5 C,Si Ge Sn Pb; N P As Sb Bi By P. G. HARRISON Department of Chemistry University of Nottingham University Park Nottingham NG7 2RD 1 Carbon The infrared-matrix-isolation technique has been applied in the study of several carbon systems. The reaction of oxygen with phenylcarbene produced by irradiation of phenyldiazomethane PhCHN2 in an argon matrix affords both benzaldehyde and benzoic acid. The ratio of these products depends on the oxygen content of the matrix and on the thermal treatment of the matrix. With short irradiation times and at low (8 K) temperatures benzaldehyde is the sole product; benzoic acid is produced at higher temperatures. Reaction proceeds via the diffusion of atomic oxygen 3PhHC= + O(3P)+3PhCHO+PhCH0 + hv PhCHO + O(3P) + PhCOOH Diffusion of O2 only occurs at higher temperatures.' matrix-isolated tricarbon monoxide has been produced by pyrolysing fumaroyl dichloride seeded in excess argon.A normal co-ordinate analysis of the assigned infrared spectrum yielded a general harmonic force field.2 The microwave spectra of the same molecule isotopi- cally substituted with 13C or l80at each of its four atoms have yielded accurate geometrical parameters (C-1-0 115.0 pm C-1-C-2 130.6 pm C-2-C-3 125.4 pm). Discrepancies with ab initio MO calculations are somewhat larger than usual attributed to the effect of a low-frequency bending vibration^.^ Codeposition of CF31 and ozone in excess argon on a CsI window at 17 K gives a CF3-03 molecular complex which photodissociates upon irradiation yielding CF310.Further photo- lysis produces CF301 and two CF20-IF molecular complexes? The oxide-transfer technique involving transfer of 02-from T120 to a suitable acceptor coupled with matrix isolation has been employed to synthesize and characterize the mono- and di-thiocarbonate anions C02S2-and C0S22- and the CO2F;- anion all as triple ions with two Tl+cations.5i6 The C02S2- anion was characterized by sharp intense C-0 stretching bands at 1445 and 1202 cm-' and by a C-S stretching mode at 603 cm-'. The two most intense bands of the COS22-anion occurred at 1506 cm-' (C-0 stretch) and 606 cm-' (antisymmetric C-S stretch). The calculated force ' W. Sander Angew. Chem Int. Ed. Engl 24 988. 'R. D. Brown D. E. Pullin E. H. N. Rice and M. Rodler J. Am.Chem.SOC.,1985 107 7877. ' R. D. Brown P. D. Godfrey P. S. Elmes,M. Rodler and L. M. Tack 1Am.Chem. SOC.,1985,107,4112. L. Andrews M. Hawkins and R. Withnall Znorg. Chem 1985 24,4234. S. J. David and B. S. Auk Inorg. Chem. 1985 24 1048 1238. L. Manceron and L. Andrews J. Am.Chem. Soc. 1985 107 563. 107 108 P. G. Harrison constants suggest increased localization of the T-bonding on the carbon-oxygen bonds as the number of sulphur atoms in the anion is increased. On warming the matrix-isolated Tl+2C02F22- triple ion eliminates TlF giving Tl+C02F-. The simul- taneous matrix deposition of lithium atoms and acetylene molecules at high dilution in argon at 15 K yields infrared spectra due to four species. The major product (1) has a LiC2H2 stoicheiometry that is most likely to be planar with the lithium bridging the wsystem and cis-C-H groups and CCH angles estimated to be 140 f 10".The C-C stretching mode is reduced to 1655 cm-l near to that of ethylene and rationalized by the sharing of electron density between the T-system of acetylene and lithium rather than lithium valence-electron transfer into an antibonding T*-orbital of acetylene. The minor reaction products have different stoicheiometries. Conclusions from the propyne-lithium reaction were similar. All the observed species were unstable above 30K.6 The three minima (2)-(4) have been located on the potential surface of CLi2F2 the most stable being the lithium-bridged species // ,c=c F-L \ H H Only one type of low-binding-energy carbon and lithium environment has been observed for both methyl-lithium and dilithiomethane in accord with previous structural (MeLi) and spectroscopic data.In addition the direction of the carbon 1s core-level shifts and the 13C chemical shifts suggest an increased charge density of the methylene carbon in the latter compound. The data also indicate a single lithium environment for CH2Li2 strongly suggesting a highly symmetrical structure.' H 7Li and l3 C n.m.r. have demonstrated that lithium 2-lithio-1,1,3,3-tetraphenylpropenide adopts the ionic allyl-lithium structure (5) with C, symmetry. The second lithium is covalently bonded to the central carbon atoms.' Deltic acid molecules (6) probably form infinite chains linked by two very strong unsymmetrical OH--Ohydrogen bonds.All fundamentals of the vibrational spectra in the range 4000-20 cm-' have been assigned." Attempts to record the microwave spectrum of dichloroketene Cl2C=C=0 were unsuccessful probably owing to the near-zero dipole moment. However it was possible to record the Fourier-transform infrared J. D. Watts and J. G. Stamper J. Chem SOC.,Chem. Commun. 1985 5. G. F. Meyers M. B. Hall J. W. Chinn and R. J. Lagow J. Am. Chem. SOC.,1985 107 1413. J. Bernard C. Schnieders and K. Mullen J. Chem. SOC.,Chem. Commun. 1985 12. A. Lautit M.-F. Lautit and A. Novak Can. 1. Chem. 1985 63 1394. C Si Ge Sn Pb; N P As Sb Bi 109 spectrum under the same conditions." Theoretical calculations on fluoroacetones and their conjugate acids exhibit an inverse dependence of the proton affinity on the number of fluorine substituents.The good correlation found between increasing proton affinity and decreasing ionization potential is attributed to the observation that the ionization of a non-bonding electron is essentially localized at a single atom that is also the site of protonation.'2 The CARS (coherent anti-Stokes Raman spectroscopy) technique has been employed to study the photodissociation of trans-azomethane MeN= NMe vapours.13 The dissociation is complete within 2 ns and the nascent N2 vibrational distribution appears to be consistent with the theoretical prediction of the sequential bond-cleavage mechanism MeN=NMe -* R-N=N' + R' -+ 2R + N The photolysis and thermal decomposition of both pyruvic acid MeC( =O)C02H l4 and glyoxylic acid HC( =0)CO2H,l5 have been investigated.The major products from the photolysis of glyoxylic acid (1-6 Torr and 355 K) were CO and formaldehyde with minor amounts of CO and H,. Primary processes involve H-atom transfer followed by dissociation. The same major products were also formed during thermal decomposition at 470-710 K although the formation of formaldehyde was always less than stoicheiometric and the CO/C02 ratio was observed to increase with increasing temperature. COz and acetaldehyde were formed in the photolysis of pyruvic acid. Again the primary process was an internal H-atom transfer followed by dissociation into C02 and MeC-OH with this species rear- ranging to give acetaldehyde and other products.The thermal decomposition of the potentially explosive azide F2HCN3 has been studied in a controlled way by using a flow system under reduced pressure and gas analysis by photoelectron spectroscopy. Decomposition leads to the formation of N, FCN and HF presumably via the intermediate nitrene F2HCN.I6 Hydrogen halide addition to trifluoromethyl isocyanide results in the formation of both isomers of the compounds CF,N=CHF CF3N=CHCl and CF,CHBr. Electron-diffraction studies indicate that the E isomers of the fluoro and chloro compounds predominate with isomeric ratios (from n.m.r. data) of 15.4 1 (fluoro compound) 6.7 1 (chloro compound) and 3.8 :1 (bromo compound). All three methanimines dimerize slowly forming the corresponding aminomethanimines CF,N=C( H)N(CF,)(CX,H) (X = F C1 or Br).The addition of SF,Br to CF,NzC yields the pentafluorothio- substituted methanimine CF,N=C( Br)SF,." Both em conformers eq-exo and ax-exo fit the experimental electron-diffraction data for perfluoronitrosocyc-lobutane C3F5N0 almost equally well not permitting any estimation of the ratio of isomers." Several new methods for the synthesis of bis(trifluoromethyl)sulphine M. C. L. Gerry W. Lewis-Bevan and N. P. C. Westwood Can. J. Chem. 1985 63 676. 12 S. C. Choi and R. J. Boyd Can. J. Chem. 1985 63 836. l3 P. L. Holt K. E. McCurdy J. S. Adams K. A. Burton R. B. Weisman and P. S. Engel J. Am. Chem. Soc. 1985 107 2180. 14 R. A. Back and S. Yamamoto Can. J. Chem. 1985,63 542. 15 S. Yamamoto and S. Back Can.J. Chem. 1985 63 549. 16 H. Bock and R. Dammel Inorg. Chem 1985 24 4427. 17 D. Lentz and H. Oberhammer Inorg. Chem. 1985 24,4665. 18 H. M. Marsden H. Oberhammer and J. M. Shreeve Inorg. Chem. 1985 24 4756. 110 P. G. Harrison F3C-k-S A anthracene c- KFIDMF I I I p H2O J 1 F3C 40 .ES-OH) + ,c=s F3C anthracene MCPBA = rn-chloroperoxybenzoic acid Scheme 1 (CF3)2C=S0 have been reported; they are summarized in Scheme 1. Reactions are summarized in Scheme 2.19 All five corresponding S-oxides (7)-( 11) have been obtained by the oxidation of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietane(12). Thermal decomposition of these S-oxides yields (F3C)2C=S=0 the thi-irane (13) (F,C)(F2C=)CS02F and (F,C)C=C(CF,), depending on the oxide.Oxidation of the thi-irane (13) affords only the episulphoxide (14) but not the episulphone (15) (Scheme 3).20 The behaviour of 1,1,3,3-tetrachloro- and 1,1,3,3-tetrabromo-l,3-dithietanes [(16 and (17) respectively] is generally quite similar (Schemes 4 and 5). Thermolysis of the tetrachloro-l,3-dithietane1,l-dioxide (18) provides a convenient synthesis of the tetrachlorothi-irane (19).21 Reaction of 2,2,4,4-tetrafluoro-1,3-dithietane with the Lewis acids MF (M=As or Sb) affords the stable 2,4,4-trifluoro-1,3-dithietan-2-ylium salts (20).22 The crystal structure of the arsenic derivative has been determined. The C-F and C-S bonds to the cationic carbon are significantly shorter than those to the saturated carbon.23 Ozonolysis of 2-(benzoylmethylene)-1,3-dithietane1,l-dioxide (21) prepared via the oxidation of 2-(benzoylmethylene)-1,3-dithietane(22) affords 1,3-dithietane (23) the first dithietane containing an a-oxosulphone structure.24 Trifluoroethylidynesulphur trifluoride CF,C=SF3 the first compound with a carbon-sulphur triple bond has been prepared by the dehydrofluorination of 19 A.Elsasser and W. Sundermeyer Chem. Ber. 1985 118 4553. 2o A. Elsasser W. Sundermeyer and D. S. Stephenson Chern. Ber. 1985 118 116. 21 R. Schork and W. Sundermeyer Chem. Ber. 1985 118 1415. 22 A. Waterfeld and R. Mews Chem. Ber. 1985 118 4997. 23 J. Antel K. Harms P. G. Jones R. Mews G. M. Sheldrick and A. Waterfeld Chem. Ber. 1985,118,5006. 24 U. Rheude R. Schork and W.Sundermeyer Chem. Ber. 1985 118 2852. 