Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 76. Alkylidyne–alkyne coupling reactions involving the complexes [WCo(CR)(CO)8](R = Me or C6H4Me-4)

Abstract

In light petroleum, at room temperature, the reaction between [WCo(CC₆H₄Me-4)(CO)₈] and the alkyne C₂(C₆H₄Me-4)₂ affords the complex [WCo{µ-C₃(C₆H₄Me-4)₃}(CO)₇]. The latter reacts reversibly with CO to give a product tentatively identified as [WCo{µ-C(C₆H₄Me-4)C(C₆H₄Me-4)-C(C₆H₄Me-4)C(O)}(CO)₇]. Treatment of [WCo(CC₆H₄Me-4)(CO)₈] with PhCCPh affords a mixture of the isomeric compounds [WCo{µ-C(R¹)C(R²)C(R³)}(CO)₇](R¹= C₆H₄Me-4, R²= R³= Ph; R²= C₆H₄Me-4, R¹= R³= Ph). With MeCCSiMe₃, the compounds [WCo(CR)(CO)₈](R = C₆H₄Me-4 or Me) react to give the complexes [WCo{µ-C(R)C(Me)C(SiMe₃)C(O)}(CO)₇] which reversibly lose CO to yield the species [WCo{µ-C(R)C(Me)C(SiMe₃)}(CO)₇]. Both the former and the latter products on treatment with PPh₃ give the complexes [WCo{µ-C(R)C(Me)C(SiMe₃)C(O)}(CO)₆(PPh₃)] quantitatively. The compound [WCo(CMe)(CO)₈] reacts with EtCCEt to afford an inseparable mixture of three isomeric compounds [WCo{µ-C(R¹)C(R²)C(R³)C(O)}(CO)₇](R¹= R²= Et, R³= Me; R¹= R³= Et, R²= Me; R²= R³= Et, R¹= Me). The ¹H and ¹³C-{¹H} n.m.r. data for the various tungsten–cobalt complexes are reported and discussed in the context of the structures proposed.