Electrochemically induced transformations of bi- and trinuclear heterometallic vinylidene complexes containing Re, Pd and Fe

Abstract

Redox-induced transformations of bi-Cp(CO)2RePd(μ-Cdouble bond; length as m-dashCHPh)(PPh3)2 (2), Cp(CO)2RePd(μ-Cdouble bond; length as m-dashCHPh)(P-P) [P-P = η2-Ph2P(CH2)2PPh2 (dppe) (3), η2-Ph2P(CH2)3PPh2 (dppp) (4)], Cp(CO)2ReFe(μ-Cdouble bond; length as m-dashCHPh)(CO)4 (5) and trinuclear Cp(CO)2ReFe2(μ3-Cdouble bond; length as m-dashCHPh)(CO)6 (6), CpReFePd(µ3-Cdouble bond; length as m-dashCHPh)(CO)5(P-P) [P-P = dppe (7), dppp (8)] heterometallic vinylidene complexes derived from Cp(CO)2Redouble bond; length as m-dashCdouble bond; length as m-dashCHPh (1) were investigated by electrochemical methods. The oxidation processes of clusters 7 and 8 were studied by EPR spectroscopy. The electrochemical properties of clusters 7 and 8 were shown to depend on the nature of the chelate diphosphine ligand at the palladium center in contrast to complexes 3 and 4. The oxidation of complexes 2–4 was found to result in the Re-Pd, Pd-C bond cleavage and formation of rhenium complex 1 and Pd-containing fragments. The oxidation of 7 and 8 resulted in the formation of the radical cations 7+radical dot and 8+radical dot, which sequentially transformed into a number of intermediate products: Cp(CO)2RePd(μ-Cdouble bond; length as m-dashCHPh)(P-P), [Fe(CO)3]+radical dot, [CpReFe2(µ3-Cdouble bond; length as m-dashCHPh)(CO)6]+radical dot and others. The final products of their oxidation in both cases were triangular clusters (CO)8Fe2Pd(P-P) [P-P = dppe (9), dppp (10)] and rhenium complex 1. The molecular structure of cluster 7 was established by X-ray diffraction analysis.