Electrochemically induced ligand substitutions on [OsCl3(PMe2Ph)3]: rational pathways to osmium(II) complexes

Abstract

Following electroreduction of [OsCl₃(PMe₂Ph)₃] it is possible to stabilise and characterise the reactive monoanion [OsCl₃(PMe₂Ph)₃]^–. This monoanion readily releases chloride to give a detectable five-co-ordinate intermediate which further reacts with a donor solvent or available ligands to produce [OsCl₂(PMe₂Ph)₃L](L = MeCN, dimethylformamide, dimethyl sulphoxide, PhCN, CO,N₂, or C₂H₄), initially as the trans isomer. The latter can be converted into the cis form. When L = PMe₂Ph, the ‘trans isomer’ formed is not trans-[OsCl₂(PMe₂Ph)₄] and should be formulated as trans-[OsCl₂(PMe₂Ph)3(P′Me₂Ph)] with a unique weakly bound phosphine. In non-co-ordinating media, concentrated solutions of [OsCl₂(PMe₂Ph)₃] undergo further reactions to form doubly and triply bridged binuclear species such as [Os₂Clq(PMe₂Ph)₆] and [Os₂Cl₃(PMe₂Ph)₆]⁺. This series of electroinitiated reactions of mer-[OsCl₃(PMe₂Ph)₃] has so far yielded over 20 separate complexes individually identified by both spectroscopic methods and voltammetric data.