DYNAMICS OF THE ELECTROCHEMICAL-BEHAVIOR OF DIIMINE TRICARBONYL RHENIUM(I) COMPLEXES IN STRICTLY APROTIC MEDIA

The electrochemical behavior of the family of mononuclear Re(I) comple xes, [Re-1((COLX)-L-3](n+), with L = 2,2'-bipyridine (bpy), l,10-phena nthroline (phen) and X = Cl, CN (n = 0); ACN (n = 1) and that of the m etal-metal-bonded dimeric complexes [(L)(CO)(3)Re-Re(CO)(3)(L)] (L bpy , phen) has been studied in various aprotic solvents using cyclic volt ammetry (CV), chronoamperometry, and spectroelectrochemistry. The wide cathodic potential window investigated has permitted the observation of the largest number of redox processes so far obtained for these spe cies. A detailed description of the kinetics of both oxidation and red uction processes of such species is given. The electrochemistry of the complexes [Re(CO)(3)(L)CN] (L = bpy, phen) is reported here for the f irst time. The electrochemical behavior of the monomeric species is gr eatly influenced by the nature of the monodentate ligand X. The concen tration dependence of the cyclic voltammetric reductive behavior has e videnced the occurrence of bimolecular homogeneous processes. Such pro cesses include homogeneous electron transfers and the competitive form ation of metal-metal or mu-Cl bridged dimeric species. The influence o f the solvent and that due to the presence or absence of Cl- ions in s olution is discussed. Digital simulation of the cyclic voltammetric cu rves is extensively used both for confirming the reaction mechanisms a nd for the evaluation of the relevant thermodynamic (E-1/2) and kineti c parameters. Linear correlation between spectroscopic and electrochem ical data for the whole family of monomeric and dimeric complexes has been found.