Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 48. Reactions of the cluster complex [Fe2W(µ3-CC6H4Me-4)(µ-CO)(CO)8(η-C5H5)] with [W(CR)(CO)2(η-C5H5)](R = Me or C6H4Me-4); crystal structures of [FeW2(µ3-σ:σ′:η2-CCH2)(CO)7(η-C5H5)2] and [FeW2(µ3-MeC2C6H4Me-4)(CO)7(η-C5H5)2]

In toluene at 80 °C the compounds [Fe2W(µ3-CC6H4Me-4)(µ-CO)(CO)8(η-C5H5)] and [W(CC6H4Me-4)(CO)2(η-C5H5)] react to give the ditungsten complex [W2{µ-C2(C6H4Me-4)2}(CO)4(η-C5H5)2] as the major product. In contrast, the corresponding reaction with [W(CMe)(CO)2(η-C5H5)] yields a separable mixture of three cluster complexes: [FeW2(µ3-σ:σ′:η2CCH2)(CO)7(η-C5H5)2], [FeW2(µ3- MeC2C6H4Me-4)(CO)7(η-C5H5)2], and [FeW2(µ3-CMe)(µ3-CC6H4Me-4)(CO)6(η-C5H5)2] with the last formed in trace amounts. The structures of [FeW2(µ3σ:σ′:η2-CCH2)(CO)7(η-C5H5)2] and [FeW2(µ3-MeC2C6H4Me-4)(CO)7(η-C5H5)2] have been established by X-ray diffraction. In the vinylidene complex an ironditungsten triangle [mean Fe–W 2.854, W–W 3.030(1)A] is bridged by the CCH2 ligand in such a manner that the latter is σ-bonded to the tungsten atoms (mean µ-C–W 2.06 A) and if η2-co-ordinated to the iron [C–Fe 1.96(2) and 2.21(2)A]. The iron atom is bonded by three terminal CO ligands, while the tungsten atoms are each ligated by a C5H5 and two CO groups. Three of the latter weakly semi-bridge the metal–metal bonds. The structure of the alkyne complex [FeW2(µ3-MeC2C6H4Me-4)(CO)7(η-C5H5)2] is based on a triangle of metal atoms [W–W 2.949(1), Fe–W 2.730(1) and 2.992(1)A]. The MeC2C6H4Me-4 ligand lies on the face of the triangle with its C2 axis parallel to a Fe–W bond. The iron atom carries three CO groups and the tungsten atoms two such groups and a C5H5 ligand. Three of the tungsten-ligated CO groups semi-bridge the three edges of the metal triangle [W–C–O 1 64.5(9), 1 67.7(9), and 169.2(9)°]. The n.m.r. data for the compounds are reported, and possible pathways for formation of the three cluster complexes are discussed.