9 Organometallic Compounds Part (ii) Transitional Elements By J. P. CANDLIN A. W. PARKINS and K. A. TAYLOR I.C.I.L td. Petrochemical and Polymer Laboratory Runcorn Cheshire THEtheme of this section is the modification of organic compounds by transition- metal complexes. A brief survey of unusual ligands bonded to transition metals is also included. 1 Reviews This year has seen the appearance of a new journal in this area of chemistry Organometallics in Chemical Synthesis.' An extensive review of olefin complexes has appeared,2 together with two useful reviews on homogeneous ~atalysis.~.~ Accounts have been written of Pd" organosilver7 and organogold' compounds. A useful survey of work from Wilke's group on the use of n-ally1 intermediates in organic synthesis has been published.' Isomerisation," decarbonylation,' 'and hydrogenation' * have also been reviewed.The formation of aryl-metal bonds,' and oxidative addition reaction^'^ have been studied sufficiently for reviews to be written. A useful survey citing many Russian references deals with the structures of n-olefin and n-acetylene complexes. 2 Novel Complexes HydrocarbonComplexes.-Work on transition-metal derivatives of trimethylene-methane (1) has been extended to Cr and Mo,16 and the heptafulvene ligand has Elsevier Publishing Company Amsterdam. H. W. Quinn and J. H. Tsai Adv. Inorg. Chem. Radiochem. 1969 12 217. R. Ugo Chimica e Industria 1969 51 1319. J. P. Candlin K. A. Taylor and D. T. Thompson Ind. chim. belge 1970 35 1085. R. Huttel Brennstoff-Chem.1969 50 281 331. R. Huttel Synthesis 1970 225. ' C. D. M. Beverwijk G. J. M. van der Kerk A. J. Leusink and J. G. Noltes Organo-metallic Chem. Rev. (A) 1970,5,215. ' B. Armer and H. Schmidbaur Angew. Chem. Internat. Edn. 1970 9 161. P. Heimbach P. W. Jolly and G. Wilke Adv. Organometallic Chem. 1970 8 29. lo A. J. Hubert and H. Reimlinger Synthesis 1970 405. J. Tsuji and K. Ohno Synthesis 1970 157. M. E. Vol'pin and I. S. Kolomnikov Russ. Chem. Rev. 1969 38 273. l3 G. W. Parshall Accounts Chem. Res. 1970 3 139. l4 J. Halpern Accounts Chem. Res. 1970 3 386. l5 A. I. Gusevand Yu. T. Struchkov J. Struct. Chem. (U.S.S.R.),1970 11 340. " J. S. Ward and R. Pettit Chem. Comm. 1970 1419. Organometallic Compounds-Part (ii) Transitional Elements been stabilised as its Fe(CO) derivative (2) with a trimethylenemethane system forming an integral part of the ligand.” The X-ray structure of the compound produced in an earlier attempt to stabilise this ligandI8 has shown that it is an (1) (2) (3) alkyl comp~und.’~ A useful method for the preparation of 1,2-disubstituted cyclobutadiene complexes e.g.(1,2-dimethylcyclobutadiene)Fe(CO) has ap- The reaction of 2,3-dichlorobutadiene with Fe,(CO), leads to a C ligand which contains two 71-ally1 groups (3).2 Bis-(butadiene)Fe(CO) has been reported. Carbene Complexes.-This year has seen continued activity in this field. (Phenyl- methoxycarbene)Fe(CO) has been prepared by a photochemical exchange rea~tion.’~ (la-C H ,)Mo(CO)(NO)[C( Ph)OMe] + Fe( CO) 3Fe(CO),[C( Ph)OMe] + (z-C,H~)MO(CO),NO This compound cannot be obtained from the reaction of the acylmetallate salt [Fe(CO),C(Ph)O]-with Me30+ a dimer being f~rmed.~~,~’ Reaction with Ph,CCl also produces a dimer.26 Ph [Fe(CO),C(Ph)O]-+ Ph,CCl -+ \/c-9(CO)3Fe-Fe(CO),\ /c -0 / Ph However using (Ph,P)Fe(CO), CH,Li and Et,O+BF,- a carbene complex can be obtained dire~tly.~’ Last year the reaction of lithium organyls with Mn2(CO), was reported to give carbene complexes.28 Further work29 on the reaction of [Mn(CO),]-D.J. Ehntholt and R. C. Kerber Chem. Comm. 1970 1451. D. J. Ehntholt G. F. Emerson and R. C. Kerber J. Amer. Chem. SOC.,1969,91,7547. l9 M. R. Churchill and J. P. Fennessey Chem. Cornrn. 1970 1056. ‘O R.H. Grubbs J. Amer. Chem. SOC.,1970,92 6693. H. A. Brune W. Schwab and H. P. Wolff Z. Naturforsch. 1970,25b 892. 22 A. Carbonaro and A. Greco J. Orgsnomerallic Chem. 1970 25,477. 23 E. 0.Fischer and H. J. Beck Angew. Chem. Internat. Edn. 1970 9 72. 24 E. 0. Fischer and V. Kiener J. Organometallic Chem. 1970 23,215. 25 E. 0.Fischer V. Kiener and R. D. Fischer J. Organometallic Chem. 1969 16 P60. 26 E. 0. Fischer V. Kiener D. St. P. Bunbury E. Frank P. F. Lindley and 0.S. Mills Chem. Comm. 1968 1378. ’’ D. J. Darensbourg and M. V. Darensbourg Inorg. Chern. 1970,9 1691. 28 E. 0. Fischer and E. Ofiaus Chem. Ber. 1969 102 2449. ’’ C. P. Casey Chem. Comm. 1970 1220. J. P. Candlin A. W. ParkinsandK. A. Taylor with Br(CH2),Br3' has shown that the product is a carbene (4).Reaction of a double Wittig reagent (Ph,P=C=PPh,) with Mn(CO),Br yields a keten derivative (S).31 (4) (5) (6) Several new carbene complexes of chromium have been reported,32 including a bis-carbene derivative obtained by a photolytic exchange reaction,33 Me I N 2R-Cr(CO) !% R,Cr(CO) where R = Q I Me and a chromium carbene complex containing two heteroatoms (6).34The transfer of a carbene ligand to an organic substrate has now been reported for chrorni~rn.,~ -+ Me yo;2Me :,OMe (CO),Cr -2 + _/Co2Me 'Ph Me Ph This reaction recalls similar work with iron,36 although previous attempts led to the dimerisation of the carbene ligand.37 Dimerisation with elimination of a carbonyl group occurs38 with Cr(CO),[C(Ph)NMe,] forming Cr( CO),[ CH( Ph)N Me,] .Several new complexes of the platinum metals have been rep~rted~~-,~ e.g. PhNC-c1 Ph-NHC. 'C1 \-. OEt 30 R. B. King J. Amer. Chem. Soc. 1963,85 1922. 31 D. K. Mitchell W. D. Korte and W. C. Kaska Chem. Comm. 1970 1384. 32 E. 0.Fischer H. J. Kollmeier C. G. Kreiter J. Muller and R. D. Fischer J. Organo-metallic Chem. 1970 22 C39. 33 K. Ofele and M. Herbehold Angew. Chem. Internat. Edn. 1970 9 739. 34 E. 0.Fischer and H. J. Kollmeier Angew. Chem. Internat. Edn. 1970 9 309. Js E. 0. Fischer and K. H. Dotz Chem. Ber. 1970 103 1273. 36 P. W. Jolly and R. Pettit J. Amer. Chem. SOC.,1966 88 5044. 