ELECTROCHEMICAL STUDY OF SOME CHLORO COMPLEXES OF TITANIUM, MOLYBDENUM, IRON, ALUMINUM OR TIN IN HIGH OXIDATION-STATES

The electrochemical behavior of some bimetallic complexes, commonly wi th a transition (M = Ti, Mo or Fe) and a non-transition metal (Mg, Al or Sn), in high oxidation states, in particular [TiCl4(mu t-Cl)(2)Mg(t hf)(4)] (thf = tetrahydrofuran), [Mg(thf)(6)][TiC5(thf)](2), [Mg-2(mu- Cl)(3)(thf)(6)][TiCl5(thf)], Cl)(3)(thf)(6)][MoOCl4(thf)],[MgCl(thf)(5 )][FeCl4] or [MgCl(thf)(5)][AlCl4], as well as of the related species [Bu(4)N](2)[TiCl6] and [Bu(4)N][AlCl4], has been investigated in aprot ic media by cyclic voltammetry (CV) and controlled potential electroly sis (CPE) at Pt electrodes. The complexes exhibit, by CV, one quasi-re versible cathodic wave (with the exception of the Fe compound for whic h this wave presents a reversible character) which, by CPE, usually in volves one electron per transition metal atom or per aluminium atom. T heir reduction potential [ca. -0.5 to -1.0 V vs. SCE (M = Ti), ca. -0. 9 V (M = Mo) or ca. -0.1 V (M = Fe)] is discussed in terms of charge, metal oxidation state, and ligand effects. A partial chloride ligand d issociation, which is promoted by cathodic reduction, has been detecte d by CV for the Ti complexes. Some of the cathodic processes were also studied by digital simulation of the cyclic voltammograms, which allo wed to investigate their electrochemical and/or chemical irreversibili ty and to estimate relevant kinetic parameters, and suggested the poss ibility of occurrence of cathodically induced trimerization of titaniu m species. The application of one of the titanium complexes to the ele ctroactivation of small unsaturated molecules, such as olefins, was al so successfully tested.