9 0rga nometa IIic Chemistry Part (ii) Main-Group Elements By P. D. LlCKlSS Department of Chemistry and Applied Chemistry University of Salford Salford M5 4WT This year this section covers all of the main-group metals and is therefore somewhat longer than last year. Despite this increase in length the continuing great interest in the preparation of novel main-group organometallic compounds particularly as species of potential use as precursors to new materials has meant that much of interest has been omitted. This report concentrates mainly on novel structural features and new or potentially useful reactions. 1 Group I Reviews on the structure and reactivity of lithium enolates' and the mechanistic aspects of the lithium-halogen exchange reaction have been published, as has a book 'Organolithium Methods' by B.J. Wakefield (Academic Press London 1988) giving practical details and information on a wide variety of organolithium reagents. A detailed theoretical study of methyllithium oligomers (MeLi), n = 1-4 has been carried The H3C-Li bond dissociation energy is calculated to be 11.1 f 0.6 kJ mol-' and the rotation barrier of the Me group in (MeLi) is about 0.24 kJ mol-'. The use of CH2LiC1 has been limited by its thermal instability but ultrasonic irradiation has led to its generation at -15 "C from CH,BrCl and lithium. It reacts cleanly with carbonyl compounds to give chlorohydrins and epoxides. Thermolysis of monosubstituted lithium reagents e.g. Me3SiCHRLi provides a general synthesis of 1,l -dilithio compounds containing no p-hydrogens [e.g.Me3CCHLi2 and (Me,Si),CLi,] apparently via a bimolecular reaction involving lithium-R exchange to afford the dilithium reagent (Me3Si)CRLi and Me,SiCH,R (R = H or Me,Si).' The highly elusive LiCH2CH2Li has been prepared in low yield by condensing lithium into ethylene at -196 "C. The dilithium reagent was trapped using Me3SnC1 or C02.6 ' D. Seebach Angew. Chem. Int. Ed. Engl. 1988 27 1624. ' W. F. Bailey and J. J. Patricia J. Organornet. Chem. 1988 352 1. E. Kaufmann K. Raghavachari A. E. Reed and P. von R. Schleyer Organometallics 1988 7 1597. C. Einhorn C. Allavena and J.-L. Luche J. Chem. SOC.,Chem. Commun. 1988 333. ' H. Kawa B. C. Manley and R. J. Lagow Polyhedron 1988 7 2023. N. J. R. van Eikema Hommes F.Bickelhaupt and G. W. Klumpp Angew. Chem. Int. Ed. Engl. 1988 27 1083. 241 242 P. D. Lickiss Short Li...Li distances have been found in the solid state by X-ray crystallography and coupling between 'Li nuclei in solution has been detected by n.m.r. spectroscopy for the tetramer (0-LiC6H4CH2NLiCH2CH,NMe2)4 .' This work provides more conclusive evidence for what had previously been thought to be significant interac- tions in organolithium aggregates. Evidence for Li.. CH interactions in both solid and solution has been found in [(PhCH,),NLi] where the formal coordination number of Li is 2. This low coordination number appears to promote close interac- tions with aromatic C and C-H groups.8 The solid-state structure of ( 1) has been determined by X-ray crystallography and is shown to be polymeric with the TMEDA bridging between dimeric centrosym- metric subunits.In THF solution however the compound is monomeric with the lithium apparently not bound by the TMEDA but showing close contacts to the vicinal H and to the But group.' A detailed study of the reaction of Bu"LiTMEDA with phenylacetylene" confirms that both mono- and dilithium products are formed. Both MNDO calculations and 2D n.m.r. spectroscopic data indicate a short Li...H distance suggesting an 'agostic' interaction in the monolithium product. The second lithiation site is predicted to be at this agostic hydrogen and this was confirmed by the X-ray crystal structure of (2). A unique planar quinquedentate environment has been found for Li in (3; M = Li) by X-ray Crystallography." There are no close interactions between the cations the lithium in (3; M = Li) does not exchange with that in LiCl ill solution and it does not react with hot water.The analogues (3; M = Na K Rb or Cs) have also been prepared. The first monomeric diboryldilithiomethane (4)has been prepared and structurally characterized.I2 The compound has Li-C-Li and B-C-B angles of 120.1 (3)" and 168.4(4)" respectively and the lithium atom; have a close contact (2.3 A) and with the ips0 carbons of the mesityl groups. A tetralithio compound containing both u-and .rr-bonded lithium atoms is thought to have the structure (5) and is prepared by treating benzo[b]biphenylene with 1ithi~m.I~ ' D. Barr W. Clegg S.M. Hodgson R. E. Mulvey D. Reed R. Smith and D. S. Wright J. Chem. SOC. Chem. Cornmun. 1988 367. D. R. Armstrong R. E. Mulvey G. T. Walder D. Barr R. Snaith W. Clegg and D. Reed J. Chem. SOC.,Dalton Trans. 1988 617. W. Bauer P. A. A. Klusenor S. Harder J. A. Kanters A. J. M. Duisenberg L. Brandsma and P. von R. Schleyer Organometallics 1988 7 552. 10 W. Bauer M. Feigel G. Muller and P. von R. Schleyer J. Am. Chem. Soc. 1988 110 6033. " E. C. Constable M. J. Doyle J. Healy and P. R. Raithby J. Chem. SOC.,Chem. Commun. 1988 1262. 12 M. Pilz J. Allwohn R. Hunold W. Massa and A. Berndt Angew. Chem. Int. Ed. Engl. 1988,27 1370. l3 M. Pilz J. Allwohn R. Hunold W. Massa and A. Berndt Angew. Chem. In?. Ed. Engb 1988,27 1182. 243 Organometallic Chemistry -Part (ii) The Main-Group Elements Li.Et,O Li Mesityl I ,Mesityl 8;\ B-C-B -,, " (3) (4) The X-ray crystal structure of (2,6-dimethoxyphenyl)lithiumhas been reported by two group^.'^.'^ The structure comprises two connected dimeric units with the C-Li carbons having overall five-coordination within the tetramer but having an approximate planar tetracoordinate geometry (as had previously been postulated for a compound where oxygen-lithium chelation occurs) in the dimer.The effects of silyl substitution on the structures of lithium phosphinornethanes has been investigated in {(TMEDA)Li[(Me,P)CH(SiMe,)l) and (TMEDA)-{Li[( Me,P)C( SiMe,),]} .16 Increasing the degree of silylation weakens the Li-C interactions but promotes additional bridging Lie..P interactions to the second Li atom in the dimer. Similar Li. -.P interactions are also seen in the solid-state structures of { (THF) Li[ (Me,P)*C( and { (THF) Li[ (Ph2P)2CH])2 .I7. Treatment of (E,E)-1,4-bis( trimethylstanny1)buta- 1,3-diene with excess MeLi affords (Z,Z)-1,4-dilithiobuta-l,3-diene, thus providing experimental evidence for greater stability of the (2,Z)-over the (E,E)-dilithio isomer.'* The synthesis of various 9,lO-disubstituted anthracenes (e.g. dimethyl difluoro diiodo and diacetyl) can be accomplished by treatment of 9,lO-dilithioanthracene with electr~philes.'~ An X-ray crystal structure of a lithium triorganostannate lithium tris-(a-furyl)stannate has been determined for the first time.,' The structure consists of an anion containing a lithium atom coordinated to the six oxygens from two tris-(a- fury1)stannate groups and a Li(dioxane) cation together with two free dioxane molecules.Mossbauer spectra for Ph3SnM (M = Li Na or K) have been remeasured and reinterpreted.21 The X-ray crystal structure of Ph,SnK.( 18-crown-6) shows a naked Ph,Sn- anion to be present with the K+ being >6 8 distant from the Sn. The potassium rubidium and caesium salts of the strong acid (CF3S02)3CH are readily formed in the reaction between metal carbonate and the acid.22 The X-ray crystal structure of the (CF3S02)3C- anion in the potassium salt shows the CS3 core to be planar and none of the salts react with Xe derivatives to give Xe-C containing species. The crystal structure of the widely used reagent cyclooctatetraenylpotassium I4 H.Dietrich W. Mahdi and W. Storck J. Organomer. Chem. 1988 349 1. S. Harder J. Boersma L. Brandsma A. van Heteren J. A. Kanters W. Bauer and P. von R. Schleyer J. Am. Chem. SOC.,1988 110 7802. H. H. Karsch A. Appelt B. Deubelly K. Zellmer J. Riede and G. Muller Z. Naturforsch. Teil B 1988 43 1416. 17 H. H. Karsch B. Deubelly and G. Muller J. Organomet. Chem. 1988 352 47. lg A. J. Ashe I11 and S. Mahmoud Organometallics 1988 7 1878. 