloxane di-n- butylsiloxane or di-n-pentyisiloxane comonomeric units.The random copolymers (2) were prepared by cationic ring-opening polymerization of mixed cyclic trimers. The presence of irregular structures was found to destabilize the crystalline phase as demonstrated by lowering of the transition temperatures and by a decrease of the fi-Qgz-n (2) Inorganic and Organometallic Polymers transition enthalpies. The copoly(di-n-pentylsiloxane/di-n-hexylsiloxane) material retained an ability to form a columnar mesophase. However for the other copolymers with a difference in the side chain length greater than one no mesophase was formed.Strain-induced crystallization of poly[methyl(trifluoropropyl)siloxane] (4) has been reported by Saam and co-worker~.'~ This can lead to improvements in mechanical properties without the need for reinforcement with particulate fillers. Crosslinked materials were prepared via the ring-opening polymerization of the isomeric mixed- substituent cyclic siloxanes cis- and trans-(3) using the difunctional initiator Ph,Si(OLi) and termination with a vinylchlorosilane (Scheme 2) followed by hydrosilylation with tetrakis(dimethylsi1oxy)silane. The strain-induced crystallization detected which led to pronounced reinforcement took advantage of the fact that a degree of stereoregularity can be introduced by changing the cis-trans composition of the cyclic isomers in the reactant mixture.The enthalpies of fusion for the elastomers increased with the cis content of the monomer mixture. R. rMe o/si. 0 Me.. I I ...Me R'si.o,sI 'R cis 43) trans 43) Scheme 2 R = (CH2),CF,. (i) Room temperature 6 h CH,Cl, 3-5% thf; (ii) ClMe,SiCH=CH, NEt In other interesting developments in polysiloxane chemistry Stadler and co-workers" successfulIy achieved the enzymatic grafting of amylose from poly(dimethy1- siloxane). In addition novel polymers derived from 2,3,5,6-tetrasila- 1,4-di0xane'~ and polyhedral silsesquioxanes l7 have been described. In addition the surface properties of poly(methylpheny1siloxane)-polystyrene block copolymers have been studied.I8 3 Polyphosphazenes Polyphosphazenes are a remarkably diverse class of inorganic macromolecules that continue to attract intense attention.130 I. Manners RO ,OR N//P" R0.I IIOOR ROOp* 0p. OR N 4) m=2 t5) m=3 12-OCH2CH20CH3 or CH2CF3. (i) 250 "C; (ii) NaOR thf -NaC1; (iii) NaOR' thf -NaCl Allcock and Klingenberglg have reported detailed studies of liquid crystalline phosphazenes containing chiral mesogens. A series of homopolymers (5) and mixed- substituent polymers (6)was prepared using the synthetic sequence shown in Scheme 3. All of the polymers showed enantiotropic liquid crystalline behaviour. Materials with mixed spacer lengths proved to be the most interesting and formed highly ordered smectic mesophases with very broad mesophase temperature ranges.A potentially important development in polyphosphazene chemistry was reported in 1995 and involved the discovery of a synthetic route to poly(dich1orophosphazene) which operates at room temperature.20 The route involves the treatment of a trichlorophosphoranimine with catalytic quantities of PCl (Scheme 4). The functionalization of polyphosphazenes continues to attract significant atten- Scheme 4 tion. For example Gleria et have reported radical induced grafting of anhydride groups onto poly(4-ethy1phenoxy)phosphazene.In addition de Jaeger and co-workers22 have reported the cleavage of alkoxy groups from polyphosphazenes with Me3SiI to yield silylated polymers which can be hydrolysed to give materials with pendant hydroxy groups.In other interesting developments the morphology of poly(diethy1phosphazene) has been studied.23 In addition polyphosphazenes with high refractive indices have been Inorganic and Organometallic Polymers 131 studied in detail by Olshavsky and All~ock~~ and fluorinated polyphosphazenes have been prepared from the reaction of deprotonated poly(methylpheny1phosphazene) with fluorinated aldehydes and ketones by Wisian-Neilson et aL2’ The thermal properties of polyphosphazenes synthesized uia the anionically initiated polymeriz- ation of phosphoranimines have been studied by Matyjaszewski and co-workers.26 In addition Singler and co-~orkers~~ have reported studies of the liquid crystalline behaviour of polyphosphazenes containing (pheny1phenoxy)hexyloxy side groups.Novel dendritic polyphosphazenes have been synthesized to the fifth generation by La barre and co-workers. 