37 E. 0. Fischer B. Heckl K. H. Dotz J. Muller and H. Werner J. Organometaffic Chem. 1969,16 P29.38 J. A. Connor and J. P. Lloyd J. Chem. SOC.(A) 1970 3237. 39 E. M. Badley J. Chatt R. L. Richards and G. A. Sim Chem. Comm. 1969 1322. 'O B. Crociani and T. Boschi J. Organometallic Chem. 1970 24 C1. 41 G. Rouschias and B. L. Shaw Chem. Comm. 1970 183. 42 F. Bonati and G. Minghetti J. Organometallic Chem. 1970 24 251. 43 B. Crociani T. Boschi and U. Belluco Inorg. Chem. 1970,9 2021. Organometallic Compounds-Part (ii) Transitional Elements Sulphur Compounds.-Some interesting reactions of Fe(CO) with sulphur- containing compounds have been reported. Some of these stoicheiometric reactions have synthetic utility for example the formation of RS-SR from RSCl and Fe(CO) ,44and the preparation of(P-naphthyl),S from (P-naphthyl)-SSCN.45 Attack on co-ordinated norbornadiene by Me2S2 yields the tetrasulphur deriva- tive (7),”6 whereas the reaction of co-ordinated cyclo-octene with CS2 probably (7) (8) yields an episulphide (8).47 The first complex containing a thioketo-carbene has been reported.48 Physical Aspects of wComp1exes.-There is still great activity in this field much of it with comprehensive n.m.r.studies of the compounds to establish the fluxional nature of the molecules or homoaromaticity of the ligands. X-Ray work has also continued to give structural information. For example the reac- tion of (9) with (NH,),Cr(CO) yields which has been shown by X-ray” and n.m.r.” analysis to be homoaromatic. Cyclo-o~tatriene~~ complexes of chromium have been reported in which the organic ligand is fluxional.Rearrangement of the bullvalene ligand does not occur on complexation with Group VI metals,’ although it is thought to occur with iron.54 The n.m.r. spectrum of (ethylene),IrCl in the presence of ethylene shows that some exchange between co-ordinated and unco-ordinated ethylene OCCU~S.~ 44 E. Lindner and G. Vitzthum Angew Chem. Internat. Edn. 1969 8 518. 45 J. Roy Z. Naturforsch 1970,25b 1062. 46 R. B. King J. Org. Chem. 1970,35 274. 47 I. S. Butler and A. E. Fenster Chem. Comm. 1970 933. 48 G. N. Schrauzer H. N. Rabinowitz,J. A. K. Frank and I. C. Paul J. Amer. Chem. Suc. 1970 92 212. 49 W. E. Bleck W. Grimme H. Gunther and E. Vogel Angew. Chem. Internat. Edn. 1970 9 303. R. L. Beddoes P. F. Lindley and 0.S.Mills Angew. Chem. Internat. Edn. 1970,9,304. H. Gunther R. Wenzl and H. Klose Chem. Comm. 1970 605. 52 R. Aumann Angew. Chem. Internat. Edn. 1970,9 638. 53 R. Aumann Angew. Chem. Internat. Edn. 1970,9 800. 54 G. N. Schrauzer P. Glockner K. I. G. Reid and I. C. Paul J. Amer. Chem. Soc. 1970,92,4479. ” A. van der Ent and T. C. Van Soest Chem. Comm. 1970,225. 310 J. P. Candlin,A. W.Parkins and K. A. Taylor Work on the temperature dependence of the n.m.r. spectra of substituted arene chromium tricarbonyl complexes has been p~blished.~~-~ a-Complexes.-It was noted several years ago that simple methyl compounds are often more stable than the higher alkyls owing to the absence of P-hydrogen atoms.59 This year has seen the decomposition mechanism of a copper alkyl experimentally established.60 Therefore stable metal alkyls may be formed with hydrocarbyl ligands containing no P-hydrogen atoms.Using this approach stable o-complexes have been prepared using trimethyl~ilylmethyl~~-~~ and benzyl ligands. Some useful synthetic applications of R,CuLi complexes for example the introduction of R into organic compounds have been rep~rted.~~-~~ ‘Grignard’ reagents of ytterbium have been prepared.70 3 Hydrogenation and Hydrogen Exchange Reactions Several new homogeneous catalysts for the hydrogenation of carbon-carbon unsaturation have been discovered during the past year. These include + [RUCl2(C6H,)],,7 [Rh( 1,5-cyclo-octadiene) (MeCN),] and [Ir(l,5-~yclo-octadiene)(MeCN)~]+,~~ IrCl(PPh,) ,73 Rh24+,74Ru2 4+7 74 Rh2(OCOCH3)4,75 [RhH2P’L2]+ 76 [where P‘ = PPh2Me PPhMe, or PMe and L =solvent (e.g.acetone)] COH,(PP~,),,~~ CoH(CO)(PPh,) ,77 and CoH(CO)(PPh,) +AIEt .77 Progress has been made on the homogeneous reduction of other functional groups such as ket~-,’~ azo- imino- and nitro-groups [using Rh(py),Cl,-NaBH as ~atalyst’~]. Thus the homogeneous reduction of pyridine to piperidine has been 56 W. R. Jackson W. B. Jennings S. C. Rennison and R. Spratt J. Chem. SOC.(B) 1969 1214. 57 G. Barbieri and F. Taddei Chem. Comm. 1970 312. 58 W. R. Jackson W. B. Jennings and R. Spratt Chem. Comm. 1970 593. 59 G. Calvin and G. E. Coates J. Chem. SOC.,1960 2008. 60 G. M. Whitesides E. R. Stedronsky C. P. Casey and J. San Filippo J.Amer. Chem. Soc. 1970 92 1426. 61 M. F. Lappert Angew. Chem. Internut. Edn. 1970 9 910. 62 G. Yagupsky. W. Mowat A.Shortland and G. Wilkinson Chem. Comm. 1970 1369. b3 A. Shotani and H. Schimdbaur J. Amer. Chem. SOC.,1970 92 7004. 64 M. R. Collier M. F. Lappert and M. M. Truelock J. Organometaffic Chem. 1970 25 C36. 65 U. Zucchini U. Giannini E. Albizzati and R. D’Angelo Chem. Comm. 1969 1174. 66 G. H. Posner and C. E. Whitten Tetrahedron Letters 1970 4647. 67 N-T Luong Thi and H. Riviere Tetrahedron Letters 1970 1579. 68 E. P. Woo and F. Sondheimer Tetrahedron 1970 26 3933. 69 E. J. Corey and I. Kawajima J. Amer. Chem. SOC.1970 92 395. 70 D. F. Evans G. V. Fazakerley and R. F. Phillips Chem. Comm. 1970 244. 71 I.Ogata R. Iwata and Y. Ikeda Tetrahedron Letters 1970 301 1. 72 M. Green T. A. Kuc and S. H. Taylor Chem. Comm. 1970 1553. 73 H. van Gaal H. G. A. M. Cuppers and A. van der Ent Chem. Comm. 1970 1694. 74 P. Legzdins R. W. Mitchell G. L. Rempel J. D. Ruddick and G. Wilkinson J. Chem. SOC.(A) 1970 3322. 75 B. C. Hui and G. L. Rempel Chem. Cornrn.,1970 1195. 76 R. R. Schrock and J. A.Osborn. Chem. Comm. 1970. 567. 17 M. Hidai T. Kuse T. Htkita Y. Uchida and A. Misono Tetrahedron Letters 1970 1715. 7M I. Jardine and F. J. McQuillin Chem. Comm. 1970 626. Organometallic Compounds-Part (ii) Transitional Elements 31 I a~hieved.’