19 B. F. Duerr Y.3. Chung and A. W. Czarnik J. Org. Chem. 1988 53 2120. 20 M. Veith C. Ruloff V. Huch and F. Tollner Angew. Chem. Int. Ed. EngL 1988 27 1381. T. Birchall and J. A. Ventrone J. Chem. Soc. Chem. Comrn. 1988 877. 22 L. Turowsky and K. Seppelt Inorg.Chem. 1988 27 2135. 244 P. D. Lickiss C8H8K2.(THF)3 has been determined.23 The C8H8 ring is planar and bonded to two equivalent K+ ions one on either side of the ring which are connected via bridging THF molecules to K+ ions of adjacent molecules so as to form a chain structure. A chain structure is also found in the solid state for the 2,4-dimethylpen- tadienylpotassium- TMEDA complex which contains planar U-shaped 2,4-dimethyl- pentadienyl anions. Each anion has a K+ cation on either side which is chelated by TMEDA; the cations are linked by bridging anions.24 The potassium-graphite laminate C8K cleanly and rapidly forms silyl potassium reagents R'R;SiK (e.g. R' = R2 = Me; R' = Me R2 = Ph). For some of the reagents e.g. Me,SiK this preparation is more convenient than that for the analogous lithium reagent and the potassium species are easily coverted into silyl cuprates manganates etc.which can be used for various substitution and addition reactions.2s 2 Group I1 Co-condensation of t-butyllithium with BubBe at -196 "C affords a good yield of Li[ BeBu;] which can be crystallized from pentane as a solvent-free dimer in which each lithium interacts with the beryllium atom and four carbons of one [BeBuil- anion and one carbon from the second anion in the dimer.26 Novel Grignard reagents (6;n = 0 or 1)in which there is intramolecular coordina- tion in a crown ether have been prepared by treatment of the parent aryl bromide with magnesium.27 The X-ray crystal structure of (6; n = 0) shows the magnesium coordinated to four oxygens and a carbon in the crown ether ring and the bromine giving a distorted pentagonal pyramid structure.A 0 (6) n = 0 or 1 Metal-halogen and metal-hydrogen exchange reactions while common for organolithium reagents are very rare in Grignard reagent chemistry. Such reactions will occur readily however if activation by a crown ether system is available. For example Ph,Mg will metallate both (7a) and (7b) to give (8) the structure of which has been determined crystallographically showing the magnesium to be coordinated to all of oxygens in the ring as well as two aromatic carbons.28 23 N. Hu,L. Gong Z. Jin and W. Chen J. Organornet. Chern. 1988 352 61. 24 L. Gong N. Hu Z. Jin and W. Chen J.Organornet. Chern. 1988 352 67. 25 A. Furstner and H. Weidmann J. Organornet. Chern. 1988 354 IS. 26 J. R. Wermer D. F. Gaines and H. A. Harris Organornefallics,1988 7 2421. 27 P. R. Markies 0. S. Akkerman F. Bickelhaupt W. J. J. Smeets and A. L. Spek J. Am. Chern. Soc. 1988 110 4284. 28 P. R. Markies T. Nomoto 0. S. Akkerman F. Bickelhaupt W. J. J. Smeets and A. L. Spek Angew. Chern. Int. Ed. EngL 1988 27 1084. Organometallic Chemistry -Part (ii) The Main-Group Elements n 0 /-O 4.'Ph W (7a) X = H (7b) X = Br The use of [Mg(anthracene)(THF),1 as a soluble source of magnesium has been extended to the preparation in high yield of benzylic Grignard reagents bearing 0-or p-halogeno ring substituents; for example 0-BrC,H4CH2CI affords o-BrC6H4CH2MgC1 in 90% yield.Both 0-and p-chloromethyl(methoxymethyl)-benzenes give di-Grignard reagents but the m-isomer gives a mono-Grignard only.29 The problem of removal of anthracene from product mixtures after using [Mg(anthracene)(THF),1 can be overcome by attaching the anthracene group to a polystyrene backbone via an SiMe linkage. The polymer-supported Mg( anthracene) reagent gives good yields of benzylic Grignard reagents from the corresponding halides and the spent polymer can then be removed by filtrati~n.~' Direct observation of magnesiate ions R,Mg has been achieved by studying solution and solid-state structures of RMg( 15-crown-5)+ R,Mg species derived from reaction of R,Mg with 15-crown-5.3' Crystalline MeMg( 1 5-crown-5)Me5Mg2 contains cations in which the magnesium lies close to the plane of the crown ether oxygens and is bound to all of them and to an apical Me group.A methyl group from the Me,Mg anionic polymer chain occupies the other apical position. 'H n.m.r. spectra of the neopentyl analogue in solution suggest that it adopts a structure similar to that for the Me analogue in the solid state. A series of substituted cyclopentadienyl derivatives (9) of Group I1 elements have been prepared by co-condensation of ligand solvent and metal vapour at -196 "C. X-Ray crystal structural analysis of (10; M = Ca or Sr) shows the compounds to be monomeric isomorphous and isostructural. The Sr compound appears to be the SiMe THF M[C,H,-1,3-( SiMe,),] cp heat -THF M -03 (9) M = Ca Sr or Ba / 29 M.J. Gallagher S. Harvey C. L. Raston and R. E. Sue J. Chem. SOC.,Chem. Commun. 1988 289. 30 S. Harvey and C. L. Raston J. Chem. SOC.,Chem. Commun. 1988 652. 31 A. D. Pajerski M. Parvez and H. G. Richey jun. J. Am. Chem. SOC.,1989 110 2660. 246 P. D. Lickiss first solid-state structural determination of an organostrontium compound. The Sr-ring centroid distance is 2.551 8 and the ring centroid-Sr-ring centroid angle is 134".32 The 'bent metallocene' structure was also found in the first X-ray structure determination of an organobarium compound (~'-(c,Me,),Ba.~~ It has a ring centroid-Ba-ring centroid angle of 131" and an average Ba-C distance of 2.987 (18) A. 3 Group 111 A dialane {[ (Me3Si)2CH]2A1}2 has been prepared by reduction of [(Me3Si),CHl2A1C1 with potassium.The compound has an Al-A1 bond length of 2.660( 1) A with the four CH carbons and the two A1 atoms being almost ~o-planar.~~ The first trimeric iminoalane [MeAlN(2,6-Pr;C,H3)] has been prepared from AIMe and H2N(2,6-Pr&H,).35 It has a planar six-membered ring of alternating A1 and N atoms and an average AI-N bond length of 1.78 A. N.m.r. spectroscopy of the compound does not indicate the AI,N ring to be aromatic. Treatment of AIMe with 2 equivalents of the bulky phenol 2,6-Bu\C,H30H or a deficiency of the phenol leads to formation of (2,6-Bu:C,H30),AIMe and (2,6- Bu&H,0)AlMe2 respectively. Both of the aluminium aryl oxides form complexes with PMe . The X-ray crystal structure of (2,6-Bu:C,H30)AIMe2.PMe3 shows the usual distorted tetrahedral geometry around the Al but an unusually large AI-0-C angle of 164.5 (4)" and a short A1-0 distance of 1.736 (5) A.These features are interpreted in terms of a rr-type interaction between the A1 and the 0 atoms.36 There is continuing interest in the preparation of organometallic compounds containing bonds between Group 111 and Group V elements and their use as precursors to electronic materials via Metal-Organic Chemical Vapour Deposition (MOCVD) techniq~es.~' The first aluminium-arsenido complex (Et,AIAsBu:) ,to be structurally characterized has an AI-As distance of 2.571 (2) A and is made by treatment of AIEt with BUSASH.~' This material is seen as a precursor to electroni- cally useful thin films via MOCVD techniques as is the dinuclear gallium phosphide compound [Bu\G~PHC,H~]~ .38 1 Me AIMez 32 L.M. Engelhardt P. C. Junk C. L. Raston and A. H. White J. Chem. SOC.,Chem. Commun. 1988 1500. 33 R. A. Williams T. P. Hanusa and J. C. Huffman J. Chem. Soc. Chern. Cornmun. 1988 1045. 34 W. Uhl 2. Narurjorsch. Ted B,1988 43 1113. 3s K. M. Waggoner H. Hope and P. P. Power Angew. Chem. Int. Ed. Engl 1988 27 1699. 36 M. D. Healy D. A. Wierda and A. R. Barron Organornefallics,1988 7 2543. 37 A. H. Cowley B. L. Benac J. G. Ekerdt R. A. Jones K. B. Kidd J. Y. Lee and J. E. Miller J. Am. Chem. Soc. 1988 110 6248. 