Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 73. Reactions of [WCo(CR)(CO)8](R = C6H4Me-4 or Me) with alkynes. Crystal structures of [WCo{µ-C(C6H4Me-4)C(Me)C(Me)C(O)}(CO)6(PPh3)] and [WCo{µ-C(Ph)C(Me)C(Me)C(OH)}(CO)6(PPh3)][BF4

Abstract

In light petroleum at room temperature the compound [WCo(CR)(CO)8](R = C6H4Me-4) reacts with MeCCMe or EtCCEt to give the complexes [WCo{µ-C(R)C(R1)C(R1)C(O)}(CO)7](R1= Me or Et), whereas MeCCEt affords an inseparable mixture of the species [WCo{µ-C(R)C(R1)C(R2)C(O)}(CO)7](R1= Me, R2= Et; R1= Et, R2= Me). Reactions between [WCo(CMe)(CO)8] and MeCCMe or MeCCPh yield the compounds [WCo{µ-C(Me)C(Me)C(Me)C(O)}(CO)7] and [WCo{µ-C(Ph)C(Me)C(Me)C(O)}(CO)7], respectively. Treatment of these various products with PPh3 leads to substitution of a CO ligand on the cobalt atom by the phosphine, and the structure of one of these derivatives [WCo{µ-C(C6H4Me-4)C(Me)C(Me)C(O)}(CO)6(PPh3)] has been established by X-ray diffraction. The W–Co bond [2.737(1)A] is spanned by the C(C6H4Me-4)C(Me)C(Me)C(O) fragment, with the terminal carbon atoms of the chain σ bonded to the cobalt, and with the carbon atoms of the C(C6H4Me-4)C(Me)C(Me) moiety η3 co-ordinated to the tungsten. The latter carries four terminal CO groups, and the cobalt two such ligands and the PPh3 group [Co–P 2.237(2)A, P–Co–W 146.4(1)°]. Protonation of the complex [WCo{µ-C(Me)C(Me)C(Me)C(O)}(CO)7] with HBF4·Et2O affords the salt [WCo{µ-C(Me)C(Me)C(Me)C(OH)}(CO)7][BF4]. Three PPh3 derivatives of the alkyne-adducts of [WCo(CR)(CO)8](R = C6H4Me-4 or Me) have also been protonated, and the structure of the salt [WCo{µ-C(Ph)C(Me)C(Me)C(OH)}(CO)6(PPh3)][BF4] has been established by X-ray diffraction. The results confirm that in the latter the phenyl group is attached to the carbon atom at the end of the µ-C4 chain, and that this carbon atom and that of the C(OH) group are σ bonded to the cobalt. The tungsten atom is ligated by all four carbon atoms of the bridging ligand, by the cobalt atom [W–Co 2.660(1)A], and by four terminal carbonyl groups. The cobalt atom carries two terminal carbonyl ligands and the PPh3 group [Co–P 2.261(1)A] with the latter sited transoid to the W–Co bond [P–Co–W 144.8(1)°]. The n.m.r. data (1H, 13C-{1H}, 31P-{1H}) for the new compounds are reported and discussed in relation to their structures.