~ The hydrogenation of aromatic systems however can only be performed using heterogeneous catalysts or Ziegler-type systems.79 The latter catalysts have also been used to hydrogenate unsaturated polymers; thus Cr(acety1acetonate),-A1Bu3 hydrogenates polybutadiene polymers,8o and Ni(octoate),-AIEt reduces the unsaturation present in polythene.’ A study of the hydrogenation activity and selectivity of soluble Ziegler-type catalysts has been made.82 The combination Co(acetylacetonate),-AlBu showed the highest activity and it is possible to hydrogenate very selectively hex-1-ene in the presence of cyclohexene and also phenylacetylene in the presence of hex-1-ene.Tris( triphen ylphosphine)chlororhodium(r)’ continues to at tract atten tion. The extent of dissociation in benzene and methylene chloride RhCI(PPh,) * RhCl(PPh,) + PPh which is thought to be a key step in hydrogenation reactions has been shown to be increased by traces of oxygen84 and decreased by the presence of alcohol^.'^ These results explain the conflicting results previously obtained from osmometry and n.m.r.data. In benzene solution traces of oxygen promote hydrogenation but inhibit isomerisation of olefins whereas in the presence of alcohols isomerisa- tion as well as hydrogenation OCCU~S.~~,~~ These results indicate that extreme caution should be taken when handling RhCl(PPh,) in solution with the added complication that different solvents can alter the reactivity pattern. Further mechanistic studies using RhCI(PPh,) include the hydrogenation (in some cases deuteriation or tritiation) of cyclo-olefins,88 substituted exocyclic methylene compounds,90 various olefinic derivatives,” and ap-unsaturated A carbonyl cornpo~nds.~~ comparison of the hydrogenation activity of RhCI(PPh,) and heterogeneous catalyits has been made.92 Rhodium and cobalt carbonyl complexes have catalytic hydrogenation activity.Olefins can be hydrogenated9 and i~omerised~~ by RhH(CO)(PPh,) ,but the activity decreases during the experiment due to the formation of inactive [Rh(CO)2(PPh,),],.g4*95 Deuteriation studiesg6 on the co-ordinated ligand in the ’’ S. J. Lapporte and W. R. Schuett J. Org. Chem. 1963 28 1947. B. I. Tikhomirov I. A. Klopotova and A. I. Yakubchik European Polymer J. (Suppl.) 1969 561. D. R. Witt and J. P. Hogan J. Polymer Sci.(Part A-I) 1970,8 2689. ” W. R. Kroll J. Catalysis 1969 15 281.83 R. S. Coffey Ann. Reports (B) 1969,66 313. D. D. Lehman D. F. Shriver and I. Wharf Chem. Comm. 1970 1486. 85 R. L. Augustine and J. F. Van Peppen Chem. Comm.,1970 497. 86 R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970 571. R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970,495. *’ A. S. Hussey and Y. Takeuchi J. Org. Chem. 1970,35 643. 13’ G. V. Smith and R. J. Shaford Tetrahedron Letters 1970 525. T. R. B. Mitchell J. Chem. SOC.(B) 1970 823. 91 W. Strohmeier and R.Endres 2.Naturforsch 1970 25b 1068. ’’ H. Simon and 0.Berngruber Tetrahedron 1970 26 1401. 93 H.Strohmeier and S. Hohmann 2.Naturforsch 1970 25b,1309. 94 M.Yagupsky and G. Wilkinson J. Chem. SOC.(A) 1970,941. 9s M. Yagupsky C. K. Brown G. Yagupski and G. Wilkinson J.Chem. SOC.(A) 1970,937. 96 G. E. Hartwell and P. W. Clark Chem. Comm. 1970 11 15. J. P. Candlin A. W.Parkins and K. A. Taylor complex [Rh(CO)(Ph,PCH2CH,CH=CH2),]{[Rh(CO)L,]+ f in methanol + show that five- and six-membered ring intermediates (11) and (12) are formed -[(CO)L(H)RhPh2PCH2CH2CHMe]+ [(CO)L(H)RhPh2PCH2CH2CH2kH2]+ This suggests that in the hydrogenation of olefins by similar rhodium complexes e.g. perhaps RhCl(PPh,) ,the two hydrogens are probably transferred in a step- wise manner rather than simultaneously. Hydrosilylation of 0lefins.-Many of the complexes which catalyse the hydro- genation of olefins are also useful catalysts for analogous hydrosilylation reac- tions using silanes e.g. R3SiH. Thus the rhodium complexes RhC1(PPh3), RhCl(CO)(PPh,) and RhH(CO)(PPh,) ,97 Ni(P-P)C1,98 (where P-P is a chelating ditertiary phosphine) and [Pt(substituted ~tyrene)Cl,],~~ catalyse the addition of silanes to olefins.Metal-catalysed Intermolecular Hydrogen Exchange.-Hydride transfer from hydride donors (e.g. secondary alcohols) to reducible groups (e.g. ketones) is catalysed by many transition-metal complexes. Thus RhCl(PPh,) and IrCl,-H,PO catalyse the formation of axial alcohols from ketones in high yields using isopropanol as re duct ant."'^' Mechanistic studies using RhC1,-SnCl mixtures suggest the formation of a rhodium hydride species.lo2 Rhodium complexes e.g. RhCl(C0) (PR3)2 catalyse the formation of aldehydes from aryl chlorides and Et,SiH. A possible mechanism involves hydride trans- fer.'' Homogeneous and heterogeneous hydrogenaeuterium exchange in aromatic compounds has been catalysed by [Pt"C1,I2 -and metallic platinum.7c-Com-plexes are thought to be possible intermediate^.'^^'^^^ Intramolecular Oxidative Addition Reactions.' 3-Thi~ is a relatively new class of reactions in which intramolecular cleavage of a carbon-hydrogen bond by the central metal ion (oxidative state M) results in the formation of a metal- hydride and a metalkarbon bond (oxidation state M2+). In some cases the hydride is lost as H'. 97 A. J. Chalk J. Organometallic Chem. 1970 21 207. 98 M. Kumada Y. Kiso and M. Umeno Chem. Comm. 1970,611. 99 V. 0. Reikhsfel'd M. I. Astrakhanov and E. G. Kagan Zhur. obshchei Khim. 1970 40 699 (Chem.Abs. 1970,73 14324). loo J. C. Orr M. Merserreau and A. Sanford Chem. Comm. 1970 162. lo' H. B. Henbest and T. R. B. Mitchell J. Chem. Soc. (C) 1970 785. H. B. Charman J. Chem. Soc. (B) 1970 584. lo3 S. P. Dent C. Eaborn and A. Pidcock Chem. Comm. 1970 1703. '04 J. L. Garnett and R. S. Kenyon Chem. Comm. 1970 698. K. P. Davis J. L. Garnett and J. H. O'Keefe Chem. Comm. 1970 1672. Organometallic Compounds-Part (ii) Transitional Elements 313 Increase of electron density at the metal centre promotes the oxidative addition reaction. This can be achieved if the complex contains good donor ligands (e.g. PR,) but not ligands having good acceptor properties (e.g.CO). Many aromatic ortho-metallations of P-and N-donor ligands have been rep~rted.'