38 D. E. Heaton R. A. Jones K. B. Kidd A. H. Cowley and C. M. Nunn Polyhedron 1988 7 1901.Organometallic Chemistry -Part (ii) The Main-Group Elements 247 The product (11) from the reaction between AIMe and N,N’-bis-(3-aminopropy1)ethylenediamine has a pentacoordinate aluminium atom in a trigonal- bipyramidal en~ironment.,~ This unusual coordination is thought to be preferred over the usual square-pyramidal coordination owing to the greater flexibility of the open-chain amine over the cyclic amines usually found in such complexes. Treatment of (T’-C~M~,)~Y~(THF) with aluminium alkyls AIR (R = Me Et or Bu’) gives ytterbium-organoaluminium complexes. The crystal structure of one (12) shows an unusual Yb-(p-Et)-Al linkage to be present with a Yb-C-A1 angle of 177.7’ and a Yb-CH2 distance of 2.854( 18) A. The complex polymerizes CH2=CH2 methyl methacrylate and styrene.40 The reaction between AIMe and (T’-C~M~~)~S~(THF), affords complex (131 which polymerizes ethylene and in which a pair of bent metallocene units is bridged by two tetrahedral (p-Me),AlMe groups via nearly linear Sm-( p-Me)-A1 linkage^.^' THF I .AI-Et / I Sm Et Convenient high-yield preparations of neopentyl (Np) gallium compounds GaNp ,GaNp,CI GaNp,Br GaNpCI, and GaNpI have been described with the reaction between NpMgCl and GaCI giving the synthetically useful GaNp .42 The synthesis and properties of AlMe, GaMe ,and InMe adducts with involatile phosphines such as PPh and (Ph,PCH,) have been reported.43 Such compounds are more easily handled than the free alkyls are readily purified and thermally dissociate to give free pure R3M which can be used for MOCVD purposes.Intramolecular stabilization in organogallium compounds such as ( 14) also gives compounds that are relatively easy to handle melting at 34°C and reacting only slowly with O2.44 Reaction of Me,Ga with l-hydroxymethyl-3,5-dimethylpyrazole affords ( 15).45 The novel terdentate ligand (16) forms complexes with Ni4’ and Mo.~~ Treatment of Ga[GaCI,] with hexaethylbenzene in toluene affords a complex (17) in which each Gat centre is q6-bonded to one molecule of toluene and one of C6Et, the 3’4 G. H. Robinson S. A. Sangokoya F. Moise and W. T. Pennington Organomerallics 1988 7 1887. 40 H. Yamamoto H. Yasuda K. Yodota A. Nakamura Y. Kai and N. Kasai Chem. Lerr. 1988 1963. 41 W.J. Evans L. R. Chamberlain T. A. Ulibarri and J. W. Ziller J. Am. Chem. SOC.,1988 110 6423. 42 0. T. Beachley jun. and J. C. Pad Organometallics 1988 7 1516. D. C. Bradley H. Chudzynska M. M. Faktor D. M. Frigo M. B. Hursthouse B. Hussain and L. M. 43 Smith Polyhedron 1988 7 1289. 44 H. Schumann U. Hartmann A. Dietrich and J. Pickardt Angew. Chem. Int. Ed. Engl. 1988 27 1077. 45 A. Mar S. J. Rettig A. Storr and J. Trotter Can. J. Chem. 1988 66 101. 46 S. J. Rettig A. Storr and J. Trotter Can. J. Chem. 1988 66 355. 248 P. D. Lickiss Me Me2 Me A!?! Ga-N 'OH--0 Me Me Me2 9-t rings fp-ming an angle of 38.8'. One molecule of C6Et6 is situated between each pair of molecules (17).47 New organoindium compounds Me2Sn(CH21nMe2) and Me,Sn[CH21n(OCH2- CH,NMe,),] have been prepared by treatment of Me,Sn(CH,Li) with Me,InCl and (Me2NCH2CH20)21nCI Such compounds may be useful precur- re~pectively.~' sors to metal oxides with a ratio 1n:Sn > 1.X- Ray crystallography shows that [Me,InAsMe,] contains two independent molecules in the unit cell one contains a planar In,As ring and the other a puckered ring the In-As distances being about 2.67 A."" A review of thallium n.m.r. spectroscopy including organothallium compounds has been p~blished.~' The synthetically useful reagents benzyl- and phenyl-cyclopentadienylthallium are prepared in good yields from TlOEt and benzyl- or phenyl-cyclopentadiene re~pectively.~' The X-ray crystal structure of the needle modification of pentabenzyl-cyclopentadienylthallium has been determined.52 The structure consists of a chain of monomeric molecules in which the thallium is shielded by two benzyl groups attached to the cyclopentadienyl ring to which it is bonded and three benzyl groups of the next monomer in the chain.A gas-phase electron diffraction study5 of pentamethylcyclopentadienylthallium shows that the TI-C distance r2.663 (5) %.I 47 H. Schmidbaur R. Nowak B. Huber and G. Miiller Z. Nutirrforsch. Teil B 1988 43 1447. 48 H. Schumann R. Mohtachemi and M. Schwichtenberg Z. Nuturforsch. Teil B 1988 43 1510. 49 A. H. Cowley R. A. Jones K. B. Kidd C. M. Nunn and D. L. Westmoreland J. Organornet. Chern. 1988 341 C1. 50 J. F. Hinton K. R. Metz and R.W. Briggs Bog. Nucl. Magn. Reson. Spectrosc. 1988 20 423. 5' P. Singh M. D. Rausch and T. E. Bitterwolf J. Organornet. Chern. 1988 352 273. 52 H. Schumann C. Janiak M. A. Khan and J. J. Zuckerman J. Orgunornet. Chern. 1988,354 7. 53 R. Blom H. Werner and J. Wolf J. Orgunornet. Chern. 1988 354 293. Organometallic Chemistry -Part (ii) The Main-Group Elements is shorter than that in the non-methylated compound as was found previously in the indium analogues. 4 Group IV Reviews have been published covering silyl-directed stereocontrol in organic syn- thesis,54 the characteristic reactions of allylsilane~,~~ the synthetic uses of organosilanes under nucleophilic catalysis conditions,s6 how gas-kinetic studies have aided the understanding of organosilicon reaction mechanisrn~,~~ the reactions between halogenosilanes and acetals orthoesters or their analogues," the physical and chemical properties of pyridine and quinoline derivatives of Si Ge Sn and Pb,s9 and phase transfer catalysis in organosilicon chemistry.6o A book in the 'Best Synthetic Methods' series 'Silicon Reagents in Organic Synthesis' by E.W. Colvin (Academic Press London 1988) gives details about the practical aspects of using a wide range of silicon reagents. A series of silacyclohexadienes with bulky substituents (e.g.Bur) and good leaving groups on silicon (e.g. OMe) have been prepared as precursors to silabenzenes.61 The most stable silabenzene reported so far (18),which can be observed spectroscopi- cally up to -100 "C has been prepared by photolysis of the diazo compound (19).The silabenzene has a characteristic 29Si n.m.r. shift of 26.8 p.p.m. and can be trapped by MeOH.62 BU' BU' The stable silanimine Bu\Si=NSiBu\ can be prepared by reaction of Bu\SiNa with Bu\SiCIN3 and forms adducts with donors e.g.NMe,Et and THF. The reactions of the Si=N double bond in the free compound and its adducts with a wide range of protic and unsaturated species have also been studied.63 The silene (Me3Si)2Si=CPh(OSiMe,) reacts with the azete (20) to give pyrrole (21) uia a complicated rearrangement whilst with 1,2,3,4,5-pentamethylcyclopen-tadiene and cyclohexa-1,3-diene normal Diels- Alder products are obtained.64 54 I. Fleming Pure Appl. Chem. 1988 60 71. 55 A. Hosomi Acc.Chem. Res. 1988 21 200. 56 G. G. Furin 0.A. Vyazankina B. A. Gostevsky and N. S. Vyankin Tetrahedron 1988 44 2675. 57 I. M. T. Davidson J. Organornet. Chem. 1988 341 255. 5x R. S. Musavirov E. P. Nedogrey I. N. Syraeva E. A. Kantor and D. L. Rakhmankulov J. Organomet. Chern. 1988 350 139. 5V E. Lukevics and I. D. Segal g. Organomef. Chem. Library 1988 20 69. 60 Yu. Goldberg V. Dirnens and E. Luckevics J. Organomer. Chem. Library 1988 20 21 1. 61 P. Jutzi and M. Meyer Chem. Ber. 1988 121 1393. 62 G. Mark1 and W. Schlosser Angew. Chem. In/. Ed. Engl. 1988 27 963. 63 N. Wiberg and K. Schurz Chem. Ber. 1988 121 581. 64 H. Richter S. Arenz. G. Michels J. Scheider 0. Wagner and M. Regitz Chem. Ber. 1988 121 1363. 250 P.D. Lickiss Si(SiMe3)2 I OSiMe3 (21) Pyrolysis of (22) in the presence of an alkyne affords (23) in low yield. The reaction is thought to involve extrusion of MeSiESiMe which rapidly reacts with RC=CR present to give a 1,4-disilabenzene or 1,4-disila Dewar benzene which subsequently reacts with RC=CR to give the observed 1,4-disiIabarrelene (23).65 The first compound (24) containing an q2-silene coordinated to a transition metal has been isolated and characterized by X-ray crystallography.66 The Si=C bond length is about 1.78 A and the Ru-Si=C angle about 64”. Addition of isonitriles RNC (R=Bu‘ or CMe2CH,CMe3) to a stable silene e.g. (Me,Si),Si=C(OSiMe,)-C10H15 initially gives a silacyclopropanimine which rapidly rearranges to a silaaziridine e.g.(25).These compounds are the first to be isolated and structurally characterized which contain a three-membered SiCN ring ~ystem.