111 C Si Ge,Sn Pb; N P As Sb Bi (CF3)ZCHZ t F3c)4cF3 + s + so2 F3C CF3 F3c>0 + (HpS:;J F3C CF3 \ // CF -x* F3C\ /c=s ,o/ NaForPF \\ Fzc)==SOF XGS-X F3C F3C CF3 anthraceny c13c-cc13 0-= (CF3)$2Cl-S-Cl Scbeme 2 CF3CH=SF4 or CF3CH2SF,;it is a colourless gas and has a m.p. of -122.8 "C and an estimated b.p. of -15 "C. The C-C-S linkage is almost linear (angle 171.5") with a C-S bond distance of 1.394A determined by low-temperature (-130 "C) crystallography. Dimerization of the molecule occurs on warming up to -3O"C which is probably formed on internal cleavage into the carbene CF3C-SF,. The dimer is a substituted butene CF3(SF3)C=C(CF3)SF3,with a trans (E) configur-ati~n.~~ The alkenes CF3SF4CF=CF2and CF3SF4CH=CF2are formed on dehydro-chlorination of C F3SF4C H FC F2C1 and CF3S F4C H2C F,C1 respectively.Addition across the C=C double bond of CF3SF4CF=CF2 occurs on reaction with S02F2 SF4 (or SOF2) S206F2 and CIF to afford the compounds (CF3SF4CFCF3),S02 B. Potter K. Seppelt A. Simon,E. M. Peters and B. Hettich J. Am. Chem. SOC.,1985 107 980. P. G. Harrison PI N n n r;: u W u II 0 W 5 n $ II 0,n 0,5 W Nn PIh r; L L L W v W 0 \I \=\ n LL + hN W 2 113 C Si Ge,Sn,Pb; N P As Sb Bi CF,CO,H/CH,CI,/O "C / (I6) S"O SNo CF,CO,H/O "C /o ~r2< >r2 Br2< >Br2 -%Br2C=S/ S \ KMnO, \I CF,CO,H S S 0" Scheme 4 0 // S' S MCPBA c12c=s//O c12< >a2-c12< >C12 S S 140s J 00 NS4 CF,CO,H c12< >C12 68 "C S 1 0'.\s//0 S F&O F2< >FCI Clz\C12 CI2< S>C12 S S S F2 (19) \ glass H20v S F2< >c12 S Scheme 5 Z? G.Harrison CF,SF,CF[S(O)F]CF, CF3SF4CF(S0,F)CF2(S03F) and CF,SF,CFClCF respectively. CF3SF4Cl behaves as a chlorofluorinating agent towards highly hin- dered alkenes such as FSO2C(CF3)FCF2OCF2CF=CF and CF,SF4CF=CF2 although with CF3=CH equimolecular amounts of CF,SF,C(CF,)=CHCl and CF,C(Cl)=C( SF,CF,)H are obtained.26 Hexafluoroacetone reacts with the Group V nitriles CF,P(CN), P(CN), and Sb(CN) via E-CN bond cleavage to yield the compounds (24)-(26) re~pectively.~' R I \ /*-rCN Sb .p\ P 0-C-CN R RI \ R R (25) Sodium thiocyanate reacts with hexafluoroacetone in a 1:2 molar ratio to give the anion (28) (Scheme 6) possibly via $he anion (27).Hydrolysis of (28) in aqueous Ph,P+Cl- affords the crystalline hydrate [(CF,)C(OH),. (CF3),C(0)OH]-[Ph4P]'.28 The nitriles R-CN (R = C1 CF, CCl, or Me) react with chlorine and bromine in the presence of HgF to form the N,N-dihalogeno-1,l-difluoroamines R-CF2-NX2 (X = C1 or Br) in high yields. The analogous bromochloroamines RCF2NBrCl could not be isolated in a pure state. The diazines (R-CF,-N=) were obtained 26 K. D. Gupta and J. M. Shreeve Znorg. Chem. 1985,24 1457. 27 H. W. Roesky J. Lucas K. L. Weber H.Djarrah E. Egeret M. Noltemeyer and G. M. Sheldrick Chem. Ber. 1985 118 2396. 28 H. W. Roesky J. Lucas K. Keller K. S. Dhathathreyan M. Noltemeyer and G. M. Sheldrick Chem. Ber. 1985 118 2659. C Si,Ge Sn,Pb; N P As Sb Bi either by photolysis or by thermolysis of the amine~.~~ A new general method for the synthesis of perfluoropolyethers from hydrocarbon polyesters has been described which involves three steps (1) perfluorination of the hydrocarbon polyester (2) reaction of SF4 with the ester carbonyl to produce a CF unit and (3) high-temperature cleavage to volatile perfluoropolyethers and ~ligomers.~' The chemistry of hexafluoropropene oxide has been re~iewed.~' Formamide reacts with carbon disulphide in the presence of sodium hydride to yield crude sodium N-formyl dithiocarbamate Na[ S,C-CH -CO-HI.Acidolysis with HCl produces the free N-formyl dithiocarbamic acid which can be converted into other M' salts by treatment with the metal alk~xide.~' Crystals of the potassium salt comprise a hydrogen-bonded sixteen-membered ring system formed by four [S,C-NH-CO-HI-anions.33 Alkyl esters H-CO-NH-CS2R have also been ~haracterized.~~ Analogous N-thioformyldithiocarbamate salts can be prepared by using thi~formamide.~~ The crystal structure of the tetra-n-butylammonium N-thioformyl dithiocarbamate salt is built up of dimeric aggregates consisting of two alkylammonium cations and two [S,C-NH-CS-H]-anions which are linked together by -CS-S.-.H-N bridges.36 The alkyl esters H-CS-NH-CS-SR are obtained from the reaction of this salt with an alkyl iodide.Oxidation of N-thioformyl dithiocarbamates with iodine yields 1,2,4-dithiazole-3-thione H-C=N-CS-S-S.37 The reaction of a solution of potassium N-methyl N-formyl dithiocarbamate K[S,C-NMe-CO-H] (obtained as before from N-methyl f~rmamide),~~ in [*H,]acetone with gaseous HC1 at -78 "C affords unstable N-methyl N-formyl di thiocarbamic acid H -CO-NM e -CS-SH characterized by n.m.r.,39 whilst reaction with alkyl iodides produces the N-methyl N-formyl dithiocarbamate ester^.^' N- Methyl thioformamide has been obtained by the treat- ment of N-methylformamide with P4S10 and reacts with carbon disulphide in the presence of metal hydroxides to yield the corresponding N-methyl N-thioformyl dithiocarbamate salts M[S,C-NMe-CS-HI.Attempts to prepare the free acid were unsuccessful.41 The S-methyl ester of N-methyl N-thioformyl dithiocarbamic 29 M. Geisel A. Waterfeld and R. Mews Chem. Ber. 1985 118 4459. 30 D. F. Persico G. E. Gerhardt and R. J. Lagow J. Am. Chem. SOC.,1985 107 1197. 31 H. Millauer W. Schwertfeger and G. Siegemund Angew. Chem. Int. Ed. Engl. 1985 24 161. 32 R. Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 522 145. 33 R. Gerner G. Gel and G. Gattow Z. Anorg. Allg. Chem. 1985 523 76. 34 R. Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 524 117. 35 R. Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 524 122. 36 R. Gerner G. Gel and G. Gattow Z. Anorg. Allg. Chem. 1985 525 101. 37 R. Gerner and G. Gattow Z.Anorg. Allg. Chem. 1985 525 112. 38 R. Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 526 122. 39 R. Gemer and G. Gattow Z. Anorg. Allg. Chem. 1985 527 125. 40 R. Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 527 130. 41 R. Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 528 157. 116 l? G. Harrison acid H-CS-NMe-CS-SMe has been obtained from the reaction of potassium N-methyl N-thioformyl dithiocarbamate with methyl iodide.42 Reaction of metal 1,2-ethanedithiolates with carbon disulphide gives the corresponding 1,2-ethanebis(trithiocarbonates) M2[ S2C-SCH2CH2S-CS2].43 With hydrochloric acid at 0 "C the potassium salt gives the unstable deep-yellow 1,2-ethanebis(trithiocar-bonic) acid whilst alkyl iodies afford the corresponding esters.44 Crystals of the dimethyl ester MeS-CS-SCH2CH2S-CS-SMe comprise isolated molecules.45 The mixed dithiocarbamate-dithiocarbimate Na2[ S2C-NH-N=CS2]-7H20 and the 1,2-hydrazine-bis(dithioformates)M2[ S2C- NH- NH -CS2] have been pre- pared by the reaction of hydrazine hydrate carbon disulphide and NaOH in aqueous [S2C-NH-NH-CS2I2-anions are linked together by N-H--S hydrogen bonds in crystals of the potassium salt.48 The S-methyl ester of dithiocar- bazic acid reacts with carbon disulphide in the presence of sodium or potassium hydride at -15 "C to yield the salts of the S-methyl ester of N-dithiomethylene- dithiocarbazic acid M2[S2C=N-NH-CS-SMe].49 2 Silicon Germanium Tin and Lead Transient Intermediates and Their Stable Analogues.-The structures and energies of SiH;+ dications (n = 1-5) have been calculated.SiH2+ is predicted to be a strongly bound species and SiH22+ a kinetically stable species. The higher homologues SiH32+ SiH42+ and SiH52+ in contrast are weakly bound complexes of SiH22+ with atomic and/or molecular hydrogen." Studies of the two-dimensional potential-energy sur- face for the insertion of singlet silylene into the H2 molecule have shown that this reaction proceeds in a similar fashion to the insertion of singlet methylene with an activation energy of 6.3 kcal mol-' at 600 K. The data also yielded an activation energy for the thermal decomposition of silane of 60.2 kcal mol-' at 600 K." Least-motion versus non-least-motion pathways for the dimerization of methylene and silylene in both singlet and triplet states has been investigated.Ground-state triplet methylenes combine in the non-least-motion path to give ground-state ethylene without barrier. Ground-state singlet silylenes give a ground-state disilene with barrier in the least-motion path and without barrier in the non-least-motion path. A ground-state methylene and an excited-state silylene give a ground-state silaethyl- ene without barrier in the least-motion path and an excited-state methylene and a ground-state silylene also give ground-state silaethylene without barrier in the non-least-motion path.52 Ab initio MO calculations for Si2H2 have been reviewed.53 Dimethyldiazidosilane Me,Si( N,), and the trisilane PhMe2Si-SiMe,-SiPhMe2 have also been employed as precursors for the photochemical generation of dimethyl- 42 R.Gerner and G. Gattow Z. Anorg. Allg. Chem. 1985 528 168. 43 G. Gattow and U. Schubert Z. Anorg. Allg. Chem. 1985 530 94. 44 G. Gattow and U. Schubert Z. Anorg. Allg. Chem. 1985 530 101. 45 G. Gel G. Gattow and U. Schubert 2.Anorg. Allg..Chem. 1985 530 109. 46 G. Gattow and S. Lotz Z. Anorg. Allg. Chem. 1985 531 97. 47 G. Gattow and S. Lotz Z. Anorg. Allg. Chem. 1985 531 82. 48 G. Gel G. Gattow and S. Lotz Z. Anorg. Allg. Chem. 1985 531 89. 49 G. Gattow and S. Lotz Z. Anorg. Allg. Chem. 1985 531 101. 50 W. Koch G. Frenking and H. Schwarz J. Chem. Soc. Chem. Commun. 1985 1119. 5' A. Sax and G. Olbrich J. Am. Chem. SOC.,1985 107 4868. 52 K. Ohta E. R. Davidson and K. Morokuma J.Am. Chem. SOC.,1985 107 3466. 53 N. C. Baird Can. J. Chem. 1985 63 71. C Si Ge Sn Pb; N P As Sb Bi 117 silylene the assignment of the u.v.-visible spectrum of which has been ~onfirmed.’~ The photoelectron spectrum of dichlorosilyene exhibits three single and two double bands and has been employed to optimize synthetic routes theret~.’~ Ab initio MO calculations with basis sets of split valence plus polarization function quality have been carried out on the fully substituted silylenes Six2 disilenes X2SiSiX2 and silylsilenes XSiSiX3 (X = Me Li or F). All three silylenes are strongly bent in both their singlet ground states and triplet excited states except for SiLi, which has a triplet ground state with a linear geometry and a bent singlet excited state.The Si,Me4 isomers resemble the analogous Si2H4 species. Thus the singlet disilenes and silylsilylenes are almost isoenergetic the disilene dissociation energies toward two simple silylenes are comparable and both disilenes feature very flat potential- energy surfaces for bending of the geminal groups in a mutual trans fashion or twisting around the Si-Si bond. In contrast no closed-shell minimum could be located for F2SiSiF2 corresponding to a disilene. A minimum was obtained for the diradical-like triplet F,SiSiF, but this was considerably less stable than the singlet silylsilylene :FSiSiF3. No minima could be located either for a conventional disilene or a silylsilylene for the model Si2Li4 species. The global minimum for singlet Si2Li4 was a distorted planar structure with two bridging lithium atoms with C, sym-met~y.’