4 Polysilanes Polysilanes continue to attract considerable interest from both fundamental and applied perspectives. Fossum and Matyjas~ewski~’ have reported detailed studies of the ring-opening polymerization (ROP) of cyclotetrasilanes (Scheme 5). Ring-opening polymerization of the all-trans isomer of the cyclotetrasilane (MePhSi) using the silyl cuprate (PhMe,Si),Cu(CN)Li was found to yield poly(methylphenylsi1ane) (7) with 75% heterotactic and 25% isotactic triads according to *’Si NMR. Polymerization of a mixture of stereoisomers of (MePhSi) also yielded (7) with 58% heterotactic 15% syndiotactic and 27% isotactic triads.The ROP initiated by silylcuprates occurs with inversion of configuration at the attacked silicon atom and the newly formed reactive centre. The molecular weights of the polymers (7) were up to 30 000 with polydispersi- ties > 1.5. Kinetic measurements showed a first order dependence on monomer concentration and initiator concentration. Ph. Me \I Me Me Me Me Me-Si-Si-Ph II Ph-Si-Si-Me /\ Ph Ph Ph Ph Md Ph Scheme 5 The properties of polysilanes continue to attract attention. The electrochromic characteristics of some polysilane random copolymers have been studied by Fujino et aL3*In addition full details of the chirooptical properties of polysilanes incorporating S-2-methylbutyl side groups have been rep~rted.~’ A series of water soluble non-ionic polysilanes (9) has been reported by Jenneskens and co-~orkers~~ via the synthetic route shown in Scheme 6.The optical properties of these materials are similar to those of other unsymmetrically substituted polysilanes. Full details of the properties of novel polysilane-polythiophene multiblock alternat- ing copolymers have been reported by Hadziioannou and co-~orkers.~~ Copolymers (10) or (1 1) with four or six thiophene units per block were prepared via the synthetic routes described in Schemes 7 and 8. These materials are of interest for the construction of polymer-based light-emitting diodes. The first well characterized examples of polysilane dendrimers were reported in 1995 132 I.Manners (9) n =2~3 Scheme 6 (i) NaH thf; (ii) Cl,SiHMe H,PtCl,; (iii) Nay toluene 12-crown-4 Scheme 7 (i) 2LiBu; (ii) 2ZnC1,; (iii) [Pd(PPh,),] thf by several different The route used by Sakurai and co-~orkers~~ to prepare examples of these materials (12) is shown in Scheme 9. Other Polymer Systems Based on Main-group Elements The design synthesis and development of new polymer systems containing main- group elements in the main polymer chain continues to attract significant attention. Polymers based on backbones of sulfur nitrogen and phosphorus atoms continue to be of interest. Ab initio calculations of poly(thiony1phosphazenes) have shown that isotactic halogenated examples of these materials are predicted to possess a cis-trans helical structure.37 In addition 12-and 24-membered macrocyclic rings have been isolated and characterized as byproducts from the thermal ROP of the cyclic thionylphosphazene NSOC1(NPC12)2.38 Inorganic and Organometallic Polymers Scheme 8 (i) 2iBu; (ii) 2MgBr,*OEt,; (iii) [NiCl,(dppp)] CI Me-Si-Me I I Ph (4 - Me Me R,I Me I R I Me/ 7‘ Me R si I Si/,Me’ ‘Si’ Me (id-(0 R F! Scheme 9 (i) Li[SiMe(SiMe,R),] (R = Me or Ph) toluene or hexane; (ii) F,CSO CH,Cl 134 I.Manners OEt I EtO-Si-CH2 I I -{ECHzt CH2- Si-OEt \ OEt (13) Scheme 10 A new class of poly(carbosi1anes) with alkoxy side groups has been prepared by Rushkin and Interrante.39 Ring-opening polymerization of tetraethoxydisila cyclobutane was achieved using a Pt catalyst at 100"C and poly(diethoxysi1y- 1ene)methylene (1 3) was isolated as a moisture-sensitive material (Scheme 10).Molecular weight analysis uia gel permeation chromatography was carried out after reduction with LiAIH to yield poly(silaethy1ene) with molecular weight M,ca. 24000 M,ca. 6000 and a PDI ca. 4.Differential