10 Organometallic Chemistry By A. J. DEEMING Department of Chemistry University College London London WClH OAJ and J. EVANS Department of Chemistry The University Southampton SO95NH This chapter covering the literature received between January and December 1978 is divided into two parts. In the first one 0-bonded carbon ligands are of primary interest whilst in the second the complexes of q-bonded ligands are classified according to their hapticity. Some general items are presented below. A new system of designation of co-ordination sites has been presented in which the letter s1 is used to define co-ordination." Texts of the plenary lectures of the 8th International Conference on Organometallic Chemistry at Kyoto in September 1977 have been publishedb and papers produced at a workshop on homogeneous catalysis at Shiga Japan in 1977 are also available.' Reviews on the following have appeared matrix isolation studies on transition metal carbonyls,d use of organo-aluminium compounds in organic synthesis,' reactions of electrophiles with tran- sition metal alkyls,' organo-lanthanide complexes,g olefin metathesis," clusters' and their rearrangements and relation with surface science,k the formation of ally1 and diene complexes from cyclopropyl alkenes,' the organometallic and other chemistry of multiple metal-metal bonded compounds,m and catalytic aspects of pentamethylcyclopentadienyl-rhodiumand -iridium complexes." a G.J. Leigh Inorg. Chem. 1978 17 2047. Pure Appl. Chem. 1978,50,1-64 and 677-742. Y.Ishii and M. Tsutsui Fundamental Research in Homogeneous Catalysis Vol. 2 Plenum Press 1978. J. K. Burdett Coord. Chem. Rev. 1978,27 1. ' H. Yamamoto and H. Nozaki Angew. Chem. Internat. Edn. 1978,17 169. M. D. Johnson Ace. Chem. Res. 1978,11 57. 'T. K. Marks Prog. Inorg. Chem. 1978,24 51. R. H. Grubbs Prog. Inorg. Chem. 1978,24 1. ' H. Vahrenkamp Angew. Chem. Internat. Edn. 1978 17 379; G. Schmid ibid. 1978 17 392. E. Band and E. L. Muetterties Chem. Rev. 1978,78,639. 'E. L. Muetterties Angew. Chem. Internat. Edn. 1978 17 545. ' S. Savel Ace. Chem. Res. 1978,11 204. F. A. Cotton Ace. Chem. Res. 1978,11,225;M. H. Chisholm and F. A. Cotton ibid. 1978,11,356,and M. H. Chisholm Trans. Met. Chem. 1978 3 321. P. M. Maitlis Ace. Chem. Res. 1978 11 301.311 A. J. Deeming and J. Evans Part I Alkyls Aryls Carbonyls Cyanides Carbenes Carbynes By J. Evans 1 Metal Carbonyls Mononuclear Carbonyls.-Calorimetric measurements on the carbonyl complexes M(C0)4L2 and M(CO)3L3 (M = Cr Mo or W; L = py or MeCN) have been used to estimate the M-L bond enthalpies.' The DMM-= values increase along the series NCMe < py < CO the total differences being of the order of 10-20 kJ mol-'. Calculation of the proton affinity of (MeC,H,)Mn(C0)3 (825f 8 kJ mol-I) was possible from ion cyclotron resonance equilibrium measurements.' Although Fe(CO)5 has no permanent dipole moment it appears to have one at microwave frequencies and this is thought to arise from a square pyramidal i~omer.~ Data obtained from this dielectric relaxation study indicate an 8 kJ mol-' activation energy to pseudorotation.There has been an extensive vibrational study of single and mixed crystals of metal carbonyl complexe~.~ Intermolecular coupling between vco vibrations was absent in W(CO)(PhCCPh)3 but was evident for at least some such modes in more complicated examples. Resonance Raman excitation profiles have been particularly useful in resolving and assigning MLCT electronic absorptions in Mo(CO) complexes of unsaturated bidentate nitrogen donor ligands e.g. diazabutadienes and pyridine-2- ~arbaldehydeimines.~Electronic properties have also been studied by u.v.~ and X-ray7 photoelectron spectroscopy. Deductions of CT donation and T acceptance abilities of PX3 ligands are in line with electronegativity arguments.The shape of the 01,peak of the X-ray p.e.s. spectrum of Fe(CO)5 vapour appears to consist of two overlapping curves with the axial and equatorial peaks being separated by 0.8 eV:7a the axial oxygens have the higher binding energy. Spectra of Group VI hexacar- bonyls and their derivatives have satellites due to electron shape the most prominent of which were assigned as MLCT transitions for the M(C0)6 species.7c ' F. A. Adedeji J. A. Connor C. P. Demain J. A. Martinho-Simoes H. A. Skinner and M. T. Z. Moattar J. Organomefallic Chem. 1978,149 333. ' J. Fernando G. Faigle A. M. Da Costa S. E. Galembeck and J. M. Riveras J.C.S.Chem. Comm. 1978 126. E.N.Di Carlo and E. P. Zurback J. Arner. Chem. Soc. 1978 100 3959.44D. N. Kariuki and S. F. A. Kettle Inorg. Chem. 1978 17,41. 4b D. N.Kariuki and S. F. A. Kettle Inorg. Chem. 1978 17 1018. 4c D. N.Kariuki and S. F. A. Kettle J.C.S. Dalton 1978,262. 4dM,Arif S. F. A. Kettle and C. C. Tso Inorg. Chim. Actu 1978,31 191. 4c S. L.Barker L. Harland and S. F. A. Kettle Inorg. Chim.Acra 1978 31 217. 4fS.L. Barker L. Harland S. F. A. Kettle andF. F. S. Stephens Znorg. Chim. Acfa 1978 31 223. '"R. W.Balk D. J. Stufkens and A. Oskam J.C.S. Chem. Comm. 1978 1016. 5bL.H.Stahl D. J. Stufkens and A. Oskam Znorg. Chim. Am 1978,26,255. ''R.W.Balk D. J. Stufkens and A. Oskam Inorg. Chim. Acfa 1978 28 133. ""H. Daamen and A. Oskam Inorg. Chim. Acfa 1978 26 81. 6bL.W.Yarbrough 111 and M. B. Hall Znorg. Chem. 1978 17 2269."M. A. Ukimer and M. Lattman Inorg. Chem. 1978 17 1084. "dH. Daamen G. Boxhoorn and A. Oskam Znorg. Chim. Acfa 1978,28,263. "'A. Flamini E. Semprini F. Stefani,G. Cardaci G. Bellachioma and M. Andreocci J.C.S. Dalton 1978 695. 7aS. C. Avanzino W. L. Jolly P.-A. Malmquist and K. Siegebahn Inorg. Chem. 1978 17,489. "H. Binder and D. Sellman 2.Nuturforsch. 1978,33b 173. 7c G. M.Bancroft B. D. Boyd and D. K. Crober Inorg. Chem. 1978,17 1008. Organometallic Chemistry 313 The first stable amine carbonyl complexes of Cu have been synthesized.* [Cu(dien)(CO)] BPh has a distorted tetrahedral co-ordination geometry (Cu-C = 177.6 pm) and in the ethylenediamine analogue [Cu(en)(CO)]BPh4 (Cu-C = 180.6 pm) the fourth co-ordination site is occupied by a weak interaction with two carbon atoms of one of the rings in the BPh4 moiety.Treatment of trans-M~(N,)~(dppe)~ with benzyl propionate givesrise to trans-Mo(N2)(CO)(dppe) which reversibly loses N2 to form the 16-electron species M~(CO)(dppe)~.~ This square pyramidal complex has an apical carbonyl and there is a secondary interaction with an ortho-hydrogen of one of the ligand phenyl groups. New synthetic routes to substituted carbonyl cations have been reported,loa some of which are shown in Scheme 1. Formation of the strong Lewis acids [(CsH5)M(C0)3]' (M =Mo or W) by hydride abstraction with CPh3+ is notewor- thy.lob This carbonium ion will also abstract alkyl groups from RMn(C0),PPh3 derivatives to give synthetically useful solvated cations."' (CSHS)M(C~)~C~ [(CSHS)M(CO),(N~H~)I+ lPR3 [(CsHs) M(CO)&I+ T" (CSHS)M(C0)3HCPh3+h [(C,Hs) M(C0)31+ L =PR3 C2H4 CHzClz (CsHs)M(CO),H; M =Mo W.Scheme 1 New quantitative syntheses of metal carbonylate anions have been reported by cleavage of dimers with KH"O and reaction of Fe(CO) with K[BU~~BH]."~ The latter synthesis affords pure K,Fe(CO) uia the formyl complex (HCO)Fe(CO),-. The highly reduced anions Na,M(CO) (M =Cr Mo or W) have been synthesized.'* These insoluble salts have two very low frequency vco i.r. absorptions at ca. 1680cm-' and 1470cm-' thought to be due to M-C-0-Na interactions. Such interactions have been identified for NaCo(CO) in the crystal of [C~(salen)]~NaCo(CO),thf'~~ Ion pair formation has been found and in ~ol~tion~.~~~ to catalyse 13C0 incorporation into HFe(CO),-; this reagent has been exchanged onto the Amberlite A-26 resin and this simplifies purification procedures when using it to synthesize aldehydes from alkyl halides.14' 8aM. Pasquali F. Marchetti. and C. Floriani Inorg. Chem. 1978,17 1684. "M. Pasquali C. Floriani and A. G. Manfredotti J.C.S. Chem. Comm. 1978,921. M. Sato T. Tatsurni T. Kodama M. Hidai T. Uchida and Y. Uchida J. Amer. Chem. Soc. 1978,100 4447. IoaM.J. Nolte and R. H. Reirnann J.C.S. Dalton 1978 932. lobW.Beck and K. Schloter 2.Naturforsch. 1978 33b 1214. lo' P. J. Harris S. A. R. Knox R. J. McKinney and F. G. A. Stone J.C.S. Dalton 1978 1009. 'la K.Inkrott R. Goetze and S. G. Shore J. Organometallic Chem. 1978,154,337.'Ib J. A.Gladysz and W. Tam J. Ore. Chem. 1978,43,2279. l2 J. E.Ellis C. P. Parnell and G. P. Hagern J. Amer. Chem. SOC.,1978,100,3605. 13"G. Fachinetti C. Floriani P. F. Zanazzi and A. R. Zanzari Znorg. Chem. 1978,17 3002. 136 W.F.Edgell S. Hegde. and A. Barbetta J. Amer. Chem. SOC.,1978,100 1406. 14aM.Y.Darensbourg D. J. Darensbourg and H. L. C. Barros Inorg. Chem. 1978,17,297. 14bG. Cianelli F.Monescalchi A. Urnani-Ronchi and M. Panunzio J. Org. Chem.. 1978 43 1598. 