~ Dimethylsilylene abstracts chlorine atoms from carbon tetrachloride.The resulting ccl3 radicals dimerize to hexa~hloroethane.’~ Extrusion of dimethylsilylene from l,l-dimethyl-l-silacyclopent-3-enes occurs on vacuum flow pyrolysis at 700 “C and can be trapped by addition to 1,3-diene~.~~ The formation of cis-3,3-dimethyl-3- silahepta-l,4-diene (29) as the major product from addition of dimethylsilylene to cis cis-hexa-2,4-diene is probably a result of a concerted 1,5-sigmatropic hydrogen shift in the rearrangement of the vinylsilacyclopropane intermediate formed by a concerted 1,2-cis-addition of the silylene (Scheme 7).59 Free dimethylgermylene undergoes cycloadditions with two molecules of a-substituted styrenes via a regios- pecific but not stereospecific mechanism forming equal amounts of syn/ anti 3,4-diphenylgermacyclopentanes.The 4,4,5,5-tetraphenyl derivative has an extra-ordinarily strained five-membered ring with a very long C-3-C-4 bond (1.626 A).6o In dilute solution 1,8-diazabicylco[5.4.0]undec-7-enedehydrochlorinates organo- chlorohydrogermanes such as PhC1,GeH and R2C1GeH leading to the correspond- ing germylene uia an anionic germanate species.61 Me2Si + > -+ \-Me2Si Me& LJ (29) Scheme 7 54 H. Vancik G. Raabe M. J. Michalezyk R. West and J. Michl J. Am. Chem. SOC.,1985 107 1097. 55 H. Bock B. Solouki and G. Maier Angew. Chem. Int. Ed. Engl. 1985 24 205. 56 K.Krogh-Jespersen J. Am. Chem. SOC.,1985 107 537. 57 R. Nakao K. Oka T. Dohmaru Y. Nagata and T. Fukumoto 1.Chem. SOC. Chem. Commun. 1985,766. 58 D. Lei and P. P. Gaspar Organometallics 1985 4 1471. 59 D. Lei and P. P. Gaspar 1.Chem. SOC.,Chem. Commun. 1985. 1149. 6o J. Kocher and W. P. Neumann Organometallics 1985 4 400. 61 P. Riviire A. Castel D. Guyot and J. Satge J. Organomet. Chem. 1985 290 C15. 118 P. G. Harrison The photochemically induced or palladium-salt-catalysed cleavage of hexa-t- butylcyclotrisilane leads to di-t-butylsilylene But2Si and tetra-t-butyldisilene But2Si=MiBut2 both of which can be trapped by a wide variety of multiply bonded reagents such as phenylacetylene and ketones.62 The stable disilenes (30) react with elemental sulphur in benzene at 25 "C to give the disilathi-iranes (31) the crystal structure of one of which (R = mesityl) has been determined.63 Similar sterically congested disilenes interact with alkali metals to produce tetraorganodisilenyl radical anions [R2Si=SiR2]-.64 Hexakis (2,4,6-tri-isopropylphenyl)cyclotristannanemay be transformed photochemically into tetrakis-(2,4,6-tri-isopropylphenyl)distannene with which it is in rapid equilibrium at room temperature or above.6s Mes.R But \ (33) (34) (35) Significant advances have been made in the chemistry of compounds containing Group IV-V multiple bonds. The first stable silaketimine (32),66 silaphosphene (33),67 germaphosphene (34),68 and stannaphosphene (35)69 have been reported whilst phenyl silaisocyanide (36) the first example of a species containing a SiGN triple bond has been generated according to Scheme 8.70 Two ab initio MO studies of bonding between silicon and phosphorus have been p~blished.~~,'~ Nominally normal single (pyramidal) double (planar) and triple (linear) Si-P bonds were predicted to be stable with positive harmonic force fields.Both studies included data for phosphasilene HP=SiH2 which were in close agreement. 62 A. Schafer M. Weidenbruch and S. Pohl J. Orgnnomet. Chem. 1985 282 305. 63 R. West D. J. De Young and K. J. Haller J. Am. Chem. Soc. 1985 107 4942. 64 M. Weidenbruch K. Kramer A. Schafer and J. K. Blum Chem. Ber. 1985 118 107. 65 S. Matsamune and L. R. Sita J. Am. Chem. Soc. 1985 107 6390.66 N. Wiberg K. Schurz and G. Fischer Angew. Chem. In?. Ed. Engl. 1985 24 1053. 67 C. N. Smit F. M. Lock and F. Bickelhaupt Tetrahedron Lett. 1984 25 3011. 68 J. EscudiC C. Couret J. SatgC M. Andrianarison and J. D. Andriamizaka J. Am. Chem. SOC.,1985 107 3378. 69 C. Couret J. EscudiC J. Satgt A. Raharinirina and J. D. Andriamizaka J. Am. Chem. Soc. 1985 107 8280. 70 H. Bock and R. Dammel Angew. Chem. Int. Ed. Engl. 1985 24 111. " K. J. Dykema T. N. Truong and M. S. Gordon J. Am. Chem. Soc. 1985 107 4535. 72 J. G. Lee J. E. Boggs and A. H. Cowley J. Chem. Soc. Chem. Commun. 1985 773. C Si Ge Sn Pb; N P As Sb Bi 119 (36) Scheme 8 Pyrolysis of 6-oxa-3,3-dimethyl-3-silabicyclo[ 3.1.O]hexane is a convenient method for the generation of dimethylsilanone.The decomposition most probably involves the intermediacy of silaoxetane which could be formed by either a concerted or a biradical mechanism (Scheme 9).73,74 The dominant feature in the visible portion of the chemiluminescence spectrum obtained from the reaction of ozone with silane at low pressure in a beam-gas apparatus was thought to correspond to emission from silanone H2Si0.75 The potential-energy surface of the dimerization of silanone has been predicted to proceed with no barrier to yield the cyclic product (H2Si0)2 by the stepwise formation of two new bonds. The dimer like (H2SiS)2 has a planar four-membered ring with D2, ~ymrnetry.'~The Si=O stretching frequency in silanone has been assigned as 1202cm-' close to that in dimethylsilanone (1204 ~m-').'~ / ///*Me2sie ,\ \ \ a Me2SiO-0 L\=-Me,Si=O + Me2sie: \ \ \ \ * / / / / Scheme 9 Silenes have been obtained in a number of ways thermolysis of the strained molecule (37) at 300°C,78 photolysis of acylsilanes such as (38) and (39),79980 or elimination of LiF from (40).8' The product (41) from the latter reaction is stable and has an essentially planar C2Si=CSi2 skeleton.The Si-C .rr-bond strength has been calculated to be 37 kcal mol-' intermediate between the values for the C-C (65 kcal mol-') and Si-Si (22 kcal mol-') .rr-bond strengths.82 The reaction of silene " I. M. T. Davidson A. Fenton G. Manuel and G. Bertrand Organometallics 1985 4 1324. 74 1. M. T. Davidson and A.Fenton Organometallics 1985 4 2060. 75 R. J. Glinski J. L. Cole and D. A. Dixon J. Am. Chem. Soc. 1985 107 5891. 76 T. Kudo and S. Nagase J. Am. Chem. SOC. 1985 107 2589. 77 R. Withnall and L. Andrews J. Am. Chem. Soc. 1985 107 2567. A. H. B. Cheng P. R. Jones M. E. Lee and P. Roussi Organometallics 1985 4 581. 79 A. G. Brook and H. J. Wessely OrganometaNics 1985 4 1487. 80 A. G. Brook K. D. Safa P. D. Lickiss and K. M. Baines J. Am. Chem. SOC.,1985 107 4338. 81 N. Wiberg G. Wagner and G. Muller Angew. Chem. Int. Ed. Engl. 1985 24 229. 82 M. W. Schmidt M. S. Gordon and M. Dupuis J. Am. Chem. Soc. 1985 107 2585. P. G. Harrison with formaldehyde to give silanone and ethylene uia a 1,2-~ilaoxetane intermediate has been studied at the SCF level.Whilst the reaction is exothermic by ca. 30 kcal mol-' the proposed intermediate is more stable than both the reactants and products by at least 50 kcal mol-' although if the product is the silanone dimer the reaction is more exothermic with the products lying 25 kcal mol-' below the sila~xetane.~~ Ab initio calculations for monosilabenzene 1,4-disilabenzene hexasilabenzene and their valence isomers illustrate the reduced aromaticity of the silabenzenes and the relative weakness of Si-C T bonds compared to C-C .rr-bonds and Si-Si a-bond~.~~~~~ neo-Pent Me SiMe Me SiMe, II Me 'Si=C Me-S i -C-Si M e (Bu') \/ II F Li \SiMe(Bu') (40) (41) Low-valent Compounds.-The most stable form of (CSH5),Si has beer! calculated to be the bis-monohapto isomer with a CSiC angle of 105.4".The bis-pentahapto isomer is of comparable energy with a minimum energy (but not a genuine minimum) for a structure of Dsd symmetry.g6 MNDO calculations have also been performed on stannylenes and their insertion and cycloaddition reactionsg7 and on a number of bivalent lead compounds including (CSH5),Pb.88 Decabenzylgermanocene is monomeric and air stable with an angle of 31" between the planes of the two C5 rings. One of the phenyl groups appears to form an additional interaction with the lone pair of the metal atoms.89 Ge[CH(SiMe,),] is a V-shaped monomer in the gas phase at ca. 430 K with a CGeC angle of 107".90 Bis(dichloromethy1)stannylene has been obtained as a tetrahydrofuran solvate (CHCl2),Sn-xTHF from the low- temperature reaction of LiCHCl with tin( 11) chloride.The stannylene associates via Sn-Sn bond formation upon removal of the solvent.'' r)'-Acetyl- and alkoxycar- bonyl-cyclopentadienyltin(I1) compounds q5-RC( =O)C5H,SnC5H,-q5 (R =Me OMe or OEt) have been obtained from the reaction of the substituted cyclopen- 83 S. M. Bachrach and A. Streitweiser J. Am. Chem. SOC.,1985 107 1186. 84 J. Chandrasekhar and P. yon R. Schleyer J. Organomet. Chem. 1985 289 51. 85 S. Nagase T. Kudo and M. Aoki J. Chem. Soc, Chem. Commun. 1985 1121. 86 C. Glidewell J. Organornet. Chem. 1985 286 289. 87 M. J. S. Dewar J. E. Friedheim and G. L. Grady Organometalfics,1985 4 1784. 88 M. J. S. Dewar M. K. Holloway G. L. Grady and J. J. P.Stewart Organomeraflics 1985 4 1973. 89 H. Schumann C. Janiak E. Hahn J. Loebel and J. J. Zuckerman Angew. Chem. Znr. Ed. Engf.,1985 24 773. 90 T. Fjeldberg A. Haaland B. E. R. Schilling H. V. Volden M. F. Lappert and A. J. Thorne 1. Organornet. Chern. 1985 280 C43. 91 R. Hani and R. A. Geanangel Znorg. Chim. Ac~Q, 1985. 96 225. 121 C Si,Ge,Sn Pb; N P As Sb Bi tadienylsodium salts and q5-cyclopentadienyltin( 11) chloride.92 The structure of Main Group Lewis acid complexes is not as simple as first thought. The material originally formulated as the donor-acceptor couples (C5H5),Sn + BF3 is actually a three-dimensional lattice comprising the four types of unit { [ BF,]-) [ q5-C5H5)2Sn],{[ q5-C5H5Sn]'} and THF. The lone pair of electrons plays no role in bonding.93 The reaction of 1 ,l'-di-t-butylstannocenewith BF3 in dichloromethane affords [ q5-Bu'C,H,Sn]+[ BFJ whose structure comprises anions and cations.94 Pentacarbonyl-chromium and -tungsten complexes of chloro( cyclopentadieny1)ger- mylenes and stannylenes have been prepared by the alkylation of the dichlorometal complexes C12(THF)MIV + M(CO)5 (MIv = Ge or Sn; M = Cr or W).An X-ray analysis of the germylene complex Me,C,(Cl)Ge -+ W(CO)5 confirms the general structure and shows further that the bonding of the C5 ring changes on complexation from q5 to q2 in nature.95 A novel boron-nitrogen ring-substituted stannocene bis( 1-t-butyl-2,3-dimethyldihydro-1,2-azaborolyl)tin has been synthesized by the reaction of tin( 11) chloride with 1-t-butyl-2,3-dimethyldihydro-l,2-azaborolyl-lithium in THF at -45°C.The compound is unstable and decomposes to form metallic tin above -20 "C. Structurally the compound resembles other stannocenes with q5 rings forming an angle of 46.5" with each other.96 The analogous reaction with Li[C( PMe2)J in ether does not afford a tin( 11)-carbon-bonded species. Rather the tetraphosphanetin(I1) complex (42) with a pseudo-trigonal-bipyramidal geometry is f~rmed.