ELECTROCHEMISTRY OF THE NICKEL(II) TRIS(2-DIPHENYLPHOSPHINOETHYL)PHOSPHINE HALIDE CATIONS AND AN X-RAY CRYSTALLOGRAPHIC STRUCTURE OF [NI(ETA(4)-P3P')BR][PF6]CENTER-DOT-1/2MECN-CENTER-DOT-H2O

摘要

The electrochemistry of the nickel(II) tris(2-diphenylphosphinoethyl)phosphine (P3P') halide cations [Ni(eta 4(l)-P3P')X](+) (X = Cl, Br, I) has been studied in acetonitrile and dichloromethane. The cations undergo reduction to the nickel(0) [Ni(eta(4)-(PP)-P-3')X](-) species. For the bromo and iodo complexes, reduction is followed by loss of halide and the formation of a P3P'-bridged nickel(0) dimer. In acetrnitrile [Ni(eta(4)-P3P')I](+) also loses iodide via a solvent exchange equilibrium. All the complexes are reversibly oxidized to the analogous nickel(III) species, and irreversibly oxidized to the corresponding nickel(IV) species. The structure of [Ni(eta(4)-P3P')Br][PF6].1/2(MeCN)-(H2O) was determined by single-crystal X-ray crystallography. The complex crystallizes as dark purple plates in space group P