3 14 A. J. Deeming and J. Evans Substitution of the organic ligand in C9H10Mo(C0)3(13CO) by several ligands e.g. PPh3 SbPh3 occurs stereospecifically (Scheme 2)? This may be due to the basal site preference of L in the MO(CO)~L intermediate and accordingly if L=CO [or P(OMe)3] there is 13C0 scrambling.Fenske-Hall molecular orbital calculations have been used to follow CO dissociation from MXI(CO)~' and Mn(CO),X (X = H or Br).l6 cis-Labilization effects arise from stabilization of the unsaturated intermediate rather than any interactions in the reactant. l80incorporation into neutral metal carbonyls from aqueous Na"0H has been activated by phase-transfer catalysis using Bun4NI.l7 Scheme 2 The (C,H,)V(CO),' radical anion has been shown to be involved in reduction of alkyl halides by (C,H,)V(CO)3H-.'8 Rates of CO substitution of (C,H,)W(CO),H are non-reproducible and occur photochemically with a quantum yield of >30.19 Small amounts of (CSH5)2M2(C0)6increase the quantum yield and the (C,H,)W(CO); radical is thought to be the chain propagator.Mn(C0); has been generated by pulse radiolysis of Mn,(CO), and Mn(CO),X (X = Br or I)20aand the more stable Mn(C0),(PBu3)~ by extended U.V. irradiation of substituted dimers.206 A number of 17-electron complexes of Groups VI and VII substituted carbonyls have been synthesized by chemical and electrochemical oxidation.21 They are markedly more reactive than their 18-electron counterparts with respect to iso- merization and CO labilization. The effectiveness of CO factored force fields in studying isotopically enriched matrix-isolated metal carbonyls has been discussed,22 and full reports of the photo- chemistry of M(CO) in matrices have been pre~ented.~ Matrix adducts of M(CO) are formed. Polarized photolysis of Ar--MO(CO)~ in Ar-N2 matrices leaves it oriented because of dichroic photodepletion; this does not occur for N2Mo(C0)5.Reorientation to positions less favourable to absorption is thought to involve an Is D. J. Darensbourg and A. Salzer J. Amer. Chem. SOC.,1978. 100,4119. l6 D. L. Lichtenberger and T. L. Brown J. Amer. Chem. Soc. 1978,100,366. '' D. J. Darensbourg and J. A. Froelich J. Amer. Chem. SOC.,1978,100,338. R. J. Kinney W. D. Jones and R. G. Bergman J. Amer. Chem. SOC.,1978,100,635. l9 N. W. Hoffman and T. L. Brown Znorg. Chem. 1978,17,613. W.L. Watz 0.Hackelberg L. M. Dorfman. and A. Wojcicki J. Amer. Chem. SOC.,1978,100 7259. 'Ob D. R. Kidd C. P. Cheng and T. L. Brown J. Amer. Chem. Soc. 1978 100,4103. "OA. M. Bond B. S. Grabaric and J. J.Jackowski Znorg. Chem. 1978,17,2153. 21b A. M. Bond B. S. Grabaric and Z. Grabaric Znorg. Chem. 1978,17 1013. 'Ic A. M Bond R. Colton and M. E. McDonald Znorg. Chem. 1978,17,2842. 22 J. K. Burdett M. Poliakoff J. A. Timney and J. J. Turner Znorg. Chem. 1978,17,948. 23 J. K. Burdett J. M. Grzybowski,R. N. Perutz M. Poliakoff J. J. Turner and R. F. Turner Znorg. Chem. 1978,17,147; J. K. Burdett A. J. Downs G. P. Gaskill M. A. Graham J. J. Turner and R. F. Turner ibid. 1978 17 523. Organometallic Chemistry 315 internal rearrangement of the M(CO)5 frzgment via a trigonal bipyramidal isomer. Ab initio calculations on Cr(C0)5 predict a 'AI(C4")ground state with a 3A;(D3h) state 38 kJ mol-' higher in energy.24 The electronic absorption at -500 nm was attributed to a 'A1+'E transition and should be very sensitive to the matrix environment.The primary process in the photosubstitution of Cr(C0)6 has been assigned as a 1Ale+3T1gtransition (366 nm light) and loss of dissociation efficiency from 100% must be due to radiationless decay.25 Cr(CO),(NO) has been observed as an intermediate in the photochemical reactions sequences between Cr(C0)6 and Cr(N0)4.26 CO dissociation was considered to be the first step in the photo- substitution and -oxidation reactions of Mn(C0)5-;27" the quantum efficiency of the loss of W(CO),X- (X =Br NCO or N3) in CO saturated CHCl was found to vary by 300% with different co~nter-ions.~~~ 1.r. laser irradiation has been used to study change in 13C180 enriched Fe(CO) in a nitrogen matrix.28 A solution of Fe(CO)5 and metal hydroxides in alcohols catalyses the water-gas shift reaction.29a Fe(CO)5 and HFe(CO),- were identified under a high CO pressure at 60 "C and room temperature respectively; formyl complexes were not observed.The salt [HPt(CO)PPr',),]OH has been observed in the catalysis system involving Pt(PPri3) in HCo(CO) has been found to catalyse the H2 reduction of CO to methanol and methyl f~rrnate,~'" and some ruthenium systems which contain [RuI,(CO)~]- in solution catalyse the conversion of MeOAc and even Me20 into EtOAc in the presence of CO (150 atm);306 this last step requires a small pressure of H2 (3-5atm). Small amounts of CH and C2H6 have been detected from the reduction of a co-ordinated CO group in (C5H5)NbH(CO) with hydr~gen.~" Spectroscopic studies on the W(CO)5PR3 AlBr3 metathesis catalyst system indicate that a solvated W(C0),PR3 species is formed via Br3Alt OCW(C0)4PR3.31"O2oxidation then gives rise to W(C0)4Br2.This kind of catalyst system shows stereoselectivity unusual for rnetathesi~.~'~ Selectivity decreases with increasing size of R in cis-and trans-RCH=CHMe. Steric interactions in the formation of the olefin carbene complex must be important rather than those within the metallacyclobutane ring. Dinuclear Carbony1s.-Light induced calorimetry has been used to measure the normal reaction enthalpy for the cleavage of Re2(CO), by 12;32the Re-Re bond 24 P. J. Hay J. Amer. Chem. SOC.,1978 100 241 1. 25 J. Nasielski and A. Colas Inorg. Chem.1978,17 237. 26 S.K.Satika B. I. Swanson 0.Crichton and A. J. Rest Inorg. Chem. 1978 17 1737. 27aR. A. Faltynek and M. S. Wrighton J. Amer. Chem. Soc. 1978,100,2701. 27b R.M. Dahlgren and J. I. Zink J.C.S. Chem. Comm. 1978,863. 28 B. Davies A. McNeish M. Poliakoff M. Tranquille and J. J. Turner J.C.S. Chem. Comm. 1978,36. 29aR. B. King C. C. Frazier R. M. Hanes and A. D. King jun. J. Aqer. Chem. SOC.,1978,100,2985. 29b Y. Yoshida Y. Ueda and S. Otsuka J. Amer. Chem. Soc. 1978 100 3941. 30aJ. W.Rathke and H. M. Feder J. Amer. Chem. SOC..1978,100,3623. 30b G.Braca G. Sbrana G. Valentini G. Andrich and G. Gregorio J. Amer. Chem. Soc. 1978,100,6238. 30c J. A. Labinger K. S. Wong and W. R. Scheidt J. Amer. Chem. SOC.,1978,100,3254. 31aY. Ben Taarit J.L. Bilhou M. Lecomte and J. M. Basset J.C.S. Chem. Comm. 1978,38;J. L.Bilhou A. K.Smith and J. M. Basset J. Organometallic Chem. 1978,148 53. 31b M. Lecomte J. L. Bilhou W. Reimann and J. M. Bassett J.C.S. Chem. Comm. 1978 341. 32 A. W. Adamson A. Vogler. H. Kunkely and R. Wachtor. I. Amer. Chem. SOC..1978,100 1298. 316 A. J. Deeming and J. Evans strength is very much less (218 kJ mol-') than twice the Re-I one. Photodis-sociation of Re2(CO)lo with a 300 nm laser only involves Re-Re cleavage.33 It was estimated that 3 of the available energy (126 kJ mol-') was retained as internal energy in the photofragments. A comparison of the AH' values for homolytic fission of series of Mn2(CO)lo-nL and [CO(CO)~L]~ complexes has been made with the energy of the u+u+ electronic tran~ition.~~ values are substantially smaller AH' and reflect a steric weakening of the metal-metal bond especially for PCy complexes as well as substituent electronic effects.CO~(CO)~ has been found to exist as a mixture of the bridged and two non-bridged forms in solution and frozen The two non-bridged forms have D3dand D2d symmetries with the latter being the high-temperature form. Bridging hydride ligands have been located in a number of crystallographic studies on dinuclear carbonyl~.~~ The different scattering properties of neutrons and X-rays can lead to an apparent discrepancy between the two methods. The electron density maximum of the bridging hydride in Mo~(C,H,)~(CO),(~-H)(~-PM~,) is 0.2 A closer to the Mo-Mo axis than !he centre of nuclear density leading to a shrinkage in the Mo-H distance (by 0.07 A) and a widening of the Mo-H-Mo angle (by 11") in the X-ray Electron deformation densities have been measured by combined X-ray and neutron diffraction measurements on tran~-[(C,H,)Fe(Co)~J~ at low temperatures.37a There are no significant residues along the Fe-Fe axis.Ab initio calculations reproduce the deformation density in this complex.37b A Mulliken overlap population of -0.05 was calculated for the Fe-Fe interaction and it is apparent that a delocalized multicentre picture is better than a simple metal-metal bond when there are bridging ligands present. There has been some discussion about the binding of the bridging carbonyl in Pd' and Pt' dimer~.~~ The CO stretching frequency in Pt2C12(p-CO)(p-dppm)2 is 1638 cm-' suggesting that the ligand may be acting as a four-electron donor as in (l).38a This proposal has been countered with the suggestion that the ligand acts as a a-I \ \ /Ph,P-/-PPh2 two-electron donor-bridging a long metal-metal distance !s the Pd dimers3" [Pd2C12(p-CO)(p-dpam)2 (2) has a Pd-Pd distance of 3.274 A38c1; CO stretching 33 A.Freedman and R. Bersohn J. Amer. Chem. SOC.,1978,100.4116. 34 R. A. Jackson and A. J. Pk Inorg. Chem. 1978,17,997,2330. 35 D. L. Lichtenberger and T. L. Brown Inorg. Chem. 1978,17 1381. 36aH.B. Chin and R. Bau Inorg. Chem. 1978,17,2314. 36b J. L. Peterson P. L. Johnson J. O'Conner L. F. Dahl and J. M. Williams ibid. 1978 17 3460. 36c J.L. Peterson and J. M. Williams ibid. 1978,17 1308. 37rA.Mitschler B. Rees and M. S. Lehman J. Amer. Chem. SOC.,1978,100,3390. 37bM.Bknard ibid. 1978,100,7740. 38aM. P. Brown R. J. Puddephatt M. Rashidi and K. R. Seddon J.C.S. Dalton 1978 1540. 3*bL.Benner and A. L. Balch J. Amer. Chem. SOC.,1978,100,6099. 38c R. Colton M. J. McCormick and C. D. Pannan Ausr. J. Chem. 1978,31 1425. 