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

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.