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 Huckel 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.