~’ The disilene Bu\Si=SiBu\ undergoes addition reactions with 2,2’-bipyridyf8 and a thia~ole.~~ The reactions of the first siliconocene (q5-C5Me,),Si with protic species have been compared with those of its heavier analogues (T~-C~M~,)~M (M = Ge Sn or Pb).” Unlike the derivatives of the heavier analogues HX (X = C1 Br 02CCF, 65 A. Sekiguchi G. R. Gillette and R. West Organometallics 1988 7 1226. 66 B. K. Carnpion R. H. Heyn and T. D. Tilley J. Am. Chem. SOC. 1988 110 7558. 67 A. G. Brook Y. K. Kong A. K. Saxena and J. F. Sawyer Organometallics 1988 7 2245. 68 M. Weidenbruch A. Schafer and H. Marsmann J.Organomet. Chem. 1988 354,C12. 69 M. Weidenbruch B. Flinther S. Pohl D. Haase and J. Martens J. Organomet. Chem. 1988 338 C1. 70 P. Jutzi U. Heltrnann H. Briigge and A. Muller J. Chem. SOC.,Chem. Commun. 1988 305. Organometallic Chemistry -Part (ii) The Main-Group Elements 25 1 03SCF3 etc.) attacks (q5-C5Me,),Si at the lone pair giving compounds of type (C5Me5)2SiHX although treatment with HBF affords the cyclotetrasilane (C,Me,SiF) apparently via dimerization of the unstable disilene C,Me,( F)Si=Si( F)C5Me5. A range of mono- and di-( q' -pentamethylcyclopen-tadieny1)silanes C,Me,SiX (X = F Br H etc.) and (C,Me,),SiXY (X = Y = F or H; X = H Y = C1 or NH,) have been prepared.71 Both chemical and X-ray crystallographic studies show the significant degree of steric hindrance afforded by the q1-bound ligand.Details of the convenient chemical thermal and photochemical generation of silylene Bu:Si from various of precursors should encourage further study of this and other sterically hindered ~ilylenes.~ In an argon matrix Bu',Si has A,, = 480 nm reacts with alcohols and inserts into SiH and SiOMe bonds.73 In contrast to less bulky silylenes (2,4,6-PrjC6H2),Si reacts with cis-and trans-but-2-enes non-stereospecifically giving both cis and trans silirane products. The reason for this bulk effect is not known.74 Reaction of Rh,H,(CO),(dppm) with primary silanes PhSiH or EtSiH gives fluxional products which contain silylenes bridging between Rh atoms e.g. Rh,(p-SiPhH),(CO)2(dppm)2,the crystal structure of which shows Si-Rh distances of 2.35 A and Rh-Si-Rh angles of about 73.5°.75 The stabilization energy of a carbenium ion by a p-silyl group has been measured in the gas phase for Me3Si(CH2CH,)+ and found to be 9.3 kJ mol-' relative to CH3CHi.76 The magnitude of the well-known stabilization of a carbanion by an a-silyl group has been determined via measurement of the electron affinity of the Me,SiCH; radical.The derived proton affinity of the anion Me,SiCH is 93.5 f 0.4 kJ mol-' from which a value of 4.8 kJ mol-' for a-silyl carbanion stabilization is ~alculated.~~ Further evidence for the existence of Ph,Si+ and Me,Si+ species in low concentra- tion in solution has been provided by 35Cl and ,'Cl n.m.r. studies of Ph,SiOC1O3 and Me3SiOC103.Below about 0.01M and 0.006M for Me,SiOClO and Ph,SiOC103 respectively the C1 n.m.r. signals are sharp indicating >90% ionic character but at higher concentration e.g. 0.584M for Me,SiOC10, the C1 n.m.r. signals are broad indicating predominantly covalent ~haracter.'~ Detailed evidence for the existence of silicocations (RS),Si+ (R = Me Et or Prl) in dilute solution in CH2C12 MeCN or sulpholane has been reported. The ions are prepared by hydride abstraction from (RS),SiH using Ph3COC103 and the ionic nature of (RS),Si0C1O3 at low concentration is indicated by conductance n.m.r. spectroscopy and molecular weight determination. At higher concentrations (>O.lOM) as for Ph,SiOClO and Me,SiOClO, the compounds appear to be predominantly covalent in nat~re.'~ 7' P.Jutzi D. Kanne M. Hursthouse and A. J. Howes Chem. Ber. 1988 121 1299. 72 P. Boudjouk U. Sarnaraseera R. Sooriyakumaran J. Chrusciel and K. R. Anderson Angew. Chem. Int. Ed. Engl. 1988 27 1355. 73 K. M. Welsh J. Michl and R. West J. Am. Chem. SOC.,1988 110 6689. 74 W. Ando M. Fujita H. Yoshida and A. Sekiguchi J. Am. Chem. SOC.,1988 110 3310. 75 W.-D. Wang S. I. Hornmeltoft and R. Eisenberg Organometallics 1988 7 2417. 76 D. Hajdaz and R. Squires J. Chem. SOC., Chem. Commun. 1988 1211. 77 D. M. Wetzel and J. I. Brauman J. Am. Chem. SOC.,1988 110 8333. 78 J. B. Lambert and W. Schilf J. Am. Chem. SOC.,1988 110 6364. 79 J. B. Larnbert W. J. Schulz jun. J. A. McConnell and W. Schilf J. Am. Chem. SOC.,1988 110 2201.252 I? D. Lickiss Compounds containing the new ring system 1,2-dihydro- 1,2,5-disilaborepine (26) are formed when 1,2-diethynyltetramethyldisilaneis treated with an excess of Me,B or Et3B.80 A new class of cyclic organosilicon compounds cyclopoly( silapro- pynylenes) (R,SiC=C) (where R = Me or Ph) have been prepared by treatment of dilithium derivatives R,Si(C_CLi) with the corresponding R2SiCI2. Treatment of R,Si(C_CLi) with RiSiCl leads to products in which the R2Si and the RiSi units are distributed randomly.81 The smaller strained ring system 1,2,5,6-tetrasilacyc- loocta-3,7-diyne (27) can be prepared in good yield by treatment of di-Grignard derivatives of disilanes (R,SiCrCMgBr) with ClRiSiSiRiC1.82 MelSiHg R2Si-C=C-SiR; I I Me2Si R,Si-CfC-SiR; I HR (27) R = R' = Me; R = R' = Bun; (26) R = Me or Et R = Me R' = Bun The X-ray crystal structure of decaisopropylhexasilabicyclo[2.2.0lhexane (28) has been determined (the first of such a ring system).The rings are puckered and the central Si-Si bond of 2.396 8 is similar in length to those in the periphery of the molecule (2.385-2.426 The first compound (29) containing the octasilacubane ring system has been prepared by condensation of Br,RSiSiRBr or RSiBr (R = Bu'Me2Si) with sodium giving 55 and 72% yields respectively. The compound is air-sensitive but stable in an inert atmo~phere.~ R R R2Si-Si-SiR2 RSi I. I. I R2Si-Si-SiR2 R RSi R (28) R = Pr' (29) R = Bu'Me,Si Reduction of Cl[Si(C6HI 1)2]4C1 by potassium affords octacyclohexyl-cyclotetrasilane in 89% yield.The Si ring is not planar but has a fold angle of 27.6" and the Si-Si bond lengths in the ring are 2.391 A.85The reductive oligomeriz- ation of [C1,( Bu')Si] with lithium naphthalenide gives several products among which are the first examples of the tricyclo[2.2.0.02~s]hexasilane(30) and tetracyclo[3.3.0.02~7.03~6]octasilane (31) ring systems.86 UO B. Wrackmeyer J. Chem. SOC. Chem. Commun. 1988 1623. '' R. Bortolin B. Parbhoo and S. S. D. Brown J. Chem. SOC.,Chem. Commun.,1988 1079. 82 T. Iwahara and R. West. J. Chem. SOC.,Chem. Commun.,1988 954. n3 H. Matsumoto H. Miyamoto N. Kojima Y. Nagai and M. Goto Chem. Len. 1988 629. 84 H. Matsumoto K. Higuchi Y. Hoshino H. Koike Y. Naoi and Y.Nagai J. Chem. SOC.,Chem. Commun. 1988 1083. 85 M. Weidenbruch K.-L. Thom S. Pohl and W. Saak Montash. Chem. 1988 119 65. 86 Y. Kabe M. Kuroda Y. Honda 0.Yamashita T. Kawase and S. Masamune Angew. Chem. Int. Ed. Engl. 1988 27 1725. Organometallic Chemistry -Part (ii) The Main-Group Elements Bu' B u' \ But Two new types of polysilane (PhMeSiMe,Si) and [(PhMe,Si)MeSi], have been prepared from the disilane fraction from the Direct Process via initial phenylation of C1,MeSiSiMe2C1 to give ClMePhSiSiMe,Cl and C1,MeSiSiMe2Ph with sub- sequent condensation using sodium. This reaction sequence thus turns a Direct Process residue into polysilanes which are currently of great interest as ceramic precursor^.^^ The first 'polyalkylsilyne' [(n-hexyl)Si],,,has been prepared by treat- ment of (n-hexyl)SiCl with Na/ K alloy with ultrasound irradiation.The polymer is yellow soluble in hexane more stable to photodegradation than linear polysilanes and has other properties different to simple polysilanes that should make this new class of polymer the subject of considerable interest." The condensation of dichlorosilanes R'R2SiC12 (R'= R2 = n-hexyl; R' = Ph R2 = Me) with sodium to give polysilanes has been carried out under irradiation by ultrasound. The polysilanes produced are of high molecular weight only (M,> lo5) and do not contain the usual low molecular weight (M,l -lo3)p~lyrner.'