317 Organometallic Chemistry Ph2AsTAsPh2 I CI C1- Pd' 'Pd -C1 I I Ph As,,AsPh (2) frequencies of -1715 cm-' were reported for the Pd2X2(p-CO)(p-dppm)2 series. The bridging ligand in these dimers at which the Pd-C-Pd angle is 119",has been termed a dimetallated f~rmaldehyde.~~'' Rh' and Ir' dimers have been synthesi~ed.~~ The Rh-Rh distance in (3) is 2.841 8 and the complex participates in a rapid dynamic equilibrium with (4).+ Ph,P /\PP LC1\l-I P,I 'h2 L ,Rh-\ ,Rh,CO -OCIC I The synthesis of (C5H5)2M02(C0)4 has been by thermolysis of (C5H5)2M~Z(C0)6 shown to involve (C5H5)M~(C0)3 The Mo-Mo distance (2.448 8,)is larger than other triple bonded complexes and an interaction between the CO and Mo2 7r systems is This complex forms addition products with soft nucleophiles and electrophiles (I2 and HCl).40" It also reacts with PtL species to form air-sensitive trinuclear complexes (5); [(C5H5)Mo(CO),]2[p-Fe(C0)4]was also synthesized. Both heating and photolysing mixtures of (C5H5),M2(CO) (M = Mo or W) produces some mixed metal dimer~.~" The disappearance quantum yield at 350 nm of Mn2(CO)lo in the presence of PBu3 or P(OEt) is reduced by the presence of CO;41" caged radical pairs are formed by homolysis and these substitute rapidly on separating.Photolysis of the mixed metal and (C5H5)M(CO)3Fe(C5H,)(CO)2 complexes (C5H5)M(CO)3Co(C0)4 (M = Mo or W) also causes homolytic cleavage.416 Rate orders of C1 abstraction from CCl were established. D. Robinson Inorg. Chim. Acra 1978,27 L108. M. Cowie J. T. Mague and A. R. Sanger I. Amer. Chem. SOC.,1978,100,3628. 40rM.D.Curtis and R. J. Klinger J. Organometallic Chem. 1978,161 23. "*R. J. Klinger W. M. Butler and M. D. Curtis J. Amer. Chem. SOC.,1978,100 5034. *&M. H.Chisholm M. W. Extine R. L.Kelly W. C. Mills C. A. Murillo L.A. Rankel and W. W. Reichert Inorg. Chem. 1978 17 1673.41aD. R. Kidd and T. L.Brown J. Amer. Chem. SOC.,1978,100,4095. 41b H.B. Abrahamson and M. S. Wrighton J. Amer. Chem. Soc. 1978,100 1003. A. J. Deeming and J. Evans An efficient synthesis of NaHFe2(C0)8 has been rep~rted."~ This anion was demonstrated to be involved in the first step of the reduction of the olefinic bonds of LYPunsaturated systems viz. formation of Na[RCH2.CH(COR).Fe2(C0)8]. Polynuclear Carbony1s.-The bonding capabilities of transition metal clusters have been assessed by extended Hiickel calculations on ligand-free assemblies of rhodium atoms." An energy separation between the cluster valence orbitals (4d 5s and partly 5p) and high lying sets was considered to give a cut-off which governs the choice of stoicheiometry and structure of polynuclear carbonyls.New methods of treating thermochemical data of carbonyl clusters have been Metal-metal bond strengths were estimated from data on pure metals using a dependence on internuclear distance (adMM-".,) and their proportion of the total bonding energy considered to have been previously overestimated. A neutron diffraction study on H20s3(CO)lo has demonstrated that the two hydride ligands symmetrically bridge the short 0s-0s edge. (0s-H 1.850 A)."' is formed when this hydride reacts with CO~(C~)~~~~~ H3C~O~3(C0)12 and other mixed metal tetranuclear clusters found by treating it with nucleophilic metal cornplexe~."~~ [(C2H4)2PtPR3] [(C2H4)Ni(PPh3)3] MeAuPPh, and [(C2H4)2Rhacac] yielded [H2Os3Pt(C0),,(PR3)] [H20s3Ni(CO)10(PPh3)2] [HAuOs3(CO) 10(PPh3)] and [H20s3Rh(acac)(CO) respectively.Condensation of (C2H4),PtPPh3 with H20s(CO) allowed isolation of (6). Liberation of CO groups by R3N0 oxidation has been used to form substituted metal carbonyls of Mn Re and 0s."' OS~(CO)~,(NCM~)~, thus produced reacts with NEt to form equal amounts of H20s3(C0)10 and HOS,(CO)~~(~-CH-CH:NEt2).48" A similar dehydrogenated ligand has been implicated in the Rh,(CO), catalysed H-D exchange between NEt and D20.48b OS~(CO)~~(NCM~)~ also reacts with HW(CO),(C,H5) to yield the new clusters [HOS~W(CO)~~(C~H~)] 42 J. P. Collman R. G. Finke P. L. Matlock R. Wahren R. G.Komoto and J. I. Brauman J. Amer. Chem. SOC., 1978,100,1119. 43 J. W. Lauher J. Amer. Chem. SOC., 1978,100,5305.44 K. Wade Inurg. Nucl. Chem. Letters 1978,14,71; C. C. Housecroft K. Wade and B. C. Smith J.C.S. Chem. Comm. 1978,765. 45 A. G. Orpen A. V. Rivera E. G. Bryan D. Pippard G. M. Sheldrick and K. D. Rouse J.C.S. Chem. Comm. 1978,723. 46aS. Bhaduri,B.F. G.Johnson J. Lewis,P. R.Raithby,andD. J. Watson J.C.S. Chem. Comm. 1978,343. 46bL.J. Farrugia J. A. K. Howard P. Mitrprachachan J. L. Spencer F. G. A. Stone and P. Woodward ibid.; 1978 260. 47 U. Koelle J. Organornetallic Chem. 1978 155 53; B. F. G. Johnson J. Lewis and D. Pippard ibid. 1978 145 C4. 48aJ. R. Shapley M. Tachikawa M. R. Churchill and R. A. Lashewycz J. Organometallic Chem. 1978 162 C39. 48b R. M. Laine D. W. Thomas,L. W. Cary and S. E. Bottrill J. Amer. Chem. Suc. 1978 100,6527.Organometallic Chemistry 319 and [H30~3W(CO)ll(C5HS) Pyrolysis of OS~(CO)~~P(OM~) has yielded three pentanuclear products with fragmented phosphite ligands.” Two of these [HOs,C(CO)14{ OP(OMe)2}] and [HOs5C(CO)13{OP(OMe)OP(OMe)2}], have central carbides and a distorted trigonal bipyramidal Oss arrangement; the third Os5(CO)lSP(OMe) possesses a square pyramidal Oss geometry with a face bridging P(0Me) group. Extended Huckel calculations based on Fe4(C5H5)48-and Fe,(CO),;- have been used to probe hydride site preferences and the orientation of the M(CO) groups.s1 The M(CO)3 groups prefer to be staggered with respect to the Fe-Fe bonds in the second anion but there was little energy difference between possible arrangements of four added hydrogens bridging four edges in H4R~4(C0)12 (with DZdsym-rnetr~’~~); edge bridging arrangements of C3 (Ru) and C2 (Ru and 0s) were observed for the H3M4(C0)12- ions.526*c Up to three protons have been quan- titatively removed from H,RU,(CO)~~ was using KH.53” While HzR~3(C0)122- found to have three bridging carbonyl groups in solution (using 13C r~.m.r.),’~= the osmium analogue possesses terminal carbonyls only in the HOS~(CO)~S-can be alkylated on the sulphur atom to form a reactive cluster which readily forms adducts in which the thiolate ligand migrates from a p3to a p2site.’ Alkylation of HOS~(CO)~~-with MeS0,F occurs on the oxygen of the bridged carbonyl group;”” site exchange in the M(CO) group in HOS~(CO)~,(COE~) occurs in two stages suggesting a trigonal twist process.Low-temperature protonation of HFe3(C0)11- also occurs on the oxygen of the bridging CO group so H2Fe3(CO)ll has a very different structure from its osmium analogue.556 49 M. R. Churchill F. J. Hollander J. R. Shapley and D. S. Foose J.C.S. Chem. Comm. 1978 534. J. M. Fernandez B. F. G. Johnson J. Lewis P. R. Raithby and G. M. Sheldrick Acta Cryst. 1978 B34 1994;A. G.Orpen and G. M. Sheldrick ibid. 1978 B34,1992; J. M. Fernandez B. F. G. Johnson J. Lewis and P. R. Raithby J.C.S. Chem. Comm. 1978,1015. 51 R. Hoffmann B. E. R. Schilling R. Bau H. D. Kaesz and D. M. P. Mingos J. Amer. Chem. SOC.,1978 100,6088. ’*=R.D.Wilson S. M. Wu R. A. Lowe and R. Bau Znorg. Chem. 1978,17 1271. 52b B. F. G. Johnson J. Lewis P.R. Raithby and C. Zuccaro Acta Cryst. 1978 B34 3765. P. F. Jackson B. F. G. Johnson J. Lewis M. McPartlin and W. J. H. Nelson J.C.S. Chem. Comm. 1978 920. 53aK. E. Inkrott and S. G. Shore J. Amer. Chem. SOC.,1978,100 3954. 53bB. F. G. Johnson J. Lewis P. R. Raithby G. M. Sheldrick and G. Suss J. Organornetallic Chem. 1978 162 179. s4 B. F. G. Johnson J. Lewis D. Pippard and P. R. Raithby J.C.S. Chem. Comm. 1978,551, Acra Cryst. 1978 B34,3767 D. Gavens and M. J. Mays J. Organometallic Chem. 1978,162 389. 55bH. A. Hodali D. F. Schriver and C. A. Ammlung J. Amer. Chem. SOC.,1978,100,5739. A. J. Deeming and J. Evans OS~(CO)~~ reacts with ethylene and PhCCPh under forcing conditions to form OS6(C0),6(CR)2 (R = Me or Ph) derivatives (7).56 Continued reaction with C2H4 yielded OS6(C0)16(MeCCMe)C (8).One of the products of the reaction between OS~(CO)~~ and PhOH at 175-185 "C is H20~3(C0)9(OC6H4) (9; R=H) the structure of which was established by comparison with the benzyl deri~ative.~' This carbon bridged OC6H4 ligand is converted into an oxygen bridged OPh one {in HOs3(CO)l,(p2-OPh)} on treatment with CO at 140 "C. The dynamical properties of M4(CO)12(M = Co or Rh) derivatives in solution have been reported58 and an alternative approach to rationalizing these exchange proces- ses pre~ented.~~ These bridged structures possess an icosahedra of carbonyl groups and site exchange is thought to be via a cuboctahedral transition state as adopted by Ir4(CO)12.60 The symmetry restrictions outlined depend on the cuboctahedron being a transition state rather than an intermediate.The C,isomer of (C5H5)3Rh3(C0)3 undergoes a rapid intramolecular exchange process without isomerizing to the C3 structure probably involving one CO group migrating from a p2to a p3site.61 A reinvestigation of the reduction of (C5H5)2Rh(C0)2 by sodium amalgam has led to the isolation of [PPN][(C5H5)2Rh3(CO)4] (10) which possesses semi face bridging carbonyl groups.62 Extended Huckel calculations suggest that the organic ligand in CO~(CO)~CCH~+ would avoid a central position.63 CO~F~(CO)~S acts as a sulphur donor in its Cr(C0)5 It was observed that pyrolysis of ASM~~M(CO)~(C~H~) add~ct.