C Si Ge Sn and Pb By D. A. ARMITAGE Department of Chemistry King's College Strand London WC2R 2LS UK Fullerene research continues apace with about 1000 references in 1992 around twice that of 1991. Reviews cover personal reminiscences and perspectives' and the contributions of the various research groups are surveyed. Synthetic approaches toward molecular and polymeric carbon allotropes have been surveyed3 and a complete volume of both Accounts of Chemical Research4 and Carbon' devoted to aspects of fullerene chemistry. Brief summaries occured periodically in Nature6 and in Organometallic News7 as well as part of the ACS Symposium Series.* Australian semi-anthracite from the Yarrabee mine Queensland provides a useful source of fullerenes and once they have been separated using hexane and toluene mixtures the spent coal can be used for further purification of the C,o/C70 mixtures.Shungite from Shunga Karelia Russia comprises metamorphosed carbon-rich rock with meta-anthracite characteristics. Negative ion FTMS showed the presence of C, and C,,.9 Subjecting c6 to rapid non-hydrostatic compression of 20 GPa gives bulk polycrystalline diamond instantly at room temperature in contrast to the hydrostatic (anisotropic) compression which gave an insulating phase above 20 GPa.' The hot dense vapour produced by laser desorption of a fullerene film induces coalescence of fullerenes to give Con-(a = 2,3 n = 60; a = 2 n = 70).' ' Calculations support such a coalescence loss of C,. c60 and C, can be produced in ratios varying from 0.17 to 3.8 using laminar benzene/O,/argon flames and HPIX separation.Polycyclic aromatic hydrocarbons H. W. Kroto Angew. Chem. lnt. Ed. Enql. 1992 31 111 and J. Chem. Soc.. Dalton Trans. 1992 2141. R. M. Baum. Chem. Eng. News. 1992. June 1st. p. 25 H. Schwarz. Angew. Chem.. lnt. Ed. Engl.. 1992.31. 293. F. Diederich and Y. Rubin Angew. Chem. Inr. Ed. Engl.. 1992. 31. 1101. Acc. Chem. Res. 1992 25 No. 3. p. 97. Carbon 1992 30. No. 8 p. 1139. P. Ball Nature 1992,355 205; J. R. Heflin and A. F. Garito. ibid. 1992. 356 192; P. W. Stephens ihid.. 1992,356 383; L. F. Lindoy ihid.,1992. 357,443; M.S. Dresselhaus ihid. 1992. 358 195; H. W. Kroto ibid. 1992. 359 670. K. Itoh and H. Nagashima Organomet. News 1992. (I) 12; G. Matsubayashi. ibid..1992. (2). 80 (Chem. Ahsfr. 1992 117. 171 494c and 171 496e). P. J. Fagan J.C. Calabrese. and B. Malone ACS Symp. Ser.. 1992 481 177 (Chem. Absrr. 1992 116. 128 987h). M. A. Wilson L. S. K. Pang and A. M. Vassallo Nature. 1992,355,117; P. R. Buseck S.J. Tsipursky. and R. Hettich. Science. 1992 257 215. M. N. Regueiro. P. Monceau and J.-L. I-Iodeau. Nature. 1992 355 237. C. Yeretzian K. Hansen F. Diederich and R. L. Whetten Nururr 1992. 359. 44. 33 D. A. Armitage and oxides and higher fullerenes were also detected.' A plasma discharge reaction has been designed to produce gram quantities of fullerenes over an eight hour period,' while heating graphite to 2700°C in an atmosphere of He gives 10% fullerenes dominated by c6 and C70 (ratio 8 :3) but with some 7% comprising c84,c78,c82 c76 C90 c88 and (order of decreasing yield).l4 Extracts from the soot produced by the Kratschmer-Huffman technique suggests the presence of fullerenes with up to 330 carbon atoms but no nanotubes.15 Mechanisms have been suggested for both fullerene formation and photofragmentation. ' Methods of separation of C, and C, include recrystallization from toluene chromatography on alumina graphite and polystyrene gel or silica gel and a simple Soxhlet chromatographic separation.' Among the higher fullerenes chiral C, (0,symmetry) shows unusual electrochemi- cal properties. While c60 and C, readily undergo reversible reduction steps there is no reversible oxidation.I8 This is explained in terms of the six pyracyclene units in the structure each taking one electron to give 67c delocalization at one of the five-membered rings of this unit.C,, however exhibits both reversible reduction and oxidation due to the acene substructural units (a straight chain of at least three six-membered rings) which are absent in C60 and C7,. C, can be isolated as two distinct isomers in the ratio 5 1. They can be separated by HPLC and their 3C NMR spectra are consistent with C,,and D (chiral) structures respectively." The former can result from the D, isomer which possesses more structural strain through three flat coronene faces via a pyracyclene rearrangement first proposed by Stone and Wales (Equation 1). It appears that experimental conditions are crucial. A third isomer has also been characterized point group C2D, with ratio CZv,:C,, D as 5 :2 :2,' or 1 :6 2,2' depending on conditions.J. B. Howard J. T. McKinnon M. E. Johnson. Y. Makarovsky and A. L. Lafleur J. Phys. Chem. 1992,% 6657. l3 W. A. Scrivens and J. M. Tour. J. Org. Chem. 1992. 57 6932. l4 G. Peters and M. Jansen Angew. Chem. Int. Ed. Engl. 1992 31 223. l5 L. D. Lamb D. R. Huffman R. K. Workman S. Howells T. Chen D. Sarid and R. F. Ziolo Science 1992 255. 1413. l6 T.-M. Chang A. Naim. S.N. Ahmed G. Goodloe and P. B. Shevlin J. Am. Chem. Soc.. 1992 114,7603; R. L. DeMuro D.A. Jelski and T. F. George J. Phys. Chem. 1992 96 !0603. l7 N. Coustel P. Bernier R. Aznar A. Zahab J.-M. Lambert and P. Lyard J. Chem.Soc.. Chem. Commun. 1992 1402; P. Bhyrappa A. Penicaud M.Kawamoto and C. A. Reed ibid. 936; W. A. Scrivens P.V. Bedworth and J. M. Tour J. Am. Chem. Soc. 1992 114 7917; A.M. Vassallo A. J. Palmisano L. S. K. Pang and M. A. Wilson J. Chem. Soc. Chem. Commun.. 1992,60:A. Gugel M. Becker D. Hammel L. Mindach J. Rader T. Simon. M. Wagner and K. Mullen Angew. Chem. In?. Ed. Engl. 1992,31,644;A. Mittelbach W. Honk H. G. von Schnering J. Carlsen R. Janiak and H. Quast ibid. 1992,31,1640; K. C. Khemani M. Prato. and F. Wudl J. Org. Chem. 1992 57 3254. Is Q. Li F. Wudl. C. Thilgen. R. L. Whetten and F. Diederich J. Am. Chem. SOC. 1992 114 3994. '' F. Diederich R. L. Whetten C. Thilgen R. Ettl I. Chao and M. M. Alvarez Science 1991 254 1768. 2o K. Kikuchi. N. Nakahara T. Wakabayashi S. Suzuki H. Shiromaru Y. Miyake K. Saito I.Ikemoto M. Kainosho. and Y. Achiba Nature 1992 357 142. '*R. Taylor G.J. Langley. T.J.S. Dennis H. W Kroto and D.R.M. Walton J. Chem. Soc.. Chem. Commun. 