Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 65. Reactions of the complexes [FeW(µ-CR)(CO)5(η-C5Me5)] and [Fe2W(µ3-CR)(µ-CO)(CO)8(η-C5Me5)](R = C6H4Me-4) with alkynes R′C2R′(R′= Me or Ph); crystal structures of [FeW{µ-C(R)C(O)C(Me)C(Me)}(CO)5(η-C5Me5)]·CH2Cl2 and [FeW{µ-C(R)C(Et)C(H)C(Me)C(Me)}(µ-CO)(CO)3(η-C5Me5)]

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Abstract
The compounds [FeW(µ-CC6H4Me-4)(CO)5(η-C5Me5)] and [Fe2W(µ3-CC6H4Me-4)(µ-CO)(CO)8(η-C5Me5)] react with PhCCPh in toluene at ca. 85 °C to afford the complex [FeW{µ-C(C6H4Me-4)C(Ph)C(Ph)}(CO)5(η-C5Me5)]. Similarly, the di-iron–tungsten compound and MeCCMe afford the related species [FeW{µ-C(C6H4Me-4)C(Me)C(Me)}(CO)5(η-C5Me5)]. In contrast, the dimetal compound [FeW(µ-CC6H4Me-4)(CO)5(η-C5Me5)] and MeCCMe under mild conditions (ca. 0 °C, in Et2O) yield a mixture of the two complexes [FeW{µ-C(C6H4Me-4)C(O)C(Me)C(Me)}(CO)5(η-C5Me5)](ca. 50–60%) and [FeW{µ-C(C6H4Me-4)C(Et)C(H)C(Me)C(Me)}(µ-CO)(CO)3(η-C5Me5)](ca. 5–10%). The structures of both these products have been established by X-ray diffraction studies. In the former the Fe–W bond [2.722(1)Å] is transversely bridged by a µ-C(C6H4Me-4)C(O)C(Me)C(Me) group, with the end carbon atoms of the chain σ-bonded to the tungsten, and the iron attached to the three carbon atoms carrying the two methyl and the tolyl substituents. The ketonic carbonyl group is at a non-bonding distance from both metal centres. The minor reaction product has an Fe–W bond [2.729(1)Å] bridged by a carbonyl group, the other three carbonyl groups being terminally bound to the iron. The iron atom is part of a [graphic omitted](Me) metallacycle, with all the atoms of this six-membered ring being attached to the tungsten atom which is also ligated by the η-C5Me5 group. The 1H and 13C-{1H} n.m.r. data of the new compounds are reported and discussed.

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