Reactions of nickelocene with an Ru_5 cluster: crystal structures of two nickel-ruthrnium clusters containing C_2 ligands

摘要

Reactions of nickelocene with Ru_5(#mu#_5-C_2)(#mu#_SM)_2(#mu#-PPh_2)_2(CO)_(11) have given NiRu_5(#mu#_6-C_2)(#mu#-Sme)_2(#mu#-PPh_2)_2(CO)_9Cp_2 and Ni_2Ru_4(#mu#_6-C_2)(#mu#-Sme)_2(#mu#-PPh_2)_2(CO)_8Cp_2 whose molecular structures have been determined. The NiRu_5 cluster is related to other heterometallic clusters containing FeRu_5, Ru_6 or Co_2Ru_5 cores which contain two edge-fused squares supporting the C_2 ligand, one carbon occupying the center 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 Ni_2Ru_4 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 Ni_2Ru_4(#mu#_6-C_2)(#mu#-Sme)_2(#mu#-PPh_2)_2(CO)_8Cp_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.