1992 1043. C Si,Ge Sn and Pb 35 C, has nine isolated pentagon isomers and the 13C NMR spectra suggest a C isomer as the dominant one.,’ The 24 isomers of C84 that obey the isolated pentagon rule (IPR) fall into two disjoint families members of which can be interconverted by the pyracyclene transformation.22 The 3CNMR spectrum shows c84 to comprise two isomers one of each family with D,and D,,symmetry and in the ratio 2 l.20,23The molecular graph of fullerenes provides a method for predicting their point group I3C NMR spectral pattern and vibrational spectra.24 Stable fullerenes are thought to share the features of 12 isolated pentagons high delocalization energy and HOMO-LUMO gap and low strain energy.25 Further stabilization results if no five-membered ring contains a double bond and the number of benzenoid rings is a maximum as can be predicted by leap-frog carbon clusters C (n = 60 + 6k,k > 1) which have closed-shell electronic structures.26 These rules can be extended to include fulleroid carbon cylinders -which possess terminal heptagonal octagonal and nonagonal rings of atoms at the poles and so are not strictly fullerenes., Magic numbers for stable structures have been predicted for fullerenes and their doubly-charged derivatives.Anions have two carbon atoms less than the stable neutral cluster and the cations two carbon atoms more.28 The experimental enthalpy of formation of crystalline C, has been determined as 2422 and 2278 kJ mol-’ by two research groups.29 C, shows orientation disorder in the low temperature modification and isomers of C, with pentagonal rings adjacent are predicted to be 1-2eV higher in energy than the I is0mer.j’ The vibrational frequencies of 13C, have been predi~ted.~’ The ‘rugby ball’ structure of C, (falmerene) is confirmed by electron diffraction and shows the slight pinching at the waist.The bonds within the pentagons are 146-147pm and the rest 137-139~m.~~ Powder X-ray diffraction shows sublimed C, to comprise small quantities of a second HCP form as well as FCC phase both of which slowly transform to the dominating HCP form on annealing.33 The endohedral derivative He@lC& results from bombarding helium with highly accelerated moiecular beams of C& and both cations can be reduced to the neutral species by Me,N.34 Further support for inclusion in the 7 8 cavity of C, comes from similar insertion through bombardment using first 3He then 4He.35 Both are inserted 22 P.W. Fowler D. E. Manolopoulos and R. P. Ryan J. Chem. Soc. Chem. Commun. 1992 408. ” D. E. Manolopoulos P. W. Fowler. R. Taylor. H. W. Kroto,and D. R. M. Walton. J. Chem. Soc.,Furuduy Trans. 1992 88 3117. 24 D. E. Manolopoulos and P. W. Fowler. J. Chem. Phys. 1992. 96 7603. 25 R. Taylor J. Chem. Soc. Perkin Trans. ;I 1992 3. ” P.W. Fowler J. Chem. Soc. Perkin Trany. 2 1992. 145 D. E. Manolopoulos D. R. Woodall and P.W. Fowler J. Chem. Soc. Faraday Trans. 1992 88. 2427. ’’ P. W. Fowler and V. Morvan J. Chem. Soc. Furaday Trans. 1992. 88 2631. 28 P. W. Fowler and D. E. Manolopoulos Nature 1992 355 428. 29 W. V. Steele R. D. Chirico N. K. Smith W. E. Billups P. R. Elmore and A. E. Wheeler J. Phys. Chem.. 1992 96 4731; H.-D. Beckhaus. C. Ruchardt M. Kao F. Diederich and C.S. Foote Angew. Chem. Int. Ed. Enyl. 1992 31 63. ’() H.-B. Burgi E. Blanc. D. Schwartzenbach S. Liu Y.-j. Lu. M. M. Kappes and J.A. Ibers. Angew. Chem. Int. Ed. Engl. 1992,31,640; K. Raghavachari and C. M. Rohlfing J. Phys. Chem. 1992. 96 2463. 31 B. N. Cyvin E. Brendsdal J. Brunvoll and S.J. Cyvin Spectrochim. Actu A 1992 48 1355. 32 D. R. McKenzie C. A. Davis D.J. H. Cockayne D. A. Muller.and A. M. Vassallo. Nature 1992,355,622. 33 M.A. Green M. Kurmoo P. Day and K.Kikuchi J. Chem. Soc. Chem. Commun. 1992 1676. 34 T. Weiske T. Wong W. Kratschmer J. K Terlouw and H. Schwarz Angew. Chem.. Int. Ed. Engl.. 1992. 31 183. 35 T. Weiske and H. Schwarz. Anyew. Chem.. lnt. Ed. Engl. 1992 31 605. 36 D.A. Armitage to give a MS peak at 727 along with smaller odd ones formed from loss of up to four C2 units. Helium will also insert in the C;o cluster and neon 8 keV Clo calculations indicating chaotic motion of Ne in the neutral C, cage.36 Positive muons (p+)will bind an electron to form a muonium atom (Mu = p’e-) of mass about 11YOthat of hydrogen. Because of its easy encapsulation in fullerenes muonium can act as a microscopic probe.In C70 an axially symmetric hyperfine interaction is present and a small 2p admixture in the ground state wave function of Mu@C7 enables the internal shape to be reproduced including the ‘pinching’ at the equator. The ESR spectra suggest the formation of two isomers of M@C82 (M = Sc Y La) prepared from M20 and graphite with one dominating for each metal proposed to be the C isomer of the four postulated for C8,.38 There is space available for more than one metal atom and evidence supports the formation of sc3@c8239 and Y2@C82,40 and for M2@C80,41 where M is a rare earth metal. However YC82 through time-of-flight mass spectrometry and examined by extended X-ray absorption fine structure appears to have an exohedral structure such as c82YcYc82 in view of the coordination number and Y-C bond distances.42 However strong evidence supports the encapsulation of lanthanum into the c82 fullerene.The Stone-Wales pyracyclene transformation allows the interconversion of all nine isolated pentagon fullerene isomers of c82 and Hiickel arguments predict a C, structure for C’,, but a C structure for C”,. EPR and XPS studies support the latter structure though arguments do support a C,,structure with La3+ in a low symmetry high coordination number site with the unpaired electron del~calized.~~ Laser vaporization of graphite-UO gave uranium encapsulation with U@c28 as the most abundant species. The uranium shows no tendancy to oxdize and has a 4f binding energy only about 0.5 eV greater than that of the uranium metal.It has orbitals compatible with those within the cage.44 Zirconium dioxide gives a similar compound. The anions Cz; and C:; have been detected electrochemically the former with LUMOs t, and t, and the latter el” and a;l for the neutral cage.45 0 affects the EPR signal of the Ck radical4 and there is evidence of a dynamic Jahn-Teller effect in 36 T. Weiske J. Hrusak D. K. Bohme and H. Schwarz Helc. Chim. Acta 1992 75 79; A.L.R. Bug A. Wilson and G.A. Voth J. Phys. Chem. 1992. 96 7864. 37 K. Prassides T. J. S. Dennis C. Christides E. Roduner H. W. Kroto R. Taylor and D. R. M. Walton J. Phys. Chem. 1992 96 10600. S. Suzuki S. Kawata H. Shiromaru K. Yamauchi K. Kikuchi. T. Kato and Y. Achiba J. Phys. Chem. 1992,% 7159; D. E. Manolopoulos P. W. Fowler and R.P. Ryan J. Chem. Soc. Faraday Trans.. 1992 88 1225. 39 H. Shinohara H. Sato M. Ohkohchi. Y. Ando T. Kodama T. Shida,T. Kato and Y. Saito Nature. 1992 357 52. 40 H. Shinohara H. Sato Y. Saito. M. Ohkohchi and Y. Ando J. Phys. Chem. 1992. 96 3571. 4’ E.G. Gillan C. Yeretzian K. S. Min. M. M. Alvarez. R. L. Whetten and R. B. Kaner J. Phys. Chem. 1992 96 6869; M. M. Ross H. H. Nelson J. H. Callahan and S. W. McElvany ihid. 1992 96 5231. 42 L. Soderholm P. Wurz K.R. Lykke D.H. Parker and F. W. Lytle. J. Phys. Chem. 1992 96 7153. 43 R.D. Johnson M.S. de Vries. J. Salem D. S. Bethune and C. S. Yannoni. Nature 1992 355 239; K. Laasonen W. Andreoni and M. Parrinello Science. 1992 258. 1916. 44 T. Guo. M. D. Diener. Y. Chai M. J. Alford R. E. Haufler S.M. McClure T. Ohno. J. H. Weaver G.E. Scuseria and R. E. Srnalley Science. 1992 257. 1661. 45 Y. Ohsawa and T. Saji. J. Chem. Soc. Chem. Commun. 1992 781; Q. Xie. E. Perez-Cordero. and L. Echegoyen J. Am. Chem. Soc.. 1992. 114. 3978 F. Negri. G. Orlandi and F. Zerbetto ihid.. 1992. 114 2909. 