scanning calorimetry showed the presence of a melting transition at 31 "C. Polybis(trifluoroethoxy)silylenemethylenewas prepared similarly and possessed a T of 132-138°C.This polymer was moisture stable. The mixed-substituent polymer poly[methyl(ethoxy)silylene]methylene was also prepared (M ca. 10000 PDI 1.9)and possessed a T.at -50 "Cand no T,. In this case a higher molecular weight sample (M 40000 PDI 4.5)was prepared via the ring-opening polymerization of 1,1,3,3,-tetrachloro-1,3-disilacyclobutane followed by reaction with ethanol-triethylamine (Scheme 11).The NMR spectra of the polymer were consistent with an atactic structure.CI Scheme 11 The living anionic ROP of silacyclobutanes has been reported by Matsumoto and In Yama~ka.~~mixtures of thf-hexanes at -48 "C polycarbosilanes with M 2400-6100 were prepared with polydispersities of 1.1s1.26(Scheme 12).The living nature of the polymerization was demonstrated by the addition of more monomer to the living anionic polycarbosilane to afford a polymer with the expected molecular weight increase. H2C-CH2 -II LiR H2C-SiMe2 Scheme 12 Inorganic and Organometallic Polymers Novel periodic polycarbodisilanes (14) have been prepared by Isaka et aL4' These interesting materials show evidence of ~7conjugation and the theoretically calculated effective hole mass at the valence band edge and ionization potential were found to be intermediate between those for polyethylene and polysilylene.Tilley and co-~orkers~~ have reported detailed studies of polystannanes which were prepared via the transition-metal-catalysed dehydrogenative coupling of secondary stannanes R,SnH,. Yellow polystannanes (15) (R = e.g. n-butyl n-hexyl n-octyl) of substantial molecular weight (up to M,ca. 96 000 M ca. 22 000)were prepared using various zirconium catalysts (Scheme 13). These materials possess CT electrons that are extensively delocalized as illustrated by the band gap transition which occurs at 384-388 nm (in thf).In addition exposure of thin films of the polymers to the oxidant AsF leads to significant electronic conductivities of ca. 0.01-0.3 S cm-'. The polystannanes are highly photosensitive and exhibit photobleaching behaviour and on UV irradiation depolymerize to yield cyclic oligomers. The materials are thermally stable up to 200-270 "Cin air and at more elevated temperatures function as interesting precursors to Sn0,.42 R2SnH2 Zrcatalyst -E"-l-25 "C 1 1 Scheme 13 The cationic polymerization of cyclic sulfites has been examined and yielded polymers with molecular weights up to M 19 100 and M 10 400.43 Structural analysis of random network polycarbynes via semiempirical quantum mechanical and force- field calculations has been reported by Bianconi and co-~orkers.~~ In addition a radical mechanism has been elucidated from the polymerization of germylenes with q~inones.~ 6 Polymers Containing Skeletal Transition-metal Atoms Polymers containing skeletal transition-metal atoms continue to represent a rapidly growing area of research.Interesting work has been reported concerning polymers with metallacyclopen-tadiene units in the main chain. Endo and co-~orkers~~ have reported additional details of the organocobalt polymers (16) derived from the oxidative coupling/ring- closure reaction of diynes with [Co(PPh,),(q-C,H,)] (Scheme 14). Polymers (16) 136 I. Manners + PhCf CRC ECPh (16) Scheme 14 0,,PPh3 t/c~~~n + RNCO [R = Bun Et IFC~~H~, Ph PhCO OCN(CH&NCO] Ph/%L\ Ph 120 "C,6 h thf 1 Scheme 16 Inorganic and Organometallic Polymers rearrange thermally and undergo carbonyl substitution with phosphines (Scheme 15) and reaction with isocyanates yielded the novel polymers (17) with 2-pyridone and cyclobutadiene cobalt units in the main chain (Scheme 16).The latter polymers possessed molecular weights of M 9000-16000 and PDI ca. 2.5. Mao and Tilley4' have also reported coupling reactions of this type for the early transition element zirconium which has provided access to interesting polymers containing zirconacyclopentadiene units in the main chain. Further advances have also been reported concerning high molecular weight poly(ferrocenylsi1anes) (18) which were first synthesized in 1992 by a ROP route.An extensive review of this area was published in early 1995.48 (18) The first examples of random copolymers derived from metallocenophanes were reported in early 1995 by Manners and co-worker~.