~' R Bis( ary1oxy)germylenes and diaminogermylenes are formed in the reaction of GeCl,*dioxane and lithiated ortho-substituted phenols and sterically hindered amines respectively. Mixed compounds of the type R( Me3Si)N-Ge-OBu' are obtained on lithiation of the amines with t-butyl-lithium in n-hexane/THF.The use of dilithiated amines leads to the formation of the diazagermacyclopentanes (43).'* Gaseous tin( 11) t-burbxide has a trans-dimeric structure with the remarkably small endocyclic OSnO angle of 76". Both germanium(11) and tin(I1) bis[tri-t-buty1)lmethoxides exhibit V shaped monomeric structures in the solid Bis(di-t-butylphosphino)tin(11) [ ( BU')~P],S~, has been obtained by metathesis using the 92 T. S. Dory J. J. Zuckerman and M. D. Rausch J. Organornet. Chem. 1985 281 C8. 93 T. S. Dory J. J. Zuckerman and C. L. Barnes J. Organornet. Chem. 1985 281 C1. 94 R. Hani and R. A. Geanangel J. Organomer. Chem. 1985 293 197. 95 P. Jutzi B. Hampel K. Stroppel C. Kriiger K. Angermund and P. Hofmann Chem. Ber. 1985,118,2789. 96 G. Schmid D.Zaika and R. Boese Angew. Chem. Inr. Ed. Engl. 1985 24 602. 97 H. H. Karsch A. Apelt and G. Muller Angew. Chem. Znf. Ed. EngL 1985 24 402. 98 A. Meller and C. P. Graber Chem. Ber. 1985 118 2020. 99 T. Fjeldberg P. B. Hitchcock M. F. Lappert S. J. Smith and A. J. Thorne J. Chem. SOC. Chem. Commun. 1985. 939. 122 P. G. Harrison potassium salt of the phosphide whilst bis-t-butylthio)tin(Ir) (Bu'S),Sn results either from the reaction of tin( 11) chloride and (t-buty1thio)trimethylsilane or from the protolysis of stannocene. In solution both compounds are dimers with bridging electronegative groups.'oo 5-t-Buty1-5-aza-2,S-dithia-1 -stanna( 11)bicyclo[ 3.3 .0'35]oc- tane [Sn(SC2H,),NBu'I2 is also dimeric with a central four-membered[Sn2S2] ring (44).lo' The crystal structure of lead( 11) ethane-l,2-thiolate comprises polymeric sheets of lead and sulphur atoms.Each dithiolate ligand chelates one lead atom which interacts further with four additional sulphur atoms to give distorted six-co-ordina- tion for lead. The valence angles at the metal suggest some stereochemical activity for the lone pair.'' The thiolato- and selenato-stannate( 11) anions [Sn( EPh)J- are obtained on addition of tin(I1) chloride to solutions containing 23 moles of the appropriate sodium salts. Both have the expected pyramidal geometry.'03 1,3-Di-t- butyl-2,2-dimethyl- 1,2,3,4h 2-diazasilastannetidine forms 1:1 crystalline adducts with triphenylphosphine oxide and triorganophosphorus ylides. No stable adducts could be isolated with triorganophosphines or with triphenylphosphine sulphide.Protolysis occurs with triphenylphosphineimine and Sn (NPPh3)4 is obtained. The structures of both the latter compound which contains tetrahedrally co-ordinated tin and the adduct with Ph3BCH2 have been detem~ined."~ The cubane-like cage compunds (MNBu') (M = Ge or Sn) from 1:2 adducts with two moles of aluminium trichloride which unlike other adducts do contain Ge- Al and Sn- Al bonds."' Several modes of behaviour of silylamidometal( 11) compounds with transition- metal complexes have been distinguished function as a neutral two-electron donor insertion into transition-metal-halogen bonds and cleavage of the amido group from the Group IV metal to give other metal(I1) derivatives.'06-''' Typical chemistry is illustrated in Scheme 10.100 W. W. du Mont and M. Gtenz Chem. Ber. 1985 118 1045. 101 K. Jurkschat M. Scheer A. Tzschach J. Meunier-Piret and M. van Meersche J. Organomet. Chem. 1985 281 173. 102 P. A. W. Dean J. J. Vittal and N. C. Payne Inorg. Chem. 1985 24 3594. 103 P. A. W. Dean J. J. Vittal and N. C. Payne Can. J. Chem. 1985 63 394. 104 M. Veith and V. Huch J. Organomet. Chem. 1985 293 161. M. Weith and W. Frank Angew. Chem. Int. Ed. Engl. 1985 24 223. I06 J. E. Shade B. V. Johnson D. H. Gibson W. L. Hsua and C. D. Schaeffer Inorg. Chem. Acra 1985 99,99. I07 M. F. Lappert and P. P. Power J. Chem. Soc. Dalton Trans. 1985 51. 108 P. B. Hitchcock M. F. Lappert and M. C. Misra J.Chem. SOC.,Chem. Commun.. 1985. 863. 105) S. M. Hawkins P. B. Hitchcock and M. F. Lappert J. Chem. SOC.,Chem. Commun. 1985 1592. 110 T. A. K. Al-Allaf C. Eaborn P. B. Hitchcock M. F. Lappert and A. Pidcock J. Chem. SOC.,Chem. Commun. 1985 548. 111 G. K. Campbell P. B. Hitchcock M. F. Lappert and M. C. Misra J. Organomer. Chem. 1985,289 cl M2 = Ge,Sn,orPb 0 Reagents i [M(CO),] n-C6H,, irradiation 3 ~ h 25 "C; ii [M(CO),(nbd)] n-C,H,, reflux 12-24 h; iii [Sc(77-C5H,),(p-Me)2AIMe21 n-C6H14 25 "C 24h; iV [(Pd(~-C,H,)(p-cl)}~) n-C6H1,-Phh4e 06C; v [MnBr(CO),] n-C6H14 20 "C 1 h; vi C5H5)(CO)2X] n-C,H,, 25 "c; vii [{Pr(p-CI)C1(PEt3)},1 n-C,H,, 25 "C; viii cis-[PtCl,(cod)] n-C5HI2 0"C 2 h; ix C5H5)(CO),Hl n-CsH14 25 "C Scheme 10 124 Z? G.Harrison Excess of amido-germylene or -stannylene M1(NR2)' (M' = Ge or Sn R = SiMe,) with [Pd(cod)C12] or [Pt(cod),] yields the d" complexes [M2{M1(NR2)2}3] (M2 = Pd or pt). With carbon monoxide the trinuclear clusters [(M2{p-M'(NR,),}- (CO) both undergo reversible one-electron reduction in THF at ca. -1.2 V yielding e.s.r.-characterized reduction products. With the rhodium-alkene complexes the silylamidotin( 11) derivative gives the neutral arene-RH' complexes [Rh(r)-ArH) ( r)-C8Hl4)(SnCl(NR2),}] with excess arene. The crystal structure of several of the complexes have been determined. Molecular Tetravalent Compounds.-The results of combined gas-phase U.V. photo- electron spectra and pseudo-potential ab initio calculations clearly indicate that a/.rr-conjugation is quite extensive in alkyltin acetylides and that the mechanism is critically controlled by the substituents at both the tin atom and the alkynyl group."' Striking similarities in the spectra of TCNE complexes of the Group IV element tetraphenyl derivatives indicate that there is no appreciable p.rr +-d.rr bond-ing between the phenyl groups and the central atoms and that the energies of the phenyl .Ir-orbitals are unaffected by the size or electronegativities of the central atoms.' l3 The main reaction in the gas-phase pyrolysis of diallyldimethylsilane is the retroene elimination of propene with the formation of a silacyclobutene (Scheme 11).Extensive secondary reactions also 0~cur.l'~ Flash vacuum pyrolysis of {o-(dimethylsily1)phenyl)acetylene at 800 "C produces 1,l -dimethyl-1 -silaindene (45) (Scheme 12) in 84% yield uia largely an insertion of an intermediate vinylidene MelSi -CH2 II HC=CH Scheme 11 Scheme 12 112 C.Cauletti C. Furlani G. Granozzi A. Sebald and B. Wrackmeyer Organometallics 1985 4 290. 113 J. E. Frey R. D. Cole E. C. Kitchen L. M. Suprenant and M. S. Sylwestrzak J. Am. Chem. Soc. 1985 107 748. I14 N. Auner I. M. T. Davidson and S. Ijadi-Maghsoodi Organometallics 1985 4 2210. C,Si,Ge Sn,Pb; N P As Sb Bi 125 into the Si-H bond. At 650 "C however the isomeric l,l-dimethyl-2-methyl- enebenzo- 1-silacyclobutene (46) arising from an initial 1,5-hydrogen shift from silicon is also obtained."' The first-stage intercalation compound of potassium in graphite CaK reacts with tin(11) chloride to afford tin-graphite which with ally1 bromide gives diallyltin dibromide via a double oxidation-addition reaction.' l6 Treatment of CH2( MgBr)2 with THF gives another Grignard reagent of approximate composition CH2CH2(MgBr),.Both of these reagents are useful for the synthesis of metal- lomethanes such as (Me,M),CH,( M = Si Ge or Sn) polygermacycloalkanes (Me2MCH2) (n = 24) and polystannacycloalkanes (Me2SnCH2) (n = 3 or 4).' l7 The reactions of n-butyl-lithium and t-butyl-lithium with tetramethyltin have been examined in order to determine the degree of competition between proton abstraction from the methyl groups and nucleophilic displacement of these groups from the tin atom. Only the latter type of reaction is observed for n-butyl-lithium with all four methyl groups being successively displaced.Only two methyl groups were displaced by t-butyl-lithium. Evidence was obtained for the formation of t-BuMe2SnCH2Li by trapping the anionoid by reaction with ethyl bromide.'** Both Sn-Me and Sn-CH sites in Me3SnCH2MMe3 (M = C Si Ge or Sn) are attacked by iodine and bromine in various solvents with Sn-CH cleavage favoured in non-polar solvents and for M = Sn. Protolysis leads to Sn-CH cleavage only and this site appears to be activated by the Me,M substitutent. In contrast organometallic electrophiles attack exclusively the Sn-Me site and the Me3MCH2 groups are deactivating.' l9 Treatment of (Me3Sn),C with one equivalent of methyl-lithium followed by one equivalent of Me3MCl (M = Si or Pb) gives mixtures of the metallomethanes C(SnMe3),(MMe3)4- (n = 0-3).120 Me'T3 Me Me The carbasilatrane derivatives (47) and (48) have been prepared by the Grignard method.',' The Si t N co-ordinate bond distance (2.291 A) in l-phenylcarbasi- latrane is some 0.13 A longer than in other phenylsilatranes.lz2 1-Methyl-1-germa- adamantane (49) has been synthesized according to Scheme 13.The methyl group can be replaced by chlorine using excess trichlorosilane with a catalytic amount of 1 I5 T. J. Barton and B. L. Groh Organornetallics 1985 4 575. 116 G. P. Boldrini D. Savoia E. Tagliavini C. Trornbini and A. Umani-Ronchi 1.Organornet. Chern. 1985,280 307. 117 J. W. Bruin G. Schat 0.S. Akkerman and F.Bickelhaupt 1.Organornet. Chern. 1985 288 13. 118 D. Darah T. J. Karol and H. G. Kuivila Organornetallics 1985 4 662. 119 D. W. Hawker and P. R. Wells Organornetallics 1985 4 821. 120 T. N. Mitchell and R. Wickenkarnp J. Organornet. Chern. 1985 291 179. 121 K. Jurkschat C. Mugge J. Schmidt and A. Tzschach J. Organornet. Chern. 1985 287 C1. 122 P. Hencsel I. Kovacs and L. Parkanyi J. Organornet. Chern. 1985 293 185. P. G. Harrison B Me :ruBr Mg BrMgr M > H MgBr Me3Ge 3 G e u GeMe --Me ,GeC I Me I Scheme 13 (49) chloroplatinic acid.'23 Molecules of ClSn(CH2CH2CH2)3Ncontain trigonal-bipyramidally co-ordinated tin with the tin nitrogen and chlorine atoms lying on the crystallographic three-fold MNDO calculations confirm the high reac- tivity of the bridgehead hydrogen of the trithiatristanna-adamantane(50) to hydride absfracti~n.'~' Stannane and the methylstannanes react in fluorosulphuric acid at -90°C to produce SnMe3-,H,+ (n= 0-3) cations.At higher temperatures decomposition to Sn2+ and/or SnMeZ2+ cations occurs.126 H The Lewis acidities of trimethylchloro-silane -germane and -stannane have been determined calorimetrically and follow the order Sn > Ge > Si. The chlorosilane exhibits Lewis behaviour similar to that of the germane and the previously reported acidity of the chlorosilane is attributed to hydroly~is.'