46 M. D. Pace. T.C. Christidis J.J. Yin and J. Milliken J. Phys. Chem.. 1992 96 6855; S. Kawata K. Yamauchi S. Suzuki K. Kikuchi H. Shirornaru M. Katada. K. Saito. I. Ikemoto. and Y. Achiba Chem. Lett. 1992 1659. C Si Ge Sn and Pb triplet C60.47 Photoexcited porphyrin undergoes electron transfer with both ground state and excited C, and C,0,48 and a range of electrochemical reductions of both fullerenes has been reported.49 Doping c60 with alkaline earth metals gives supercon- ducting fullerides with Ca,C, superconducting below 8.4K and Ba,C,o below 7 K,,' showing occupation oft, as well as t, of C,,.,l Pure 13C, depresses T for K3C, by 0.45 K from the value for 12C6, and Rb3C, behaves similarly.52 Radicals add to C, at the bond between two six-membered rings (6 6) with the electron confined mostly to this bond giving two coupled cyclohexadienyl radicals.These radicals exist in equilibrium with dimers RC,,C,,R if R is relatively bulky. Thus dimerization is thought to occur through the positions para to where R is ~ubstituted.,~ There is no evidence for radical stability if R is small. The racial Bu'C; results as a mixture of three isomers the dominant one involving attack at a carbon atom of the polar five-membered ring with the other two at the two types of carbon adjacent to or on the Addition of Bu'Li to c60 gave Ru'C;,.Protonation is thought to occur at the para position in the substituted ring as is hydrogenation of the radical by Bu;SnH. Isomerization to the ortho-isomer occurs thereby removing the double bond from the five-membered ring (Equation 2). This reaction and that involving the less reactive EtMgBr to give C,,EtH has been used as a method coupled with HPLC for titrating c,,? Diazomethane gives an unstable adduct with c60 that decomposes to C61H2 in which CH bridges a 6 5 bond.56 Using 0-benzyl or 0-pivaloyl protected monosac- charide spiro-diazirines c60 gives the spiro 'adduct' thereby providing the first chiral 47 G.L. Closs P. Gautam D. Zhang P. J Krusic S.A. Hill and E. Wasserman. J. Phys. Chern. 1992. 96. 5228; H. Levanon V. Meiklyar. A. Michaeli and A. Regev J. Phys. Chem. 1992 96 6128. 4H K.C. Hwang and D. Mauzerall J. Am. Chem. Soc. 1992 114. 9505. 49 F. Zhou S.-L. Yau C. Jehoulet D. A. Laude Jr. Z. Guan and A. J. Bard. J. Phys. Chem.,1992.96,4160; D. Dubois. G. Moninot. W. Kutner M. T.Jones and K. M. Kadish. ihid. 1992,96,7137; D. Dubois M. T. Jones and K. M. Kadish J. Am. Cheni. Soc,.. 1992 114 6446; G.A. Heath J. E. McGrady and R. L. Martin J. Chem. Soc.. Chem. Commun. 1992 1272; D. R. Lawson D. L. Feldheim C.A. Foss P. K. Dorhout C. M. Elliot C. R. Martin. and B. Parkinson J. Phys. Chem. 1992 96 7175. SO A. R. Kortan N. Kopylov S. Glarum. E. M. Gyorgy A.P. Ramirez. R. M. Fleming F. A. Thiel. and R. C. Haddon Nature 1992. 355 529; A. R. Kortan N. Kopylov S. Glarum E. M. Gyorgy. A. P. Ramirez R. M. Fleming 0.Zhou F.A. Thiel P. L. Trevor and R.C. Haddon. ihid. 1992 360. 566. 41 R.C. Haddon G. P. Kochanski A. F. Hebard A.T. Fiory and R.C. Morris Science. 1992. 258; 1636; G. K. Wertheim D.N. E. Buchanan and J.E. Rowe. ihid.. 1992 258. 1638. 52 C.-C. Chen and C. M. Lieber,J. Am. Chrm. So(..,1992.114,3141;T. W. Ebbesen J. S. Tsai K. Tanigaki. J. Tabuchi Y. Shimakawa Y. Kubo I. Hirosawa and J. Mizuki Nature 1992. 355 620. 53 J. R. Morton K. F. Preston P. J. Krusic. S.A. Hill and E. Wasserman.J. Phys. Chem..1992.96.3576; J. R. Morton. K. F. Preston. P. J. Krusic. and E. Wasserman J. Chem. Soc..Prrkin Truns. 2 1992. 1425; J. R. Morton K. F. Preston P. J. Krusic S. A. Hill. and E. Wasserman. J. Am. Chem. Soc. 1992. 114. 5454. 54 P. N. Keizer. J. R. Morton and K. F. Preston. J. Chern. Soc. Chem. Cornmun.. 1992. 1259. 5s P. J. Fagan P. J. Krusic D. H. Evans S. A. Lerke. and E. Johnston. J. Am. Chem.SOL..,1992114,9697; A. Hirsch A. Soi. and H. R. Karfunkel. Anqew. Chem. [nt. Ed. Enyl.. 1992. 31. 766. 56 T. Suzuki Q. 'Chan' Li K.C. Khemani. and F. Wudl. J. Am. Chem. Soc,.. 1992. 114 7301. 38 D. A. Armitage and enantiomerically pure fullerene deri~ative.~' Up to six Ph,C residues will add to c60 across the 6:6 bonds NMR evidence supporting the formation of a diphenyl- methano[ IOlannulene structure. Such addition with appropriately functionalized aryl groups provides for polymer synthesis while PhC(N,)C,H,C(N,)Ph enables two C, units to be coupled to provide the units of 'pearl necklace' polymers.58 Benzyne adds to c60 to give C,o(C,H,) (n= 14) with C,,C,H being the best characterized,additionoccurringacross the6 :6 bond.59 Electrophilicphenylationgives C,,Ph, as the major product though C,,Ph and mono and dioxides are also formed.,' Paraxyxylene and C, copolymerize under free radical conditions at 650 T.The dications of C, and C,, and their radical mono cations readily react with atomic hydrogen and C; shows a near-IR absorption at 973nrn., C: with ammonia gives a series of solvated amides C,,NH,(NH3)J (n = 0-3) in which the NH group is thought to bridge a 6 5bond.63 Methylamines give the radical cations of both amine and c60 whereas coulombic adducts form with unsaturated hydrocar- bon~.,~ While CO gives two IR bands when absorbed on c,, indicating two absorption sites NO shows a multiplet between the two NO bands suggesting absorption as the dime^-.,^ Bombarding C, with C' gives Ci which decomposes to C; and C while N+ gives C and N.At high energy C19 and C,,N+ were detected., C, reacts with NO,' to give C,,(NO,+) which with nucleophiles such as carboxylates or water leads to mixed hydroxybenzoates. These with alkali give water-soluble fullerols with up to 20 hydroxyl groups per cage. They cannot be prepared directly from KOH and C, as addition is reversible and 0 sensitive.,' Reaction of c60 with dimethyldioxirane yields the 1,3-dioxolane adduct as a yellow solution through addition across the 6 :6 bond.The epoxide (purple solution) also results though not directly from the dioxolane; it is however formed by the photolytic oxidation of C, in benzene.,' C,,O has the same lattice symmetry FCC as C, at room temperature and the lattice parameters are only 2 pm (0.1O/O) greater than those of C,,. The oxygen atoms occupy vacant octahedral interstitial sites.,' '' A. Vasella. P. Uhlmann C.A. A. Waldraff. E. Diederich and C. Thilgen. Anyew. Chem.. Inr. Ed. Enyl. 1992. 31 1388. '' T. Suziki. Q. Li K.C. Khernani F. Wudl. and 0.Alrnarsson J. Am. Chrm. Soc. 1992 114 7300 S. Shi K. X. C. Khernani Q. Than' Li. and F. Wudl. ihid.. 1992. 114. 10656. '' S. H. Hoke. 11. J. Molstad D.Dilettato M. J. Jay D. Carlson. B. Kahr. and R. G. Cooks. J. Org. Chem.. 1992 57 5069. 60 R. Taylor G. J. Langley. M. F. Meidine J. P. Parsons A. K. Abdul-Sada T. J. Dennis J. P. Hare H. W. Kroto. and D. R. M. Walton. J. Chem. Soc.. Chem. Commun.. 1992. 667. 61 D.A. Loy and R. A. Assink. J. Am. Cheni. Soc.. 1992 114. 3977. 62 S. Petrie G. Javahery J. Wang. and D. K. Bohme. J. Am. Chrm. Soc. 1992. 114 6268; Z. Gasyna. L. Andrews. and P. N. Schatz J. Phvs. Chrm. 1992,96 1525; S. Nonell. J. W. Arbogast and C.S. Foote J. Phys. Chem. 1992 96 4169. 63 J.J. Stry. M.T. Coolbaugh. E. Turos. and J. F. Garvey J. Am. Chrm. Soc. 1992. 96.7914. 64 S. Petrie G.Javahery. J. Wang. and D.K. Bohrne. J. Am. Chrm. Soc.. 1992 114 9177; idem.. J. Phys. Chem..1992. 96,6121. 