~Recent examples are the formation of Ir1L*HCl[P(OPh)20C,H4] [P(OPh),] ,Io6 Ru"(CO)CI[P(OPh) OC6H4] [P(OPh)312 O ' and [(2-phenylazophenyl)Ru(C0),C1] lo* which contains a Ru-C bond.Intra- molecular cleavage of an aliphatic C-H bond has been found to occur in the compounds [(8-methylquin01ine)PdCl]~'~~ and PtCl(-CH,CH,CH,PBu',)(PPr"Bu~).' lo Bulky substituents on the tertiary phosphine ligands are thought to promote the latter reaction; the expulsion of a C1- ion and the formation of a Pt-C bond results in less steric crowding. The formyl group reacts with Pt(PPh,),; in the case of benzaldehyde the product is Pt(COPh),(PPh,),." ' In a similar manner the formation of [(n-CSH,)(CSH,)TiH] may occur through [(n-C,H,),Ti] followed by hydride abstraction and Ti-C bond formation.''2 The formation and subsequent cleavage of a metal-carbon bond has been used for the specific introduction of a substituent into the aromatic ring."3 Thus chlorination of [(2-phenylazophenyl)PdCI] yields ortho-chlorinated azobenzene.Deuterium exchange in the ortho-positions of aromatic rings in complexes has been shown to occur using D or D20,even in cases where the metal-carbon compound has not been isolated.' 4 Isomerisation Metal-catalysed C=C Isomerisation.-Three mechanisms have been suggested for the isomerisation of olefins ;(i) hydride addition followed by elimination (ii) n-ally1 mechanism (iii) carbene involvement. The possible intermediates in the n-ally1 mechanism have been isolated at low temperatures and the following equilibrium has been observed ;'l4 Me H The intermediate formation of an ally1 chromium hydride is suggested during the conjugation of polyunsaturated materials catalysed by (arene)Cr(CO),.' lS lo6 E.W. Ainsworth and S. D. Robinson Chem. Comm. 1970 863. lo' J. J. Levison and S. D. Robinson J. Chem. SOC.(A) 1970 639. lo' M. I. Bruce M. Z. Iqbal and F. G. A. Stone Chem. Comm. 1970 1325. G. E. Hartwell R. V. Lawrence and M. F. Smais Chem. Comm. 1970,912. lo A. J. Cherry B. E. Mann B. L. Shaw and R. M. Slade Chem. Comm. 1970 1176. " I. Harvie and R. D. W. Kemmitt Chem. Comm. 1970 198. H. H. Brintzinger and J. E. Bercaw J. Amer. Chem. Soc. 1970,92 6182. 'I3 D. R. Fahey Chem. Comm. 1970,417. I l4 H. Bonnemann Angew.Chem. Internat. Edn. 1970,9 736. E. N. Frankel J. Amer. Oil Chemists' SOC.,1970 47 33. J. P. Candlin A. W. Parkins and K. A. Taylor Ru1I1 Rh'" and Pd" have been used as catalysts for the isomerisation of hex-l- ene,' 16,' '' allylbenzene and phenyl butene."* A semiquantitative correlation of their activity in a variety of complexes has been established. The catalysed isomerisation of hex-1-ene by Co(N,)(PPh,) is thought to involve initial replace- ment of N by the olefin.'" As there are many similarities in mechanism between metal-catalysed isomeri- sation and hydrogenation it is not surprising that many complexes perform both transformations simultaneously. Care is therefore required in analysing the data obtained. Thus RhH(CO)(PPh,) (an active hydrogenation catalystg5) causes the isomerisation of cr-~lefins.~~,'Other active rhodium catalysts include 2o RhCl(PPh,) .l2 Interesting examples are the stereochemically-controlled intra-molecular isomerisation of the ligand in RhCl(CO)(PPh,CH,CH,CH =CH2)296 and the formation of PtCl,(MeCOCH,CMe=CH,) from MeCOCH=CMe by a 1,3-hydride shift.', The following 1,5-hydride shift occurs on heating.', Me H Metal-catalysed Carbon Skeletal Isomerisation.-This is a relatively new area of catalysis in which certain thermodynamically unstable organic compounds are transformed into a more stable isomer by metal complexes the process occuring with or without simultaneous hydrogen transfer.An example of the former reaction is the skeletal rearrangement of 1,4-pentadi- ene to 2-methyl-1.3-butadiene using a NiCl,(PR,),-AlBu;CI ~ata1yst.l~~ The conversion is thought to involve a cylopropylcarbinyl organometallic species.If the cyclopropyl group is part of another ring system ring-expansion takes place.' 'I6 H. Hirai H. Sawai E.-I. Ochiai and S. Makishima J. Catalysis 1970 17 119. '' W. H. Clement and T. Speidel Ind. and Eng. Chem. (Product Res. and Development) 1970,9 220. I * J. Blum and Y.Pickholtz Israel J. Chem. 1969 7 723 ;(Chem. Abs. 1970,72,99825). Il9 J. Kovacs G. Speier and L. Marko Inorg. Chim. Acta 1970,4,412. 2o W. Strohmeier and W. Rehder-Stirnwess J. Organometallic Chem. 1970,22 C27. 2' R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970,495. Iz2 R. D. Gillard B. T. Heaton and M.F. Pilbrow J. Chem. SOC.(A) 1970,353. 23 M. 1. Foreman G. R. Knox P. L. Pauson K. H. Todd and W. E. Watts Chem. Comm. 1970 843. 124 R. G. Miller P. A. Pinke and D. J. Baker J. Amer. Chem. SOC.,1970,92,4490. Iz5 C. B. Reese and A. Shaw J. Amer. Chem. SOC.,1970,92,2566. Organometallic Compounds-Part (ii)Transitional Elements 315 Many three- and four-membered rings undergo bond cleavage under the influence of transition-metal complexes. These transformations are frequently thermally forbidden according to the Woodward-Hoffman rules of orbital symmetry conservation,'26-' 29 but catalysis of these reactions by metal com- plexes occurs either by removal of the symmetry constraints by utilising the appropriate &orbitals of the or by an oxidative addition reac- tion involving C< bond breakage.' Thus the Rhl-catalysed conversions of quadricyclene (13) into n~rbornadiene,'~~ cubane (14) into tricy~lo-octadiene,'~~ and cuneane (15) into semibullvalene'35 are considered to proceed via Rh"' intermediates.