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]

Abstract

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)Å] 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 Å) and if η²-co-ordinated to the iron [C–Fe 1.96(2) and 2.21(2)Å]. 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)Å]. 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.