65 M. Fastow Y. Kozirovski M. Folman. and J. Heidberg. J. Phys. Chum. 1992 96.6126. " J. F. Christian Z. Wan and S. L. Anderson J. Phys. Chem.. 1992,96 3514 and 10597. " L. Y. Chiang. R. B. Upasani and J. W. Swirczewski. J. Am. Chem. Soc. 1992. 114. 10 154; L. Y. Chiang. J. W. Swirczewski C. S. Hsu. S.K. Chowdhury. S. Cameron. and K. Creegan J. Chern. Soc,.. Chrm. Commun. 1992 1791; A. Naim and P. B. Shevlin. Tetrahedron Lett. 1992. 33 7097. " Y. Elernes. S. K. Silverman C. Sheu. M. Kao C.S. Foote M.M. Alvarez and R. L. Whetten Angrw. Chrm.. Int. Ed. Engl. 1992.31. 351;K. M. Kreegan. J. L. Robbins. W. K. Robbins. J. M. Millar R. D. Sherwood P. J. Tindall D. M. Cox. A. B. Smith Ill J. P. McCauley Jr.. D. R. Jones. and R.T. Gallagher J.Am. Chern. Soc,.. 1992. 114. 1103. " A. Cheng and M. L. Klein. J. <'hem. Soc,.. Furuduy Truns. 1992. 88. 1949. C Si,Ge Sn and Pb Fluorinated c60 reacts readily with Na,CO, and slowly hydrolyses with HF release reactivity increasing with the degree of fl~orination.~' Many other nuc- leophiles react similarly including organic anions complexed hydrides methoxide and amines.,l Fluorination of C, and C, gives up to 80% addition.72 Bromination of c60 in solution gives C,,Br6 (l) (magenta plates) and C,,Br (2) (dark brown prisms). Compound (1) has a structure involving one brominated pentagon with a long C-Br bond of 203 pm itself adjacent to five other brominated pentagons (C-Br 196pm). It disporportionates on warming to give C, and (2),which has a C, structure with pairs of bromine atoms arranged meta on four six-membered rings.73 C,,Br, results from C, and liquid bromine and has Thsymmetry with twelve hexagons disubstituted para and in pairs with boat conformations but mutually meta on the other eight hexagons which have a chair conformation (3).Such symmetry predicts three IR active bands observed at 604,546 and 527 cm -' and shows 18C=C double bonds arranged one per pentagon and one at each 6 :6 bond. All these bromides contain intercalated bromine and completely debrominate on heating.74 Iodine forms an intercalated product with c60 but there is no evidence of addition.75 A range of intercalation products for C, results with benzene and ferr~cene,~ the latter like the tetrathia and tell~rafulvalene~~ and tetrakis(dimethy1amino)ethene derivative^,^^ shows charge transfer to c60.c60 behaves chemically as an electron-poor species. The electrochemical reduction 7 0 R. Taylor A.G. Avent. T. J. Dennis J. P. Hare H. W. Kroto. D. R. M. Walton J. H. Holloway E.G. Hope and G.J. Langley Nature 1992 355,2. 71 R. Taylor J. H. Holloway. E. G. Hope A.G. Avent G.J. Langley T.J. Dennis J. P. Hare. H. W. Kroto and D. R. M. Walton J. Chem. Soc. Chem. Commun. 1992 665. 12 A. A. Tuinman P. Mukherjee J. L. Adcock R. L. Hettich and R. N. Compton J. Phys. Chern. 1992,96. 7584. 73 P. R. Birkett P. B. Hitchcock H. W. Kroto R. Taylor. and D. R. M. Walton. Nature 1992 357.479. 14 F. N.Tebbe R. L. Harlow D. B. Chase. I). L. Thorn,G.C. Campbell.Jr.. J.C. Calabrese N. Herron. R. J. Young Jr. and E. Wasserman. Science 1992. 256,822. 15 Q. Zhu D.E. Cox J.E. Fischer. K. Kniaz A. R. McGhie and 0.Zhou Nature 1992 355,712; T.R. Ohno G.H. Kroll J.H. Weaver L. P. F. Chibante and R. E. Smalley ihid.. 1992 355,401. 76 M. F.Meidine P. B. Hitchcock H. W. Kroto R. Taylor and D. R. M. Walton J. Chem. Soc. Chem. Commun. 1992 1534; J. D. Crane P. B. Hitchcock. H. W. Kroto. R. Taylor and D. R. M. Walton ihid. 1992 1764. 71 A. Izuoka T. Tachikawa T. Sugawara Y. Suzuki. M. Konno Y. Saito and H. Shinohara J. Chern. SOC. Chem.Comrnun. 1992 1472; A. Izuoka T. Tachikawa. T. Sugawara Y. Saito. and H. Shinohara Chem. Lett. 1992,1049;T. Pradeep K. K. Singh,A. P. B. Sinha.and D. E. Morris J. Chem.Soc.. Chem. Commun.1992. 1747. 78 P. W. Stephens D. Cox J. W. Lauher. L. Mihaly J. B. Wiley P.-M. Allemand. A. Hirsch. K. Holczer. Q. Li J. D. Thompson and F. Wudl. Nature. 1992. 355.331; Y. Wang Nature 1992 356.585. D. A. Armitage of phosphine substituted nickel group complexes shows the metal to decrease the electron affinity of C, by raising the energy of the LUMO due to removal of one conjugated double bond. This effect increases with the degree of substitution in a linear manner.79 The dibenzylidene-acetone ligand is readily replaced on Pd by c60 to give air-stable C,,Pd as a one-dimensional linear polymer. This on refluxing in toluene quickly gives C,,Pd (2D) then slowly C,,Pd (3D).The latter readily catalyses the hydrogenation of olefins and acetylenes.80 The compound ‘15-C9H,Ir(CO)(r12-C60) gives a triplet species on laser irradiation since it readily transfers its energy to 0,.81 The complex (PhCH,OC,H,CH,- PPh,)21r(CO)Cl(~2-C,,) crystallizes with both benzyloxyphenyl groups clasping the adjacent c60unit to give a linear polymer.82 Reacting excess Ir(CO)Cl(PPhMe,) with C, gives the disubstituted complex the two Ir atoms occupying double bonds near opposite poles and adjacent to the polar five-membered rings.This results in 60% yield indicating distinction between the double bonds of C,,.83 Bisosmylation of C,, however gives a mixture of five products and with initial addition to a 6 :6 bond the second osmylation occurs at the five such positions not sterically close to that already substit~ted.~~ Calculations predict that C,,H would be formed exothermically from C, and H or alkanes if substituted ortho or para at a six-membered ring.85 The addition should become more exothermic with increasing substitution for alkanes and perchloroal- kanes but not for perfluoroalkanes.Exothermicity decreases with increasing size of the halogen and para substitution becomes more stable relative to ortho with size.86 Both ortho and para substitution of six-membered rings of C, is also anticipated and if the five types of carbon atom are labelled e(equator),l,2,3,N(northpole) then 2/2 and N/3 ortho derivatives are predicted to be the more stable together with para addition at equatorial and polar hexagon^.^ As all stable fullerenes contain the C, decacyclene unit (4),it is suggested that addition reactions that still maintain this unit will be 79 S.A. Lerke 9. A. Parkinson D. H. Evans and P. J. Fagan. J. Am. Chrm. Sot.. 1992 114 7807. no H. Nagashima,A. Nakaoka Y. Saito. M. Kato,T. KawanishLand K. Itoh J. Chem. Soc.. Chem. Commun.. 1992 377; H. Nagashima. A. Nakaoka S. Tajima Y. Saito and K. Itoh Chem. Lett. 1992 1361. 81 Y. Zhu R.S. Koefod C. Devadoss J. R. Shapley and G.9. Schuster Inorg. Chem. 1992 31 3505. 82 A. L. Balch V. V. Catalano J. W. Lee and M. M. Olmstead J. Am. Chem. Soc. 1992 114. 5455. 83 A. L. Balch J. W. Lee and M. M. Olmstead. Angrw. Chem.. Int. Ed. Engl. 1992. 31. 1356. 84 J. M. Hawkins A. Meyer T. A. Lewis. U. Bunz R. Nunlist. G. E. Ball T. W. Ebbesen. and K. Tanigaki,J. Am.Chem. Sot.. 1992 114. 7954. 85 N. Matsuzawa D. A. Dixon and T. Fukunaga J. Phys. Chrm. 1992 96. 7594. 86 D.A. Dixon N. Matsuzawa. T. Fukunaga. and F.N. Tebbe J. Phys. Chem.. 1992 96. 6107; N. Matsuzawa T. Fukunaga and D.A. Dixon J. Phys. Chem. 1992 96. 10747. 87 H. R. Karfunkel and A. Hirsch. Anyebv. Chem. Int. Ed. Engl. 1992 31. 