~~ (M = Cr Mo or W) substituted tricobalt carbon clusters resulted in incorporation of the hetero transition metal centre 65a and this reaction has been used to synthesize the chiral clusters (1l).656 It is interesting in this regard that the carbide Rh12C2(C0)25 forms "T.R.Eady J. M. Fernandez B. F. G. Johnson J. Lewis P. R. Raithby and G. M. Sheldrick J.C.S. Chem. Comm. 1978,421. 56bJ. M. Fernandez B. F. G. Johnson J. Lewis and P. R. Raithby Acta Cryst. 1978 B34 3086. 57 K. A. Azam A. J. Deeming I. P. Rothwell M. B. Hursthouse and L. New J.C.S. Chem. Comm. 1978 1086. '* S. Aime L. Milone D. Osella and A. Poli Inorg. Chim. Acta 1978,30,45;J. Evans B. F. G.Johnson J. Lewis T. W. Matheson and J. R. Norton J.C.S. Dalton 1978 626. 59 B. F. G. Johnson and R. Benfield J.C.S. Dalton 1978 1554. 6o M.R. Churchill and J. P. Hutchinson Inorg. Chem. 1978,17,3528. R. J. Lawson and J. R. Shapley Inorg. Chem.. 1978,17,772. 62 W. D. Jones M. A. White and R. G. Bergman J. Amer. Chem. SOC.,1978,100,6770. 63 B. E. R. Schilling and R. Hoffmann J. Amer. Chem. SOC.,1978,100,6274. 64 F. Richter and H. Vahrenkamp Angew. Chem. Internat. Edn. 1978,17,444. 65"H. Beurich and H. Vahrenkamp Angew. Chem. Internat. Edn. 1978,17 863. 6sbF.Richter and H. Vahrenkamp ibid. 1978,17,864. Organometallic Chemistry 321 M = Cr Mo and W (11) enantiomorphous crystals.66 Treatment of tetraglyme solution of [Rh(CO),?acac] with a metal carbonylate and H2S (or SO,) under 300 atmospheres of H and CO yields a salt of [Rh17(S)2(C0)32]3-, which has an encapsulated S-Rh-S linkage within a D4d Rh16 envir~nment.~~ Two new centred polynuclear anions Rh15(C0)273-and Rh14(C0)254- have been isolated.68 While the former has a Rhls structure with hcp and bcc character the latter is a bcc fragment.Pt12(C0)242- undergoes a rapid metal exchange'with Rh12(CO)302- under CO to form the mixed metal PtRh,(CO),,- a derivative of Rh,(CO),, characterized by X-ray diffraction and 19'Pt Treatment of PtL2C12 complexes with metal carbonyl anions has yielded a number of new These include Pt2C02(CO)s(p2-CO)3(PEt3)2, Pt3C02(CO),(p2-CO),(PEt,) (trigonal bipyramidal Pt3C02 a~rangement),~~' Pt5(CO)(p2-CO)s(PR3) (edge bridged tetrahedron of Pt atom^)^" and Pd2M02(CsH5)2(p3-CO)2(p2-CO),(PEt,) (12)70d possessing a Pd-Pd bond (2.582 A).Carbonylation of P~(OAC)~ has yielded a rectangular cluster [Pd(CO)(OAc)] (13);71the CO bridged 0 66 V. G. Albano P. Chini S. Martinengo M. Sansoni and D. Strumolo J.C.S. Dalton 1978,459. 67 J. L. Vidal R. A. Fiato L. A. Cosby and R. L.Pruett Inorg. Chem. 1978,17 2574. "S.Martinengo G. Ciani A. Sironi and P. Chini J. Amer. Chem. Soc. 1978,100 7096. 69 A.Fumagilli S.Martinengo P. Chini A. Albinati S. Bruckner and B. T. Heaton J.C.S. Chem. Comm. 1978,195. 'OOJ. P. Barbier and P. Braunstein J. Chem. Research (S),1978,412. 70bJ. P. Barbier P. Braunstein J. Fischer and L. Ricard Inorg. Chim. Acra 1978 31 L361. 70c J. P. Barbier R. Bender P. Braunstein J. Fischer and L. Ricard J. Chem. Research (S),1978 230. 70d R. Bender P. Braunstein Y.Dusavoy and J. Protus Angew. Chem. Internat. Edn. 1978,17 596. 71 I. I. Moiseev T. A. Stromnova M. N. Vargaftig G. Ja. Mazo L.G. Kozima and Yu.T. Struchkov J.C.S. Chem. Comm. 1978,27. A. J. Deeming and J. Evans edges (2.663A) are substantially shorter than the acetate bridged ones (2.909A). The product of co-condensing nickel and pentane at -196 "C and subsequent warming in stages is a powder containing nickel carbon and hydrogen.72 ESCA measurements fit sp2 or sp3 carbon environments and treatment of the powder with H2or H20yields C1-C5 hydrocarbons. Pentane cleavage is thought to occur before warm up. Materials produced by pyrolysing supported Rh Ir and Pt carbonyl clusters catalyse H reduction of C0.73 Both initial cluster nuclearity and support basicity influence the product distributions with more basic supports favouring alcohols rather than hydrocarbons.Hydrocarbons are also produced on 7-A1203in the absence of hydrogen due to involvement of surface hydroxy-gro~ps.~~ Total cluster decomposition was generally observed above 250 "C;Os3(CO)1z and OS~(CO)~~ were exceptions. Water is cleaved by Ru3(CO) 12-Si02pyrolysed systems liberating H2.75 Subsequent exposure with methane liberates CO and more H,; addition of N2to the gas mixture yields NH3. The interactions between Rh6(CO), and Si02,76a functionalized silicas766 and functionalized polymers76c have been studied. Substi- tuted clusters are formed at first and subsequent aggregation of the rhodium particles was observed in the polymer system.Triosmium clusters have been anchored to silica by phosphine and bridging ethynyl ligands and characterized by i.r. comparisons with isolable analogues,77u a technique also used to establish the binding of phosphine substituted Ir4(CO)12 derivatives to -PPh2 functionalized The bridging ligand may hinder metal aggregation or breakdown. An alternative method using the terdentate M~S~(PBU~)~ ligand has been [RU~(CO)~(M~S~(PBU~)~}] was synthesized and found to have three semi-bridging carbonyl groups. 72 S. C. Davis and K. J. Klabunde J. Amer. Chem. SOC. 1978 100 5974. 73 M.Ichikawa Bull. Chem. SOC.Japan 1978,51 2268 2273; J.C.S. Chem. Comm. 1978 566. 74 A. K. Smith A. Theolier J. M. Basset R. Ugo D. Commereuc and Y. Chavin J. Amer.Chem. SOC. 1978,100,2590. 75 S. Naito and K. Tamaru J.C.S. Chem. Comm. 1978 1105. 76nJ. L.Bilhou V. Bilhou-Bougnol W. F. Graydon J. M. Basset A. K. Smith G. M. Zanderighi and R. Ugo J. Organometallic Chem. 1978 153 78. 76bH. Knozinger and E. Rumpf Inorg. Chim. Acta 1978,30 51. 76c M.S.Jarell B. C. Gates and E. D. Nicholson J. Amer. Chem. SOC. 1978 100 5727. 77aS. C.Brown and J. Evans J.C.S. Chem. Comm. 1978,1063. 77b J. J. Rafalko J. Leito B. C. Gates and G. L. Schrader jun. J.C.S. Chem. Comm. 1978 540. 77rJ. J. De Boer J. A. van Doorn and C. Masters J.C.S. Chem. Comm. 1978 1005. 323 Organometallic Chemistry 2 Carbonyl Analogues and CO Complexes The reported anions Re(CN)64- and Re(CN)s3- have been reformulated as Re(CN)74-.78a Some chalcogenide bridged polynuclear cyanides of the types [Re4(CN),,(p3-E)I4-(E = S and Se) and [Rez(CN)8(p2-S)]2- were chara~terized.'~' Fe(bip~)~(CN)~ The reduces Br03- and S2Og2-by an outer-sphere mechanis~n.'~~ rate of the second reaction in aqueous methanol decreases with increasing propor- tions of methanol and this appears to be due to a destabilization of the transition Change transfer excitation of tran~-[Pt(CN)~X~]'-(X = C1 Br or N3) promotes reductive elimination of two X radicals.80 The unstable N; radicals liberate Nz rapidly and do not recombine with the Pt atoms.The mechanisms of luminescence quenching of Cr(bi~y),~' and M(bipy),'+ (M = Ru or 0s) by cyano complexes include energy transfer e.g. CI-(CN)~~- reductive electron transfer (e.g.Fe(CN),"-) and oxidative electron transfer e.g. Fe(CN)63-.81a Solutions and salts of [RU(NH~)~~~]~+ with Fe(CN);- exhibit an outer-sphere intervalence charge transfer absorption in the near i.r.81b An extended Hiickel tight-binding scheme has been used to study the band structure in Pt(CN),'-chains.82 Partial oxidation of 0.3 electrons per Pt was found to give an energy minimum when the Pt-Pt separation was less than 3 A. This separation has a marked effect on the conductivity of these materials and depends upon the counter ions.83a Pt-Pt distances of 2.910 and 2.930 A were observed for (NH4)2[Pt(CN)4]Clo,3, 3H20 whereas in the potassium and some anhydrous separations of -2.85 A were apparent. The thiocarbonyl complexes Fe(C0)4CS84a and Fe(TPP)CSg4' have_ been synthesized using C12CS.Interaction of (CsHS)Fe(CO)z- with (PhO),CS has yielded (CSHS)zFez(CO)3(CS).8s S-alkylation of the bridging CS group occurs with OsHX( CO) ( Cs)(PPh3)25Os(CO)2X(PPh,)2(CHS) NaBH4 OS(CO)~(PP~~)Z(V 2-CHzS) OSC~~(CO)~(PP~~)~ + MeSH aOSC~(CO)~(PP~~)~(SM~) Scheme 3 78aW. P. Griffith P. M. Kiernan and J. M. Bregeault J.C.S. Dalton 1978 1411. 78bM. Laing J. M. Bregeault and W. J. Griffith Znorg. Chim. Acra 1978 26 L27. 79aJ. P. Birk and S. G. Kozub Znorg. Chem. 1978 17 1186. 79bM. J. Blandamer J. Burgess and R. J. Haines J.C.S. Chem. Comm. 1978 963. A. Vogler A. Kern B. Fusseder and J. Huttermann Z. Nafurforsch 1978 33b 1352; A. Vogler A. Kern and J. Huttermann Angew. Chem. Internat. Edn.1978 17 524. 'laA. Juris M. F. Manfrin M. Maestri and N. Serpone Znorg. Chem. 1978 17 2258. 'lbJ. C. Curtis and T. J. Meyer J. Amer. Chem. Soc. 1978,100,6284. '* M.-H. Whangbo and R. Hoffrnann J. Amer. Chem. SOC. 1978,100,6093. 83aP. L. Johnson A. J. Schulz A. E. Underhill D. M. Watkins D. J. Wood and J. M. Williams Inorg. Chem. 1978,17,839. 83b G. Hegor H. .I.Dieseroth and H. Schulz Acta. Cryst. 1978 B34 725. 83c R. K. Brown and J. M. Williams Znorg. Chem. 1978,17 2607; A. J. Schultz D. P. Gerrity and J. M. Williams Actu Cryst. 1978 B34 1673. 84aW. Preetz J. Organomelallic Chem. 1978 146 C23. 