(15) Ag' and sometimes Pd" compounds catalyse many of these changes usually in a different manner from the Rh' reaction. Thus cubane (14)is isomerised into Agl or Pd"43 126 R. B. Woodward and R. Hoffman Angew. Chem. Internat. Edn. 1969 8 781. 12' G. B. Gill 'Essays in Chemistry' ed. J. N. Bradley R. D. Gillard and R. F. Hudson Academic Press New York 1970. vol. 1 p. 43. 28 J. J. Vollmer and K. L. Servis J. Chem. Educ. 1970,47,491. 129 R. G. Pearson Theor. Chim. Acta 1970 16 107.I3O W. T. A. M. van der Lugt Tetrahedron Letters 1970 2281. 13' J. Manassen J. Catalysis 1970 16 38. 132 G. L. Caldow and R. A. MacGregor Inorg. Nuclear Chem. Letters 1970,6 645. 133 L. Cassar and J. Halpern Chem. Comm. 1970 1082. 134 1970 92 3518. L. Cassar P. E. Eaton and J. Halpern J. Amer. Chem. SOC., ' L. Cassar P. E. Eaton and J. Halpern J. Amer. Chem. SOC.,1970 92 6366. J. P. Candlin A. W.Parkins and K. A. Taylor cuneane (15),13' 1,l'-bishomocubane (16) into a new CloHlo isomer (17),'369'37 and the azo-compound (18) into the rearranged product (19).138 (16) (17) (18) (19) A carbon-carbon bond-making and -breaking reaction that is commanding increasing attention is olefin disproportionation' 39 (also called olefin metathesis or dismutation).The general reaction is R'R2C=CR3R4 + R5R6C=CR7R8 R1R2C=CR5R6 + R3R4C=CR7R8 where R is hydrogen or hydrocarbon groups. Although this general reaction has been known for several years to be heterogeneously cataly~ed,'~~-'~~ it is only in the last three years that homogeneous catalysts of comparable activity have been di~c0vered.l~~ The catalysts in general are Group VI metal halide- aluminium-alkyl-alcohol or carboxylic acid combinations. Thus MoCl,(NO) -(PPh3)2-Me3A12CI disproportionates pent-1-ene at room temperature to its equilibrium mixture of ethylene and oct-4-ene in under 1 h.I4' (ratio of catalyst substrate is 0.1 mmol 10 ml). Various combinations of substrates illustrate the versatile nature of this catalyst system. The kinetics of the disproportionation of pent-2-ene have been The reaction intermediate is a diolefin-molybdenum complex although a carbene 136 W.G. Dauben M. G. Buzzolini C. H. Schallhorn D. L. Whalen and K. J. Palmer Tetrahedron Letters 1970,787 121 8. 13' L. A. Paquette and J. C. Stowell J. Amer. Chem. SOC.,1970,92,2584. R. Askani Tetrahedron Letters 1970 3349. 139 G. C. Bailey Catalysis Rev. 1969 3 37. J. C. Mol F. R. Visser and C. Boelhouwer J. Catalysis 1970 17 114. 14' A. J. Moffat and A. Clark J. Catalysis 1970 17 264. 14' A. Clark and C. Cook J. Catalysis 1969 15 420. 143 V. V. Atlas I. I. Pis'man and A. M. Baksshi-Zade Khim. Prom. (The Soviet Chemical Industry) 1969 10 17. 144 H. R. Menapace J. Org. Chem. 1968,33,2133. 145 E.A. Zuech W. B. Hughes D. €3. Kubieck and E. T. Kittleman J. Amer. Chem. SOC. 1970 92 528. 146 W. B. Hughes J. Amer. Chem. SOC.,1970,92,532. Organometallic Compounds-Part (ii) Transitional Elements intermediate may explain the appearance of odd-numbered carbon alkenes formed in the disproportionation of ~ct-l-ene.'~' The variety of products obtained from the olefin disproportionation reaction appear to be endless. Catenanes are thought to be formed (mass spectral evidence) when large cyclic dienes are used. '48*149 5 Oligomerisa tion of Unsaturated Hydrocarbons Mono-olefins.-The dimerisation of olefins catalysed by nickel complexes in combination with aluminium alkyls has been studied by many groups of workers following the introduction of n-ally1 nickel catalysts by Wilke and co-workers in theearly 1960's.Recent work includes the system R4P+ [NiCl3(PR3)]-Et3Al2C1 which selectively dimerises propylene to 2,3-dimethylbut-l-ene150 and (n-C4Me4)NiC1,-Et3A1,C1 which dimerises ethylene propylene and butene.' 5' The effect of various Lewis acids (LA) in the olefin dimerisation catalyst system Ni(CO),(PPh3),-LA has been studied. 52 Diethyl(bipyridyl)nickel(rI) although inactive for olefin dimerisation becomes an active catalyst for this reaction when treated with aluminium alkyl halides.' 53 The dimerisation and trimerisation of ethylene' 54 and butene' 55 using Ni(oleate),-AlBu\Cl occurs in common with many of these systems at atmospheric pressure and room temperature or below. 1,3-Diphenylbut-l-ene can be obtained in yields approaching 90 % by the dimeri- sation of styrene using n-ally1 nickel halides.' 56 Pd" complexes e.g.(PhCN),PdCI ,dimerise various olefins in high yields e.g.ethylene propylene methyl acrylate styrene ;'57 in general however the rate of reaction is less than the corresponding reaction catalysed by nickel complexes. Co-dimerisation e.g. ethylene-cyclopentene methyl acrylate-styrene ethylene- styrene can also be performed.'57,'58 14' K. Hummel and W. Ast Naturwiss. 1970,57,245. 148 R. Wolovsky J. Amer. Chem. SOC. 1970,92,2132. 149 D. A. Ben-Efraim C. Batich and E. Wasserman J. Amer. Chem. SOC. 1970 92 2133. lS0 G. G. Eberhardt and W. P. Griffen J. Catalysis 1970,16,245. 15' 0-T. Onsager H. Wang and U. Blindheim Helv.Chim. Acta 1969 52 187 196,215 224 230. M. Born Y. Chauvin G. Lefebre and N.-H. Phung Compt. rend. 1969,268 C 1600. IS3 M. Uchino A. Yamamoto and S. Ikeda J. Organometallic Chem. 1970 24 C63. V. S. Fel'dblyum A. I. Leshcheva and N. V. Obeshchalova Zhur. org. Khim. 1970 6,213; (Chem. Ah. 1970,72 121953). 55 V. S. Fel'dblyum A. I. Lechcheva 0.P. Yablonskii and N. M. Pashchenko Perroleurn Chemistry (U.S.S.R)1968 8 176. L. I. Red'kina K. L. Makovetskii E. I. Tinyakova and B. A. Dolgoplosk Doklady Akad. Nauk S.S.S.R. 1969 186 397. (Chem. Ah. 1969,71,60887). M. C. Barlow M. J. Bryant R. N. Haszeldine and A. G. Mackie J. Organometallic Chem. 1970,21 215. 15' K. Kawamoto T. Imanaka and S. Teranishi Bull. Chem. Sac. Japan 1970,43,2512. 318 J.P. Candlin,A. W.Parkins and K. A. Taylor Recently soluble Ziegler catalysts for oligomerisation of ethylene rather than polymerisation have been reported. Thus (EtO),TiCl-AlEtCl ' 59 and (n-CSH5)2TiRC1-R,Al'60 yield a distribution of products from dimers (but-1-ene) up to -C, . Low molecular weight polypropylene (-C40)can also be obtained from similar catalyst systems.' 