1468. C Si Ge Sn and Ph 41 favoured. With higher fullerenes the presence of two decacyclene units is possible and in C78 both C, and D, structures interconvertible through the pyracyclene transformation should form C7,X through addition to the three C multiply-bonded units outside the two decacyclene units. Such addition should not occur with the D isomer., Optimized conditions for maximum yields of nanotubes are 18V d.c.at 500tor under He but calculations indicate that the nanotubes are higher in energy per carbon atom than their spherical isomer^.^' The compound C12B1,N2, with s6 symmetry should be stable and a suggested synthesis involves pyrolysis of boron-nitrogen analogues of naphthalene with alternating B N and C atoms in the ratio 2 2 1 and substituted to encourage conden~ation.’~ Calculations indicate C ,B2,N24 to be more stable than C,, itself slightly more stable than B,,N,o.~~ The mass spectra of products formed from the gas-phase reaction of titanium with CH, C,H, C,H, C,H, and C,H all show a dominant peak corresponding to Ti,C:,. This cage is thought to possess a pentagonal dodecahedral structure (Th) with fused five-membered rings containing two titanium and three carbon atoms each Ti bonding to three carbon atoms.Similar peaks are observed for Zr Hf and V the latter also taking up ND at each vanadium site.92 The structure is thought to be built from small units such as Ti,C,. With the heavier metals e.g. Zr Ta fused multicages are also formed with up to four dodecahedral units through face fusion. No hexagons are formed in contrast to the expansion of the C, structure.’ The stability of the Ti,C, structure is a result of stronger bonding between Ti and C than in TIC incorporating weak metal-carbon d,-p,-interactions and strong C=C n-bonding. As the metals connect six C=C bonds through a-bonds M,C, clusters will be less stable for transition metals with more than five valence electrons.Also a Jahn-Teller distortion would be predicted for T symmetry but not if distorted to D, or D,,. Similar calculations also support high stability for Si,Cl 2.94 The structure and reactivity of silicon clusters show Sinwith n = 21 25 33 39 and 45 to be particularly unreactive while Si, is predicted to have a structure resembling a stack of six planar bicyclic (silanaphthalene) units with all but the upper and lower stacks involving four coordinate silicon.95 Reductively coupling Me,CHCMe,SiCl with sodium gives the octasilacubane in 2.6% yield as a red-orange air-stable crystalline solid. The structure is distorted from an idealized cube with Si-Si and C-C bonds longer than normal due to the strained Si framework; a UV absorption at 500 nm the longest reported for any polysilane that nx R.Taylor J. Chem. Soc. Perkin Trans. 2. 1992 1667. 89 T. W. Ebbesen and P. M. Ajayan Nuture 1992 358 220; G. B. Adams 0.F. Sankey. J.B. Page M. O’Keeffe and D. A. Drabold Science 1992 256. 1792. 90 J. R. Bowser D.A. Jelski and T. F. George Inorg. Chem. 1992 31. 154. ’’ X. Xia D.A. Jelski J. R. Bowser and T. F. George J. Am. Chem. Soc. 1992. 114 6493. ’’ B. C. Guo K. P. Kerns and A. W. Castleman Jr.. Science. 1992,255. 141 1 B. C.Guo S.Wei J. Purnell. S. Buzza and A. W. Castleman Jr. ihid. 1992 256 515. 93 S. Wei B. C. Guo J. Purnell. S. Buzza and A. W. Castleman. Jr. J. Phys. Chem. 1992. 96 4166; idem.. Science 1992 256 818. 94 B. V. Reddy S. N. Khanna and P. Jena Science 1992.258.1640; Z. Lin and M. B. Hall J.Am. Chem.Soc.. 1992,114 10054; A. Ceulemans and P.W. Fowler J. Chem. Soc. Faradag Trans. 1992,88,2797; M.-M. Rohmer P. de Vaal and M. Benard J. Am. Chem. Soc. 1992.114,9696 R. W. Grimes and J. D. Gale J. Chem. Soc.. Chem. Commun. 1992 1222. 95 T. Lange and T. P. Martin Angew. Chem. Int. Ed. Engl. 1992 31. 172 S. Li R. L. Johnston and J. N. Murrell. J. Chem. Soc. Faraday Trans.. 1992.88 1229; C. Zybill. Angew. Chern. Int. Ed. EnqI. 1992 31 173. 42 D. A. Armitage accounts for the c~lour.~~ The 2,6-diethylphenyl analogue can be prepared similarly and has rather shorter Si-Si bonds and is yellow-orange in colour. The germanium substituted cubane (Et,MeCGe) results in 3% yield directly from the trichloride or in 16% yield from [Et,MeC(Cl)Ge] using Mg/MgBr as reducing agent.97 Treating IsMgBr with SnCl gives the cyclotristannane (Is,Sn) which dissociates in solution to give the stannylene and distannene (Is = 2,4,6-Pr\C6H2).Typically it adds phenylacetylene to give the 1,2-di~tannacyclobutene.~~ Reducing [(2,6-diethyl-phenyl),Sn] with excess lithium gives the propellene (5)in 31YOyield along with about 1Yo of octakis(2,6-diethylphenyl)tetracyclo[4.1 .O.O' .s.02q6]heptastannane (6).Less lithium gives the cyclotetrastannane (7) as intermediate (Scheme 1).99 IS2 Is2 1% '"A '"L Si 2.3Li Sn Sn / \ Is 1.2Li ([s2sn13 - s:-- /,I/ I Is3SnH + Is2Sn\ /SnH c- /,A Sn + Sn--=Sn I Sn NH4C1 NH4C1 /,I I c- In Sn Sn Sn IsSn SnIs ' Is2 Is2 Is2 ' / 1 I%Sn-SnIs2 n-SnIs2 (7) (5) (6) Scheme 1 Laser flash photolysis of the cyclotetragermane PrgGe gives germylene extrusion and dimerization to the digermene together with the cyclotrigermane.O0 (BuiGe) inserts phenyl isocyanide to give the trigermabutanimine and sulfur selenium and tellurium all insert to give the chalcotrigermetane with a planar structure found for selenium and tellurium.'01 The hindered cyclotrisilane (BuiSi) also reacts with aryl isocyanides through ring insertion subsequent photolysis results in isobutene loss to give (8) and (9).lo2 If the isocyanide is electron-withdrawing for example with CF,N=C then further insertion occurs to give the 1,3-disilacyclobutane (10) (Scheme 2).'03 Thermolysing Mes,Ge (Ge-Ge 253.8 pm) with Et,SiH gives the silylgermane through insertion of germylene into the Si-H bond and the silyldigermane by insertion of Mes,Ge(Mes)Ge formed through rearrangement of Mes,Ge=GeMes,.' O4 The siladigermirane Mes,SiGe loses germylene on pyrolysis to give the silylgermane with Et,SiH and the germasilene rearranges to the silylgermylene which also inserts Et,SiH.' OS The structures of the isomers of Me,MM'Ph (M,M' = Si or Ge) show different 96 H.Matsumoto K. Higuchi S. Kyushin and M. Goto Angew. Chem. Int. Ed. Eng/. 1992. 31 1354. 97 A. Sekiguchi T. Yatabe H. Kamatani C. Kabuto and H. Sakurai. J. Am. Chem. SOC. 1992 114 6260. 98 M. Weidenbruch A. Schaefer H. Kilian. S. Pohl W. Saak and H. Marsmann Chem. Ber. 1992,125,563. 99 L. R. Sita and I. Kinoshita J.Am. Chem. SOC..1992 114 7024. 100 K. Mochida and S. Tokura Organomera//ics,1992 11 2752. 101 M. Weidenbruch A. Ritschl K. Peters and H. G. von Schnering J. Orgunomrt. Chem. 1992,438,39 and 1992 437 C25. 102 M. Weidenbruch J. Hamann S. Pohl and W. Saak Chem. Ber. 1992. 125 1043; M. Weidenbruch J. Hamann K. Peters H.G. von Schnering and H. Marsmann J. Organomet. Chem. 1992 441 185. 103 M. Weidenbruch J. Hamann H. Piel D. Lentz K. Peters. and H. G. von Schnering J. Organomet.Chem. 1992 426. 35. I04 K. M. Baines J. A. Cooke and J. J. Vittal J. Chem. Soc. Chem. Commun.. 1992 1484. 105 K. M. Baines and J. A. Cooke Organornetal/ics 1992 11 3487. 