~~ Novel poly(ferroceny1-silanebpolysilane random copolymers (19) were prepared uia the thermal ROP of mixtures of a [llsilaferrocenophane and a cyclotetrasilane (Scheme 17). The random copolymeric nature of the product was demonstrated by photolysis which cleaved the Si-Si bonds present in the oligosilane segments and left the oligo(ferrocenylsi1ane) segments intact. The length of the latter chains decreased with an increasing amount of the cyclotetrasilane in the monomer mixture.Fe Si Me Me Me Me -'t 150 "C + I Fe I Me Me \I 1" Ph-Si-Si-Ph II Me-Si-Si-Me Pk 'Ph Scheme 17 Random copolymers derived from the thermal copolymerization of different silicon-bridged [1)ferrocenophanes were also reported later in the year. Specifically soluble poly(ferrocenyldimethylsilane~poly(ferrocenyldihydrosi1ane)copolymers (20) 138 I. Manners were prepared via the thermal copolymerization of the respective monomers (Scheme 18).50 Poly(ferrocenyldihydrosi1ane) homopolymer was found to be insoluble in organic solvents. Wide-angle X-ray scattering studies showed the materials to be crystalline and a T at 18 and T at 150"C were detected by DSC. This material also afforded the highest ceramic yields detected so far for poly(ferrocenes) with a weight retention of 90% at 600°C and 63% at 1000°C.r Me + heat ____c Scheme 18 Novel mixed-metal random copolymers were also first reported in 1995. Specifically silicon-bridged bis(benzene)chromium complexes were found to copolymerize with silicon-bridged C1)ferrocenophanes either thermally or in the presence of anionic initiators to yield poly[chromarenylsilane]-poly(ferrocenylsi1ane) random copolymers (21)(Scheme 19).51Attempts to homopolymerize the chromium-containing monomers were however unsuccessful and the formation of chromium metal and Ph,SiMe was detected at elevated temperatures. heat + -Scheme 19 Inorganic and Organometallic Polymers Details of the ROP of a series of strained ring-tilted phosphorus(II1)-bridged [llferrocenophanes to yield poly(ferrocenylphosphines)(22)have also been rep~rted.~' Sulfurization of these materials yielded poly(ferroceny1phosphinesulfides) (23) (Scheme 20).Sulfurized phosphorus(v)-bridged [llferrocenophanes also underwent thermally- induced ROP but the resulting polymer was found to partially decompose under the thermolysis conditions. Scheme 20 Full details of the thermal stability and pyrolysis studies of a series of poly(ferrocenylsi1anes) (1 8) have been published.' Poly(ferroceny1silanes) yield black lustrous ferromagnetic iron silicon carbon-containing ceramics when heated at or above 400 "C. Thermogravimetric analysis showed that the functionalized polymers (with SiH or vinyl side groups) give the highest ceramic yields at 600°C under dinitrogen (ca.60-65%) and a 1 1 polymer blend of such polymers was found to give the highest ceramic yield at 1000°C (56%). The ceramics were characterized by scanning electron microscopy with energy-dispersive X-ray microanalysis and back- scattered electron imaging. These techniques indicated that the materials were iron silicon carbides. The ceramic formed from poly(ferrocenyldimethylsi1ane) at 600 "C was found to be amorphous whereas the corresponding ceramic formed at 1000°C was shown to contain sc-Fe crystallites by powder X-ray diffraction. Mossbauer and magnetization measurements indicated that the materials were soft ferromagnets. Identification of several volatile molecular byproducts produced during pyrolysis provided evidence for the operation of unusual decomposition/depolymerization pathways.Ring-opening polymerization studies of silicon-bridged [l]ferrocenophanes and disilane-bridged C2lferrocenophanes with trimethylsilyl substituents attached to the cyclopentadienyl ligands have also been reported.54 The [llferrocenophane was found to polymerize to yield a soluble polymer whereas the disilane-bridged species which was much less strained was resistant to polymerization and decomposed above 380"C. Studies of the synthesis and ROP of strained silicon-bridged [1)ferrocenophanes with methylated cyclopentadienyl ligands have also been de~cribed.