~ Group transfer polymerization of polyunsaturated esters has been achieved using silyl ketene acetals or silyl polyenolates.Better control over M,and low polydisper- sity is achieved using silyl polyenolates for initiation." The preparation of optically pure organosilanes containing chiral silicon centres has been further explored by utilizing the reaction between (R)-(1-naphthyl)phenyl-methylsilylmethyllithium (naphthPhMeSiCH,Li) and carbonyl compounds. Although the p-hydroxysilanes formed had only a 3"% diastereoisomeric excess it was possible to study the stereochemistry at silicon of p-elimination. With BF,-OEt, H2S04 or AcOH-NaOAc elimination occurred with inversion of stereochemistry but with KH retention of configuration occurred." Transfer of chirality from silicon to an a-carbon has been achieved using the chiral thioketone (R)-( -) -naphthMePhSiC( S)Ph which gives diastereoisomeric sulphides naph- thMePhSiCHPhSMe when treated with MeLi followed by MeOH and thiopyrans when treated with buta-1,3-diene with 40 and 50% d.e.re~pectively.'~ This success should prompt further work in this potentially very useful field. 87 H. Watanabe Y. Akutsu A. Shinohara S. Shinohara Y. Yamaguchi A. Ohta M. Onozuka and Y. Nagai Chem. Lett. 1988 1883. 88 P. A. Bianconi and T. W. Weidman J. Am. Chem. Soc. 1988 110 2342. 89 H. K. Kim and K. Matyjaszewski J. Am. Chem. SOC.,1988 110 3321. 90 W. R. Hertler T. V. RajanBabu D. W. Ovenall G. S. Reddy and D. Y. Sogah J. Am. Chem. Soc. 1988 110 5481. G. L. Larson A. Prieto and E. Ortiz Tetrahedron 1988 44 3781. 92 B. F. Bonini F. Mazzanti P. Zani and G.Maccagnani J. Chem. SOC. Chem. Commun. 1988 365. 254 P. D. Lickiss A new route for the preparation of alkoxysilanes by hydrosilylation of ketones using diphenyltitanocene as catalyst has been described. For example Ph2SiH, MeC(0)C5Hll and (q5-C5H5),TiPh gave Ph,HSiOCHMe(C,H,,) in 91% yield after reaction at 120"for 11 h.93 The convenient synthesis of rare trialkylsiloxyalkynes such as HC_COSiR and Me3SiC~COSiR3 (SiR3 = SiBukMe) is achieved by dehydrobromination of (2)-2-bromovinyl silyl ethers.94 The transition-metal cata- lysed reaction between R3SiH compounds and diazo esters or diazo ketones leads Aeanly to the formation of a-silyl esters and a-silyl ketones respectively providing a new and synthetically useful route to these widely used compounds:95 Both Na,SiF6 and (NH4),SiF6 have been found to be good fluorinating agents for chlorosilanes with the latter working well even for hindered chlorosilanes such as Bu\SiCl and mesity12SiC12.The ammonium salt should be particularly useful as it does not affect Si-H Si-Si or Si-0-Si bonds as do many other reagents used for the Si-C1 to Si-F conver~ion.~~ The use of NaN impregnated on an Amberlite resin converts silyl chlorides into silyl azides in good yields with short reaction times in common solvents such as CH2C12 benzene and he~ane.~~ This convenient method can also be used to prepare silyl azides containing Si-H or Si-CH=CH groups and should become a common route to this useful group of compounds. The use of silica as starting material for the preparation of R3SiX species has been demonstrated thus avoiding the need to prepare elemental silicon for use as a feedstock in the Direct Process.The method involves breakdown of Si02 by catechol in the presence of a base such as KOH to give a tricatecholate e.g. [(C6H4Oz),Sil2-2K+ and subsequent reaction of this hexacoordinate species with a Grignard or lithium reagent to give R3SiH7 &Si or 0-(R3SiO)C6H40H (R = Me Et CH,Ph Ph etc.). It will be interesting to see if this type of synthesis can be scaled up and become commercially viable.98 The first example of oxidative addition of an Si-halogen bond to a Ptocomplex has been observed in the reaction between Pt(PEt,) and Me3Si-Br to give trans-Me,SiPtBr( PEt3)2; thus Me3SiBr behaves like an organic halide in the reaction.99 The one-pot synthesis of a range of aliphatic aromatic and heteroaromatic acylsilanes can be achieved by treatment of an acid chloride with the silyl cuprate (Me Si )2CuLi.loo The use of (Me3Si),SiH as a reducing agent to replace Bu;SnH has been redis- covered"' 18 years after the initial reportlo2 of this compound's reducing ability! The reduction of alkyl chlorides bromides and iodides can be achieved using the silane alone or in the presence of a radical initiator such as benzoyl peroxide.93 T. Makano and Y. Nagai Chem. Lett. 1988 481. 94 R. L. Danheiser A. Nishida S. Savariar and M. P. Trova Tetrahedron Lett. 1988 29 4917. 9s V. Bagheri M. P. Doyle J. Taunton and E. E. Claxton J. Org. Chem. 1988 53 6158.96 R. Damrauer R. A. Simon and B. Kanner Organornetallics 1988 7 1161. 97 K. Sukata J. Org. Chem. 1988 53 4867. 98 A. Bouding G. Cerveau C. Chuit R. J. P. Corriu and C. Reye Organornetallics 1988 7 1165. 99 H. Yamashita T. Hayashi T. Kobayashi M. Tanaka and M. Goto J. Am. Chem. Soc. 1988,110,4417. 100 A. C. Copperucci A. Degl'Innocenti C. Faggi A. Ricci P. Dembech and G. Seconi J. Org. Chem. 1988 53 3612. 101 C. Chatgilialoglu D. Griller and M. Lesage J. Org. Chem. 1988 53 3641. H. Burger W. Kilian and K. Burczyck J. Organomet. Chem. 1970 21 291. Organometalfic Chemistry -Part (ii) The Main-Group Elements 255 Reduction of MeCH(SiCl,) by LiAlH, affords MeCH(SiH,), which may be a useful precursor to hydrogen-containing silicon-carbon alloys.'03 Air-stable metallocenes of Ge Sn and Pb containing tetraphenylcyclopentadienyl or (4-t-butylphenyl)tetraphenylcyclopentadienylligands can be prepared from the metal dihalide and the appropriate cyclopentadienyl alkali-metal salt.lo4 The syn- thesis and properties of the air- and moisture-stable (v5-C5Ph5)*M (M = Ge Sn or Pb) have been described together with their solid-state n.m.r.spectra.'05 The pentaphenyl tin analogue (q5-C5H5)( q5-C5Ph5)Sn is also moderately air-stable and has a ring centroid-Sn-ring centroid angle of 151.1(3)0.'06 Photolysis of Me,GeGeMe,Ph gives a range of products predominantly diger- manes e.g. Me,GeGeMe3 and hydrogermanes e.g. Me,GeH which are thought to be derived from homolysis of the Ge-Ge bond giving Me,Ge' and PhMe2Ge' and also from formation of Me2Ge:.'07~'08 The treatment of 1-alkenylsulphides R' R2C=CHSPh or 1-alkenylstannanes R'R2C=CHSnPh3 with Ph,GeH in the presence of Et,B gives good yields of 1-alkenylgermanes R'R2C=CHGePh3 (R' = R2 = Ph or Et; R' = n-CloH21 R2 = H etc.).'" The first preparation of bis(phenylseleno)germanes,R'R2Ge( SePh) ,has been achieved by reaction of PhSeNa and R'R2GeX2 (R' = R2 = Me X = C1; R' = R2 = Ph X = Br etc.).The X-ray crystal structure of 1,l-bis(phenylse1eno)-1-germacyclopentane shows a Ge-Se bond length of -2.36A and an Si-Ge-Se angle of 101.7°."0 A review of 73Ge n.m.r.spectroscopic studies of organogermanium compounds has been published,"' and ',Ge n.m.r. data for a series of germacyclohexanes have been reported.' l2 Allylic germanes and stannanes are formed in good yield when allenes are treated with Ph,GeH or Ph,SnH in the presence of Pd(PPh,),.Thus allene gave CH,=CHCH,GePh and CH,=CHCH,SnPh in 88 and 40% yields re~pectively."~ An absorption at 420 nm in the products from room-temperature laser photolysis of Me,Ge(SePh) has been attributed to Me,Ge and is the first time that its U.V. spectrum has been rep~rted."~ Laser flash photolysis of (Me3Si)2GePh2 in cyclo- hexane generates a species with A,, 445nm attributable to Ph,Ge which can be trapped by various reagents and dimerizes to give Ph2Ge=GePh2 .l15 The reactions of dimethylgermylene Me,Ge with various acetylenes to give several new germa- heterocycles have been described."6 Various diarylgermylenes e.g.Ph,Ge and 103 H. Schrnidbaur and R. Hager Z. Naturforsch Teil B 1988 43 571. 104 H. Schurnann C. Janiak and J. J. Zuckerrnan Chem. Ber. 1988 121 207. 105 C. Janiak H. Schurnann C. Stader B. Wrackrneyer and J. J. Zuckerrnan Chem. Ber. 1988 121 1745. 106 M. J. Heeg R. H. Herber C. Janiak J. J. Zuckerrnan H. Schumann and W. F. Manders J. Organomet. Chem. 1988 346 321. 