C-4-RING LIGAND-TRANSFER REACTIONS - APPLICATIONS TO CLUSTER CHEMISTRY - CRYSTAL-STRUCTURES OF [RU5C(CO)(13)(ETA-C(4)PH(4))] AND [RU6C(CO)(15)(ETA-C(4)PH(4))]

Redox-mediated ligand-transfer reactions between the cationic complex [Pd(eta-C(4)Ph(4))(Me(2)CO)(2)](2+) and the dianionic clusters, [Ru5C(CO)(14)](2-) and [Ru6C(CO)(16)](2-) afforded [Ru5C(CO)(13)(eta-C(4)Ph(4))] 1 and [Ru6C(CO)(15)(eta-C(4)Ph(4))] 2, respectively. The new clusters 1 and 2 have been characterised by spectroscopic techniques in solution and in the solid-state by single crystal X-ray diffraction. In 1 the ring is co-ordinated to a basal ruthenium atom of the square-pyramidal cluster framework, while in 2 the octahedral metal core of the parent complex has opened slightly through the elongation of one Ru-Ru bond. The reasons for this structural change have been analysed using extended-Huckel molecular-orbital calculations.