~~ The structures of three organotin halides are worthy of note. That of bis( chlorodiphenylstanny1)methane is illustrated schematically in (51) showing both the inter- and intra-molecular chlorine bridging.12* Dicyclohexyltin dichloride is also associated by chlorine bridging giving a severely distorted trans-octahedral geometry at tin,'29 but crystals 123 P.Boudjouk and C. A Kapfer J. Organomet. Chem. 1985 339. 124 K. Jurkschat A. Tzschach J. Meunier-Pieret and M. van Meerssche J. Organomet. Chem. 1985 290 285. 125 M. J. S. Dewar and G. L. Grady Organometallics 1985 4 1327. 126 T. Birchall and V. Manivannan J. Chem. Soc. Dalton Trans. 1985 2671. 127 J. N. Spencer S. W. Barton B. M. Cader C. D. Corsico L. E. Harrison M. E. Mankuta and C. H. Yoder Organometallics 1985 4 394. 128 J. Meunier-Piret M. van Meersche K. Jurkschat and M. Gielen J. Organomet. Chem. 1985 288 139.129 K. C. Molloy K. Quill and I. W. Nowell J. Organomet. Chem. 1985 289 271. C Si,Ge,Sn Pb; N P As Sb Bi of bis(biphenyly1-2)tin dichloride comprise discrete monomeric units with very distorted tetrahedral co-ordination at tin.'30 Air-stable chlororoform solutions of Schiff-base complexes of Co" undergo rapid cobalt oxidation on addition of n- butyltin trichloride affording complexes such as Bu"Sn(OMe)Cl,-CoCl(sa1en). In this complex the methoxy group bridges the two rnetals.l3' Both cis and trans isomers of the complex of dichlorobis-(4-chlorophenyl)tinwith 4,4'-dimethyl-2,2'-bipyridine have been ~haracterized.'~' Four different phases have been isolated from the PC1,-SnCl system depending on the conditions such as solvent relative concentra- tions and temperature [PCl,],[ SnC16] [PCl,],[ SnCl,][ PC16] [PC14][ Sn,Cllo],.and [pC14][ ~nCl,].'~~ I Cl -Ph Several papers report studies on sterically hindered silane and stannane com- pounds.The crystal structures of five silanols have been described. Bu',Si(OH)F crystallizes as an 0-H. -0 hydrogen-bonded tetramer. The fluorine atoms do not participate in the a~sociation.'~~ Bu',Si(OH) forms hydrogen-bonded dimers that are linked by additional hydrogen bonds into a ladder structure (52).'35The structures of [(Me3Si),C]( Ph)Si(OH) and [(Me,Si),C]( Ph)Si(OMe)OH also comprise hydro- gen-bonded dimers but in the latter compound the two components are held together by a single hydrogen bond.'36 The trio1 [(Me,SiO,CSi(OH),] has a hexameric cage structure that is extremely table.'^'*'^* Tin-119 n.m.r.and Mossbauer data for tetrakis(adamanty1)stannane indicate some charge separation of the type Ad3SnA'-. .AdA+ Other sterically hindered compounds exhibit similar but less 130 J. L. Baxter E. M. Holt and J. J. Zuckerman Organomefallics 1985 4 255. 131 D. Cunningham T. Higgins B. Kneafsey P. McArdle and J. Simmie J. Chem. SOC. Chem. Commun. 1985 231. 132 V. G. Kumar Das Y. C. Keong and P. J. Smith J. Organomef. Chem. 1985 291 C17. 133 J. Shamir S. Luski A. Bino S. Cohen and D. Gibson Znorg. Chem. 1985 24 2301. 134 N. H. Buttrus C. Eaborn P. B. Hitchcock and A. K. Saxena J. Organomet. Chem. 1985 287 157. 135 N. H. Buttrus C. Eaborn P. B. Hitchcock and A. K. Saxena J. Organomet.Chem. 1985 284 291. 136 Z. H. Aiube N. H. Buttrus C. Eaborn P. B. Hitchcock and J. A. Zora J. Organomet. Chem. 1985 292 177. 137 N. H. Buttrus R. I. Damja C. Eaborn P. B. Hitchcock and P. D. Lickiss J. Chem. SOC.,Chem. Commun. 1985 1385. 138 R. I. Damja and C. Eaborn 1.Organornet. Chem. 1985 267 267. 128 P. G. Harrison dramatic effects.'39 Tin-119 n.m.r. has been employed to examine the stability and self-association of (neophyl,Sn),O neophyl,SnOH and (neophy13Sn),C03 in sol-ution. Facile dehydration of the hydroxide occurs even at room temperature thus preventing its isolation from solution in sharp contrast to previous reports that the bulky alkyl groups render the hydroxide stable with respect to dehydration. Both the hydroxide and carbonate unlike their n-alkyl homologues are unassociated in solution.'40 Di-t-butyltin hydroxide halides Bu+,Sn(OH)X (X = F C1 or Br) have been obtained either by hydrolysis of the corresponding dihalides or by reaction of the oxide with hydrogen halide.All three compounds are dimeric with two five-co- ordinated tin atoms linked by oxygen atoms in a central four-membered [Sn,O,] ring (53). These dimeric molecules are further held together in the crystal by 0-H. -.Xhydrogen bonding.141 t-Butyltris(diethylamino)stannane,Bu'S~(NE~,)~ has been synthesized by alkylation of tetrakis(diethylamino)stannane using t-butyl- lithium. Alcoholysis with t-butanol affords Bu+Sn(OBu'), whilst reaction with trimethylchlorosilane gives Bu'SnCl, which decomposes rapidly at room tem-perature to tin( 11) chloride and t-butyl ch10ride.l~~ MNDO calculations have been performed on simple five-co-ordinated silicon species.When tetrahedral silicon is involved in the formation of an additional donor-acceptor Si-Y bond it acquires a higher positive charge compared with the four-co-ordinated state and electron density is transferred to the equatorial and axial ligands affecting predominantly the charge on the other axial atom.'43 The expansion of the co-ordination sphere of silicon from four to five has been mapped using known structural data. The correlation diagrams are interpreted in terms of geometrical transformations along the SN2 inversion pathway and provide a possible model for the molecular motions of dynamic rearrangements involving an intermedi- ate co-ordination number (5 + 4 + 5) at sibcon in chelated complexes of five-co- ordinated silicon.'44 Rapid positional exchange of the fluorine atoms occurs for 1-(trifluorosilyl)-l,2,3,4-tetrahydro-1,lO-phenanthroline at room temperature (19F n.m.r.) which occurs as an intramolecular reaction by an irregular mechanism involving the instability of the co-ordinative bonding.Intermolecular fluorine 139 C. S. Frampton R.M. G. Roberts J. Silver J. F. Warmsley and B. Yavari J. Chern.Soc. Dalton Trans. 1985 169. 140 T. P. Lockhart J. Organornet. Chem. 1985,287 179. 141 H. Puff,H. Hevendehl K. Hofer H. Reuter and W. Schuh J. Organornet. Chem. 1985 287 163. 142 D. Hanssgen H. Puff,and N. Beckermann J. Organornet.Chern. 1985 293 191. 143 Yu. L. Frolov S. G. Schevchenko and M. G. Voronkov J. Organornet. Chem. 1985 292 159. 144 G. Klebe J. Organornet. Chem. 1985 293 147. C,Si,Ge Sn Pb; N P As Sb Bi exchange does occur but is relatively s10w.l~~ The structures of two analogues (54) and (55) have been determined both of which exhibit trigonal-bipyramidal five-co- ordination at silicon. Whereas the silicon is achiral in (54) that in (55) is chiral and both enantiomers are found in the ~rysta1.l~~ The structures of no less than eleven spirocyclic five-co-ordinated silicates and germanates (56)-(63) have been dete~-mined.'~~-'~~ Hydrogen bonding between the cation and the oxygen atoms of the spirocyclic framework e.g. in (56) causes displacement of the geometry towards a rectangular pyramid.When this is precluded -1 v I,O [EtZNH] Ph-Si -R (59) R = a-Np Bu",or Bu' 145 G. Klebe and K. Hensen J. Chem. Soc. Dalton Trans. 1985 5. 146 G. Klebe J. W. Bats and K. Hensen J. Chem. SOC.,Dalron Trans. 2985 1. 147 R. R. Holmes R. 0. Day V. Chandrasekhar and J. M. Holmes Inorg. Chem 1985 24 2009. 148 R. R. Holmes R. 0.Day V. Chandrasekhar J. J. Harland and J. M. Holmes Inorg. Chem. 1985,24 2016. 149 R. R. Holmes R. 0.Day A. C. Sau and C. A. Poutasse Inorg. Chem. 1985 24 193. P. G. Harrison by bulky substituents e.g. in (57) the trigonal-bipyramidal geometry is found. Increase in the electron-donor ability of the organic substituent on the silicon also causes a displacement of the geometry towards a rectangular pyramid.The same general rules for the observation of a trigonal-bipyramidal versus a rectangular- bipyramidal geometry also apply for five-co-ordinated germanium species. Di-n- butyltin dimethoxide reacts with organo-bis-a-hydroxyphenylphosphines to afford the five-co-ordinated benzoxaphosphastannolins (64).I5O Germyl acetate adopts a cis-planar conformation in the gas phase with the Ge-0 bond eclipsing the C=O bond.'51 Trimethylsilyl trichloroacetate in refluxing solvent (toluene chloroform or dichloromethane) in the presence of a phase-transfer catalyst and solid dry potassium fluoride is a useful dichlorocarbene source.152 Flash pyrolysis of alkyltributyltin acetates at temperatures of 600-850 "C under a moderate vacuum leads to the formation of vinyltin compounds (Scheme 14).'53 OCOMe Scheme 14 Phenyltin oxycyclohexanecarboxylate has an extremely unusual hexameric structure (65) in which the tin has an octahedral ~o-ordination.'~~ Other crystal structures worthy of note include the diphenyltin dinitrate complexes of cis-and trans-1,2-bis(diphenylphosphoryl)ethylene which both contain tin in a pentagonal-bipyramidal en~ironment,'~~ the silver-tin complexes [Ag(A~Ph,)~11SnPh~(N01)73 and [Ag( AsPh,),][SnPh,( N03)2C1],'56 and the dimeric trichlorotin phenoxide (66).15' The structures of tin compounds containing a four-membered [Sn202] ring have been critically analy~ed.'~' I50 A.Tzschach K. Nieteschmann and C. Mugger Z. Anorg.Allg. Chem. 1985 523 21. I51 E. A. V. Ebsworth C. M. Huntley and D. W. H. Rankin J. Organornet. Chem. 1985 281 63. 152 E. V. Dehmlow and W. Leffers J. Organornet. Chem. 1985 288 C41. 153 J. G. Duboudin M. Petraud M. Ratier and B. Trouve J. Organomef. Chern. 1985 288 C6. 154 V. Chandrasekhar R. 0. Day and R. R. Holmes Inorg. Chem. 1985 24 1979. 155 S. Dondi M. Nardelli C. Pelizzi G. Pelizzi and G. Predieri J. Chem. SOC.,Dalton Trans. 1985 487. I56 M. Nardelli C. Pelizzi G. Pelizzi and P. Tarasconi J. Chern. Soc. Dalton Trans. 1985 321. 157 H. Jolibois F. Theobald R. Mercier and C. Devin Inorg. Chim. Acta 1985 97,119. 158 T. S. Cameron 0.Knop and B. R. Vincent Can. J. Chem. 1985 63 759. C,Si Ge Sn Pb; N P As Sb Bi \ cyclohexyi cyclohexyl Ph The trimethyltin complexes of two terminally protected dipeptides (67) and (68) have been synthesized as models for the interaction of trimethyltin with protein^."^ In the solid state intermolecular association occurs for both compounds (variable- temperature Mossbauer); in solution however it is broken down and isomers due to the restricted rotation about the peptide and amide bond are observed (13Cn.m.r.).Variable-temperature Mossbauer data for a large number of phenyl- and cyclohexyl- tin compounds have extended further the me of these data for the classification of 159 P. G. Harrison and N. W. Sharpe lnoyg. Chim. Acta 1985 108 7. 160 K. C. Molloy and K. Quill J. Chem. SOC. Dalton Trans. 1985. 