84bH. D. Mansuy J. P. Battioni and J. C. Chottard J. Amer. Chem. SOC. 1978 100,4311. R. E. Wagner R. A. Jacobson R. J. Angelici and M. H. Quick J. Organometallic Chem.1978,148 C35; M. H. Quick and R. J. Angelici ibid. 1978 160 C31. A. J. Deeming and J. Evans Meerwein reagents. A thiocarbonyl group bound to 0s has been reduced in a stepwise manner ultimately to MeSH as in Scheme 3.86 Isocyanide analogues of iron and cobalt dinuclear carbonyls have been reported. Fe2(qNEt)9 produced by photolysis of Fe(CNEt), has three bridging ligands with a CNC mean of 123°.87" Co2(CNAr) derivatives have two isocyanide bridges."' The dimers of [Rh(CNR)4]' and [Rh2{CN(CH2),NC}4]2' have been studied." A Rh-Rh distance of 3.193 A was observed in a crystal of [Rh(CNPh)4]2(BPh4)2.88c Oxidation of the p-tolyl derivative with I resulted in isolation of Rh2(CN-p-tolyl)812 the Rh-Rh separation being 2.785 Dissociation of [Ir(CNMe)4]22' in solution has been photoindu~ed.~~ While pyrolysis of OS~(CO)~ ICNBu' yielded a disubstituted derivative of OS~(CO)~~, direct interaction of the hexamer with CN-p-tolyl gave an addition compound (14) in which one isocyanide ligand is a four-electron donor.91 An alternative four electron arrangement has been observed for Mn2(dppm)2(C0)4(p2- CN-p-tolyl) in which one Mn atom bonds to the carbon atom and the other to both C and N atoms.92 Co(Pr-sa1en)K reversibly binds CO in thf solution to give the red adduct Co(Pr- ~alen)KCO~(thf).~~ The C02 ligand is carbon-bonded to the cobalt atom and the oxygen atoms interact with two K' ions.An 7' bonding mode has been observed for AgC02 prepared in an Ar-C02 matrix at -10-25 K.94 T.J. Collins and W. R. Roper J. Organometallic Chem. 1978,159 73. 870J.M. Bassett M. Green J. A. K. Howard and F. G. A. Stone J.C.S. Chem. Comm. 1978 1000. 'l6Y. Yamamoto and H. Yamazaki Inorg. Chem. 1978,17 3111. 88aV.M. Miskowski G. L. Nobinger D. S. Kliger G. S. Hammond N. S. Lewis K. R. Mann and H. B. Gray J. Amer. Chem. Soc. 1978,100,485. 886K. Kawakami M. Okajima and T. Tanaka Bull. Chem. SOC.Japan 1978,51,2327. 88c K. R. Mann N. S. Lewis H. B. Gray and J. G. Gordon 11 Znorg. Chem. 1978,17 829. 89 M.M. Olmstead and A. L. Balch J. Organometallic Chem. 1978,148 C15. 90 G. L. Geoffroy M. G. Bradley and M. E. Keeney Znorg. Chem. 1978,17,777. " C. R. Eady P. D. Gavens B. F. G. Johnson J. Lewis M. C. Malatesta M. J. Mays A. G. Orpen A. V. Rivera G. M. Sheldrick and M.B.Hursthouse J. Organometallic Chem. 1978,149 C43; A. V. Rivera G. M. Sheldrick and M. B. Hursthouse Acra Cryst. 1978 B34 1984; A. G. Orpen and G. M. Sheldrick ibid. 1978 B34 1989. 92 L. S. Benner M. M. Olmstead and A. L. Balch J. Organometallic Chem. 1978 159,289. 93 G. Fachinetti C. Floriani and C. F. Zanuzzi J. Amer. Chem. SOC., 1978,100,7405. 94 G. A. Ozin H. Huber and D. McIntosh Znorg. Chem. 1978 17 1472. Organometallic Chemistry 325 3 Alkyls Aryls and Acyls Photolysis of Li2C2 at -45°C produced a species which gave a mass spectrum attributable to Li4C4.95 Ab initio calculations indicate face-bridging sites for the Li atoms. Hydrolysis liberated acetylene rather than tetrahedrane. Inversion proces- ses of alkyl-lithiums have also been studied by ab initio calculations and it was concluded that the planar intermediate was best stabilized by an Li-Li edge.96 Inversion of silyl- and germyl-lithiums is slow having an activation energy of at least 100 kJ m01-l.~' Co-condensation of alkyl iodides with Ca Sr or Ba has yielded RMI derivative^.^^ I The reaction between Me3& C(SiMe3)SiMe2 and DMSO to give (SiMe,)C:C(SiMe3)SiMe20SiMe2 is considered to involve Me2Si0.99 The reactivity -of Me2CCMe2SiMe2 (a source of SiMe2) is modified by the presence of PPh3 suggesting the involvement of the ylide Ph3P'-SiMe2.loo Elimination of Me,SiCl from (SiMe3)2SiMeC1 at 700 "C leaves the Me,Si-SiMe moiety which dimerizes to Me2SiCH2SiH2kH2 and MeHSiCH2SiHMeCH2. lo' This fragment appears to be responsible for reactions involving Me2% SiMe2.Flash vacuum pyrolysis (-7 10 "C) of diallylsilanes provided a simple route to silacyclobutanes. lo* STO-3G ab initio calculations indicate that the resonance energy of the unstable silabenzene is 3 that of benzene;103a pyrolysis of C5H5Si(Me)(CH2CHCH2) in the presence of CF3CCCF3 yields the adduct of silatoluene (C,H,SiMe). lo3' Chloride abstraction from Me2SiC12 with Li has yielded a mixture of medium ring cyclosilanes (Me2Si) (n= 5-9);104 the penta- and hexa-silanes have large plastic crystal temperature ranges. Reduction of A1Bui3 by potassium produced a compound formulated as K2(B~i3AIAlB~i3).105 The A1Cl3 0-complexes of cyclobutadienes e.g. Me4C4AlC13 are dynamic and exchange predominantly by 1,2 AlCl shifts.lo6 Two Ar6Sn2 dimers (Ar = 2,4,6-Me&& and 2,4,6-Et3C,H2) reversibly cleave having Sn-Sn dissociation energies of 190 and 125 kJ mol-I respe~tively.'~' TCNE inserts into an Sn-R bond in R4Sn derivatives both thermally or photochemic- ally.lo' These processes follow a common electron transfer mechanism involving the charge transfer complexes (R,Sn'TCNE-).Oxidative addition reactions of PhBr to Sn[CH(SiMe3),12 or Sn[N(SiMe3),12 are catalysed by a more reactive halide e.g. 95 G. Rauscher T. Clark D. Poppinger and P. von R. Schleyer Angew. Chem. Internat. Edn. 1978,17 276. 9d T. Clark P. v. R. Schleyer and J. A. Pople J.C.S. Chem. Comm. 1978 137. 97 J. B. Lambert and M. Urdaneta-Perez J. Amer. Chem. SOC., 1978,100 157.98 B. G. Gowenlock W. E. Lindsell and B. Singh J.C.S. Dalton 1978,657. 99 D. Seyferth T. F. 0.Lim and D. P. Duncan J. Amer. Chem. SOC.,1978,100 1626. lo" D. Seyferth and T. F. 0.Lim J. Amer. Chem. SOC.,1978 100 7074. '01 W. D. Wulff W. F. Goure andT. J. Barton J. Amer. Chem. Soc. 1978 100,6236. Io2 F. Block and K. Revelle J. Amer. Chem. SOC., 1978 100 1630. '03..H. B. Schegel B. Coleman and M. Jones jun. J. Amer. Chem. SOC.,1978,100 6499. "I3*T. J. Barton and G. T. Burns J. Amer. Chem. SOC.,1978 100 5246. 104 K. Matsumura L. Brough and R. West J.C.S. Chem. Comm. 1978,1092; D. W. Larsen B. A. Soltz F. E. Stary and R. West J.C.S. Chem. Comm. 1978 1093. '(" H. Homberg and S. Krause Angew. Chem. Znternat. Edn. 1978 17 949. P. B. J. Driessen and H.Hogeveen J. Amer. Chem. SOC.,1978 100 1193. lo' H. U. Buchlaus and W. P.Neumann Angew.Chem. Znternat. Edn. 1978 17 59. lo' K. Mochida J. K. Kochi K. S. Chen and J. K. S. Wan J. Amer. Chem. SOC.,1978,100,2927. A. J. Deeming and J. Evans EtBr.'" The reaction products are solvent dependent and are thought to involve first Et' and the Ph' radicals; the latter are intercepted in THF. The first stable aryl complex of Iv has been synthesized (15) and in fact is stable indefinitely when crystalline.' lo AH;values have been measured for the M(C5H5)2Me2 complexes and the M-Me bond strengths estimated to be 149.5 and 197.8 kJ mol-' for Mo and W respec-tively.11' Preferred binding modes in C5H5X complexes have been investigated by exten- ded Huckel calculations."2 The critical factor is the energy of the e acceptor set on X.This is low for Mn(CO), favouring q5 co-ordinations but high for Me q1 co-ordination being adopted. The decreasing barrier to rotation on changing Me through SiH3 and GeH3 to SnH3was correlated to the stabilization of an acceptor e set of orbitals. There have been a number of examples of restricted rotation in metal alkyls. Barriers of over 18kJ mol-' were measured for rotation about metal-methyl bonds e.g. (C5H5)2ZrMe2,'13a and these were raised to 49-64 kJ mol-' in the more hindered (C5H5)2Zr(R)CH(SiMe3)2 derivative^."^^ A long Zr-C bond (2.329A) was observed for one of this series (R =Ph). A barrier of 36 kJ mol-' was found for rotation about the C-C bond in (CO)5WCHOMe-C6H3Me,.'13c The MMe63- anions of Er and Lu have been ~ynthesized;"~" although thermally stable they are very water sensitive.Seven- and eight-co-ordinate THF adducts of MBut4-(M = Sm Er or Yb) are similarly air- and rnoisture-sen~itive.'~~~ Thermo-lysis of the samarium complex at 40 "C yielded 3.25 mol of Me3CH and 0.5 mol of ethylene per mol of complex and there were no /3-hydride elimination products. While LiCH2SiMe3 forms MR3(THF)2 and M%- complexes with Y Er or Yb the more bulky LiCH(SiMe3)2 yields MClR3- found to have tetrahedral co-ordination for Yb."' No 89Y coupling was observed in the 13C n.m.r. spectrum of Y(CH,SiMe,),-at room temperature indicating a rapid intermolecular exchange of '09 M. J. S. Gynane M. F. Lappert S. J. Miles and P.P. Power J.C.S. Chem. Comm. 1978 192. R. L. hey and J. C. Martin J. Amer. Chem. SOC.,1978,100,300. 'I' J. C. G. Calado A. R. Dias J. A. Martinho Simoes and M. A. V. Ribeira Da Silva J.C.S. Chem. Comm. 1978,737. N. Trong Anh M. Elian and R. Hoffmann J. Amer. Chem. SOC.,1978,100 110. 113aR.F.Jordan E. Tsang and J. R. Norton J. OrganometallicChem. 1978 149 C53. '13' J. J. Jeffery M. F. Lappert N. T. Luong-Thi J. L. Atwood and W. E. Hunter J.C.S. Chem. Comm. 1978,1081. C. P.Casey S. W. Polichnowski H. W. Tuinstra L. D. Albin and J. C. Calabrese Znorg. Chem. 1978 17 3045. 'I4=H. Schumann and J. Miiller Angew. Chem. Znternar. Edn. 1978,17 276. 