Electrochemical behaviour and reactivity of [Os(bpy)(2)(CO)(OTf)](+) in halogenated solvents

The dimethylaminopyridine (DMAP) promoted reaction between [Os(bpy)(2)(CO)(OTf)]OTf (where OTf = CF3SO3-) and methylene chloride is reported. C-Cl bond breaking of a solvent molecule leads to the formation of the [Os(bpy)(2)(CO)(Cl)]OTf complex. The reactivity and redox properties of [Os(bpy)(2)(CO)(OTf)]OTf were investigated by means of room- and low-temperature electrochemical experiments. In CH2Cl2, at low temperature, the complex undergoes two le electrochemical and chemical reversible reductions (ErEr mechanism), but at room temperature a more complex electrochemical mechanism is observed, leading to the electro-synthesis of [Os(bpy)(2)(CO)(Cl)]OTf via electrochemical reversible and chemical irreversible reduction processes (ErCi mechanism). The DMAP nucleophilicity was used to produce the new [Os(bpy)(2)(CO)(Br)]OTf and [Os(bpy)(2)(CO)(I)]OTf complexes which have been fully characterized. (C) 2004 Elsevier B.V. All rights reserved.