Synthesis and Characterization of Diphenyl-2-thienylphosphine Derivatives

The reaction of [Co2{μ-C2(CO2Me)2}(CO)6] with the ligand diphenyl-2-thienylphosphine, PPh2(C4H3S), yields the complexes [Co2{μ-C2(CO2Me)2}(CO)5{PPh2(C4H3S)}] (1) and [Co2{μ-C2(CO2Me)2}(CO)4{PPh2(C4H3S)}2] (2). The related complex [Co3(μ3CMe)(CO)9] reacts with the same ligand to give [Co3(μ3-CMe)(CO)8{PPh2(C4H3S)}] (3) and [Co3(μ3-CMe)(CO)7{PPh2(C4H3S))2] (4). Thermolysis of 1 at 80°C leads to partial conversion of 1 into 2, which is isolated in low yield. Similarly, thermolysis of 3 at 70°C results in partial conversion of 3 to 4. Coordination of the thienyl unit of the diphenyl-2-thienylphosphine ligand to cobalt could not be detected in these thermolyses. Complexes 1–4 have been completely characterized and the crystal structure of complex 4 has been determined.