~~ Interestingly the tilt-angles detected for such species were found to decrease from ca.21" to 16" with increased ring methylation. The unsymmetrically methylated species (24) was found to undergo ROP to yield a poly(ferrocenylsi1ane) (25) with a microstructure consistent with (cp)-Si bond cleavage.56 Further experiments suggested that the ROP involves a heterolytic rather than a homolytic mechanism. 140 I. Manners Me Me I I Me Studies of the morphology of poly(ferrocenyldimethylsi1ane) have been reported by Vancso and co-worker~.~' Wide-angle X-ray diffraction studies indicated a typical crystallite size of 77A and a degree of crystallinity of cn. 50%. Optical microscopy indicated numerous small regions of birefringence and fibrillar aggregates of width 90 nm were observed by atomic force microscopy. Transition-metal-catalysed ROP of silicon-bridged [llferrocenophanes was re- ported independently by two research group~.~~,~' found Manners and co-~orkers~~ that the SiMe,-bridged [llferrocenophane polymerizes to yield high molecular weight (18)(R = Me) in the presence of cu.1mol % of PtC1,. Other MI' species such as [PdCl,] or [PdCl,(cod)] or the Rh' species [(Rh(p-CI)(C8Hl,>,},] were also found to be effective catalysts. In contrast ROP was not detected at a significant rate for C(Rh(P-Cl)(cod)}J7 CRhCWPh3)3J [PdCl,(PPh&l CPdC12(NCMe),I [Pd(PPhJJ and [Pt(PPh,),]. Tanaka and co-workers5' described the transition-metal-catalysed ROP of the %Me,-bridged [llferrocenophane using the mainly zerovalent transition- metal complexes [Pt(cod),] [PdCl,(cod)] [Pd,(dba),] and [Pd(dba),].Random copolymers of poly(ferrocenylsi1anes) and poly(ferroceny1germane.s)(26) were also prepared via the Pd- and Pt-catalysed ROP of mixtures of the [1)silaferrocenophane and the germanium-bridged anal~gue.~' r Me 1 Further studies of poly(ferroceny1germanes) (27) were reported in 1995. Pannell and co-workers reported6' further studies of some previously described61*62 poly(ferro- cenylgermane) homopolymers and also some new random copolymers. The polymers were prepared via a modification of the previously reported thermal ROP route except Inorganic and Organometallic Polymers 141 that the monomers were not purified and so lower molecular weight polymers were formed. The poly(ferroceny1germanes)with Et Bu side groups were found to exhibit similar electrochemical behaviour to the methyl analogue which had been previously studied.The morphologies of the poly(ferrocenes) derived from the ROP of metallo-cenophanes are thermal-history dependent and this was demonstrated clearly for the Bun polymer by wide-angle X-ray diffraction studies. Thus over a period of time a significant increase in crystallinity was detected. r R '-f ;'I The synthesis and ROP of the first sulfur-bridged [llferrocenophane was also reported in 1995.63 Species (28) was found to possess the most ring-tilted structure for any neutral [n]metallocenophane to date (31.05'). Thermal ring-opening polymeriz- ation occurred in the melt at ca. 150'C but the resultingpoly(ferrocenylsulfide)(29) was insoluble in organic solvents.QS-(-JT" n Further details of the properties of poly(ferroceny1ene persulphides) and poly(ferroceny1ene perselenides) derived from [3] trichalcogenidoferrocenophanes via a novel atom abstraction route have been described by Rauchfuss and co-~orkers.~~ Desulfurization of the butyl-substituted monomer (30) in thf-CH,Cl gave polymers (31) with M 12000-359000. Lower molecular weight products were formed at high CH,Cl concentration. The analogous reactions with the selenium analogue of (30) gave only low molecular weight selenium polymers. Interestingly the polymers were found to photodegrade upon exposure to UV light in air. 142 I. Manners s n Conjugated polymers with ferrocene units in the backbone have also been studied by Grubbs and co-~orkers.