1417. P. G.Harrison solid lattices. Lattices based upon non-interacting units or upon polymers that are helical (69) or S-shaped (70) show the highest temperature coefficients. The value of this parameter is generally reduced for zig-zag polymers (71) while the most rigid lattices are based upon a rod-like architecture (72).I6' 'S I -X X- N.m.r. has been employed extensively in the characterization of tin compounds. For the first time 13C data have been obtained on solid methyltin compounds by employing the proton-decoupled cross-polarization magic-angle spinning tech- nique.161-163 The methyltin 13C chemical shift is insensitive to slight variations in bond angles and bond distances. However as in solution the one-bond coupling constant 'J('19Sn-13C) varies monotonically with the MeSnMe bond angle.Multiple methyltin resonances were observed for trimethyltin acetate and trimethyltin hydroxide indicating hindered rotation of the trigonal-planar [Me,Sn] group in these one-dimensional polymers. The single 170 chemical shift observed in the spectra of tri- and di-n-butyltin carboxylates has been interpreted in terms of a fast exchange of the oxygen atoms of the carboxylato group bonded to the tin atom.'64 Triorganotin(1v) oxinates have been shown by a combination of I3C 15N,and I19Sn n.m.r. to contain five-co-ordinated tin in both non-co-ordinating and co-ordinating solvents. In the former type and in the neat liquids the geometry is cis-trigonal bipyramidal; in donor solvents a trans-trigonal-bipyramidal arrangement is found with the oxinate group ~nidentate.'~~ The '19Sn chemical shift is indicative of 161 W.F. Manders and T. P. Lockhart J. Organomet. Chem. 1985 297 143. 162 T. P. Lockhart W. F. Manders and J. J. Zuckerman J. Am. Chem. Soc. 1985 107 4546. 163 T. P. Lockhart and W. F. Manders J. Am. Chem. Soc. 1985 107 5863. 164 A. Lycka and J. Holecek J. Organomet. Chem. 1985 294 179. 165 A. Lycka J. Holecek M. Nadvornik and K. Handlit J. Organornet. Chem. 1985 280 323. C Si,Ge Sn Pb; N P As Sb Bi 133 co-ordination number in tricyclohexyltin derivatives with the chemical shift moving to lower frequency on increase in co-ordination number. Thus the oxide chloride bromide iodide hydroxide acetate and benzoate are all monomeric and four-co- ordinate in solution whereas the tropolonate is five-co-ordinate.'66 Values of the CSnC bond angles in octahedral complexes of the type R2SnCh2 (Ch = bidentate ligand) have been estimated from the n.m.r.'J( "9Sn-'3C) and 2J(1'9Sn-C-'H) coupling constants. Complexes with p -ketoenolato ligands have trans-alkyl struc- tures with angles between 174" and 180". 8-Hydroxyquinolato complexes have very nearly cis geometries with angles in the range 109-126" whereas the sterically crowded 2-methyl-8-hydroxyquinolatocomplexes have intermediate skew cis struc-tures. Trapezoidal-bipyramidal frameworks were observed for the tropolonates and l-pi~olinates.'~~ The isomers of the 1 1 adduct Ph2SnClBr.0=PBu3 undergo rapid Berry pseudo-rotation with a calculated barrier of 35 kJ mol-' above approximately -75 "C in dichloromethane Two-dimensional 'I9Sn NOESY n.m.r.spectra have demonstrated unambiguously that the ditin compound CH2[ PhSn( SCH2CH2)2NMe]2 isomerizes at the tin centre in an uncorrelated way.'69 The magnitude of the 2J(119Sn-' 17Sn) coupling constant in hexaorganodistannoxanes is strongly dependent upon the nature of the organic group. The effect is attributed to changes in the SnOSn bond angle which should strongly influence the magnitude of the Fermi contact term.17' Tin-tin coupling has also been detected for the first time in tetraorganodistannoxanes with a marked difference observed between halogen- and oxygen-bridged distannoxanes. In the former type one kind of coupling was interpreted in terms of an anionic chloride bridge whilst a covalently bonded oxygen bridge was suggested on the basis of the appearance of additional coupling in the latter corn pound^.'^^ The mixed species Sn(SPh),(SePh),(TePh)4-x-y have been characterized by 77Se '19Sn and '25Te n.m.r.172 One of the Si-Si bonds of cis trans-1,2,3-tri-t-butyl-l,2,3-trimesitylcyclotrisilane (73) is significantly longer than the other two which is consistent with the reported chelotropy of photocleavage to give both E-and 2-1,2-di-t-butyl- 1,2-dimesityl- disilenes.The structure of the cis,cis isomer (74) has also been determined.'73 I I Bu Mes 166 S. J. Blunden and R. Hill Inorg. Chirn. Acfa 1985,98 L7. 167 W. F.Howard R. W. Crecely and W. H. Nelson Znorg. Chern. 1985,24 2204.168 R. Colton and D. Daketernieks Znorg. Chirn. Acta 1985,102,L17. 169 C. Wynants G. Van Binst C. Mugge K. Jurkschat A. Tzschach H. Pepermans M. Gielen and R. Willem Orgnnornetallics 1985,4 1906. 170 T.P. Lockhart W. F. Manders and F. E. Brinckman J. Organornet. Chern. 1985,286,153. 171 T. Yano K. Nakashima J. Tera and R. Okawara Organornetallics 1985,4 1501. P. A. W. Dean and R. S. Srivastava Inorg. Chirn. Acta 1985,105 1. J. C. Dewan S. Murakami J. T. Snow S. Collins and S. Masamune J. Chern. Soc. Chern Cornrnun. 172 173 1985 892. 134 P. G. Harrison Tetraisopropyltetraneopentylcyclotetrasilaneassumes a folded structure with a large dihedral angle (39.39°).'74 Molecules of tetradecamethylcycloheptasilane (Me2Si), have approximate C2 symmetry and adopt a twist-chair c~nformation.'~~ E.s.r.spectra have been reported for anion radicals formed by reduction of a large number of cyclo-tetra- and -penta-silanes. Most give single-line spectra although proton hyperfine splittings are resolved in a few cases. In all the unpaired electron is delocalized over the cyclosilane ring.176 I3C and 29Si ENDOR signals have also been observed for the radical anions (Bu'MeSi) and (Et2Si)5. The data show only a small hyperfine anisotropy for 29Si consistent with Si-Si (T*-or 3d-spin population but not with .rr-type delo~alization.'~~ Aliphatically substituted polydiorganosilylenes display reversible thermochromic behaviour in solution with a bathochromic shift occurring with decreasing temperature.The temperature dependence of the U.V. absorption maxima is thought to be due to conformational changes occurring along the polymer backbone with temperat~re.'~~ Photolysis of the high polymer (n- C6H&kSi) in carbon tetrachloride leads to the formation of C2C16 indicating that the photodegradation pathway of these polymers includes the formation of silyl radicals. Mechanisms involving both the extrusion of silylene units and the formation of silyl-radical terminated polymer fragments were proposed to explain the observed silane The first stage of the reaction of n-decamethyltetrasilane with peroxybenzoic acid involves the oxidation of one of the two terminal Si-Si bonds rather than the oxidation of the central Si-Si bond.'80 1,2-Dichlorotetra-alkyldistannanes,C1R2SnSnR2C1 (R = Me Et or Bu) have been prepared by the electrolysis of acetonitrile solutions of the appropriate dialkyl- tin dichloride on a mercury cathode.'81 The reaction of triorganotin oxides with formic acid provides a good route to hexaorganodistannanes.In addition this route affords small quantities of several new linear polystannanes.'82 Pure dodecamethyl- cyclohexastannane and its perdeuterio analogue have been prepared in high yield according to the route 3Me2SnH + 3Me2Sn(NEt,) (Me,Sn) + 6HNEt2 -P In solution the cyclohexastannane equilibrates even at 20 "C but more extensively at 80°C with three other cyclostannanes (Me2Sn) (n = 5 7 or 8).Ig3 Controlled cleavage of (Bu',Sn) with iodine in toluene solution affords the linear 1,4-di- iodotetrastannane I( Bu',Sn),I which has an all- trans structure in the crystal.'84 Unsymmetrical diplumbanes have been synthesized from R',PbLi and R23PbCI at -60 "C in tetrahydrofuran although products exhibit migrations of R' and R2 in 174 H.Matsumoto K. Takatsuna M. Minemura Y. Nagai and M. Goto J. Chem. SOC. Chem. Commun. 1985 1366. 175 F. Shafice J. R. Damewood K. J. Haller and R. West J. Am. Chern. Soc. 1985 107,6950. 176 C. L. Wadsworth R. West Y. Nagai H. Watanabe and T. Muraoka Organornetallics 1985 4 1659. 177 B. Kirste R. West and H. Kurreck J. Am. Chem. SOC.,1985 107 3013. 178 P. Trefonas J. R. Damewood R. West and R. D. Miller Organometallics 1985 4 1318.179 P. Trefonas R. West and R. D. Miller J. Am. Chem. SOC. 1985 107 2737. 180 G. A. Razuvaev V. V. Semenov T. N. Brevnova and A. N. Kornev J. Organomet. Chem. 1985,287 C31. 181 M. Devaud M. Engele C. Feasson and J. L. Lecat J. Organomet. Chem. 1985 281 181. I82 B. Jousseaume E. Chanson M. Bevilacqua A. Saux M. Pereyre B. Barbe and M. Petraud J. Organomet. Chem. 1985 294 C41. 183 B. Watta W. P. Neumann and J. Sauer Organometallics 1985 4 1954. lS4 S.Adams and M. Drager J. Organomet. Chem. 1985 288,295. C Si,Ge,Sn,Pb; N P As Sb Bi the transition state. Thus the crystal structure of Pb2Ph3(p-tol)3shows it to comprise two independent molecules of composition Ph(p-tol),PbPbPh2(p-tol) .185 A large number of papers have appeared describing the chemistry of compounds containing Group IV-metal-transition-metal bonds; however space precludes men- tion of more than a mere handful.Of note is the report of the reversible insertion of carbon monoxide into a silicon-zirconium bond yielding the sila-acyl complex (75) in which the sila-acyl group is bonded to the zirconium atom in a bidentate fashion.'86 Structures with 'naked' germanium and lead atoms have been described. @ /%Me3 ,%Me3 7 Zr L Zr -0 t The germanium complex (76) has been obtained by the hydride route from GeH and (CSMes)Mn(CO),(THF) in the presence of sulphuric acid. In the crystal two conformers are present in a 1 1ratio. The conformers are related by a 180"rotation of the [(CSMe5)Mn(CO),] fragment around the [Mn-Ge-Mn] ve~tor.'~' The same synthetic strategy is unsuccessful in the case of lead.However the lead analogue (77) was obtained using lead(r1) chloride. The Mn-Pb-Mn unit is almost linear [ 177.2(1)0].'88 Reaction of Na2W2(CO)lo with germanium(1v) or tin(rv) chlorides Mn=Pb=Mn 185 N. Kleiner and M. Drager J. Organomet. Chem. 1985 293 323. 186 T. D. Tilley J. Am. Chem. SOC.,1985 107 4084. 187 J. D. Korp I. Bernal R. Horlein R. Serrano and W. A. Hermann Chem. Eer. 1985 118 340. W. A. Herrmann H. J. Kneuper and E. Herdweck Angew. Chem. Int. Ed. Engl. 1985 24 1062. P. 0.Harrison affords the complexes (78) and (79) respectively which contain trigonally planar co-ordinated germanium and tin.lS9 3 Nitrogen Strong Lewis acids which are also good fluoride-ion acceptors such as AsF or SbF, strongly catalyse an intramolecular redox reaction in difluoroamino com- pounds such as CF,NF, SF5NF2 ClNF, CF30NF2 and SF50NF2 to give a variety of products.In the C1NF2-AsF5 system a thermally unstable intermediate is formed at -78"C identified as the adduct C1NF2.A~F5.'90 Hydrazine is oxidized by hot nitric acid in a first-order reaction to produce N2 N20 HN3 and NH4+. The data are consistent with a reaction mechanism that involves HN3 HN02 and the N,H2 free radical as intermediates and N, N20 and NH4+ as products. The reaction is also catalysed by Fe3+ where reduction of Fe3+ is reduced to Fe2+ by hydrazine and the converse oxidation reaction by nitric acid.'" The reaction of nitric oxide with hyponitrous acid in the gas phase occurs both with and without a chain inhibitor (ethan~l).''