Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 55. Coupling of methylene and alkylidyne groups at a trimetal centre; crystal structures of [Ru2W{µ-σ:η-trans-CHC(H)R}(µ-CO)(CO)3(η-C5H5)2(η-C5Me5)]·CH2Cl2 and [Ru2W(µ3-CCH2R)(µ-CO)3(CO)(η-C5H5)3](R = C6H4Me-4)

Abstract

The compounds [Ru₂(µ-CH₂)(µ-CO)(CO)(NCMe)(η-C₅H₅)₂] and [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-4 or Me) react in CH₂Cl₂ at room temperature to give, in low yield, mixtures of the trimetal complexes [Ru₂W{µ-σ:η-trans-CHC(H)R}(µ-CO)(CO)₃(η-C₅H₅)₃](3a, R = C₆H₄Me-4; 3b, R = Me) and [Ru₂W(µ₃-CCH₂R)(µ-CO)₃(CO)(η-C₅H₅)₃](4a, R = C₆H₄Me-4; 4b, R = Me). In a similar reaction, [W(CC₆H₄Me-4)(CO)₂(η-C₅Me₅)] and [Ru₂(µ-CH₂)(µ-CO)(CO)(NCMe)(η-C₅H₅)₂] afford a mixture of [Ru₂W{µ-σ:η-trans-CHC(H)R}(µ-CO)(µ₃-CO)₂(η-C₅H₅)₂(η-C₅Me₅)](5) and [Ru₂W(µ₃-CCH₂R)(µ-CO)₃(CO)(η-C₅H₅)₂(η-C₅Me₅)](4c). The unsaturated complex (5) in solution reacts reversibly with CO to give [Ru₂W{µ-σ:η-trans-CHC(H)R}(µ-CO)(CO)₃(η-C₅H₅)₂(η-C₅Me₅)](3c). The spectroscopic properties (i.r., and ¹H and ¹³C-{¹H} n.m.r.) of the new compounds are reported and discussed. Compounds (3c) and (4a) were studied by X-ray diffraction. The former, which crystallises with a molecule of CH₂Cl₂, has a structure based on a triangle of metal atoms [Ru–Ru 2.782(1), Ru-W 2.771(1) and 2.952(1)Å] The ruthenium–ruthenium bond is symmetrically bridged by a CO ligand, and the shorter Ru–W vector is bridged by a trans-CHC(H)C₆H₄Me-4 group, which is σ bonded to the tungsten and η² co-ordinated to the ruthenium. The latter carries a C₅H₅ ligand as does the other ruthenium atom, which is also ligated by a terminal CO. The tungsten atom is bonded by two CO groups and the η-C₅Me₅ moiety. The structure of (4a) proved to be disordered, but it was apparent that the Ru₂W triangle was capped by the CCH₂C₆H₄Me-4 group with the three edges of the metal triangle bridged by CO ligands.