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

Reactions of nickelocene with Ru-5(mu (5)-C-2)(mu -SMe)(2)(mu -PPh2)(2)(CO)(11) have given NiRu5(mu (6)-C-2)(mu -SMe)(2)(mu -PPh2)(2)(CO)(9)Cp-2 and Ni2Ru4(mu (6)-C-2)(mu -SMe)(2)(mu -PPh2)(2)(CO)(8)Cp-2 whose molecular structures have been determined. The NiRu5 cluster is related to other heterometallic clusters containing FeRu5, Ru-6 or Co2Ru5 cores which contain two edge-fused squares supporting the C-2 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 C-2 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(mu (6)-C-2)(mu -SMe)(2)(mu -PPh2)(2)(CO)(8)Cp-2 to rationalise these two observed coordination modes of the C-2 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 C-2-containing polynuclear organometallic clusters.