~ Electrochemical studies have demonstrated that a rhodium wire can be used as a reference electrode in HN03-N204 mixtures.The electrode reaction NO,+ + e-+3N202 occurs on the rhodium surface. The performance of platinum is similar but slightly inferior. With this reference system it has been shown that the corrosion of stainless steels occurs by a transpassive breakdown which may be prevented by cathodic polarization or by the addition of fluoride or phosphorus(v) fluoride. The results are consistent with the fluoride functioning as an anodic film-forming inhibit~r.'~ 4 Phosphorus and Arsenic [Bis(trimethylsilyl)methylene]mesitylphosphine (80) has been prepared by dehy- drohalogenation of MesP(Cl)CH(SiMe,) using DBU.The compound undergoes addition and oxidation reactions characteristic of a polar P=C bond. Thus (81) and (82) are obtained on reaction with respectively methanol and methy1-lithi~m.l~~ The novel phosphines (CHF,),P (CHF,),PI and CHF2P12 have been synthesized in high yields from P4 and CHF21 at 190°C and could be converted into the phosphines P,(CHF,) (CHF,)PCl (CHF2),PH CHF2PH2 and CHF2PC12. All these phosphines are far less volatile than the CF analogues and a CH. .F bonding 189 G. Huttner U. Weber B. Sigwarth 0. Scheidsteger H. Lang and L. Zsolnai J. Organomet. Chem. 1985 282 331. 190 K. 0.Christie W. W. Wilson C. J. Schack an3 R. D. Wilson fnorg. Chem. 1985 24 303. 191 D.G. Karraker Inorg. Chem. 1985,24 4470. 192 M. J. Akhtar F. T. Bonner and M. N. Hughes Znorg. Chem. 1985,24 1934. 193 P. G. Cheeseman M. F. A. Dove R. C. Hibbert W. Logan and P. J. Boden J. Cfiem. SOC.,Dalton Trans. 1985 2551. 194 Z. M. Xie P. Wislan-Nelson and R. H. Nelson Organomeiallics 1985 4 339. C,Si Ge Sn Pb; N P As Sb Bi OMe Me I I R-P-CH(CiMe,)z [R-P C(SiMe3)z] Li+ Me Me interaction wa5 suggested to occur.195 The first resolution of an enantiomeric phos- phorus triester P (OPh)(OC6H4C1-p)(OC6H4Me-p), has been reported. When pure the compound is remarkably stable towards substituent exchange^.'^^ The first tris(methy1ene)phosphate ion (83) in which the central [PC,] is planar and the CPC bond angles are almost identical has been prepared according to Scheme 15.19’ The stability of a cubic form of P8 has been investigated by ab initio SCF [Li(THF)J+ Scheme 15 calculations using both double and double + d basis sets.Ps is calculated to be 26 kcal mol-’ less stable than 2P4.’98He-I photoelectron spectra and MIND0/3 calculations have been reported for the three cage compounds (84)-( 86) with the nortricyclane skeleton. The highest molecular orbitals in all three compounds are the e and a linear combinations of the lone pairs centred at the [X,] unit.’99 The proton affinities of phosphabenzene and arsabenzene have been determined by ion 195 A. B. Burg Inorg. Chem. 1985 24 3342. 196 H. P. Abicht J. T. Spencer and J. G. Verkade Inorg. Chem. 1985 24 2132. 197 R.Appel E. Gaitzsch and F. Knoch Angew. Chem. Znt. Ed. Engl. 1985 24 589. 198 G. Trinquier J. P. Daudey and N. Komiba J. Am. Chem. Soc. 1985 107 7210. 199 R. Gleiter H. Koppel P. Hoffmann H. R. Schmidt and J. Ellermann Inorg. Chem. 1985 24 4020. 138 P. G. Harrison cyclotron resonance to be 195.8 and 189.3 kcal mol-' respectively (cf 219.4 kcal- mol-' for pyridine). Protonation of phosphabenzene occurs at the phosphorus atom whereas arsabenzene is protonated at carbon.200 Although neither PPh nor AlC& alone reacts with PCl, together they effect the reductive cleavage of PCl with the formation of a chlorophosphonium and the triphosphenium ion (87) (Scheme 16).The [PPh,] groups in (87) are readily replaced PCI + 3Ph3P + 2AlC1 + [Ph,-P-PPh,]+AlCI; + Ph,PCI+AlCl; (87) Scheme 16 in a stepwise manner by more basic phosphines to afford other symmetrical and unsymmetrical triphosphenium cations.201 1-t-Butyl-2-methylphosphirane(88) which in spite of the low degree of substitution is surprisingly stable has been obtained by [2 + 11 cyclocondensation of 1,2-dichloropropane and dilithium t-butylphosphide in liquid ammonia/n-hexane.202 Ph Functionalized cyclotriphosphanes of the type (Bu'P)~PX with electropositive [SnMe,] and electronegative [Cl or Br] substituents X have been prepared by various synthetic routes.203 White phosphorus reacts with o-phenylenebis(1ithium phos- phlde) to afford (89) which in the crystal (as a tris-THF solvate) comprises isolated ion pairs with the lithium co-ordinated to the central phosphorus atom.204 The condensation of bis(dich1orophosphino)methane with primary hydrazines affords a convenient method for the synthesis of 1,2,3,5-diazadiphospholes(90) containing the conjugated [P=CH -P=N] unit (Scheme 1 7).205 200 R.V. Hodges J. L. Beauchamp A. J. Ashe and W. T. Chan Organometallics 1985 4 457. 201 A. Schmidpeter S. Lochschmidt and W. S. Sheldrick Angew. Chem. Int. Ed. Engl. 1985 24 226. 202 M. Baudler and J. Germeshausen Chem. Ber. 1985 118,4285. 203 M. Baudler and B. Makowka 2. Anorg. Allg. Chem. 1985 528 7. A. Schmidpeter G. Burget and W. S. Sheldrick Chem. Ber. 1985 118 3849. 205 A. Schmidpeter C. Leyh and K. Karaghiosoff Angew. Chem. Int. Ed. EngL 1985 24 124. C,Si Ge Sn Pb; N P As Sb Bi R-NH-NHI + R =Meor Ph R N-NH I \ \ +2Et,N ' R \N-N I \ Cl2P PCl2 -2HCI C1-pVp-Cl -2Et,NHCI PQ \/C (90) H2 Scheme 17 The novel structural type (91),the first bicyclo[3.2.0]heptaphosphane P7ButS is formed in about 20% yield on dehalogenation of a mixture of t-butyl(dich1oro)phos- phane and PCl with magnesium.206 Tris(trimethylsily1)heptaphosphanotricyclene (92)undergoes cleavage in the presence of triphos-nickel and -cobalt species to afford compounds with the triphosphirene unit.207 Condensation of Li3P7 with ClBdP-PBu'Cl leads to the formation-of the nonaphosphane (93).208Dilithium dihydrogentetradecaphosphide,Li2H2P14 has been obtained as an orange-red THF solvent adduct by reacting P2H with Bu"Li Li3P7 or LiH4Ps.The structure (94)is indicated by two-dimensional 31P n.m~.~'~ The similar dilithium hexadecaphosphide Lp4P-R I\ (91) R =But Li2PI6 has been obtained also as a THF solvent adduct by the disproportionation of Li2HP7 in tetrahydrofuran.210 The metaphosphate anion is extremely inert in the gas phase and undergoes no chemical reaction with either electrophiles or nucleophiles such as MeC1 HC1 H20 NH, MeCN and Me,0.211 The structures (gas-phase electron diffraction) of tri-(t-buty1)phosphine oxide and imide are such that the oxide and imide groups are sterically well protected from attack thereby accounting for their remarkable chemical and thermal stability.212 The influence of 206 M.Baudler M. Michels J. Hahn and M. Pieroth Angew. Chem. Int.Ed. Engf. 1985 24 504. 207 M. Peruzzini and P. Stoppioni J. Orgonomet. Chem. 1985 288 C44. 208 M. Baudler and W. Goldner Chem. Ber. 1985 118 3268. 209 M. Baudler R. Heumuller J. Germeshausen and J. Hahn Z. Anorg. Allg. Chem. 1985 526 7. 210 M. Baudler R. Heumuller and J. Hahn Z. Anorg. Allg. Chem. 1985 529 7. 21 1 M. Henchman A. A. Viggiano J. F. Paulson A. Freedman and J. Wormhoudt J. Am. Chem. SOC. 1985 107 1453. 212 D. W. H. Rankin H. E. Robertson R. Seip H. Schmidbauer and G. Blaschke 1. Chem. SOC.,Dafton Trans. 1985 827. 140 P. G.Harrison protonation upon 31P and 170 n.m.r. parameters of the phosphoryl compounds POCl and HP02F2 have been in~estigated.~~ The data for POCl indicate that the ability of HNO to protonate the phosphoryl group is significantly greater than would be anticipated on the basis of Hammett acidity-function measurements whereas the protonating ability of MeS0,H is as anticipated on the basis of its Hammett function and that of HP02F2 is lower than those and MeS0,H.The role of multiply bonded Group V element systems as ligands has been reviewed.214 Complexes of these and related ligands continue to provoke interest. Perhaps the most significant advance has been the synthesis of the complex (95) in which a planar [P6] unit functions as the central bridging ligand.2'5 Among the other complexes worthy of note are the phospha-alkenyl complex [( v5-C5H5)-(CO),FeP=C(OSiMes)( But)] which contains a Fe-P single bond,216 the cluster (96) which contains a [pc,-PR] bridge,217 the diphosphorus and diphosphene com- plexes of nickel (97) and (98) respectively,218 the (1,3-diphospha-allyl)cobaltcom-plex (99) (R = 2,4,6-tri-t-but~lphenyl),~'~ the cyclotriphosphane complex [Ni2(p-P,PT~~)~(CO)~] and which exists as a 1 :1 mixture of the isomers (100)and (101),220 the square-planar nickel( 11) complex (102).221Gaseous trans-Bu'P=NBu' has been generated by mild gas-phase thermolysis of its more stable [2 + 13 cyclodimer (103) and characterized by field-ionization mass spectrometry and U.V.photoelectron spectroscopy.222 Sophisticated SCF calculations for (NH)2PNH2,(NH2)2PN and But I Me &Me -. Me Me I Mo 0 I C Mo 213 R. C. Hibbert and N. Logan J. Chem. SOC.,Dalton Tranc.. 1985 865. 214 0.J.Scherer Angew. Chem. Int. Ed. Engl. 24 924. 215 0.J . Scherer H. Sitzrnann and G. Wolrnershauser Angew. Chem. int. Ed. Engf. 1985 24 351. L. Weber K. Reizig R. Boese and M. Polk,Angew. Chem. int. Ed. Engf. 1985 24 604. J. Bonn G. Huttner and L. Zsolnai Angew. Chem. Znt. Ed. Engl. 1985 24 1069. H. Schafer D. Binder and D. Fenske Angew. Chem. Int. Ed. EngL 1985 24 522. R. Appel. W. Schuhn and F. Knoch Angew. Chem. Int. Ed. Engf. 1985 24 420. M. Baudler F. Salzer J. Hahn and E. Darr Angew. Chem. Int. Ed. Engl. 1985 24 415. R. A. Jones M. H. Seeberger and B. R. Whittlesey J. Am. Chem. SOC.,1985 107 6424. S. Elbel A. Ellis E. Niecke H. Egsgaard and L. Carlsen J. Chem. SOC.,Dalton Trans. 1985 879. 216 217 218 219 220 221 222 C,Si,Ge Sn Pb; N P As Sb Bi Pr I Pr' co Bu'Bu' But P-P BU~-P-N-BU~ the dimer P2N6Hs have been reported.Computed geometries are in excellent agree- ment with experiment where comparisons are possible. On the highest level of theory (NH)2PNH2 was found to be 22 kcal mol-' lower in energy than its isomer (NH2)2PN but dimerization to P~N~Hs is exothermic by 45 kcal mol-'. Electroni-cally the phosphorus is best considered as P+ in all three compounds.223 The structures of a large number of both linear and cyclic phosphazenes have been determined. Studies of the linear phosphazenes (104)-( 109) suggest different values for the bond lengths and bond angles than have been employed in the past in HH CI c1 OPh OPh NPh NPh I I I I I I O=P-N=P-Cl O=P-N=P-OPh O=P-N=P-NHPh I I I I I I c1 c1 OPh OPh NPh NPh HH (104) (105) (106) HHH c1 c1 c1 NPh NPh NPh I I I I I I O=P-N=P-N=P-Cl O=P-N=P-N=P-NHPh I I I I I I c1 c1 c1 NPh NPh NPh HHH + I f' ;1I c1 71 ] Cf-P=N-P=N-P=N-P-CI PC1,-I I c1 c1 c1 c1 (109) 223 R.Ahlnchs and H.Schiffer 1.Am.Chem. Soc. 1985 107 6494. 