114bA.L. Wayda and W. J. Evans J. Amer. Chem. SOC.,1978 100,7119. J. L. Atwood W. E. Hunter R. D. Rogers J.Holton J. McMeeking R. Pearce and M. F. Lappert J.C.S. Chem. Comm. 1978,140. Organometallic Chemistry -CH2SiMe3 groups. MR3 (M=Cr V or Ti) and MR3Cl (M=V Zr or Hf) complexes of the CH(SiMe3)2 ligand have been reported.116a The CrR3 species is slightly non-planar (C-Cr-C angle 117.6'). Cr(CPhCMe2)4 has a tetrahedral geometry and there is little evidence of multiple Cr-C bond character.'l6' The Re-C bond lengths (-2.025 A) in trigonal bipyramidal RePh3(PEt2Ph) indicate some v-bonding effe~ts;"~ the phenyl rings are nearly in the equatorial plane. Several ortho-metallated Cr2 complexes e.g. (16) have been osynthesized and possess very short Cr-Cr formally quadruple bonds (-1.83 A).118The bond length in Cr2[(CH2)2PMe2]4is slightly longer (1.895 Other quadruply bonded alkyls identified have included the W2Mes4- anion and mixed acetate-alkyls of Re"'.12o Reaction of Cr2(OA~)4 with Mg(CH2SiMe3) in the presence of PMe3 has yielded (17).121 The Cr-Cr bond (2.1007 A)is asymmetrically bridged by two alkyl Me,P CH,SiMe, \/ /\ Me,SiH,C PMe (17) groups and one hydrogen of each methylene group is close (2.25 A) to a chromium atom.Bridging methyl groups have been identified in (MeCHCHCHMe),Ni,- (p-Me)2122n Lanthanide derivatives of this latter and (C5H5)2Y(p-Me)2AlMe2.'22' II6OG. K. Barker M. F. Lappert and J. A. K. Howard J.C.S. Dalton 1978 734. 116bC. J. Cardin D. J. Cardin and A. Roy J.C.S. Chem. Comm. 1978,899. 'I7 W.E.Carroll and R.Bau J.C.S. Chem. Comm. 1978,825. F. A. Cotton and S.Koch Inorg. Chem. 1978,17,2021;F.A. Cotton S. A. Koch and M. Millar ibid. 1978,17,2084,2087. 'I9 F. A. Cotton B. E. Hanson and G. W. Rice Angew. Chem. Internat. Edn. 1978,17,953. '''OD. M. Collins F. A. Cotton S. A. Koch M. Millar and C. A. Murillo Znorg. Chem. 1978,17,2017. IZobR.A. Jones and G. Wilkinson J.C.S. Dalton 1978 1063. R. A. Anderson R. A. Jones and G. Wilkinson J.C.S. Dalton 1978 446; M. B. Hursthouse K. M. Abdul Malik and K. D. Sales ibid. 1978 1314. 1220C. Kruger J. C. Sekutowski H. Berke and R. Hoffmann 2.Naturforsch. 1978,33b 1110. ""G. R. Scollary Aust. J. Chem. 1978 31,411. A. J. Deeming and J. Evans type and also [(CSH5)2MMe]2 complexes act as homogeneous ethylene poly- merization catalysts. 122c The dimers are in rapid equilibrium with monomers under polymerization conditions and are deactivated by elimination of alkanes involving hydrogen abstraction from the cyclopentadienyl rings.A large isotropic shift has been observed for the 'H resonance of partially deuteriated HOS~(CO)~~CH~.'~~" One hydrogen of the bridging group is thought to be interacting strongly with an osmium atom giving a rapid equilibrium between two inequivalent sites. This hydrogen is transferred to the metal triangle in the formation of H20s2(CO)loCH2 in rapid equilibrium with its methyl isomer.123b An unusual metal-carbon interaction has been identified in (18),formed by addition of Me1 to C6H3(CH2NMe2)2PtBF4.'24 The platinum is involved in an q' interaction to the arene ring (Pt-C 2.18 A) and this is suggested to be a model for a reductive elimination reaction co-ordinate.While oxidative addition of BzCl to Pd(PEt,) occurs with inversion of configura- tion at carbon (72% stereospecific) there is only 19% net inversion using BzB~;'~'" SN2and radical pathways may be competing. Isomerization of alkyl groups has been observed during the addition of acyl chlorides to IrC1(PPh3) (n =2 or 3)to give RIrC12(CO)(PPh,)2.'2sb This probably involves a P-hydride elimination-olefin insertion sequence. ci~-ptHMe(PPh~)~ eliminates methane at -25 "C by a first order process;'26 the rate determining step is CH elimination and PtL3 species are formed rapidly with added ligands. Two mechanisms have been identified for the cleavage of activated CH bonds by HM(Np)(dmpe) (M =Fe Ru,or 0s) to form HMR(drn~e)~.'~' One is rapid electrophilic attack (e.g.by HCN) and the other involves slow elimination of naphthalene followed by rapid oxidative addition of RH (e.g.MeCN).Elimination of methylcyclohexane from (CsHs)2Zr(H)CH2C6H1 is promoted by H2.1280 Deu- terium was incorporated into the alkyl group in the presence of D2so as well as a simple elimination procedure from a (C5H5),ZrHR-D2 addition complex the alkyl hydride is undergoing a 0-hydride elimination-olefin insertion side process. Eli- mination of isobutane from the related (CsMe5)2Zr(H)CH2CHMe2 has also been studied.128bA primary kinetic isotope effect was observed only when deuterium was 122c D. G. H. Ballard,A. Courtis,J. Holton J. McMeeking and R.Pearce,J.C.S. Chem. Comm. 1978,994. IzJaR.B. Calvert and J. R. Shapley J. Amer. Chem. SOC.,1978,100 7726. 1236 R. B. Calvert J. R.Shapley A. J. Schultz,J. M. Williams S. L. Suib and G. D. Stucky J. Amer. Chem. SOC.,1978 100 6241. G. van Koten K. Timmer J. G. Noltes and A. L. Spek J.C.S. Chem. Comm. 1978 250. It5OY. Becker and J. K. Stille J. Amer. Chem. Soc. 1978 100 838. lZJb M. A. Bennett R. Charles and T. R.B. Mitchell J. Amer. Chem. SOC.,1978 100 2737. L. Abis A. Sen and J. Halpern J. Amer. Chem. SOC.,1978 100,2915. C. A. Tolman S. D. Iltel A. D. English and J. P. Jesson J. Amer. Chem. SOC.,1978,100,4080,7577. IZsaK.I. Gel1 and J. Schwartz J. Amer. Chem. Soc. 1978,100 3246. 1Z8b D. R. McAlister D. K. Erwin and J. E. Bercaw J. Amer.Chem. Soc. 1978 100 5966. Organometallic Chemistry present in the ring methyl groups so the hydrogen is eliminated from one of these fragments. This process is also accelerated by H2 but in this case there was exclusive incorporation of H (D) from Hz(D2) gas in the isobutane. Oxidative addition to the intermediate (C5Me,)(C5MeSH)ZrR was proposed. Hydrogen addition to the cyclopentadienyl ring is also thought to be the initial step in the conversion of [(C,H,)CO(PM~~)~COM~]PF~ and CH using NaH.lZaC into (CSH5)Co(CO)(PMe3) Mo2Et2(NMe2) eliminates ethylene and ethane on treatment with C02,yielding MO~(O~CNM~~),.'~~ After initial loss of ethylene dinuclear elimination of ethane is proposed converting a formal metal-metal triple bond into a quadruple one.Reductive coupling from R,Fe(bi~y)~ and Ar2Ni(PEt3) has been induced by and in the latter case electr~chemical,'~~~ oxidation. Ni"' species were observed at -50°C and elimination occurs above that temperature. The stereo- chemistry of electrophilic M-C bond cleavage in cis-[(threo-PhCHDCHD)Mn(CO),PEt,] varies with the ele~trophile.'~' Inversion at carbon is dominant with Clz or Br in non-polar solvents but the degree of retention increases with solvent polarity and electrophile size (I2 or HgX2). SE2retention and inversion pathways are thought to compete. The extended Huckel method has been applied to the migration reaction pathway of MeMn(C0)5.'32 The five co-ordinate acetyl intermediate and transition state are close in energy and the major part of the activation is due to the destabilization energy of the uMn-Me orbital.A hydride shift was computed to have a lower energy barrier. Me(CO)Mn(CO)5 has been observed when MeMn(CO) is pressurized with CO (300atrn).', Subsequent exposure to H2 liberated acetaldehyde with the manganese as Mn,(CO),,; other systems were similarly studied but did not yield CH3CH0. The rate of alkyl migration in RFe(CO),- in the presence of PPh is highly dependent upon the counter ion.', Cation co-ordination to the carbonyl oxygen promotes alkyl migration to that group. Two diastereomers have been observed for (CSHS)2Zr(Ar)COAr (Scheme 4) and it is apparent that the initial CO attack on the diary1 is from outside the Ar groups to yield the first q2-aroyl complex.'35 Reaction of MoC1(CH2SiMe3),PMe3 with CO affords the q2-acyl > -6OT -78°C -Ar Ar Scheme 4 128c H.Werner and W. Hoffmann Angew. Chem. Internat. Edn. 1978,17,464. lZ9 M. H. Chisholm D. A. Haitko and C. A. Murillo J. Amer. Chem. Soc. 1978,100,6263. 130aT.T. Tsou and J. K. Kochi J. Amer. Chem. Soc. 1978,100 1634. 13'*M. Almemark and B. Akermark J.C.S. Chem. Comm.. 1978,66. 13' D. Dong,B. K. Hunter and M. C. Baird J.C.S. Chem. Comm. 1978.11. 13' H. Berke and R. Hoffmann J. Amer. Chem. Soc.,1978,100,7224. 133 R. B. King A. D. King jun. M. Z. Iqbal and C. C. Frazier J. Amer. Chem. Soc. 1978,100,1687. 134 J. P. Collman. R. G. Finke J. N. Cause,and J. I. Brauman J. Amer. Chem. Soc.. 1978,100,4766. 13' G. Erker and F. Rosenfeldt Angew.Chem. Znternar. Edn. 1978 17 605. 330 A. J. Deeming and J. Evans (p-C1)2[M~(q2-COCH2SiMe3)(C0)2PMe3]2. 136 CO is partially reduced by zirconium alkyls and hydrides. 13' For example insertion into (C5Me5)2ZrMe2 yields first (C5Me5),Zr(Me)COMe and then the metallocyclic complex (C,Me,),Zr-0-CMetCMe-0. The same ligand is produced by the ready CO incorporation into (C5Me5),MMe2 (M =Th or U).138 An X-ray diffraction study on the thorium complex indicated that the two metal atoms are bridged by two such ligands to form a ten-membered ring. A mononuclear complex analogous to the zirconium one is produced by the reaction of (C5Me5),M(CH2SiMe3) (M =Th or U) with CO. However an SiMe3 migration occurs on insertion into (C5Me5)M(Cl)- (CH2SiMe3)3 and (C,Mes)2M(C1)O(SiMe3)2:CH2 results.Alkyl complexes such as NiR,(bipy) and NiRX(bipy) react with CH,C12.'39 NiCl,(bipy) is the inorganic product and the organic ones indicate that CH has been inserted into a proportion of the Ni-C bonds prior to elimination. Diphenyl-acetylene is doubly methylated by (C5H5)CoMe2PPh3 (Scheme 5).14' Labelling studies demonstrate that the methyl transfers and hydrogen migration processes are all intramolecular. Q PhC:CPh* M + M + I Ph,P so Me Ph Ph Ph Ph Me 93Yo 7Yo Scheme 5 A number of tantallacyclopentane derivatives has been synthesized by the reac- tion of (C5H5)TaC12(CHBu') with olefins. For example propene moieties are coupled to yield (C5H5)TaC12(CH2CHMeCHMeCH2), and these complexes will catalyse olefin dimerization.14' The relationships between nickelacylopentanes and bis-olefin complexes have been examined in some detail. 