Synthesis, characterization, and reactivity of W2Ru3 clusters that contain oxo and carbido ligands, obtained by direct C-O bond activation

Treatment of CpWRu3(CO)12(μ-H) with CpW(CO)3H in refluxing heptane afforded the cluster compound Cp2W2Ru3(CO)13 (1). Single-crystal X-ray analysis indicates a trigonal-bipyramidal cluster arrangement with both W atoms located at the equatorial positions. Pyrolysis of 1 in refluxing toluene gave the oxo-carbido cluster CpW(O)CpWRu3(μ5-C)(CO)11 (2a) in moderate yield, whereas the condensation of LWRu3(CO)12(μ-H) and L′W(CO)3H (L = L′ = Cp*; L, L′ = Cp, Cp* or Cp*, Cp) afforded the derivatives LW(O)L′WRu3(μ5-C)(CO)11 (2b, L = L′ = Cp*; 2c, L = Cp; L′ = Cp*) exclusively. A combination of spectroscopic and structural data suggests that the complexes 2 adopt a wingtip-bridged butterfly structure and possess a terminal oxo and an interstitial carbide ligand. Thus, the transformation from 1 to 2 illustrates an example of metal-assisted cleavage of the carbonyl C-O bond. Mechanistic considerations based on the result of 17O labeling studies are discussed. Furthermore, extensive heating of 2b,c in toluene leads via elimination of two CO ligands to the formation of the new cluster complexes LL′W2(μ-O)Ru3(μ5-C)(CO)9 (3b, L = L′ = Cp*; 3c, L = Cp; L′ = Cp*), in which a distorted-square-pyramidal core structure has been confirmed by single-crystal X-ray analysis. Treatment of 3 with CO gives regeneration of the complexes 2 in high yield.