SYNTHESIS, CRYSTAL-STRUCTURE, ELECTROCHEMISTRY AND ELECTRONIC PARAMAGNETIC-RESONANCE SPECTROSCOPY OF [M((PPH2CH2)3CME)(O-S2C6H4)][PF6]N (M=FE, CO OR RH, N=0 OR 1)

Monomeric thiolate complexes of formula [M{(PPh2CH2)3CMe}(o-S2C6H4)][P F6]n (M = Fe(II), Fe(III), Co(II), Co(III), Rh(II) or Rh(III); n = 0 o r 1) have been synthesized. The molecular structure of all these compo unds has been established by single-crystal X-ray diffraction studies. All the complexes display a square-pyramidal geometry with differing degrees of distortion depending on the oxidation state and electronic configuration of the metal. Electrochemistry served to localize the fo rmal electrode potentials of the different M(II)-M(III) couples. In di chloromethane solution, the iron(III) complex (E-degree = +0.04 V vs. saturated calomel electrode) is easier to reduce than the cobalt(III) complex (E-degree = -0.39 V), which in turn is easier to reduce than t he rhodium(III) complex (E-degree = -0.69 V). In the case of the iron species, the possibility of obtaining the somewhat stable Fe(I) congen er has been realized. The paramagnetic Fe(I) and Fe(III), Co(II) and R h(II) derivatives have been studied by EPR spectroscopy under differen t experimental conditions, confirming that the unpaired electron is ma inly localized on the metal centre. For cobalt and rhodium derivatives EPR results indicate the presence in solution of a chemical equilibri um between two different isomers.