61 Reviews on the polymerisation of olefins both from theoretical and practical aspects have appeared.'62,163 Acetylenes.-The cyclotrimerisation of acetylenes to aromatic systems has been known for many years and the corresponding transition-metal-catalysed reaction has received attention during the last year. Although several mechanisms have been postulated only the metallocyclic pathway has received positive support.Thus the formation of 1,2,3,6tetramethylnaphthalene from MeCrCMe and Ph3Cr.3THF is thought to proceed through a chromocycle.' 64 Me 2111 C I + CrPh -+ [;$Cr-P] -P I Me Me Me Electron-withdrawing groups (e.g. CF,) tend to favour metallocycle formation and rhodo-and irido-cyclic compounds (20)'65and (21)'66are stable enough to have these structures confirmed by X-ray and n.m.r. analysis respectively. An organopalladium complex formed by the trimerisation of BUT-CH in the presence of (PhCN),PdCl, is thought from n.m.r. and analytical data to have the skeletal structure (22)167-169[the positions of the But groups have not been determined and therefore omitted from (22)]. The intermediate formation of a cyclobutadiene Rh' species (23)is thought to occur during the cyclotrimerisation of substituted acetylenes.' 'O PdCl 2 (22) 159 G.Henrici-Olive and S. Olive Angew. Chem. Internat. Edn. 1970 9 243. G. Henrici-Olive and S. Olive J. Polymer Sci. Part B 1970 8 271. 161 G. Henrici-Olive and S. Olive J. Polymer Sci.,Part B 1970 8 205. 16' G. Henrici-Olive and S. Olive Ado. Polymer Sci. 1969 6 421. 163 M. N. Berger G. Boocock and R. N. Howard Adu. Catalysis 1969 19 211. 164 G. M. Whitesides and W. J. Ehmann J. Amer. Chem. Soc. 1970,92 5625. J. T. Mague Inorg. Chem. 1970,9 1610. 166 B. Clarke M. Green and F. G. A. Stone J. Chem. SOC.(A) 1970,951. '' K. L. Raiser and P. M. Maitlis Chem. Comm. 1970 942. 16* H. Diet] H. Reinheimer J. Moffat and P.M. Maitlis J. Amer. Chem. Soc. 1970 92 2276. 169 H. Reinheimer J. Moffat and P. M. Maitlis J. Amer. Chem. SOC.,1970 92 2285. 'O E. Miiller and E. Langer Tetrahedron Letters 1970,989,993. 319 Organometallic Compounds-Part (ii) Transitional Elements 0 ___) mR RhCI(PPh,) \/ -\/ R 0 0 RhCI(PPh3)2 OR It appears likely that the cyclotrimerisation of substituted acetylenes using Rh,(CO),,,' 71 Ni(C0)4,' 72 and n-allylnickel halides'73 proceeds through metallocyclic intermediates. Reactions of organic substrates with metallocyclic intermediates have yielded interesting results which may have synthetic utility. Thus the reaction of a cobaltocyclic compound (n-C5H5)(PPh3)Co(C4Ph4) with ethylene yields a complex containing the n-bonded ligand tetraphenylcyclohexadiene.74 Dimerisation of acetylene to yield vinylacetylene is known to take place homo- geneously in the presence of Cu' salts.175 Diolefim-The normal thermal dimerisation of butadiene yields a mixture of 4-vinylcyclohex-1-ene (VCH) and 1,5-cyclo-octadiene (COD) the ratio depending on the conditions. It is therefore not surprising that catalytic dimerisation can be arranged to yield either of these dimers sele~tively.'~~ Thus [n-allylFe(NO),],- SnC12 with butadiene yields VCH almost excl~sively'~~ whereas bis(cyc1o- 0ctatetrene)Fe' yields COD'78 (together with a linear C, tetraene). The effect of added CO (4OOpsi) can also alter this ratio and in some cases (e.g. using Ni[P(OPh),] as catalyst} reverse it ~ompletely.'~~ Electrolytic dimerisation in the presence of Ni" salts also yields a mixture of VCH and COD."' Other butadiene dimer isomers (or their derivatives) can be obtained ; Pd(OAc),-HOAc yields linear octatrienes," 'and catalyst systems (Bu,P),NiCl I ' Y.Iwashita and F. Tamura Bull. Chem. SOC. Japan 1970 43 15 17. S. isaoka K. Kogami and J. Kumanotani Makrornol. Chem. 1970. 135 1. " V. 0.Reikhsfel'd B. I. Lein and K. L. Makovetskii Proc. Acad. Sci.(U.S.S.R.) 1970 190 31. ' H. Yamazaki and N. Hagihara J. Organometallic Chem. 1970,21 431. "' ' T. F. Rutledge 'Acetylene Compounds' Reinhold New York 1968 Chapter 6. R. S. Coffey Ann. Reports (B) 1969,66 317. '" P. L. Maxfield Inorg. Nuclear Chem. Letters 1970 6 707. 78 A. Carbonaro A.Greco and G. Dall'asta J. Organometallic Chem. 1969 20 177. 17' J. F. Kohnle L. H. Slaugh and K. L. Nakamaye J. Amer. Chem. SOC.,1969,91 5905. H. Lehmkuhl and W. Lenchte J. Organometallic Chem. 1970 23 C30. ''I W. E. Walker R. M. Maryik K. E. Atkins and M. L. Farmer Tetrahedron Letters 1970 3817. J. P. Candlin A. W.Parkins and K. A. Taylor -RLi (R = o-C,H,CH,NM~,'~~ or o-C6H4Melg3) yield an unusual five-membered cyclic compound l-vinyI-2-methylenecyclopentane,in high yields. The Nio-P(C,H ,),-catalysed dimerisation of butadiene is known to give COD. The corresponding reaction with 1,3-pentadiene gives dimethylcyclo- octadiene.' 84 The potential use of dimerisation catalysts in natural product chemistry is illustrated by the conversion of Cl0 terpenes into C20 terpenes using Pd" and Pdo catalysts.' 85 The catalytic dimerisation of norbornadiene has been studied many times over the last several years.Binor-S (24) is made using a bifunctional transition-metal catalyst e.g. Zn[Co(CO),] or X,Sn[Co(CO),] The list of catalysts for this dimerisation has been extended to include CoBr,(PPh,) and RhCI(PPh,) ,both (24) (25) in combination with BF,-Et,O as co-catalyst.'87 The action of U.V. light on the Cr(CO),-catalysed dimerisation of norbornadiene gives three stereoisomeric cyclobutane derivatives (25)' 88 The polymerisation of diolefins has been reviewed,189 and the effect of various ligands on the polymerisation of isoprene has been studied.'" Co-dimerimtion.