BINUCLEAR COMPLEXES OF RHODIUM OR COPPER WITH PENTAMETHYLCYCLOPENTADIENYLTRICARBONYLTUNGSTEN - CRYSTAL-STRUCTURE OF (ETA(5)-C(5)ME(5))(CO)W(MU-CO)(2)RH(PPH(3))(2)

The reaction of Li[W(CO)(3)Cp] (Cp* = eta(5)-C(5)Me(5)) with [RhCl(PP h(3))(3)] affords [Cp(CO)W(mu-CO)(2)Rh(PPh(3))(2)], 3, which has been structurally characterised by an X-ray diffraction study, and shown t o contain a short W-Rh bond of 2.5820(6) Angstrom and two semi-bridgin g CO ligands. Variable temperature P-31{H-1} NMR spectra show that com plex 3 is fluxional in solution and undergoes intramolecular interchan ge of inequivalent PPh(3) with Delta G double dagger ca. 30 kJ mol(-1) at -105 degrees C. Reaction of Li[W(CO)(3)Cp] with [RhCl(PPh(3))(3)] gives the mono-triphenylphosphine complex [CpW(CO)(3)Cu(PPh(3))](n) 4a, which has the same valence electron count as 3 and has been charac terised analytically and by IR and NMR spectroscopy. Evidence for a re lated molybdenum-copper species, 4b, is also presented. The structural and spectroscopic properties of new products are discussed in relatio n to those of related heterobinuclear compounds.