Synthesis, Structure, and Electrochemistry of Acetylide and Oxo Incorporated Mixed Fe/Mo and Fe/W Chalcogen-Bridged Clusters

Thermolysis of a benzene solution containing [Fe₂Mo(CO)₁₀(μ₃-Se)₂] (1) and [(η⁵-C₅Me₅)W(CO)₃C⋮CPh] (2) under an optimum concentration of oxygen in the reaction medium yields the cluster [(η⁵-C₅Me₅)MoWFe₂(O)(μ₃-Se)(μ₄-Se)(CO)₈(CCPh)] (3), containing a monooxygenated metal center. Under an argon atmosphere, thermolysis of [Fe₂Mo(CO)₁₀(μ₃-S)₂] (4) with [(η⁵-C₅Me₅)W(CO)₃C⋮CPh] (2) in benzene leads to an oxygen-free mixed metal cluster [(η⁵-C₅Me₅)MoWFe₄(μ₃-S)₃(μ₄-S)(CO)₁₄(CCPh)] (9). Interestingly, on reacting a benzene solution of 4 with 2 and [(η⁵-C₅Me₅)Mo(CO)₃C⋮CPh] (5) under an increased concentration of oxygen in the reaction medium gave way to clusters [(η⁵-C₅Me₅)WMo₂(μ-O)₂(μ-S)(μ₃-CCPh){Fe₂(CO)₆(μ₃-S)₂}₂] (6), [(η⁵-C₅Me₅)WMo(O)₂(μ-O)(μ-CCPh){Fe₂(CO)₆(μ₃-S)₂}] (7), and [(η⁵-C₅Me₅)Mo₃(μ-O)₂(μ-S)(μ₃-CCPh){Fe₂(CO)₆(μ₃-S)₂}₂] (8) with higher oxygen content. The structures of the newly formed clusters 3, 6, 7, 8, and 9 were established crystallographically and the oxo-containing Mo and W clusters investigated electrochemically.