~~ These novel materials were prepared via ring-opening metathesis polymerization (ROMP) of ferrocenophanes with C=C units in the bridge (Scheme 21).Poly(ferrocenylenebutadienediy1)(33) with chain lengths greater than 10 monomer units was found to be insoluble in organic solvents. Oxidatively doped films of (33) possessed conductivities of 10-4-10-5 S cm-'. Preliminary experiments showed that copolymerization of (32) with sec-butylcyclooctatetraene yields soluble materials with M up to 24400 (PDI 2.1). Fe (32) (33) Scheme 21 Soluble poly(ferrocenyleneviny1enes) of moderate molecular weight (M < 10000) have also been prepared via Ti-induced polycondensation of dicarbaldehyde precur- sors.Solubility was achieved using long alkyl substituents and on doping with iodine conductivities up to S cm-were realized.66 Details of the properties of rigid-rod metallocene polymers with a multistacked structure [e.g. (34)] have been reported by Rosenblum et aL6' Electrical conductivities of up to 6.7 x loy3S cm-' were measured for samples of these materials which had been oxidatively doped with iodine. The pristine polymers were found to be insulators with conductivities of less than Scm-'. R= H 2-0ctyl (34) Inorganic and Organometallic Polymers Cuadrado and co-~orkers~~,~~ have recently reported the synthesis of a series of novel organometallic polymers with structures such as (35) and (36). These materials display interesting electrochemical properties.Further significant developments in the area of well characterized lanthanide-based polymers have also been reported. Chen and Archer7' have described a series of linear co-ordination polyelectrolytes of yttrium(III) lanthanum(II1) and ytterbium(II1). Mol- 0 Q-(CHP)2 Fe -NH-(C H2) 2 tQ-; (36) Me 1" 0 ecular weights of up to 18500 were estimated for the polymers (37) by end-group analysis. Analogous cerium(1v) polymers have also been prepared and molecular weights of up to M 31 500 were achieved.'l Ln = La Gd Y Yb (37) Haddad and Lichtenhan'* have reported the incorporation of transition metals such as zirconium into silsesquioxane polymers. Thus novel polymers such as (38) have been prepared (Scheme 22) and this air- and moisture-stable material was of appreciable molecular weight with M 20000 and M 14000.Altmann and bun^'^ have reported the synthesis of novel thermotropic liquid 144 I. Manners + / \ H11C6 C6H11 X = CI Me thf 31X 1 Scheme 22 R2 Scheme 23 (i) [PdCl,(PPh,),] CuI piperidine 18 h 21 "C crystalline polymers (39)with cyclobutadiene units in the main chain. These materials were prepared via the reaction sequence shown in Scheme 23. Molecular weights (M,) of up to 65 000 were achieved. In other developments Nakarn~ra~~ has reviewed organometallic n-conjugated systems with a consideration of polymer systems. Meyer and co-~orkers~~ have Inorganic and Organometallic Polymers described their work on ruthenium and osmium polypyridyl complexes and their use as films on electrode surfaces.Rauchfuss and co-~orkers’~ have reported the synthesis of semiconducting inorganic polymers involving bridging [C,S,]’ -units. For example the nickel-containing materials (40) possessed a conductivity of 0.9 S cm-’. A number of new dendritic polymers have been reported in the past year including several systems containing organoruthenium m~ieties.~~~~~ Liquid crystalline metal- lopolymers have been reviewed in detail by Oriol and Serran~.~’ References 1 Silicon-Based Polymer Science eds. J. M. Ziegler and F. W. G. Fearon American Chemical Society Washington D. C. 1990. 2 Siloxane Polymers eds. J.A. Semlyen and S.J. Clarson Prentice Hall Englewood Cliffs N.J.1991. 3 J. E. Mark H. R. Allcock and R. West Inorganic Polymers Prentice Hall Englewood Cliffs 1992. 4 I. Manners Chem. Br. 1996 32 46. 5 I. Manners Ann. Rep. Prog. Chem. Sect. A 1991 88 77. 6 I. Manners Ann. Rep. Prog. Chem. Sect. A 1992 89 93. 7 I. Manners Ann. Rep. Prog. Chem. Sect. A 1993 90,103. 8 I. Manners Ann. Rep. Prog. Chem. Sect. A 1994 91 131. 9 I. Manners Angew. Chem. Int. Ed. Engl. 1996 35 1602. 10 B. R. Harkness M. Tachikawa and I. Mita Macromolecules 1995 28 1323. 11 B.R. Harkness M. Tachikawa and I. 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ISSN:0260-1818    

DOI:10.1039/IC9959200127

出版商:RSC    

年代:1995

数据来源: RSC