43 C Si,Ge Sn and Ph I Si-SiK2 hv * + I :YNAr !vNAr Ar = naphlhyl RSi-SiR2 R2 H (9) Scheme 2 Ge-Sn bond lengths Me,GeSnPh (259.9pm) and Ph,GeSnMe (265.2pm).The expansion of the orbitals of Ge in the Me,Ge group through the electron donating methyl groups and contraction of those of Ph,Sn through the electron attracting phenyl groups makes overlap better in the former compound."" The disilenes Is(R)Si=Si(R)Is (R = But SiMe,) result from Is(R)Si(SiMe,) on photolysis as a mixture of isomers but heating converts the cis to trans.'07 (Me,Si),SiH is an increasingly important silyl radical source and its lithium derivative (1l) prepared from (Me,Si),Si and MeLi reacts with adamantanone to give a bridgehead silene which spontaneously dimerizes. The product has long C-C and C-Si bonds reflecting the hindrance (Equation 3).'OS Compound (1 1) can also be coupled using PbCl to give the octasilane (Me,Si),SiSi(SiMe,) in which the central Si-Si bond of 240.3pm is longer than the rest by some 3 pm.lo9 TsiLi and Ga,Br give the tetrahedral cluster (TsiGa) which is stable to heat and oxygen and possesses a tetrahedral arrangement of Ga atoms.' lo The trihalides TsiSiX (X = C1 Br) show low temperature NMR spectra indicating three peaks of equal intensity.This is consistent with the three methyl groups of the Me,Si group being inequivalent.' '' Photolysing (Me,Si),Si(Mes)COAd gives a mixture of silene geometric isomers stable in solution at room temperature. Addition reactions with I Ob K. H. Pannell L. Parkanyi H. Sharma. and F. Cervantes-Lee Inorg. Chem. 1992 31. 522. '07 R.S. Archibald Y. van den Winkel A. J. Millevolte J. M. Desper and R. West Organometallics 1992 11. 3216. 'OH D. Bravo-Zhivotovskii,V. Braude. A. Stanger. M. Kapon and Y. Apeloig Uryanornerallics 1992.11,2326. S. P. Mallela 1. Bernal and R.A. Geanangel Inorg. Chem.. 1992 31 1626. ''O W. Uhl W. Hiller M. Layh and W. Schwarz Angew. Chem. Inr. Ed. Engl. 1992 31 1364. 'I1 A.G. Avent. S.G. Bott J. A Ladd. P. D. Lickiss and A.D. Pidcock J. Organomet. Chem. 1992,427.9. 44 D. A. Armitage PhC-CH is highly stereospecific and methanol gives a diastereomeric pair of adducts.' '' The stable germenes Mes,Ge=CRR' (R,R'=H,CH,Bu' or fluorenylidene) readily add both electrophiles and nucleophiles.' ' The fluorenylidenestannene substituted with Is groups at tin can also be prepared as an ether adduct.'' Stannocene reacts with C,H,Na in the presence of PMDETA to give a complexed adduct in which one C,H group is sandwiched between tin and sodium.' ' Lithiated 2,5-di-t-butylpyrrole reacts with both SnCI and PbCl to give the heterostannocene and plumbocene.' The stannylene [2,4,6-(CF,)C,H,],Sn crystallizes in two forms.One form from cold hexane gives monomers with weak intramolecular Sn.-.F interactions and the other from hexane-toluene yields weakly associated red dimers with Sn-Sn bonds of 363.9pm some 83pm longer than single. The stannylene adds MesNC to give the stannaketenimine in which the new Sn-C bond is longer than the aryl-Sn bonds supporting coordination into the p-orbital of Sn.' l7 Reacting catechol with Cp:Si gives the aryloxysilane through OH insertion.This adduct decomposes in toluene to give the novel ionic species (12) the structure of which is supported by the Si-H stretching frequency and large Si-H coupling constant (Equation 4). l1 cp;si 1- aoH-Cp;Si /H a Ho catecho1-[CsSiH]+ ~o /~ (4) ~ OH ' 0 ,o "'H (12) Three coordinate tin cations R,Sn+ have been prepared from the hydride with Ph,C+ or (C,F,)3B or from R,SnCI and AgCIO, and '19Sn chemical shifts support its presence.' l9 + The reaction of M (M = Fe Co Ni) with 1,3,5-trisilacyclohexanein the gas phase results in the loss of one or two moles of H,. With Cp,M +,however three moles of H are lost particularly for M = Ni to give CpMC,Si,H; as the 1,3,5-trisilabenzene derivative.' 2o Hexasilylbenzene (H,Si),C results from 4-MeOC6H,SiH and is an air-stable crystalline solid m.p.165 "C,with D,,symmetry. Like (PhSiH,),C, it has a planar c ring unlike (Me,Si),C and 1 ,3,5-(Me3Si),C,H,.'" Silylating Br,C,Mn(CO) with HMe,SiCI gives the pentakis(dimethylsi1yl)cymantrene.It has a paddle-wheel struc- 112 A.G. Brook A. Baumegger and A. J. Lough Organometallics 1992 11 3088. 113 C. Couret J. Escudie G. Delpon-Lacaze and J. Satge Organomerullics 1992 11. 3176; M. Lazraq. J. Escudie C. Couret J. Satge and M. Soufiaoui ibid 1992 II 555. I I4 G. Anselme H. Ranaivonjatovo. J. Escudie C. Couret and J. Satge. Organometallics 1992 11. 2748. 115 M.G. Davidson. D. Stalke and D.S. Wright Angew. Chem. Int. Ed. Engl.. 1992 31.1226. 116 N. Kuhn G. Henkel and S. Stubenrauch. J. Chem. Soc. Chem. Commun.. 1992 760; idem.. Angew. Chem. Int. Ed. Engl.. 1992 31 778. 117 U. Lay H. Pritzkow and H. Grutzrnacher J. Chem.Soc. Chem. Commun.. 1992.260; H.Grutzmacher. S. Freitag R. Herbst-Irmer and G. M. Sheldrick Angew. Chem. Int. Ed. Engl. 1992. 31 437. I18 P. Jutzi and E.-A. Bunte Angew. Chem.. Inr. Ed. Engl.. 1992. 31 1605. 119 J. B. Lambert and B. Kuhlmann. J. Chem. Soc. Chem. Commun.. 1992 931. 120 A. Bjarnason and I. Arnason Angew. Chem.. Int. Ed. Engl.. 1992 31 1633. 121 C. Rudinger H. Beruda and H. Schmidbaur. Chem. Ber. 1992. 125. 1401 C. Rudinger. P. Bissinger H. Beruda and H. Schmidbaur. Orgunometallics 1992 11 2867. C Si Ge Sn and Pb 45 ture but in solution rapid free rotation occurs about the Si-C bond indicating less steric crowding than for (HMe2Si),C,Cr(CO),.'22 The base-free cyclopentadienylide [(p-q5:qS-C,H4(SiMe,)Li),] has a chain like polymeric sandwich structure.' 23 Cleaving Ph,PbPbPh with Bu"Li in the presence of PMDETA gives the monomeric Ph,Pb-Li(pmdeta) in which the structure shows a covalent Pb-Li bond of 285.2pm while the small CPbC angles of 94.3" suggest s-orbital character of the Pb-Li bond.'24 n-Bonding between nitrogen and silicon has long been thought to provide the explanation of the planarity and lack of basicity of (H,Si),N.(PhSiH,),N is similarly planar at nitrogen with overall C symmetry.'25 The EPR spectra of a range of silylamines also support such n-bonding but while silicon d-orbitals appear to provide the most likely acceptor orbital on silicon a*-Si-C orbitals cannot be ruled out.'" The structure of (CsHNSiMe,), a caesium-based heterocubane has Cs N and Si on the three-fold axis and Si-N bond lengths of 159 pm which indicate considerable double bond character.127 (Me,Si),NLi forms donor complexes with esters; (Me,Si),NNa 1 :2 forms com- plexes with dioxan in which Na is trigonal bipyramidal five-coordinate with dioxan bridging pairs of sodium ions in a polymer array.The rubidium and caesium derivatives are amide bridged dimers with three dioxan molecules coordinating to each metal.' 28 The unsolvated alkaline earth metal derivatives are similarly bridged dimers.' 