107 K. Mochida M. Wakasa Y. Nakadaira Y. Sakaguchi and H. Hayashi Organometallics 1988 7 1869. 108 K. Mochida H. Kikkawa and Y. Nakadaira Chem. Lett. 1988 1089. 109 Y. Ichinose K. Oshima and K. Utimoto Chem. Lett. 1988 669. 110 S. Tornoda M. Shirnoda Y. Takeuchi and Y. Iitaka Chem. Lett. 1988 535. 111 E. LiepnS I. Zicrnane and E. Lukevics J. Organomet.Chem. 1988 341 315. 112 Y. Takeuchi Y. Ichikawa K. Tanaka and N. Kakirnoto Bull. Chem. Soc. Jpn. 1988 61 2875. I13 Y. Ichinose K. Oshirna and K. Utirnoto Bull. Chem. Soc. Jpn. 1988 61 2693. 114 S. Tomoda M. Shirnoda Y. Takeuchi Y. Kajii K. Obi I. Tanaka and K. Honda J. Chem. Soc. Chem. Commun. 1988,910. 115 S. Konieczny S. J. Jacobs J. K. Wilking and P. P. Gaspar J. Organomet. Chem. 1988 341 C17. 116 G. Billet W. P. Neurnann and G. Steinhoff Tetrahedron Lett. 1988 29 5245. 256 P. D. Lickiss mesityl,Ge form complexes with heteroatom-containing molecules such as Bu; P Et3N Me,S and PhCl that can be detected by U.V.spectroscopy in matrices at 77 K. On warming the matrix the germylenes dimerize to give digermenes Ar,Ge=GeAr .I1' Addition of germylene {(Me,Si),CH},Ge to the phosphaalkyne Bu'CrP gives the first phosphagermirene (32) in good yield as a yellow crystalline solid.l8 The chemistry of the digermene (2,6-Et,C6H3),Ge=Ce( 2,6-Et,C,H3) has been explored and the first digermirane (33) and azadigermirane (34) have been prepared by treatment of the digermene with CH,N2 and PhN, re~pectively.~'~ Reaction of (33) or (34) with pyridine N-oxide S8,or Se gives four-membered ring products in which insertion of 0 S or Se into the Ge-Ge bond has occurred. [CH(SiMe,),l cH2 Ph Cie N /\ /\ /\ // // beAr, Bu'-C=P Ar2Ge- Ge Ar Ar2Ge- GeAr (32) (33) Ar =2,6-Et2C,H (34) The photolysis of the cyclotrigermane (mesityl,Ge) produces the digermene mesityl,Ge=Ge( me~ityl)~ and the germylene mesityl,Ge which react with suphur to give (35) and (36; E =S) respectively.The digermene also reacts with selenium to give (36 E =Se).'" Digermene (2,6-Et2C6H,)2Ge=Ge(2,6-Et2c6H3)2 undergoes various cycloaddition reactions with for example CH2N2,PhCECH and acetone giving digermacyclopropane digermacyclobutene and digermaoxetane products S // E (Mesityl),Ge-Ge( Mesityl) (Mes it y 1)?G e /\Ge( Mesity 1)2 E (35) (36) E =S or Se The crystal structure of the first germaphosphene mesityl,Ge=P(2,4,6-Bu\C6H2) has been determined122and is found to have a Ge=P bond length of 2.138(3) A -8.5% shorter than a Ge-P single bond. Addition of S or Se to the germaphosphene leads to addition to the Ge=P bond and formation of the first structurally character-ized germathiaphosphirane and germaselenaphosphirane respectively.' 23 A Ge=C double bond can be stabilized by charge transfer into an aromatic system thus allowing mesityl,Ge(fluorenylidene) to be isolated as a crystalline solid with a Ge=C bond length of 1.803 (4) 117 W.Ando H. Itoh T. Tsumuraya and H. Yoshida Organometallics 1988 7 1880. I18 A. H. Cowley S. W. Hall C. M. Nunn and J. M. Power J. Chem. SOC.,Chem. Commun. 1988 753. I I9 W. Ando and T. Tsumuraya Organometallics 1988 7 1882. I20 T. Tsumuraya S. Sato and W. Ando Organometallics 1988 7 2015. 121 S. A. Batcheller and S. Masamune Tetrahedron Lett. 1988 29 3383. 122 M. Drager J. Escudik C. Couret H. Ranaivonjatovo and J. Satgk Organometallrcr 1988 7 1010.123 M. Andrianarison C. Couret J.-P. Declercq. A. Dubourg J. Escudie H. Ranaivonjatovo and J. Sat& Organometallics 1988 7 1545. I24 M. Lazraq J. Escudik C. Couret J. Satge M. Drager and R. Dammel Angew. Chem. Int. Ed. Engl. 1988 27 828. Organometallic Chemistry -Part (ii) The Main-Group Elements The first preparation of R,Ge' species (R = Me or Ph) in solution has been achieved using the same method as in the R,Si+ analogues i.e. hydride abstraction from R,GeH by trityl perchlorate. The ionic nature of R3GeOC103 predominates at low concentration e.g. 0.0015M but at higher concentrations e.g. 0.146M for R = Ph a covalent structure is preferred.12' The crystal structure of the arylgermane (o-Me2NCH2C6H4),GeH shows intramolecular coordination to the Ge atom by all three Me2N groups giving a pseudo-heptacoordinate environment.X-Ray powder data suggest that the silicon analogue has a similar structure.'26 The reaction of germanium powder with CH2CI at 350°C affords MeGeCl, CH2(GeC1,)2 and (C12GeCH2)3 as major products; these can be reduced by LiAIH4 to the corresponding hydrides which may have potential as precursors to ger- manium-carbon alloys using chemical vapour deposition technique^.'^^ Reductive dehalogenation of Bu'jGeC1 and BuSGeCl gives cyclotrigermane (BuiGe) and digermane BuiGeGeBuS respectively; the latter contains the longest Ge-Ge (2.710A) and Ge-C (2.076 A) bonds yet recorded.I2' Both decaphenylgermanocene and decaphenylstannocene have been shown to exhibit anti-tumour activity in mice cure rates being 40-80% and 40-90% for dose ranges of 280-700 and 160-460 mg kg-' respectively.In the tin case deaths due to the toxicity of the compound began to occur at doses greater than 440 mg kg-1.'29 The anti-mutagenic activity of pyrazoyl borate complexes of di- and triorganotins has also been in~estigated.'~' Addition of the stannylene [(Me,Si),CH12Sn to a cyclic alkyne gives the first stannacyclopropene (37) which can be crystallized and has Sn-C,,2 bond lengths of -2.135 8 and a C,,Z-Sn-C,,,~ angle of 36.6 (2)".',' Addition of {[( Me,Si),CHI2Sn} to Bu'CrP gives the first example of a phosphadistannacyc- lobutene (38) which has a planar Sn2CP ring and a Sn-Sn bond length of 2.878 (1) A.132 Regioselective hydrostannylation of terminal alkynes can be achieved using rhodium catalysts; for example PhC=CH and BuYSnH in the presence of RhCI( PPh3)3 give Ph( Bu3Sn)C=CH2 and PhHC=CHSnBu in the ratio 88 :12.13' '" J.B. Lambert and W. Schilf Organometallics 1988 7 1659. C. Breliere F. CarrC R. J. P. Corriu and G. Royo Organomefallics 1988 7 1006. H. Schmidbaur J. Rott G. Reber and G. Muller Z. Naturjorsch Ted B 1988 43 727. I 2x M. Weidenbruch F.-T. Grimm M. Herrndorf and A. Schafer J. Organomet. Chem. 1988 341 335. I29 P. Kopf-Maier C. Janiak and H. Schumann fnorg. Chim. Acra 1988 152 75. "'' S. A. A. Zaidi A. A. Hashmi and K. S. Siddigi J. Chem. Res. (S),1988 410. 131 L. R. Sita and R. D. Bickerstaff J. Am. Chem. Soc. 1988 110 5208. I32 A.H. Cowley S. W. Hall C. M. Nunn and J. M. Power Angew. Chem. Int. Ed. En& 1988 27 838. I73 K. Kikukawa H. Umekawa. F. Wada and T. Matsuda C'hem. Letr. 1988 881. 258 P. D. Lickiss A novel intramolecular tin-oxygen coordination [Sn-0 distance 2.781 (3) A] has been shown to be present in (2-methoxycarbonylcyclohexa-1 ,4-dien- 1-yl)trimethyltin by X-ray ~rystallography.'~~ An annual survey of the chemistry of lead for 1984 has been p~b1ished.l~~ 5 Group V Convenient high-yield synthesis of arsoles stiboles and bismoles e.g. (39) is achieved by using zirconium reagents in metallacycle transfer rea~ti0ns.l~~ The diene backbone can be varied readily and the zirconium reagent can be generated in situ from zirconocene dichloride which makes this an attractive route to these relatively rare compounds.This method can also be used to prepare Ga In Ge Sn and Se derivatives. The first 4-hydroxy- 1,3-azaarsole and 3-hydroxy- 1,2,4-diazaarsole have been prepared.13' Both compounds exist in the phenolic OH form with none of the keto tautomer being detected. (39) E = As Sb or Bi The first reported diarsenyl complex (q5-C5Me,)(CO),FeAs=AsAr (Ar = 2,4,6-BuiC,H2) is formed in the reaction between ArAsCI2 and (qS-C,Me,)-(CO)2FeAs(SiMe3)2. The complex could not be isolated pure but did form a chromium pentacarbonyl derivative ( q -C,Me,)(CO),FeAs[Cr( C0)5]=A~Ar.138 The arsaphosphene (40) coordinates to platinum according to Scheme 1 to give the first compound (41) containing a P-As-R ring.The crystal structure of (41) shows Fe Fe Reagent (Ph P)* RC H Scheme 1 134 B. Jousseaume P. Villeneuve M. Drager S. Roller and J. M. Chezeau J. Organornet Chem. 1988 349 c1. 135 J. Walters and D. de Vos J. Organomet. Chem. 1988 351 1. 