Study of metal exchange reactions in cobalt containing clusters

Treatment of the linked cluster {[(μ3-C)R]Co2Mo(CO)8[η5-C5H4C(O)]}2C6H4-p (1a, R=CO2Et; 1b, R=C6H5) with the substituted cyclopentadienyl tricarbonyl molybdenum anion [Mo(CO)3(η5-C5H4R′)]− in THF gave rise to the formation of the single cluster complex [(μ3-C)R]Co2Mo(CO)8(η5-C5H4R′) (2a, R=CO2Et, R′=H; 2b, R=CO2Et, R′=C(O)Me; 2c, R=R′=CO2Et; 2d, R=C6H5, R′=CO2Et) as the only product. However, reaction of cluster {(μ3-Se)RuCoMo(CO)8[η5-C5H4C(O)]}2C6H4-p (1c) with NaMo(CO)3[η5-C5H4C(O)Me] yielded the linked cluster compound (μ3-Se)RuCoMo(CO)8[η5-C5H4C(O)-p-C6H4-C(O)C5H4-η5](CO)7RuMo2(μ3-Se)[η5-C5H4C(O)Me] (3). Further reactions of 2b and cluster [(μ3-C)CO2Et]Co2Mo(CO)8[η5-C5H4C(O)-p-C6H4CO2Me] (2e), respectively, with the monoanion [Mo(CO)3(η5-C5H5)]− gave four products 2a, [(μ3-C)CO2Et]CoMo2(CO)7(η5-C5H5)2 (4), [(μ3-C)CO2Et]CoMo2(CO)8(η5-C5H4R)(η5-C5H5) (5a, R=C(O)Me; 5b, R=C(O)-p-C6H4CO2Me) and [(μ3-C)CO2Et]CoMo2(CO)8(η5-C5H4R)2 (6a, R=C(O)Me). By contrast, treatment of cluster 2a with the monoanion [Mo(CO)3(η5-C5H4R)]− afforded three cluster products 4, 2 (2b, R=C(O)Me; 2e, R=C(O)-p-C6H4CO2Me) and 5 (5a, R=C(O)Me; 5b, R=C(O)-p-C6H4CO2Me). All the compounds were fully characterized by elemental and spectroscopic analyses. The molecular structures of clusters 2a and 4 have been determined by single-crystal X-ray diffraction.