Redox-active dinuclear oxorhenium(V) pyrazolate complexes

Abstract

Four new structurally similar dinuclear oxorhenium(V) complexes, [{Re(O)X(PPh3)}2(μ-O)(μ-4-X′-pz)2], where pz = pyrazolate anion, X = X′ = Cl (1) and Br (4), X = Cl, X′ = Br (2), and X = Br, X′ = Cl (3), have been synthesized and characterized. Little variation in spectroscopic features – 1H NMR, IR, UV–Vis – exists among the four complexes. All complexes possess a bent Re-O-Re core as well as distorted octahedral coordination geometry around the rhenium centers. A reversible one-electron electrochemical process is observed at approximately 0.84 V vs. Fc+/Fc in all four complexes; however, changing the terminal halide from chloride to bromide slightly destabilizes the oxidized Re(VI) center.