142 P. G. Harrison structural studies of high polymers. The P-N distances in the short-chain species differ only by 0.07 8 or less within each molecule and planar skeletal conformations especially cis,trans-planar are preferred. The data suggest that although. the molecules are stabilized by electron delocalization the conformations originate from intramolecular non-bonding interactions.224 The mean P-N bond length in the cyclic dimethylphosphazenes (NPMe,) (n = 9-12) is independent of ring size and is greater than that found in chloro- or fluoro-phosphazenes owing to the low electronegativity of the methyl group.The geometry of the [PC,] group is also independent of ring size but electronic changes within the ring cause the NPN angle to decrease steadily. The stereochemical effectiveness of the nitrogen lone pairs is reduced by their partial delocalization into &-orbitals of phosphorus so that the PNP angles are large and variable. The conformations are controlled primarily by steric interactions between the methyl groups.225 The diarsene (Me,Si),CAs=AsC(SiMe,) is isostructural with its phosphorus analogue and adopts a trans-planar conformation.226 Bis(dipheny1arsino)methane gives only a monoquaternization product with methyl iodide but it can be converted into the bis(arsonium) salt by the use of methyl flurosulphate.The monoquaternized salt is the precursor of the monoylide MePh,As=CHAsPh, whilst the first diarsorane (1 10) was prepared by treating the diquaternized salt with sodium amide.227 The first example of an arsirane (111) has been synthesized and characterized crystal- lographically. The compound is a colourless stable crystalline solid ( cJ the phos- phorus analogue which is unstable).228 Hydrogenation of 1,4-di-iodobuta-1,3-diyne -C-/C\2 -+/ \+ Ph2A<’ kAsPh2 +-+ Ph2As AsPh2 -Ph2As=C=AsPh2 II II I I Me Me Me Me Me Me (110) R R-A~J/C( Si M e3)2 C(SiMe3)2 (111) (112) R = But with di-imide gives 1(2),4(2)-di-iodobuta-l,3-diene which on treatment with n-butyl-lithium followed by phenylarsenic dichloride or phenylantimony dichloride affords 1 -phenylarsole or 1-phenylstibole respectively.229 Another ‘first’ in arsenic chemistry is the synthesis of the dodeca-arsane (1 12) the first compound containing twelve arsenic atoms by dehalogenation of a mixture of t-butyl(dich1oro)arsane with magnesium metal in boiling tetrahydrofuran.The bright-yellow crystalline 224 H. R. Allcock N. M. Tollefson R. A. Arcus and R. R. Whittle J. Am. Chem. Soc. 1985 107 5166. 225 R. T. Oakley S. J. Rettig N. L. Paddock and J. Trotter J. Am. Chem. SOC.,1985 107 6923. 226 A.H. Cowley N. C. Norman and M. Pakulski J. Chem. Soc. Dalton Trans. 1985 383. 227 H. Schmidbaur and P. Nusstein Organometallics 1985 4 344. 228 R. Appeel T. Gaitzsch and F. Knoch Angew. Chem. Int. Ed. Engl. 1985 24 419. 229 A. J. Ashe and F. J. Drone Organornetallics 1985.4 1478. 143 C Si,Ge Sn Pb; N P As Sb Bi compound decomposes at >237 "C and is stable at room temperature in the absence of light and air.230 The structures of several spirocyclic arsoranes have been deter- mined. Those of (1 13) and (1 14)exhibit a geometry very close to a trigonal bipyramid. The hydroxy derivative (1 15) is a hydrogen-bonded dimer with a geometry intermedi- ate between the trigonal bipyramid and a rectangular pyramid.231 In the phenyl series (116)-(118) the geometry at arsenic varies from a near trigonal bipyramid (116) through an intermediate geometry (1 17) to a rectangular pyramid (1 18).This order parallels the order of ring delocalization and like the similar phosphoranes the structures follow the CZVconstraint of the Berry pseudo-rotational ~o-ordinate.~~~ Diarsenic As2 can function as a four- a six- or an eight-electron ligand as in the complexes (1 19)-( 121).233 + + (115) 230 M. Baudler and S. Wietfeldt-Haltenhoff Angew. Chem. Inr. Ed. Engl. 1985 24 991. 231 C. A. Poutasse R. 0. Day J. M. Holmes and R. R. Holmes Organometallics 1985 4 708. 232 R. R. Holmes R. 0. Day and A. C. Sau Organometallics 1985 4 714. 233 G. Hutner B. Sigwarth 0.Scheidsteger L. Zsolnai and 0.Orama Organornetallics 1985 4 326.144 P. G. Harrison 5 Antimony and Bismuth A cyclohexastibine (PhSb)6.( 1 ,4-C4H802) has been obtained as yellow needles by the slow aerobic oxidation of PhSb(SiMe3) in the presence of 1,Cdioxane. Surpris- ingly the compound is inert towards oxygen although solutions rapidly precipitate white solids in air. Conversion to a brown black solid (presumably polymeric ‘phenylantimony’) occurs on warming and subsequently cooling toluene solutions. Crystals comprise centrosymmetric molecules that adopt a chair conformation with equatorial phenyl The structures of several compounds have been described and include those of four wtype complexes with antimony( 111) halides. In the 1:2 complexes of SbC13 with pyrene 2,6-dithienyl and benzo[ blthiophene the two [SbC13] moieties are arranged on opposite sides of the organic molecule whilst the two [SbBr3] moieties are on the same side of the phenanthrene molecule in the analogous 1 :2 The bidentate sulphur ligands chelate the metal in the following [Sb(tdt)]- anion (tdt = toluene-3,4-dithiolato-S,S’) (distorted octa- hedral co-ordination at antimony),237 tris-( 0-isopropy1xanthato)-antimony and -bismuth (distorted octahedral geometry for antimony is consistent with a stereochemically active lone pair seven-co-ordination for bismuth with inter- molecular sulphur bridging).238 PhSb[S2P(OPri)2]2 (square-pyramidal geometry at antimony the lone pair occupying the sixth site of an octahedron opposite the phenyl group),239 the complex SbCl,(EtNHC(S)CH,C( S)NHEt} (which has a similar geometry),240 and MeBi( S2CNEt2) (associated into dimers by sulphur bridg- ing pentagonal-pyramidal geometry at bismuth).24’ Both types of ligand chelate the antimony in the [catecholatobis-( 1,lO-phenanthroline)antimony(III)] cation.The three ligands are arranged essentially in one half of the metal co-ordination sphere indicating a strongly stereochemical active lone pair.242 Phenyl(0xadithia)- and phenyl(trithia)-stib~canes~~~ and phenyl(oxadithia)bismocane244 have inter-molecularly associated structures as well as 1,5-transannular 0,s-metal interactions. Diphenylantimony( 111) chloride and bromide are oxidized by t-butyl hydroperoxide to soluble products ’shown by crystallography for the bromide to be dimeric [Ph,SbBrO] and to contain a central four-membered [Sb202] ring.245 Tetraphenylstibonium benzenesulphonate has a distorted trigonal-bipyramidal geometry with an unidentate sulphonate group.The Sb-0 bond is rather 5-Aza-2,8-dioxa-3,7-di-t-butyl-l-stibabicyclo[3.3.0]octa-3,6-diene (122) has a planar monomeric structure and reacts with hexafluorobiacetyl and hexafluoro-2- 234 H. J. Breunig K. Haberle M. Drager and T. Severengiz Angew. Chem. Znt. Ed. Engl. 1985 24 72. 235 D. Mootz and V. Handler 2. Anorg. Allg. Chem. 1985 521 122. 236 L. Korte A. Lipka and D. Mootz 2. Anorg. Allg. Chem. 1985 524 157. 237 J. M. Kisenyi G. R. Willey M. G. B. Drew and S. 0. Wandiga J. Chem. SOC.,Dalton Trans. 1985,69. 238 B. F. Hoskins E. R. T.Tiekink and G. Winter Znorg. Chim. Acta 1985 99 177. 239 R. K. Gupta A K. Rai R. C. Mehrotra V. K. Jain B. F. Hoskins and E. R. T. Tiekink Znorg. Chem. 1985 24 3280. 240 J. M. Kisenyi G. R.Willey and M. G. B. Drew J. Chem. SOC. Dalton Trans. 1985 1073. 24 I M. Wieber D. Wirth J. Metter and C. Burschka 2.Anorg. AIIg. Chem. 1985 520 65. 242 F. Huber H. Preut G. Alonzo and N. Bertazzi Znorg. Chim. Acta 1985 102 481. 243 H. M. Hoffmann and M. Drager J. Organomet. Chem 1985,295 33. 244 M. Drager and B. M. Schmidt J. Organomet. Chem. 1985,290 133. 245 D. M. Wesolek D. B. Sowerby and M. J. Begley J. Organomet. Chem 1985 293 C5. 246 R. Ruther F. Huber and H. Preut J. Organomet. Chem. 1985 295 21. 145 C,Si,Ge Sn,Pb; N P,As Sb Bi -+N-Sb F,CC-CCF CF3 CF3 butyne to afford the 1 :1 adducts (123) and (124) respectively.247 The bismuth atom in the related tris-(4-aza-l,7-dioxa-2,6-di-t-butylhepta-2,5-dien-1,4,7-triyl)bismuth (125) is nine-co-ordinated with a face-capped twisted trigonal-prismatic geometry.248 1,6-Distibatriptycine (126) has been synthesized by heating a mixture of antimony powder and ortho-phenylmercury trimer in a sealed evacuated Bis(dipheny1-bismuthino)methane (Ph2Bi)2CH2 has been synthesized from Ph2BiNa and CH2C12.With phenyl-lithium (Ph2Bi)2CH2Li which has a half-life of ca. 34 min at 25 "C is produced:250 The tris-antimony-nortricyclane (127) has been obtained by the reduc- tion of MeC( CH2SbC12)3 with sodium and forms pentacarbonyl-chromium -molyb- denum and -tungsten complexes (128) with M(CO)S.THF (M =Cr Mo or W).25' Me I C /\ HZC I CHz /CH2-Sb I\ I cH21 Me-C-CH2-I/Sb-M-(CO)5 Sp-\-,Sb \ Sb CH2-Sb (127) (128) 247 C.A. Stewart R. L. Harlow and A. J. Arduengo J. Am Chem. SOC.,1985 107 5543. 240 C. A. Stewart J. C. Calabrese and A. J. Arduengo J. Am. Chem. SOC.,1985 107,3397. 249 N. A. A. Al-Jabar D. Bowen and A. G. Massey J. Orgonomet. Chem 1985,295 29. 250 T. Kauffmann F. Steinseifer and N. Klas Chem. Ber. 1985 118 1039. 25 1 J. Ellermann and A. Veit .IOrganomet. Chem. 1985 290 307. P. G. Harrison Several other complexes with transition-metal systems have also been reported. The reaction of (Me3Si),CHSbC12 with Na2[Fe(CO),] affords a mixture of the distibene complex (129) and the 'closed' stibidene complex (130) both characterized by crystallography.Further reaction of (129) with Fe2(C0)9 also produces (130) as well as an unstable complex believed to be an :open' isomer of (130) and an iron-antimony cluster [{ Fe(CO),},{ (Me3Si)2CHSb)2].252 The complex Bi2Fe2(CO) has a central trigonal-bipyramidal [Bi2Fe3] core in which the bismuth atoms occupy the axial positions. Each iron carries three terminal carbonyl The stibino complexes (C,H,)(CO),M-Sb(Bu')Cl (M = Mo or W) readily disproportionate in solution to the complexes [(C,H,)(C0),MI2SbC1 and Bu'S~C~.~,~ The stibinidene complexes [(OC),M],SbR form the stable 1 1 adducts (131) with base.255*256 ,C H (SiMe3)2 (Me3Si),HC Fe(C0)4 '\ / \ 7\ Sb-Sb (C0)4Fe-Fe(C0)4 252 A.H. Cowley N. C. Norman M. Pakulski D. L. Bricker and D. H. Russell J. Am. Chem. Soc. 1985 107 8211. 253 M. R. Churchill J. C. Fettinger and K. H. Whitmire J. Organomet. Chem. 1985 284 13. 254 R. Schemm and W. Malisch J. Organomet. Chem. 1985 288 C9. 255 U. Weber G. Huttner 0. Scheidsteger and L. Zsolnai J. Organomet. Chem. 1985 289 357. 256 S. Sigwarth U. Weber L. Zsolnai and G. Huttner Chem. Ber. 1985 118 3114.