Reactions of nickelocene with an Ru₅ cluster: crystal structures of two nickel-ruthenium clusters containing C₂ ligands

Abstract

Reactions of nickelocene with Ru5(μ₅-C₂)(μ-SMe)₂(μ-PPh₂)₂(CO)₁₁ have given NiRu₅(μ₆-C₂)(μ-SMe)₂(μ-PPh2)₂- (CO)₉Cp₂ and Ni₂Ru4(μ₆-C₂)(μ-SMe)₂(μ-PPh₂)₂(CO) ₈Cp₂ whose molecular structures have been determined. The NiRu5 cluster is related to other heterometallic clusters containing FeRu₅, Ru₆ or Co₂Ru₅ cores which contain two edge-fused squares supporting the C₂ ligand, one carbon occupying the centre of each square face while retaining the C–C bond. However, there is no formal M–M interaction along the shared edge. Substitution of CO groups by Cp on one Ru atom has occurred. The structure of the Ni₂Ru₄ cluster is similar, with the six-membered ring having the boat conformation. The C₂ ligand takes up two disordered (1 : 1) positions, either parallel or perpendicular to the non-bonding Ni _ _ _ Ni vector. Extended Hückel and density functional calculations have been carried out on Ni₂Ru₄(μ₆-C₂)(μ-SMe)₂(μ-PPh₂)₂ (CO)₈Cp₂ to rationalise these two observed coordination modes of the C₂ unit to the metal framework. Results suggest that the two arrangements are isoenergetic and that the M–C bonding follows the Dewar–Chatt–Duncanson model as previously found for related C₂-containing polynuclear organometallic clusters.