Ligand effects on the electrooxidation of molybdenum halide complexes of the type CpMo(CO) 3− n(PR 3) nX and ChMo(CO) 2X

• Published in: Inorganica Chimica Acta Vol. 172; no. 1; pp. 41 - 44
• Main Authors: Yau, Yi Lau, Huckabee, William W., Gipson, Stephen L.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.06.1990; Elsevier Science
• Subjects: Chemical reactivity; Chemistry; Exact sciences and technology; Organic chemistry; Reactivity and mechanisms; Ligand effect; Tertiary phosphine; Organic ligand; Hapto complex; Transition metal Carbonyl Complexes; Oxidation; Molybdenum Organic compounds; Electrochemical reaction; Molybdenum Complexes; Halo complex
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(00)80447-8

Complexes of the type CpMo(CO) 3− n (PR 3) n X and ChMo(CO) 2X, where Cp = η 5-C 5H 5, Ch = η 7-C 7H 7 and X = halide, can be oxidized electrochemically by one electron in dichloromethane. The potential necessary for oxidation and the rate of decomposition of the resulting cation decrease as n increases or as the phosphine becomes a better electron donor. A linear correlation is observed between the highest energy carbonyl stretching frequency and the formal or peak potential for the oxidation. As the halide is changed from chloride to bromide to iodide the oxidation potential increases but the rate of decomposition of the cation decreases. Both of these trends can be traced to the inverse halide order, in which the oxidation potential increases as the electronegativity of the halide ligand decreases. This effect arises from greater metal to halide backbonding in the complexes of the heavier halogens, which decreases electron density on the metal center and thus increases the oxidation potential. However the added bond order with the heavier halogens apparently also stabilizes those cations toward decomposition.