136 P. J. Fagan and V. A. Nugent J. Am. Chem. SOC.,1988 110 2310. 137 G. Mark1 and S. Pflaum Tetrahedron Lett. 1988 29 3387. 138 L. Weber and D. Bunghardt J. Organomet. Chem. 1988 354 C1. Organometallic Chemistry -Part (ii) The Main-Group Elements 259 Pt-As and P-As bond lengths of 2.515 (1) and 2.289 (3) A respectively and a P-As-Pt angle of 58.7 (l)0.'39 The phosphidoiron complex (v5-C5Me5)( CO)FeP( SiMe3)2 reacts with ArAsCl (Ar = 2,4,6-Bu:C,H2) to give various products containing P=As or As=As bonds or ASP, As2P or As2P2 rings.The diphosphaarsane (42) can be isolated as a crystalline solid and has As-P bond lengths of 2.316(1) and 2.350(2)A and a P-As-P angle of 56.5 (l)0.'40 The Ga3As3 ring in [(Me3SiCH2),AsGaBr2I3 adopts a twist-boat conformation with Ga-As bond lengths [2.432 (2)-2.464 (1) A] shorter than those found in Ga2As2 rings of dimeric ar~inogallanes.'~' Treatment of SnCl with Bu:AsSiMe3 affords [Sn(p-AsBu;)Cl] in which the As is approximately tetrahedral the Sn-As bond lengths are -2.77 A and the Sn-As-Sn angle is -102°.'42 The first 1,3-azaarsinines (43) have been prepared'43 and their reactions with acetylenic compounds have been studied.'44 + R' R' = R2 = R3 = Ph R' = p-MeC,H4 R2 = R3 = Ph (42) (43) The 14-membered ring compound (44) forms with complete stereoselectivity according to Scheme 2.'45 The diimine can be reduced to the corresponding diamine with LiAlH4 and resolution of the racemates of both the diimine and diamine can be achieved via complexation to palladium.r 1 Me 80 "C -2 (CH,NHMe) Me (44) (R*,S*) Scheme 2 139 F. Edelmann C. Spang H. W. Roeskya and P. G. Jones Z. Naturforsch. Teil B 1988 43 517. 140 L. Weber D. Bunghardt U. Sonnenberg and R. Boese Angew. Chem. Int. Ed. EngL 1988 27 1537. 141 R. L. Wells A. P. Purdy A. T. McPhail and C. G. Pitt J. Organomet. Chem. 1988 354 287. 142 A. H. Cowley D. M. Girlando R. A. Jones C. M. Nunn J. M. Power and W.-W. du Mont Polyhedron 1988 7 1317. 143 G. Markl and S.Dietl Tetrahedron Lett. 1988 29 535. 144 G. Markl and S. Dietl Tetrahedron Lett. 1988 29 539. 145 J. W. L. Martin F. S. Stephens K. D. V. Weerasuria and S. B. Wild J. Am. Chem. SOC.,1988 110,4346. 260 P. D. Lickiss The structure of an arsinimine Ph,AsNCN has been determined by X-ray crystallography; this shows the arsenic to have an almost tetrahedral environment with an As-N distance of 1.739 (4)A which is greater than the sum of the covalent radii of As and N (1.71 A).146 The crystal structure of Me2AsAsMe2 has been determinedI4' and is shown to consist like the antimony and bismuth analogues of linear chains of molecules. There are no short intermolecular As-..As distances which is thought to be the reason for the lack of thermochromism in this compound.The syntheses of di-t-butylcyclopentadienyldichloro-arsineand -stibine are readily achieved by treatment of AsCI and SbCl with Bu&H,L~.'~* Both com- pounds are fluxional exhibiting a rapid 1,2-shift of the MCl2 group. An annual survey for 1986 of the chemistry of antimony has been publi~hed.'~~ The equilibria between symmetrical distibines R$b2 and R:Sb2 (R' = Me R2 = Et; R' = Me R2 = Ph etc.) to give unsymmetrical distibines RiSbSbR; have been investigated by n.m.r. spectros~opy.'~~ Redistribution reactions of stibines of the type R;SbER2 (e.g. R' = Me R2 = Ph E = S; R' = R2 = Me E = Se) to give products RlSb and R'Sb(ER2)2 have also been ~tudied.'~' Oxidation by H202 of several aryl stibines Ar3Sb (Ar = p-C1C6H4,0-MeOC,H, etc.) gives the correspond- ing oxides which are thought (from their i.r.spectra) to be dimers containing Sb,02 rings. Oxidation of mesity1,Sb affords me~ityl,Sb(OH)~ the structure of which shows the Sb to have a slightly distorted trigonal-bipyramidal environment the OH groups in apical positions and no hydrogen bonding between molecules to be present.'" A comparison of the physical and chemical properties of stibonium and bis- muthonium ylides for example (PhS02),C=MPh3 (M = Sb or Bi) with those of their arsonium analogues has been carried out. The close resemblance between stibonium and arsonium ylides is attributed to the interaction between substituent oxygen atoms and the antimony or arsenic atom. A similar effect also appears to be present in the bismuth corn pound^.'^^ An X-ray crystallographic study of (CI,GaSbBu\) shows the Ga,Sb3 ring to have a boat conformation with Ga-Sb distances of about 2.66 A.49 An annual survey for 1986 of the chemistry of bismuth has been publi~hed.'~~ A new class of organobismuth compounds -alkyl diarylbismuthinates Ar,Bi(O)OMe -can be prepared by treatment of Ar,Bi compounds with chloramine-T in methan01.l~~ These new compounds are mild and selective oxidizing reagents that react with activated glycols such as Ph,C(OH)C(OH)Ph to give benzophenone but do not react with unactivated species such as cyclohexane-l,2-diol.Stable crystalline bismuthonium ylides are isolated for the first time as products from the reaction between Ph3BiC03 and diones.Unlike arsonium and stibonium ylides the bismuth I46 K. Bailey I. Gosney R. 0. Could D. Lloyd and P. Taylor J. Chem. Res. 1988 (S) 386 (M) 2950. 147 K. Bailey I. Gosney R. 0. Could D. Lloyd and P. Taylor 2. Naturforsch. Teil B 1988 43 952. 148 S. T. Abu-Orabi and P. Jutzi J. Organomet. Chem. 1988 347 307. I49 L. D. Freedman and G. 0. Doak J. Organomet. Chem. 1988 351 25. 150 M. Ates H. J. Breunig and S. GiileG Polyhedron 1988 7 2601. 151 H. J. Breunig and S. GuleG Z. Naturforsch. Teil B 1988 43 998. I52 T. Westhoff F. Huber R. Ruther and H. Preut J. Organomet. Chem. 1988 352 107. I53 G. Ferguson C. Glidewell I. Gosney D. Lloyd S. Metcalfe and H. Lumbroso J. Chem. Soc. Perkin Trans. 2 1988 1829. I54 G. 0. Doak and L. D. Freedman J.Organornet. Chem. 1988 351 63. I55 T. Ogawa T. Murafuji and H. Suzuki Chern. Lett. 1988 2021. Organometallic Chemistry -Part (ii) The Main-Group Elements 261 analogues react readily with aldehydes to give cyclopropanes dihydrofurans or a,P-unsaturated carbonyl compounds depending on the nature of the aldehyde the ylide and the reaction conditi~ns.'~~~'~~ A series of stable pentacoordinate bismuth compounds of type (45) (Ar = p-tolyl or p-CF,C6H4) can be obtained according to Scheme 3.ls8 They react with S02C1 to give (46). Ar,BiCI SO,CI -____. Ar (45) Scheme 3 6 Group VI The reagent formed from Ph,Se and I, which is known and sold as phenylselenyl iodide has been shown by X-ray crystallography not to consist of simple PhSeI molecules but to be a charge transfer complex containing two Ph,Se and two I units linked together to form an eight-membered ring containing four seleniums and four iodine~."~ The first stable solid alkylselenyl iodide (Me,Si),CSeI has been prepared by treatment of [(Me,Si),CSe] with I and is isolated as blackish violet crystals in 79% yield.'60 This is also the first selenyl iodide to be stable in solution not being in equilibrium with the parent diselane and I,.Phenylselenophosphoric dichloride [PhP( Se)Cl,] has been foundI6' to be a useful reagent for the conversion of the C=O into the C=Se group thus enabling various selenoamides selenoaldehydes selenoketones etc. to be prepared in good yield using homogeneous conditions. Various selenocyanates e.g.PhSeCN Bu"SeCN and (PhS02)( Bu'Me,Si)- CHSeCN can be prepared in good yield by treatment of a cyanocuprate with (SeCN) at -78 "C. The fluoride desilylation of such a-silyl-substituted'62 selenocyanates provides a good route to various selenoaldehydes RC(Se)H (e.g. R = Me But Ph PhCH2).I6 Base-induced (e.g.with Et,N) elimination of cyanide from selenocyanates containing electron-withdrawing or conjugating substituents affords selenoketones RC(Se)R' (e.g. R = R' = Ph; R = CO,Et R' = Me) in good ~ie1ds.l~~ The cycloaddition chemistry of both selenoaldehydes and selenoketones I56 H. Suzuki T. Murafuji and T. Ogawa Chem. Lett. 1988 847. 157 T. Ogawa T. Murafuji and H. Suzuki Chem. Lett. 1988 849. I58 K. Akiba K. Ohdoi and Y. Yamamoto Tetrahedron Lett.1988 29 3817. 159 S. Kubiniok W.