Crystal and molecular structure of the complex [1,2-bis(diphenylphosphino)ethane](diethylphenylphosphine)tri-isothiocyanatorhenium(III) and the electrochemistry of isothiocyanato-derivatives of rhenium(III) and rhenium(IV)

Abstract

Crystals of the title complex are triclinic, space group P, with unit-cell dimensions a= 9.680(3), b= 12.519(4), c= 19.072(8)Å, α= 68.86(3), β= 71.82(3), γ= 75.40(2)°, and Z= 2. The intensities of 4 025 reflections above background have been collected and the structure refined by least-squares techniques to R′ 0.046. The complex exists as discrete pseudo-octahedral monomers. The rhenium atom in a given molecule is co-ordinated by three phosphorus and three nitrogen atoms in a mer configuration. Cyclic-voltametric studies on dichloromethane solutions of [Re(NCS)₃(PEt₂Ph)L′][L′= 1,2-bis(diphenylphosphino)ethane, 2,2′-bipyridyl, or 1,10-phenanthroline] show that these complexes exhibit three electrochemically reversible one-electron waves attributable to [Re]¹⁺â†�[Re]⁰→[Re]^1–→[Re]^2–, thereby demonstrating the existence of an extensive redox chemistry for these species. The results of these electrochemical studies are compared with the related behaviour of [NBu₄]₂[Re₂(NCS)₈] and [NBu₄]₂[Re(NCS)₆].