Site of Bond Breaking in mer-(Dihapto-[60]fullerene) (Dihapto-1,2-Bis-(DiphenyIphosphino)ethane Tricarbonyl Tungsten(0)

Abstract Piperidine (pip) displaces l,2-bis(diphenylphosphino)ethane (dppe) from mer-(η2-C60)(η2-dppe)W(CO)3 to produce mer*-(η2-C60)(η1-ρίρ)2\ν(ΟΟ)3. The reactions are first order and second order with respect to the molar concentrations of m£r-(r|2-C60)(r|2-dppe)W(CO)3 and pip, respectively. The proposed mechanism, based on the rate law and on the activation parameters, involves an initial pip-assisted ringopening of the dppe ligand to produce the electronically-saturated intermediate fac (η2-C60)(η'-ρίρ) (n1-dppe)W(CO)3. This mechanism differs from previously proposed mechanisms for the ligand exchange reactions of closely-related complexes such as/fac-(η1-L)(η2-dppe)W(CO)3 (L = CO, piperidine, pyridine) and is contrary to the known cis labilizing property of dppe. These results suggest that [60]fullerene has a strong steric influence on the inorganic moiety of the complex and on its chemical behavior.