-The catalytic co-dimerisation of butadiene and ethylene yields 1,4-hexadiene.This compound has been used comniercially as a termonomer in ethylene-propylene rubbers. Alterations in the ligand R,P(CH,),PR (PP)in the catalyst system CoCI,(PP)-AlEt show that the above co-dimerisation can be made to go exclusively to 1,4-hexadiene."' The co-dimerisation product from norbornadiene and butadiene depends on the catalyst. Co(acac),-AIEt gives (26) exclusively' 92 whereas Fe(cyc1o-octatetraene) gives a mixture of products which includes (27). 93 J. Kiji K. Masui and J. Furukawa Tetrahedron Letters 1970 2561. J. Kiji K. Masui and J. Furukawa Chem. Comm. 1970 1310. P. Heimbach and H. Hey Angew. Chem. Znternat. Edn. 1970,9 528. *" K. Dunne and F. J. McQuillin J. Chem. SOC.(C) 1970,2196,2200 2203.F. P. Boer J. H. Tsai and J. J. Flynn jun. J. Amer. Chem. SOC., 1970,92 6092. G. N. Schrauzer R. K. Y. Ho and G. Schlesinger Tetrahedron Letters 1970 543. W. Jennings and B. Hill J. Amer. Chem. SOC.,1970,92 3199. G. Natta and L. Porri High Polymers 1969,23 (II) 597; R. E. Rinehard ibid.,p. 867. 19* H. E. Swift J. E. Bozik and C. Y. Wa J. Catalysis 1970 17 331. 19' T. Kagawa Y. Inoue and H. Hashimoto Bull. Chem. SOC.Japan 1970,43 1250. 192 A. Takahashi and T. Inukai Chem. Comm. 1970 1473. 193 A Greco A. Carbonaro and G. Dall'asta J. Org. Chem. 1970 35 271. Organometallic Compounds-Part (ii) Transitional Elements 32 1 The reaction between butadiene and aldehydes (RCHO) is as expected catalysed by Pd" complexes. Vinyl substituted pyrans (28)are obtained and this reaction could have synthetic possibilities.'94.'9s 6 Insertion Reactions A large number of insertion reactions have been reported this year but we shall confine our attention to reactions which involve the formation of C-€ bonds since these are most useful synthetically.An interesting carbene insertion reaction is that between (29)and diphenyldi- azomethane to give (30)as one of the products.'96 OMe I (29) (30) A series of reactions of tetrafluoroethylene with low-valent transition-metal complexes has been reported. lg7 It appears that in some cases a three-membered ring containing a nickel atom may undergo an insertion reaction with C2F to form a five-membered ring Et,P (Et,P),Ni +C2F4 + \/ Ni cF2-TF2 /\ I Et,P CF -CF Tetracyanoethylene may be inserted into cyclopentadienylirondicarbonyl-benzyl.* (n-C,HJFe(CO),CH,Ph +C21CN) -+(n-C,H,)Fe(CO),(CN),C(CN),CH,Ph 194 P. Haynes Tetrahedron Letters 1970 3687. 19' R. M. Maryik W. E. Walker K. E. Atkins and E. S. Hammack Tetrahedron Letters 1970,3813. 196 M. M. Bagga G. Ferguson J. A. D. Jeffreys C. M. Mansell P. L. Pauson I. C. Robertson and J. G. Sime Chem. Comm. 1970,672. 19' C. S. Curdy M. Green and F. G. A. Stone J. Chem. SOC.(A) 1970 1647. 19' S. R. Su J. A. Hanner and A. Wojcicki J. Organometallic Chem. 1970 21 P21. 322 J. P. Candlin,A. W. Parkins and K. A. Taylor A curious insertion reaction occurs when the dinuclear Pd" complex (31) is treated with allene to give (32).199 The reactions of dimethyl and diethyl osmium tetracarbonyls with CO show interesting differences.200 Et,Os(CO) +2CO +(EtCO),Os(CO) Me,Os(CO) +CO +C2H +Os(CO) Isonitriles may be inserted into Pd-Me bonds to give successively (33) (34),and (35).201 A similar reaction to the first stage of this sequence is the isonitrile insertion into Pd" compounds202 and [(n-allyl)PdCl] .203 I PPh,Me \/ RNC+ Pd /\ MePh,P Me I PPh,Me \/ Pd MePh,P /\C-C-CH, II I1 / NR NR JRNC (34) RN'1\pd=PPh2Me C=NR $1 where R =C,H c-c II (35) NR 7 Carbonylation Decarbonylation and Carbonyls in Synthesis Carbony1ation.-Several detailed papers have appeared on the catalytic carbony- lation of olefins.Rhodium complexes continue to attract since many of the carbonylation reactions can be performed at atmospheric pressure and are therefore within the reach of synthetic organic chemists.The partial pressure of CO dictates the product distribution in the carbonyla- tion of propylene using Co,(CO),(PBu,) as cataly~t.~" It has also been shown 199 T. Okamoto Chem. Comm. 1970 1126. 'O0 F. L'Eplattenier and C. Ptlichet Helv. Chim. Acta 1970 53 1091. '01 Y. Yamamoto and H. Yamazaki Bull. Chem. SOC.Japan 1970,43 2653. '02 P. M. Treichel and R. W. Hess J. Amer. Chem. SOC.,1970,92,473 1. '03 T. Kajimoto H. Takahashi and J. Tsuji J. Organometallic Chem. 1970 23 275. 204 C. K. Brown and G. Wilkinson J. Chem. SOC.(A) 1970,2753. '05 A. Hershman K. K. Robinson J. H. Craddock and J. F. Roth Ind.and Eng. Chem. (Product Res. and Development) 1969 8 372. '06 M. Takesada and H. Wakamatsu Bull. Chem. SOC.Japan 1970,43 2192. 'O' F. Piacenti M. Bianchi E. Benedetti and P. Frediani J. Organometallic Chem. 1970 23 257. Organometallic Compounds-Part (ii) Transitional Elements 323 that the acidity of the organometallic carbonyl hydride catalyst affects the rate and product distribution in the carbonylation reaction.208 The carbonylation of olefins using Ru3(CO) has been re~iewed.~” Synthetic applications of the carbonylation reaction include the formation of linear acids or esters from olefins (Pt-Sn catalyst),” * formyl nitriles from nitriles (Co catalyst),” formamides from the corresponding secondary amines (several catalysts including Co Ir Rh and Cu complexes),2 l2 and a cyclic C1,-ring keto- compound by the action of CO on the intermediate obtained from three mole- cules of butadiene and Ni(COD) .’I3 Astudy of the mechanism of carbonylation of organochloro-compounds using z-ally1 Pd complexes CH,=CHCH2Cl+ CO -+ CH,=CHCH,COCI suggests that the active intermediate may be a polymeric complex containing three Pd atoms.214 Similar reactions e.g.carbonylation of benzyl chloride are catalysed by [Ni(CO),X]-where X = C1 Br or I.215 Acyl chlorides can also be formed from olefins [Co,(CO) catalyst] by carrying out the carbonylation in the presence of CCI,:216 CCI + CO + CH,=CHR -+ CI,CCH,CHRCOCI Decarbony1ation.