Electrochemical properties of the first Re(I)-carbonyl compound of di-2-pyridyl ketone.oxime (dpk.oxime), fac-Re(CO)3(dpk.oxime)Cl, in non-aqueous media

The reaction between Re(CO)(5)Cl and di-2-pyridyl ketone.oxime (dpk.oxime) in refluxing toluene gave fac-Re)(CO)(3) (dpk.oxime)Cl (2) in good yield. This marks the first time that a rhenium compound of di-2-pyridyl ketone.oxime has been isolated. The formulation of (2) as fac-Re(CO)(3)(dpk.oxime)Cl is based on the results of a number of spectroscopic measurements and a comparison of these results with those reported for fac-Re(CO)(3)(dpk)Cl (3) (dpk = di-2-pyridyl ketone) and other compounds of the alpha-diimine ligands of the type fac-Re(CO)(3)(L-L)X (L-L = alpha-diimine and X = halide). Compound (2) exhibits rich spectroscopic and electrochemical properties. Electrochemical measurements reveal that the oxime moiety in fac-R(CO)(3)(dpk.oxime)Cl acts as an electron sink/reservoir and its first reduction potential dpk.oxime/dpk.oxime(.-) in non-aqueous media is solvent dependent and controlled by the proton accepting ability of the solvent. Plausible mechanisms for the reduction and oxidation of fac-Re(CO)(3)(dpk.oxime)Cl to fac-Re(CO)(3)(dpkH.NH2)Cl and fac-Re(CO)(3)(dpk)Cl are proposed which are consistent with the chemical transformations following electronic transfers. (C) 1999 Published by Elsevier Science S.A. All rights reserved.