-W. du Mont S. Pohl and W. Saak Angew. Chem. Int. Ed. Engl. 1988 27 431. I60 W.-W. du Mont and I. Wagner Chem. Ber. 1988 121 2109. I61 J. P. Michael D. H. Reid B. G. Rose and R. A. Speirs J. Chern. SOC.,Chem. Comrnun. 1988 1494. I62 B. J. Meinke G. A. Krafft and A. Guram J. Org. Chem. 1988 53 3632. 163 B. J. Meinke and G. A. Krafft J. Am. Chem. SOC.,1988 110 8671. 164 B. J. Meinke and G. A. Krafft J. Am. Chem. SOC.,1988 110 8679. 262 i? D. Lickiss has also been further A convenient one-pot route to selenoalde- hydes RC(Se)H (e.g. R = Ph Pr" But) from aldehydes involves the treatment of the latter with (Me,Si),Se in the presence of a catalytic amount of Bu"Li.16' Another way to prepare RC(Se)H species involves the addition of selenium to a phos- phorane.166 For example addition of Se to Ph3P=CHPh at 90 "C leads to formation of PhC(Se)H which in the presence of a Diels-Alder trapping reagent such as 2,3-dimethylbutadiene is trapped as the selenacyclohexene.A new preparation of selenoketones gives reasonable yields and involves treatment of a dimagnesium salt derived from a hydrazone with Se,Cl and subsequent treatment with the base Bu3N. The reaction of selenoketones with RMgX or RLi differs from that of the analogous thioketone in that significant amounts of product result from addition of R to the ~e1enium.l~~ Treatment of a ketone with PhSeCl leads to formation of a ketone with an a-PhSeC1 substituent that can be readily removed by aqueous base to afford an enone.The PhSeC1 derivatives are crystalline and easy to purify and PhSeC13 thus appears to be a useful reagent for the introduction of tetravalent (rather than divalent) selenium into an organic molecule.'68 Several novel selenium coronands have been prepared'69p'70 and the structures of 1,3,7,9-tetraselenacyclododecane'69and 1,3,7,9,13,15-hexaselenacyclooctadecane'70 have been determined. The structure of the latter has an unusual ring geometry which is interpreted as the first evidence for the existence of a third-row anomeric effect. Conformational studies on compounds of type (47)also indicate that an anomeric effect exists in the S-C-Se fragment the largest effect being when R = NO2 and the smallest when R = NMe,.17' (47) R = NMe, NO, OMe H F or C1 The tetrathiafulvalene derivatives (48) have been prepared by a general route.(48; n = 3) undergoes reversible oxidation to a radical cation but not a di~ati0n.l~~ Tetraselenafulvalene can be lithiated with LDA at -80°C to give a tetralithio (48) n = 1 2 or 3 I65 M. Segi T. Nakajima and S. Suga J. Am. Chem. SOC.,1988 110 1976. L 66 G. Erker R. Hock and R. Nolte J. Am. Chem. Soc. 1988 110 624. 167 A. Ishii R. Okazaki and N. Inamoto Bull. Chem. Soc. Jpn. 1988 61 861. 168 L. Engman J. Org. Chem. 1988 53 4031. 169 B. M. Pinto B. D. Johnston R. J. Batchelor F. W. B. Einstein and I. D. Gay Can. J. Chem. 1988 66 2956. 170 B. M. Pinto R. J. Batchelor B. D. Johnston F. W. B. Einstein and I.D. Gay J. Am. Chem. SOC.,1988 110 2990. 171 B. M. Pinto B. D. Johnston J. Sandoval-Ramlrez and R. D. Sharma J. Org. Chem. 1988 53 3766. 172 P. J. Nigrey J. Org. Chem. 1988 53 201. Organometallic Chemistry -Part (ii) The Main-Group Elements 263 derivative which reacts with various electrophiles (e.g. Ph2Se2 or COJ to give moderate yields of tetrasubstituted products.'73 Oxidation of (49) with one equivalent of MCPBA gives a mixture of (50) and (51) as products in an approximate 3:2 ratio.'74 Compound (50) is the first selenoseleninate prepared to have an appreciable lifetime at room temperature whilst (51) is the first areneselenic anhydride isolated that is not stabilized by intramolecular coordination to an ortho substituent. New selenium-containing heterocycles such as (52) form charge transfer com- plexes with TCNQ which are electrically highly conductive e.g.conductivity of (52; E = S) is 1.8 S ~m-'.'~~ The novel heterocyclic system of substituted 1,2,3-selenaazaboroles [e.g. (53)] can be prepared in poor yield by treatment of dis- elenaboroles with sulphur diimide~.'~~ Et Se"'-R2 Etry'R1 (52) E = S or Se (53) R' = Me R2 = Bu' R' = Et R2 = SN(SiMe,) The sequential treatment with Me2N=CCI C1- and NaSeH in EtOH of various thiols phenols amines and some carbohydrate cis vicinal diols gives selenothiocarbamates selenodithiocarbonates selenoureas and novel cyclic seleno~arbonates.'~~ Treatment of 2-substituted 2-(chloromethyl)oxiranes with selenide ion affords good yields of 3-substituted 3-hydroxyselenetanes (e.g.3-phenyl and 3-eth~l).'~~ Several optically active selenium-functionalized binaphthyls have been prepared.'79 When used as reagents for the asymmetric ring-opening of cyclo- hexane oxide enantiomeric excesses between 16 and 50% are obtained.The ditellane (2,4,6-Bu3C6H2),Te2 is a red solid with C2 symmetry and in solution has a barrier to rotation about the Te-Te bond of 40.9 kJ mol-'. This is the first measurement of this barrier which is -20% less than that in the corresponding I73 S. Rajeswari Y. A. Jackson and M. P. Cava J. Chem. Soc. Chem. Commun. 1988 1089. 174 J. L. Kice Y.-H. Kang,and M. B. Manek J. Org. Chem. 1988 53 2435. 175 Y. Shiomi Y. Aso T. Otsubo and F. Ogura J. Chem. Soc. Chem.Cornmun. 1988 822. C. D. Habben Chem. Ber. 1988 121 1967. 177 C. M. Copeland J. Ghosh D. P. McAdam B. W. Skelton R. V. Stick and A. H. White Aust. J. Chem. 1988 41 549. 178 G. Polson and D. C. Dittmer J. Org. Chem. 1988 53 791. I79 S. Tomoda and M. Iwaoka J. Chem. Soc. Chew. Cornmun. 1988 1283. 264 P. D. Lickiss diselane.I8' In contrast to the reactions of dialkyl and diary1 tellurides with MeI which give simple telluronium salts the reaction of benzenecarbotellurates of type ArC(0)TeAr' with Me1 leads to cleavage of the Te-C(0) bond and the formation of telluronium salts of type [Ar'TeMe,]+ I-.18' Acetylenic tellurides e.g. PhCECTeEt have been prepared by treatment of PhCr CLi with tellurium followed by trapping of the intermediate lithium tellurolate with an alkyl halide.', Several Me3Te+ and Ph3Te+ salts [e.g.Me3Te+ I- Ph3Te+ NOS and (Ph3Te)2S04-5H20]have been prepared and their structures investigated by '25Te solid-state n.m.r. spectroscopy and X-ray crystallography. Evidence for weak covalent interactions in some of these compounds is seen in the coupling between the 125Te nucleus and halogen anion.'83 New thiocarbamate complexes PhTe(S2CNEt2)2[S2P(OEt)2],184 MeTeI(S,CNEt,) ,lS4 and C,H,Te( SzCNEt2)2185 have been prepared and their structures investigated by n.m.r. spectroscopy and X-ray crystallography. Synthetic routes to tellurium analogues of naturally occurring flavones and chromones have been developed'86 in order that their biological activity can be compared with that of their oxygen and selenium analogues.Tellurapyranones are reduced to the corresponding tellurapyrylium salts in good yield by diisobutyl- aluminium hydride. 187 The synthesis of RTeLi (R = Me or Ph) from RLi and tellurium at low temperature allows the convenient preparation of marry telluroethers. For example treatment of X(CH,),X (X = C1 or Br n = 1 3 6 or 10) with MeTeLi affords MeTe(CH,),TeMe and C(CH,Br) with PhTeLi gives C(CH2TePh)4.'8s Aromatic nitro compounds are reduced by PhTeNa to the corresponding azoxy compounds using NaBH in alkaline ethanol with a catalytic amount of Ph,Te present.'89 I80 W.-W. du Mont L. Lange H. H. Karsch K. Peters E.-M. Peters and H. G. von Schnering Chem. Ber. 1988 121 11. 181 H. B. Singh and N.Sudha Bull. Chem. Soc. Jpn. 1988 61 3735. 182 M. J. Dabdoub and J. V. Comasseto Organometallics 1988 7 84. M. J. Collins J. A. Ripmeester and J. F. Sawyer J. Am. Chem. SOC.,1988 110 8583. I84 D. Dakternieks R. Di Giacomo J. Am. Chem. Soc. 1988 110 6762. 185 D. Dakternieks R. Di Giacorno R. W. Gable and B. F. Hoskins J. Am. Chem. SOC.,1988 110 6753. 186 M. R.Detty Organometallics 1988 7 2188. 187 M. R. Detty Organometallics 1988 7 1122. 188 E. G. Hope T. Kemrnitt and W. Levason Organometallics 1988 7 78. 189 K. Ohe H. Takahashi S. Uemara and N. Sugita J. Chem. SOC., Chem. Commun. 1988 591.