29 The primary germylamine Mes,GeNH is only slowly cleaved by small protic reagents while Bu'COC1 gives the arnide and no Ge-N cleavage occurs.Hindrance at Ge allows acylation at nitrogen using Bu'COCl.'30 A range of aminostannanes and cyclodistannazanes have been prepared and relating structure to the 2J(119Sn' "Sn) coupling constants shows the nitrogen lone-pair to be p-type with 2,6-Pr;C,H,N(SnMe,) being planar at nitrogen. The compound MeN(SnMe,Cl) is dimeric the unexpected structure containing a diazadistannetidine unit coordinated to two Me,SnCl groups with cis orientation and involving weak Sn -. . C1 interac- tions.I3' The phosphide [(Me,Si),PLi] has a hexameric step-like structure (1 3) involving four- and five-coordinate phosphorus atoms and two- and three-coordinate lithium and Si-P bond distances of 220.7-222.1 pm.' 32 A hexamer (Et,PSiMe,OLi), also results from the reaction of Et,PLi with polysiloxane and involves a Li,O distorted hexagonal prism network (14).' 33 Coupling o-C,H,[P(SiMe,)Li(TMEDA)] with Bu'SiCl gives the novel Si-P cluster (19.' 34 122 K.Sunkel and J. Hofmann Organometal!ics. 1992 11. 3923. lZ3 W. J. Evans T. J. Boyle and J. W. Ziller Organornetallics. 1992. 11 3903. lZ4 D. R. Armstrong M.G. Davidson D. hloncrieff. D. Stalke and D. S. Wright. J. Chem. Soc.. Chem. Commun.. 1992 1413. N. Mitzel A. Schier and H. Schmidbaur Chem. Ber. 1992. 125. 271 I. IZ6 C.J. Rhodes J. Chem. Soc. Perkin Trans. 2 1992 235. K. F. Tesh B. D. Jones T. P. Hanusa and J.C. Huffman J. Am. Chem. Soc. 1992 114 6590. 12* P.G. Williard Q.-Y. Li and L. Lochmann J. Am. Chem. Soc. 1992,114,348;F.T. Edelmann F. Pauer M. Wedler. and D. Stalke Inorg. Chem.. 1992 31 4143. 129 M. Westerhausen and W. Schwarz 2. Anory. Ally. Chem. 1992 609 39. M. Riviere-Baudet. A. Morere. J. F. Britten and M. Onyszchuk J. Organornet. Chem. 1992 423 C5. 13' S. Diemer H. Noth K. Polborn and W Storch Chem. Ber.. 1992 125 389. 132 E. Hey-Hawkins and E. Sattler J. Chem. Soc.. Chem. Commun. 1992 775. '33 R. A. Jones. S.U. Koschmieder. J. L. Atwood and S.G. Bott. J. Chem. Soc. Chem. Commun.. 1992,726. D. A. Armitage (13) Me3Si substituents omitted (14) SiMe2PEt2 substituents omitted (15) Oxidizing the phosphide complex (Me,Si),PCr(CO); with BrCH,CH,Br gave the tetraphosphabutene complex [(DME),Li+],[Me,Si(Cr(CO),),P-P=P-P(Cr(CO),),SiMe3l2- as the trans product with P-P single and double bonds.'35 The phosphasilene Is,Si=PSiPr\ reacts with Ph,CN to give a range of products.At 0 "C [2 + l]cycloaddition occurs to give the azaphosphasiliridene (16) which thermolyses to give the phosphasiliridene (17) the diazaphosphacyclopentene as the [2 + 31 cycloadduct and the benzocyclopentene (18) the only product formed if the reaction is conducted at 110 "C (Scheme 3). The analogous arsasilene adds Ph,CO and Te.'36 Is2Si =PSiPr; PhZCN2 + I N I1 CPh2 Jheat SiPri 1s2si-p~ x Ph Ph Scheme 3 Coupling Cp*SiC13 with LiAI(PH,) gives Cp*Si(PH2) which at room temperature condenses to the diphosphadisilacyclobutane. 37 The hindered [Mes(Bu')SiPH] can be readily substituted at phosphorus by Bu'Hg groups the product photolysing to the bicycloCl.1 .O]butane (Equation 5).The arsenic analogues result similarly using [Mes(Bu')SiAsH] as starting material.' 38 134 P. B. Hitchcock M. F. Lappert and P. Yin J. Chem. Soc.. Chem. Commun. 1992 1598. 135 G. Fritz E. Layher H. Krautscheid B. Mayer E. Matern W. Honle and H. G.von Schnering Z. Anorg. Allg. Chem. 1992 611 56. M. Driess and H. Pritzkow Angew. Ckem. Int. Ed. Engl. 1992 31 751 and 316. 13' M. Baudler W. Oehlert and B. Tillrnanns Z. Naturforsch.. Teil B. 1992 47 379. 13' M. Driess Phosphorus Sulpur Silicon Relat. Elem.. 1992,64,39; M. Dreiss R. Janoschek and H. Pritzkow C Si Ge Sn and Ph 47 P-P Bu'Li [Mes(But)SiPHl2 -[Mes(Bu')SiPHgBu'J2 aBU~.siy\ii BU' (5 Bu'HgC1 II Mes Mes A disphosphabicyclo[ 1.1 .O]butane compound can also be made directly by heating Mes(Bu')Si=Si(Bu')Mes with white phosphorus. The initial product is an Si,P adduct which on heating give the exo-em-disiladiphosphabicyclo[1.1.O]butane as the dominant isomer. With Mes,Si=SiMes and As, the intermediate Si,As adduct can be isolated as a tricyclic Si-As ring system (19) that gives the bicycle[ 1.1 .O]butane at 95 "C (Equation 6).'39 AS-AS MqSi As-SiMq MqSi =SiMes -I.,'As-As' I I MesS!i'\h4es I (6) I + Mes,S1 (19) 'As -SiMes Mes Ma As4 Coupling Mes(Bu')GeF with LiPH,.DME gives the 1,3,2,4-diphosphadigermetane as the trans-isomer with regard to Ge substituents but a 1 :1 mixture with regard to phosphorus.Lithiation followed by reaction with Bu'HgC1 gives the 1,3-dimercury derivative which on photolysis gives the diphosphadigermabicyclo[ 1.1 .O]butane. 140 Reacting (Na/K)HP with R,SnCI gives the tetraphosphabicyclo[ 1.1 .O] butanes (20) which are only stable in solution (Equation 7).141 The diphosphadistannetanes (BubSnPR') (R' = H,Me) react with Bu\SnCl to give the distannylphosphine which can be aminated with LiNHBu' condensation with Me2SiCI2 giving the mixed heterocycle (21) (Scheme 4). 142 The stannaphosphene Is,Sn=PMes* readily adds water and methanol (Mes* = 2,4,6-B~',c,H,).'~~ (Na/K)HP4 + R3SnCl -R3Sn-P0f)\PH (7) 'P' (20) The reduction of ketones by silanes R,SiH catalysed by Ph,C+B[3,5-(F3C)2C6H3]i gives the siloxycarbenium ions such as [Ph,C=OSiMe,] as + intermediates that can be alternately considered as silyl substituted oxonium salts.44 Hydrogen bonding to aryl groups is observed in TsiSiPh(X)OH and to the ester group Angew. Chem. Int. Ed. Engl. 1992 31 460. '39 A. D. Fanta. R. P. Tan N. M. Comerlato M. Driess D. R. Powell and R. West. Inorg. Chim. Actu. 1992. 19%200,733;R. P. Tan N. M. Cornerlato D. R. Powell and R. West Angew. Chem.. Inr. Ed. Engl. 1992 31 1217. 140 M. Driess H. Pritzkow and U. Winkler Chem. Ber. 1992 125. 1541. 141 M. Baudler and B. Wingert Z. Anorg. Allg. Chem. 1992 611. 50. 142 a. Hanssgen E. Stahlhut. H. Aldenhoven and A. Dorr. J. Organomet. Chern. 1992 425 19. H. Ranaivonjatovo. J. Escudie C. Couret and J. Satge J. Chem. Soc.Chem. Commun. 1992. 1047. M. Kim T. Hino and H. Sakurai. J. Am. Chem. Soc. 1992 114. 6697. 143 144 D.A. Armitage L~NHBU' R' Scheme 4 of TS~S~(OH),(OCOCF,).'~~ A wide range of siloxides results from silanols e.g. BuiSiOH and Ba granules giving the siloxide bridged dimer Ba,(OSiBu\);THF and Me,Al and Ph,SiOH the monomeric (Ph,SiO),AI-THF which solvates water without hydroly~is;'~~ titanium substituted siloxanes result from Cp*TiC13 (Cp* = Me,C,) and CpTSi(OH) or Ph2Si(OH)2,'47 while the triol Bu'Si(OH) and Re207 give the cyclotetrasiloxane [O,R~OS~(BU')O],;'~~ the triol [(c-C,H )7Si709(OH)3] gives a range of silasesquioxanes BI and OV(OPr") giving a dimeric products and SbMe a series of monomers. '49 The silyl peroxide Me,SiOOSiMe can be conveniently prepared from the hexamethylenetetramine:H,O complex with Me,SiCl.' 50 Oxidizing the stannylene [(Me,Si),N],Sn with 0 gives the remarkable p-peroxy derivative [Sn(N(SiMe,)2}2(p-0,)] in which the ring has an almost perfect twist-boat structure with an 0-0 bond length of 150.1pm.lS1 Condensing (Bu",nO) and Re207 forms the terminally metallated distannoxane and Me,SiOReO with (Me,Sn),N the monomeric amide (Me,Sn),NReO,.' s2 While condensing RSiCl (R = Me Et) with Na2X (X = S Se) gives (RSi),X with the expected adamantane-like structure,' 53 Bu'GeC1 with H2S and pyridine gave the bisgermanethiol isomers (22) which slowly thermolyse to the adamantane-like cage (23) (Equation 8).However the reaction of Bu'GeC1 with (NH,)2S gave the 'double-decker' isomer (24) which has eight- and four-membered rings (Equation 9).The Ge-S bonds of the four-membered rings (224.3 pm) are distinctly longer than the rest (221.6pm). Heating converts (24) to (23).' 