BS8 I TSCobalt-tungsten complexes [CoW(p-CRCRtCR2) (C0)2(q-C5H5) (q-C5Me5)] (R = C6H4Me-4 ; R1 = R2 = Ph or Me; R1 = Ph or Me, R2 = M e or Ph; R1 = But, R2 = H), with ally1 groups bridging the Co-W bonds, have been prepared by heating the alkynes PhCECPh, MeC-CMe, MeCGCPh, and Bu'C-CH with the compound [CoW(p-CR)(C0),(q-C5H5) (q-C5Me5)]. Related iron-tungsten compounds [FeW(p-CRCR1CR2)(C0)5(q-C5H5)] (R1 = R2 = Me, Ph, C6H4Me-4, or CF3) have been prepared by heating the appropriate alkyne R1 C=CR2 with the cluster complex [Fe2W(p3-CR)-(p-CO) (CO)a(q-C5H5)] in toluene. In contrast, the diiron-tungsten species reacts with Me3SiC=CSiMe3 and with Bu1C=CSiMe3 to afford compounds [Fe2W(p3-CR) (p-alkyne) (p-CO) (C0)6(q-C5H5)] which retain the p3-CFe2W structural core, the product from Bu1C=CSiMe3 being formed as a mixture of isomers. The H and ?3C-(l H} n.m.r. data for all the compounds are reported and discussed, and the molecular structures of [ FeW(p-C( C6H4Me-4) C( Me) C( Me) )( CO) 5(q-C5H5)] and [ Fe2W(p3-CC6H4Me-4) (p-Me3SiC2SiMe3) (p-CO) (CO)6(q-C5H5)] have been established by X-ray diffraction. In the dimetal compound the Fe-W bond [2.720(1) A] is bridged by a three-carbon chain [mean C-C 1.438(8) A]. Whereas all the atoms of the chain are bound to the iron [2.047(6), 2.1 03(6), and 2.083(6) A], only the t w o end carbons are attached to the tungsten [2.194(6) and 2.164(7) A]. The iron * 1 ,I ,I ,2,2-Pentacarbonyl-2-q-cyclopentadienyl-~.~-[ 1',2'-dimethyl-3'-ptolylpropen-1 '-~1-3'-ylidene-C*-~( Fe)C*.3(W)]-irontungsten (Fe-W ) and 1,3-~.~-bis(trirnethylsilyi)acetylene-1,2-p-carbonyl-I , I ,2,2,2,3-hexacarbonyI-3-q-cyclopentadienyl-~~-~-tolylmethy~idyne-triangulo-di-irontungsten.compound from which they are prepared. In this event two different reaction pathways may be followed; both, however, involve C-C bond formation. Either dimerisation of the tolylmethylidynetungsten complex occurs to give [ W2(p-RC2R)-(CO)4(q-CsHs)2], or more usefully trimetal clusters are produced with MW2 triangles bridged by the alkyne C2(C,H,Me-4)2.5*9.10 The chemistry of carbyne groups when bridging metal-metal bonds is currently of interest, and this prompted us to study reactions of alkynes with some of the di-and trimetal compounds containing p-CR ligands. It was expected that C-C bond-forming processes would be observed, as found with some of the reactions of [W(XR)(CO),(q-C,H,)] mentioned above. In this paper we describe reactions of the species [CoW(~-CR)(CO),(q-CsHs)(q-C,Me,)] and [Fe2W-(p3-CR)(p-CO)(C0),(q-C5Hs)] with alkynes. A preliminary report has been given."
Results and DiscussionThe compound [CoW(p-CR)(CO),(q-C5Hs)(q-CsMe,)] proved to be relatively inert towards alkynes, and no significant reaction occurred unless the reactants were heated in toluene