142 While (PPh3)2Ni(CH,)4 eliminates mostly cyclobutane and no scrambling of CD groups was observed in a labelled complex (Scheme 6) the tris-phosphine complex which largely eliminates ethylene does scramble CD groups intramolecularly [(C5H5),fi(CD2CHZCH2CD2) behaves similarly]. PPh3 suppresses the iso-merization which is thought to occur uia an isomer of (PPh3)2Ni(CH2)4, which can uncouple to form a bis-olefin complex from which ethylene is slowly eliminated. 13' E. Carmona Guzman G. Wilkinson J. L. Atwood R. D. Rogers W. E. Hunter and M. J. Zaworotko J.C.S. Chem. Comm. 1978,465. 13' J. M. Manriquez D. R. McAlister R.D. Sanner and J. E. Bercaw J. Amer. Chem. SOC.,1978 100 2716. 13' J. M. Manriquez P. J. Fagan T. J. Marks C. S. Day and V. W. Day J. Amer. Chem. SOC., 1978,100 7112. 139 T.Yamamoto J.C.S. Chem. Comm. 1978 1003. 140 E. R. Evitt and R. G. Bergman J. Amer. Chem. SOC.,1978,100 3237. 14' S.J. McLain and R. R. Schrock J. Amer. Chem. SOC.,1978 100 1315. 142 R. H.Grubbs and A. Miyashita J. Orgattometallic Chem. 1978,161,371;J. Amer. Chem. SOC.,1978 100,1300,ibid. 1978 100 7416; R.H. Grubbs A. Miyashita M. Liu and P. Burk ibid. 1978 100 2418. Organometallic Chemistry D D D D x D D D D D D 11 D (Ph3P),Ni D etc. + (Ph,P)2Ni D -5 D * \AD Scheme 6 These metallacycles catalyse linear and cyclo-dimerizations of olefins. Thermolysis of (PPh3)3Ni(CH2)5 yields a mixture of CH4 C2H4 C5H12 C5H10 and (PPh3)2Ni(C2HJ and evidence for a transformation of the six-membered ring into a [H2C=Ni(CH2)4] moiety was I I Substituted platinacyclobutanes of the type PtC12L2(CHRCH2CH2) have been found to exist as a mixture of isomers in solution and these are in rapid equili- bri~m.~~~~ Pt(py),C12(CH2CMe2CHMe) has been found to isomerize to an olefin complex P~(PY)~C~~(~~~-CH~CM~P~~) in which there is an apparent 1,2 methyl shift;1446.a carbene-olefin complex could be a common intermediate for these processes.Thermolysis of L2Pt[CHR(CH2),] (n = 3 or 4) complexes in CH2C12 or CH2Br2 not only yields cycloalkanes and alkenes from the metallocycle but also homologous ones incorporating a solvent methylene group.145 Model experiments indicate an oxidative addition step to give a Pt1"(CH2X)(X) moiety.Platinacyclo- pentanes are also formed when butadienes and alkenes interact with Pto complexes.146 While 2,3-disubstituted butadienes yield platinacyclobutenes butadiene itself is dimerized. (Scheme 7) The ring system stereospecifically opens and closes when it reacts with one and two mols of PMe respectively. 143 R. H. Grubbs and A. Miyashita J. Amer. Chem. SOC.,1978,100 7418. 144aR. J. Al-Essa R.J. Puddephatt C. F. H. Tipper and P. J. Thompson J. Organometaffic Chem. 1978 157 C40. 144b B. M. Cushman and D. B. Brown J. Organornetallic Chem. 1978,152 C42; B. M. Cushman D. Brown S. E. Earnest and D. B. Brown ibid. 1978,159,431. 14' G.B. Young and G. M. Whitesides J. Amer. Chem. Soc. 1978,100,5808. G. L. Barker M. Green J. A. K. Howard and F. G. A. Stone J.C.S. Dalton 1978 1839. A. J. Deeming and J. Evans '5PMe %PMe Pt H Pt(cod) -5 (cod)Pt H Pt -Me3P,H$ /Me,P /Me3P ; \\ Scheme 7 Metallation of pyridines and quinolines by (CSHS),TiMe formed in situ occurs a to the nitrogen atom,'47a but palladation of 2-substituted 8-methylquinolines with Pd(OAc)* occurs at the 8-methyl group and only if the 2-substituent contains a sufficiently good ligand e.g. an imir~e.'~~' Model studies indicate that the ability of the quinoline to coincide with the co-ordination plane is important. Protonation of Ir[{P(o-OMeC,H3)(O-o-tolyl)2}{P(O-o-tolyl)~}(cod)]appears to occur simply on the metal but in fact initially electrophilic cleavage of the Ir-C bond occurs by proton addition at the metallated carbon to yield [(cod)Ir{P(OAr),}2]'.'48" Cyclometallation only follows a second protonation at the metal.This complex reacts with chlorine to yield a multiply chlorinated cyclo- metallated species. 14*' An X-ray crystal structure determination on a derivative revealed that chlorine substitution had occurred at the cyclometallated ring. Alkyl Rh"' porphyrin complexes have been synthesized using diazoalkanes. 149 For example treatment of Rh(0EP)I with N2CHC02Et in AcOH yields Rh(OEP)[CH(OAc)(CO,Et)] but N-alkylation occurs with Rh(0EP)Me under similar conditions. Nucleophilic cleavage of the Co-C bond in [1-methylheptyl C~'~(dmgH)~]' by C1- occurs with inversion of configuration consistent with this process being involved in halogen cleavage of carbon bonds to CO"'.'~~ Cyclic voltammetry has shown a single cathodic wave for methylcobinamide prior to loss of Me.''la Electrochemical cleavage of a Co-C bond in a BI2model complex has been found to proceed with retention of configuration at arbo on.'^'' The mechanism by which B12catalyses the 1,2 migration of a carbonyl group has been investigated by model Evidence was found for a carbanionic but a series of experiments on the rearrangements of butenyl- cobaloximes indicated a bimolecular process in which a Co"(dmgH) moiety binds to the w carbon of the CoTII bound butenyl This process was also proposed for butenyl-cyclopropylmethyl isomerizations.13C-labelling studies demonstrated that the a-butenyl carbon becomes bound in (C3HSCH2)Co(dmgH)2(py);'52' an intramolecular process was suggested in this case. Co-C homolysis occurs when I4'OB. Klei and J. H. Teuben J.C.S. Chem. Comm. 1978,659. A. J. Deeming and I. P. Rothwell J.C.S. Chem. Comm. 1978 334. 14'OD. J. A. De Waal E. Singleton and E. van der Stok J.C.S. Chem. Comm. 1978 1007. 148b M. J. Nolte E. Singleton and E. van der Stok J.C.S. Chem. Comm. 1978 973. H. J. Callot and E. Schaeffer J.C.S. Chem. Comm. 1978,937. Is" R. H. Magnuson J. Halpern 1. Ya. Levitin and M. E. Vol'pin J.C.S. Chem. Comm. 1978,44. lsloD. Lexa and J. M. SavCant J. Amer. Chem. Soc. 1978 100,3220. '"'L. Walder G. Rytz K. Meier and R. Scheffold Helv.Chim. Acta 1978,61 3013. 152aA.I. Scott J. Kang D. Dalton and S. K. Chung J. Amer. Chem. Soc. 1978 100 3603. A. Bury M. R. Ashcroft and M. D. Johnson J. Amer. Chem. SOC.,1978 100 3217. M. P. Atkins B. T. Golding and P. J. Sellars J.C.S. Chem. Comm. 1978 954. 14'' Organometallic Chemistry 333 Co"'-R moieties e.g.methylcobalamin are photoly~ed.'~~ Secondary reactions of the carbon radicals then occur. When formyl complexes are synthesized by reduction of a metal carbonyl with a trialkyl-borohydride e.g. Li(BEt,H) the corresponding boron alkyl is formed. Formyls appear to be strong hydride donors and whether donation is from the formyl itself or uia boron has been tested using a chiral borohydride and monitoring the optical activity induced in 1-phenylethanol produced by reducing aceto-~hen0ne.l~~~ Boron involvement was evident for [Mn2(CO),CHO]- but both [Mn(CO)4(COCHzOMe)(CHO)]- and [(C,H,)Fe(CO)(COPh)(CHO)]-act as hydr- ide donors.The hydride donating ability of [(PhO),PFe(CO),CHO]- has been inve~tigated.'~~' This formyl reduces ketones and alkyl iodides and also Re2(CO)lo to yield the dinuclear formyl Re,(CO),(CHO)- also formed by reduction of the carbonyl by alkyl-borohydrides. 154c In turn this dinuclear complex reduces Fe(CO),. 4 Carbenes and Carbynes The carbene F4SCH has been synthe~ized.'~~ The sulphur co-ordination geometry of this colourless gas is trigonal bipyramidal with the methylene group in an equatorial site. Silylene complexes of iron HFe(CO),(SiMe,R)(SiMe,) have been prepared by reaction of Fe2(C0)9 with HSiMe2SiMe,R (R=H or Me).156 Cyclo- rapidly addition of activated alkynes to (~2-CSz)Fe(C0)2(PMe3)2157" forms complexes of cyclic carbenes e.g.Fe(CO)2(PMe3)2CSC(C02Me)C(C02Me)S.'57b Full reports of the synthesis of complexes of aminocarbenes by cleavage of the olefinic bond in NRCH,CH,NRC :CNRCHZCH2NR158a or by three-fragment oxi- dative addition of [NMe2(CHCl)]Cl'58b have been presented. The preparation and reactivity of (C5H5),Ta(Me)(CH2) have also been fully Reactions like the bromide displacement from SiMe3Br to form [(C,H,)2Ta(Me)CH,SiMe3]Br reveal the nucleophilic character of the carbene carbon. Proton abstraction converts the silyl substituted carbon into a carbene The closely related complexes [(C5H,)2M(CH,SiMe3)2]X (M = Ta or Nb) afford carbene complexes (C5H5),M(CH2SiMe3)(CHSiMe3) on treatment with the base Li[N(SiMe,),].159c Crystallographic determinations on a number of tantalum carbene complexes have been reported. The preferred alignment of the methylene substituents perpendicular to the radial plane in the (C,H,),Ta(CHR)X derivatives is Is3 C. Y. Mok and J. F. Endicott J. Amer. Chem. SOC., 1978,100 123; A. J. Hartshorn A. W. Johnson S. M. Kennedy M. F. Lappert and J. J. MacQuitty J.C.S. Chem. Comm. 1978,643. 154aJ.A. Gladysz and J. H. Merrifield Znorg. Chim. Acta 1978 30 L317. 154b C. P. Casey and S. M. Neurnann J. Amer. Chem. SOC.,1978,100,2544. 154c J. A. Gladysz and W. Tam J. Amer. Chem. SOC..1978 100 2545. G. Kleeman and K.Seppelt Angew. Chem. Internat. Edn. 1978,17 516. 156 H. Sakurai Y. Kamiyarna and Y. Nakadaira Angew. Chem. Internat. Edn. 1978 17 674. 