54 14s S.S.Al-Juaid A. K. A. Al-Nasr C. Eaborn and P. B. Hitchcock J. Orgunornet. Chrm. 1992,429 C9; S.S. Al-Juaid C. Eaborn and P. B. Hitchcock ihid. 1992. 423. 5. '46 S.R. Drake W. E. Streib K. Folting M. H. Chisholm and K.G. Caulton fnorg. Chem. 1992,31 3205; A. W. Apblett A.C. Warren and A. R. Barron. Can. J. Chem. 1992 70. 771. 14' K. J. Covert P.T. Wolczanski S.A. Hill and P.J. Krusic. Inorg. Chrm. 1992 31; 66; F.-q. Liu H.-G. Schmidt M. Noltemeyer C. Freire-Erdbrugger G. M. Sheldrick and H. W. Roesky 2.Naturforsch.Teil B 1992 47 1085. 148 N. Winkhofer H. W. Roesky M. Noltemeyer and W.T. Robinson Angrw. Chem. Int. Ed. Engl. 1992 31 599. F. J. Fehr T. A. Budzichowski and J. W. Ziller. Inorg. Chem.. 1992,31,5100:F.J. Feher and R. L. Blanski J. Am. Chem. Soc. 1992 114 5886; F J. Feher T.A. Budzichowski. K. Rahimian. and J. W. Ziller ihid.. 1992 114 3859. I so P. Babin B. Bennetau. and J. Dunogues Synth. Commun.. 1992 22 2849. IS1 R. W. Chorley P. B. Hitchcock and M. F. Lappert. J Chem. Soc. Chem. Commun.. 1992. 525. Is2 U. Wirringa H. W. Roesky H.-G. Schmidt and M. Noltemeyer Chrm. Ber.. 1992 125 2359. 153 S.R. Bahr and P. Boudjouk Inorg. Chrm. 1992 31 717. IS4 W. Ando T. Kadowaki. Y. Kabe. and M. Ishii. Angew. Chrm. lnt. Ed. Engl.. 1992. 31. 59. C Si Ge Sn and Pb But But ,Ge.S-Ge-S I ButGeC1 ~~./pyridine But 1 ISI -Bu'Ge. 1 -s,GeBu' (8) * HS($ S/'Ge-' 'Ge" But But (23) (22) ButGeZs )GeBu' s\ Bu'GeC13 + (NH4),S5 -< S But\Ge1;;deBut (24) Heating the silane TsiSiH with the elements sulfur or selenium gave the tetrathia or tetraselena-l,4-disilabicyclo[2.1. llhexane. The tetraselena derivative gives the triselenac 1.1.llpropellane on photolysis the structure indicating an Si . . .Si distance of 25 1.5 pm and Si-Se bonds of 23 1.6-232.7 pm. ' Condensing Cp,TiC1 with 2Li,S and Ph,MCl (M = Si Ge) and (MeC,H,),TiCl with Li,S/Ph,SnCl, gave the four-membered titanocycles. The silicon derivative with S,Cl gave Cp,TiCl and the sulfur-rich heterocycle (25) as a colourless wax which decomposes above -20 "C(Equation lo).' 56 The more hindered tetraselenagermolane (26) which results from the hydride with Bu'Li then selenium occurs as orange crystals mp 209"C and in the presence of 2,3-dimethyl-buta- 1,3-diene gave the cis-substituted ],3,2,4-diselenadigermetane (27) (Equation 11 ).' 57 (26? Tb = 2,4,6-[(Me3Si)&H]3C6H2 H.Yoshida and W. Ando Phosphorus Siilfur Silicon Relut. Elem.. 1992.47.45;H. Yoshida Y. Takahara. T. Erata and W. Ando J. Am. Chem. Soc. 1992 114 1098. 15' J. Albertsen and R. Steudel J. Orqanomet. Chem. 1992 424 153. Is' N. Tokitoh. T. Matsurnoto and R. Okataki. Tetruhedron Let[. 1992 33. 2531. 50 D. A. Armitage The tin-sulfur and selenium analogues of (26) react with Ph,P to give the dichalcogenadistannetaneas the cis-isomer probably through the intermediacy of the monomeric stannanethione or ~elone.'~' The hindered tin heterocycle (28) (X = S) reacted with Ph,CN on heating to give three carbene insertion products (29) (30),and (31) (Equation 12).Compound (28) (X = Se) gives no selenium analogue of (31).'59 With (Me,N),P (31) (X = S) can be converted to (30) (X = S) and the 1-stanna-2,4-dithiacyclobutane, while the selenium analogue of (29) gives that of (30) under similar conditions. The hindered silyl chlorides (Mes*X),SiCI (X = S Se) react with AgClO to give a range of sulfides and selenides which are thought to result through the intermediacy of the silicenium ion which decomposes to Mes*X+ and (Mes*X),Si (X = S) or the radical Mes*X.(X = Se).16' (Me,Si),SiLi(thf) reacts with Te to give the tellurate derivative as a covalent dimer with Li-Te bridges. With 12-crown-4 or Et,NCI ion separation results.I6' The tellurol which results from the lithium derivative and triflic acid can be used to make an extensive series of covalent metal derivatives for example with alkaline earth metals'62 and for groups 4 12 and 13. Oxidation of group 4derivatives gives the dark green ditelluride (Me,Si),SiTeTeSi(SiMe,) (Scheme 5).16 ((Me3SW12M (Me3Si)3SiTeLi(THF)3 CF3S03H -(Me3S03SiTeH = Ca Sf Ba zn Cd Hg* [(Me3SihSiTehM [(Me3Si)zCHIZGaBr %M' M' = Zr Hf I I [(Me3Si)2CH]2GaTeSi(SiMe3)3[(Me3Si)3SiTeI4M' [(Me3Si)3SiTe]2 Scheme 5 Halogen bridging features extensively in tin chemistry but not in that of silicon.Consequently the reaction of fluoride with o-bis(fluorosily1)benzene is of particular interest in giving the adduct with fluorine bridging the two silicon sites. The three I58 N. Tokitoh Y. Matsuhashi M. Goto and R. Okazaki Chem. Lett. 1992 1595. I59 N. Tokitoh Y. Matsuhashi and R. OKazaki Tetrahedron Lett. 1992 33. 5551. 160 N. Tokitoh T. Imakubo. and R. Okazaki. Tetruhedron Lett.. 1992 33 5819. I61 G. Becker K. W. Klinkhammer. S. Lartiges. P. Bottcher,and W. Pol1.Z. Anorg. AIlq. Chrm.. 1992,613.7; P.J. Bonasia D. E. Gindelberger B.O. Dabbousi and J. Arnold J. Am. Chem. Soc. 1992 114 5209. 162 D. E. Gindelberger and J. Arnold J. Am. Chem. So(,.,1992,114,6242;G. Becker K. W. Klinkhammer W. Schwarz M. Westerhausen and T.Hildenbrand Z. Nuturfimch.. Teil E 1992 47 1225. 163 V. Christou and J. Arnold J. Am. Chem. Soc. 1992. 114.6240; P. J. Bonasia and J. Arnold. Inorg. Chern.. 1992,31,2508;W. Uhl M. Layh. G. Becker. K. W. Klinkhammer. and T. Hildenbrand Chem. Ber. 1992 125 1547. C Si Ge Sn and Pb fluorosiliconates (32) (33) and (34)all have bent fluorine bridges (1 18.6"to l26.lL) but even with similar substituents on each silicon the two bridge bonds differ in length by some 17 pm.16 A wide range of diorganosiliconates RR'SiF; shows inequivalent apical-fluorines due to the proximity of the counter-cation but both are longer than the equatorial Si-F bonds.'65 8-Dimethylaminonaphthyltetrafluorosiliconateinvolves six-coordination in which the Si-F bond trans to the coordinating amino group is shorter than the other three Si-F bonds.'66 1-1-1- I I Triphenyltin fluoride has a bridged polymeric one-dimensional structure with Sn five-coordinate and both Sn-F bonds of equal length.16' Adding Et,NF to Me,SnF gives the organofluorostannate salt Et,N + Me,Sn,F containing a linear fluorine bridge.The anion includes cyclic Sn,F units interconnected at two tin atoms. All tin atoms are six-coordinate. 168 Schifl bases stabilize the Me,Sn,Cl;- ion which has chloride bridges and the four methyl substituents two above and two below the Sn,C16 plane. '69 I64 K. Tarnao. T. Hayashi Y. Ito. and M. Shiro Orqunornerullics. 1992. 11 2099. I h5 K.Tarnao. T. Hayashi Y. Ito and M. Shiro Orqanomeiallics.1992. 11. 182. 166 C. Breliere. F. Carre R.J. P. Corriu. W. E. Douglas. M. Poirier. G. Royo. and M. Won& Chi Man Orqonomrtallic.s 1992. 1I 1586. 167 D.Tudela E. Gutierrez-Puebla. and A. Monge. J. Chrm. Soc.. Dalron Truns.. 1992. 1069. IhX T. H. Larnbertsen. P. G. Jones. and R. Schrnutzler Polyhedron. 1992 11. 331. 169 S.-G. Teoh. S.-B.Teo. G.-Y. Yeap and H.-K. Fun. J. Orqunomri. Chem.. 1992 439. 139.