-The decarbonylation of carbonyl compounds by organo- metallic complexes has probably reached the stage when it may be considered a synthetic tool.Although it has been known for many years that heterogeneous catalysts (e.g.Pd-C) can perform this reaction,21 recent work has extended this to homogeneous systems. In some cases depending on conditions the reaction can be made to proceed using catalytic amounts of the transition-metal complex. Thus secondary amides can be converted into nitriles [RhCI(PPh,) as cata- ly~t],~~* although the reaction fails when both hydrogen atoms on the nitrogen are replaced by alkyl groups ArCONHCH,R -+ ArCN + RCHzOH Allylic alcohols yield the corresponding hydrocarbon [RhCI(PPh,) as catalyst] :2 l9 RCH=CHCH20H -RCH,Me ’08 N. S. Imjanctov and D. M. Rudkovskij J.prakt. Chem. 1969,311 712.*09 G. Braca G. Sbrana F. Piacenti and P. Pino Chimica e Zndustriu 1970 52 1091. ’lo L. J. Kehoe and R. A. Schell J. Org. Chem. 1970,35,2846. ’I1 Y. Ono Chem. Comm. 1970 1255. ’’ P. Haynes L. H. Slough and J. F. Kohnte Tetrahedron Letters 1970 365. ‘I3 G. Wilke and H. Breil Angew. Chem. Internat. Edn. 1970,9 367. l4 H. C. Volger K. Vrieze J. W. F. M. Lemmers A. P. Praat and P. W. N. M. Leeuwen Inorg. Chim. Acta 1970,4 435. 215 L. Casser and M. Foa Znorg. Nuclear Chem. Letters 1970 6 291. ’I6 T. Susuki and J. Tsuji J. Org. Chem. 1970,35 2982. J. S. Matthews D. C. Ketter and R. F. Hall J. Urg. Chem.,-l970 35 1694. 218 J. Blum and A. Fisher Tetrahedron Letters l.970 1963. A. Emergy A. C. Oehlschlager and A. M. Unran Terrahedron Letters 1970 4401.324 J. P. Candlin,A. W. Parkins and K. A. Taylor The potential of these catalysts is illustrated by the stereoselective decarbonyla- tion of optically active aldehydes to give hydrocarbons with over 90 % retention of optical activity (Rh catalysts).220 The removal of oxygen by carbonyl complexes from many organic compounds containing N_0221*222 and S-0223 linkages may be useful for the preparation of certain organic compounds R,NO + Fe(CO) -+ R,N + C02 + ‘Fe(CO),’ R2S0 + Fe(CO) + R,S + CO + ‘Fe(CO),’ R,C=NOH + Cr(CO),C(OMe) -+R,C=NHCr(CO), I Me A reaction which involves nucleophilic attack by a carbonylmetallate on an alkyl halide can be used to transform RBr into RCH0.224 In a similar manner the nucleophile formed from Ni(C0)4 and PhLi reacts with styrene epoxide to give the lactone (36):22s 0 PhHC 3 Ph-CH-CH + Ph-C-Ni(CO) -+ I 0 I ‘0’ 0-PhHC (34) 8 Nucleophilic Attack onCo-ordinated Ligands This has been an area of great interest since Chatt’s rationalisation226 of Hof- mann and von Narbutt’s original work.Elegant work carried out in Italy has shown that nucleophilic attack on an olefin co-ordinated to platinum occurs by direct attack on the olefin and not via intramolecular attack involving initial co- ordination of the attacking nucleophile to platin~m.~~’*~~* Several groups of ~~rker~~~~-~~~ have studied the mechanistic aspects of nucleophilic attack on dienes co-ordinated to Pd”. An X-ray structure of (C,H,OMe)Pd(py),Br obtained by nucleophilic attack (by OMe-) on co-ordinated norbornadiene shows that it contains a three-membered ring.233 In addition to the work with 220 H.M. Walborsky and L. E. Allen Tetrahedron Letters 1970 823. 221 H. Alper and J. T. Edward Canad. J. Chem. 1970,48 1543. z2z L. Knauss and E. 0.Fischer Chem. Ber. 1970,103 1262 3744. 223 H.Alper and E. C. H. Keung Tetrahedron Lerters 1970 53. 224 M. P. Cooke J. Amer. Chem. SOC.,1970,92,6080. 225 S. Fukuoka M. Ryang and S. Tsutsumi J. Org. Chem. 1970,35 3184. 226 J. Chatt L. M. Vallarino and L. M.Venanzi J. Chem. SOC.,1957 2496. 22’ A. Panunzi A. De Renzi and G. Paiaro J. Amer. Chem. SOC.,1970,92,3488. 228 R. Lazzaroni P. Salvadori and P. Pino Chem. Comm. 1970 1164. 229 J. K. Stille and D. B. Fox J. Amer. Chem. SOC.,1970,92 1274.230 P. Uguagliati B. Crociani and U. Belluco J. Chem. SOC.(A) 1970 363. 231 J. K. Stille and L. F. Hines J. Amer. Chem. SOC.,1970,92 1798. 232 E. Vedejs and M. F. Salomon J. Amer. Chem. SOC.,1970,92,6965. 233 E. Forsellini G. Bombieri B. Crociani and T. Boschi Chem. Comm. 1970 1203. Organometallic Compounds-Part (ii) Transitional Elements 325 co-ordinated dienes studies have also been carried out on chelating ligands in which one of the donor centres is a tertiary phosphorus atom.234,235 Vinylic chlorine atoms are not very susceptible to nucleophilic displacement but this reaction is facilitated when the double bond is co-ordinated to Pd11.236*237 Allylic halogen atoms also show increased reactivity.238 A synthesis of vinyl chloride which may involve intramolecular nucleophilic attack of C1- on ethylene co-ordinated to Pd" has been re~0rted.l~~ 9 Electrophilic Attack on Co-ordinated Ligands This reaction is favoured by a low oxidation state of the central metal ion.In some cases synthetically useful transformations may be carried out by using the metal ion as a blocking group. For example,24o diphenylacetylene may be acetylated under Friedel-Crafts conditions by forming the Co,(CO) adduct and subsequently decomposing the product with Ce". Further work on the electrophilic substitution of (cyclobutadiene)Fe(C0) has been carried When mercuric acetate is used as the electrophile all the possible substituted mercuriacetates may be obtained. Acetylation of co-ordin- ated dimethylbutadiene [(Me2C4H4)Fe(C0)3],242and arenes [x-RC6H5Cr-(CO)3]243 has been performed.234 W. Hewertson and I. C. Taylor Chem. Comm. 1970,428. 235 P. R. Brookes and R. S. Nyholm Chem. Comm. 1970 169. 236 C. F. Kohl1 and R. Van Helden Rec. Trav. chim. 1968,87,471. 237 M. Yamaji Y. Fujiawa I. Imanaka and S. Teranishi Bull. Chem. SOC.Japan 1970 43 2659. 238 D. G. Brady Chem. Comm. 1970,434. 239 H. A. Tayim Chem. and Ind. 1970 1468. 240 D. Seyferth and A. T. Wehmann J. Amer. Chem. SOC.,1970,92 5520. 241 G. Amiet K. Nicholson and R. Pettit Chem. Comm. 1970 161. 242 A. N. Nesmeyanov K. N. Anisimov and G. K. Magomedov Izvest. Akad. Nuuk S.S.S.R. Ser. khirn. 1970,959 (Chem. Abs. 1970 73 56218). 243 W. R. Jackson and W. B. Jennings J. Chem. SOC.(B),1969 1221.