1s7aH.Le Bozec P. H. Dixneuf A. J. Carty and N. J. Taylor Znorg. Chem. 1978 17 2568. 1576 H. Le Bozec A. Gorgues,and P. H. Dixneuf J.C.S. Chem. Comm. 1978 573; J. Amer. Chem. SOC. 1978,100,3946. lSaaM.F. Lappert and P. L. Pye J.C.S. Dalton 1978,837;P. B. Hitchcock M. F. Lappert and P. L. Pye ibid. 1978 826. isnb A. J. Hartshorn M. F. Lappert and K. Turner ibid. 1978 348. IsqaR.R. Schrock and P. R. Sharp J. Amer. Chem. SOC., 1978,100 2389. R. R. Schrock L. W. Messerle C. D. Wood and L. J. Guggenberger J. Amer. Chem. SOC., 1978,100 3793. '59c M. F. Lappert and C. R. C. Milne J.C.S. Chem. Comm. 1978 925.A. J. Deeming and J. Evans increasingly distorted by the steric bulk of the R group (the angle of deviation is 0"for R = H 5.7" for R = Ph and 10.3"for R = Bu') e.g. (19).1596*159d This has the effect of lowering the energy barrier to rotation about the Ta=C bond but there are also two other structural effects in these complexes. The Ta-C-C angle becomes increas- ingly obtuse so that the geometry at carbon in one of the carbon moieties in (20) is almost T-shaped and as this angle widens so the Ta-C distance The carbene Ta(CH2Bu),(CHBu') is also nucleophilic reacting with acyl chlorides to form Ta(CH2B~')3(C1)(OCR:CHBu').'60" Although thermally stable it eliminates neopentane on treatment with phosphines the rate of which is highly dependent on the added ligand.l6Ob A phosphine adduct apparently can rapidly undergo a-elimination and the bis-carbene complexes T~(CHBU')~(CH~BU')L~ result.A variety of bis-neopentylidene complexes including (C5Me5)2Ta(CHBu')2PMe3 were synthesized starting from Ta(CHBu'),ClL. Treatment of (C5HS)TaC12(CHBu') with a base and PMe3 has yielded a carbyne complex (CsH5)TaCl(PMe3)2(CBu').'60' A crystallographic determination of the structure of (C5MeS)TaCl(PMe)2CPh found the Ta-C distance to be 1.849A. This type of chemistry has been extended to Mo and W.16' For example (Bu'CH~)~WCBU' has been isolated from the reaction of WC16 and LiCH2Bu'. This complex appears to be in equilibrium with its dimer. Neopentane is eliminated on heating with PMe3 forming a mixed alkyl-carbene- carbyne species W(PMe3)2(CHBu')(CH2Bu')(CBu').Dithiocarbene complexes have been synthesized using the reagent N~[TOSNNC(SE~)~].For example it reacts with W(CO),NCMe to form 162 W(CO),C(SEt),. A series of cycloheptatrienylidene complexes e.g. C7H6W(C0), have been synthesized and the ring appears to have substantial tropylium charac- ter.16 Fluorine abstraction by SbF from (C5H5)M~(C0)3CF2RF has allowed iso- lation of a series of perfluorocarbene complexes [(C,H,)MO(CO),CFR~IS~F~.'~~ Raman spectroscopy has been used to identify the vw= frequency in X(CO),WZCCR c~mplexes.'~~ For R =D and X = Br this is at 1315 cm-' but in 15"M. R. Churchill and F. J. Hollander Znorg. Chem. 1978,17,1957; M. R. Churchill F. J. Hollander and R.R. Schrock J. Amer. Chem. Soc. 1978,100,647. 159cM. R. Churchill and W. J. Youngs J.C.S. Chem. Comm. 1978 1048. R. R. Schrock and J. D. Fellman J. Amer. Chem. SOC.,1978 100,3359. J. D. Fellman G. A. Rupprecht C. D. Wood and R. R. Schrock J. Amer. Chem. Soc. 1978,100,5964. S. J. McLain C. D. Wood L. W. Messerle R. R. Schrock F. J. Hollander W. J. Youngs and M. R. Churchill ibid. 1978 100 5962. D..N. Clark and R. R. Schrock J. Amer. Chem. SOC.,1978,100.6774. 162 M. F. Lappert and D. B. Shaw J.C.S. Chem. Comm. 1978,146. N. T. Allison Y. Kawada and W. M. Jones J. Amer. Chem. SOC.,1978,100,5224. 164 D. L. Reger and M. D. Dukes J. Organometallic Chem. 1978,153,67. E. 0.Fischer N. Q. Dao and W. R. Wagner Angew. Chem. Znternat. Edn. 1978.17.50. Organometallic Chemistry the corresponding protio complex it mixes strongly with a symmetric methyl deformation.(C5H5)Fe(C0)2CH2+ has been identified in the gas phase using ion cyclotron resonance spectroscopy. Adding cyclohexane causes elimination of CH2 and bases form adducts. Attempts have been made to generate this ion by acidification of (CSH5)Fe(CO)2CH20Me.'666 At low temperatures the acidic solu- tions convert cyclohexane into bicyclo[4,1,0,]heptane consistent with the cation being present. Attempts to characterize the dppe substituted derivative however yielded the solvated salt [(CSHs)Fe(dppe)MeCN]BPh,. Protonation of (C,H,)Fe(CO)PPh,(C,Ph) has yielded the marginally stable vinylidene cation [(C,H5)Fe(CO)(PPh3)CCPhH)]'.'67aComplexes of the type [(C5HS)Fe(dppe)- CCR,]' (R=H or Me) are more as are [(CSH5)R~(PPh3)2-(CCHR)]' cations.167c The vinylidene group in (C,H,)MI~(CO)~-(CCHPh) can be transferred to a rhenium atom using (C5H5)Re(C0)2-(thf);'67d a bridged intermediate can be isolated.Fe(TPP) reacts with DDT in the presence of an excess of a reducing agent to form Fe(TPP)[CC( the related complex Fe(TPP)(CC12)(OH2) formed using CCL has been characterized crystallographically."" Pt2C12(dppm)2 reacts with CH2N2 to form a bridging methylene complex.'69 Photolysis of a mixture of (C,H,)CO(CO)~ and CH(C02R)N2 below -1 10"C affords (C5H5)2C02(p-CO)2{p-O-C(OR)-CH},isomerizes to {p-CH(COzR)}-which [CO(C,H,)(CO>]~ by an intramolecular rearrangement."' Dinuclear iron complexes with bridging carbyne ligands have been synthesized by two different routes.171 Li[ (C5HS)Fe(CO),] reacts with cyclopentene epoxide and subsequent acidification with HBF4 yields the salt [(p-CO)(p-C-CsH7){Fe(C5Hs)CO}2]BF4; the 13C n.m.r.signal due to the methine carbon was observed at 6448. Complexes of this type can be synthesized more readily by treating [(C,H,)Fe(CO),] first with RLi and then HBF,. [(C5H5)Re(C0),(CPh)]BCl4 is reduced by Et2AlH at -78 "C to (C5H5)Re(CO)2(CHPh).'72 Further reaction at -30 "C causes a second reduction to a benzyl complex (C5H5)Re(CO)2H(CH2Ph). Carbonylation of carbenes has also been reported. (C5H5)Mn(C0)2CPh2 incorporates CO under high pressure to yield (CSH5)Mn(CO)2(~2-Ph2CC0);173" the ketene ligand was hydrogenolysed to a mix- ture of Ph2CHCH0 and the corresponding alcohol.However (C5Hs)W(CO)- (PMe3)(C-p-tolyl) behaves differentl~.'~~' It readily absorbs two mols of CO to form 166aA.E. Stevens and J. L. Beauchamp J. Amer. Chem. SOC. 1978,100,2584. lasbP.E.Riley C. E. Capshew R. Pettit and R. E. Davis Inorg. Chem. 1978,17,408. 167aA. Davison and J. R. Solar J. Organometallic Chem. 1978 155 C8. 167bA. Davison and J. P. Selegue J. Amer. Chem. SOC. 1978,100 7763. 16" M.I. Bruce and R. C. Wallis J. Organometallic Chem. 1978 161 C1. 167d N.E. Kolobova A. B. Antonova and 0.M. Khitrova J. Organometalk Chem. 1978 146 C17. lasaD. Mansuy M.Lange and J. C. Chottard J. Amer. Chem. SOC. 1978 100,3213. l60b D. Mansuy M. Lange J. C. Chottard J. F. Bartoli B.Chevrier and R. Weiss. Angew. Chem. Internut. Edn. 1978 17 781. M.P. Brown J. R. Fischer S. J. Franklin R. J. Puddephatt and K. R. Seddon J.C.S. Chem. Comm. 1978,749. I7O W. A. Herrmann Chem. Ber. 1978 111 1077; W. A. Herrmann and I. Schweizer 2. Nuturforsch. 1978,33b 1128. l7I M.Nitay W. Priester and M. Rosenblum J. Amer. Chem. SOC. 1978,100,3620. E.0.Fischer and A. Frank Chem. Ber. 1978 111 3740. 173aW. A. Herrmann and J. Plank Angew. Chem. Internat. Edn. 1978. 17 525. 173b F. R. Kreissl W. Vedelhoven and K. Eberl Angew. Chem. Internat. Edn. 1978,17,859,860. 17' A. J. Deeming and J. Evans (C5H5)W(CO)2(PMe3)C(CO)( p-tolyl) C02is evolved when this complex is treated with CO under more forcing conditions and the initial carbyne ligand is converted into an ethynyl moiety in (C5H5)W(CO)2(PMe3)(CC-p-tolyl).Heating chromium carbonyl carbene complexes with acetylenes effectively adds a keten across the carbon-carbon bond. 174a For example Cr(C0)5(CPh2) and NEt2CCNEt2 yield (NEt,)C:C(NEt,)C(O)CPh,. Insertion of activated acetylenes readily occurs into a Cr-carbene bond and this reaction eventually can afford fused heterocyclic products as for example in Scheme 8.'746The bridging methylene Scheme 8 complex (C5H5)2Ti(p-Me)(p-CH2)AlMe2 has been synthesized by the reaction of (C5HJ2TiMe2 with AlMe3.175 (C5H5)2Ti(p-C1)(p-CH2)AlMe2, formed from (C5H5),TiCI2 and AlMe3 readily transfers CH2 to organic molecules. Cyclo-hexanone is converted into methylenecyclohexane; CH is added to ethylene to form propene.Olefin-carbene complexes have been proposed to be involved in olefin metathesis and an iron complex of these two ligand types has been ~ynthesized'~~ (Scheme 9). Q+ HBF+ EtzO 20°C -78°C ' ,r(-yoD 'ZH4* Me0 OC OMe Scheme 9 174aK.H. Dotz and R. Dietz J. Organometallic Chem. 1978 157 C55. 174bChem. Ber. 1978 111 2517; K.H.Dotz and I. Pruskil ibid. 1978 111 2059; K.H.Dotz and D. Neugebauer Angew. Chem. Internat. Edn. 1978,17,851. ''' F.N. Tebbe G. W. Parshall and G. S. Reddy J. Amer. Chem. Soc. 1978,100,3611. 176 W.Priester and M. Rosenblum J.C.S. Chem. Comm. 1978,26. Organometallic Chemistry The next step in the metathesis reaction is now accepted to be the formation of a metallacyclobutane complex.Carbon-carbon cleavage of the metallocycle effects metathesis. Alternative metal-carbon bond cleavage has been proposed as a mechanism of Ziegler-Natta olefin polymerization. *” a-Hydrogen elimination from the polymer chain will yield a hydrido-carbene complex. Following olefin co-ordination cyclization will yield a hydrido-metallacyclobutane complex. Steric control is exercised by the conformational preferences of the metallacycle.