Reactivity of cobalt(III) amine-thiolate complexes with terminal and bridging thiolate functions towards hydrogen peroxide

The reactivity of Co-III amine-thiolate complexes with terminal and bridgin g thiolate functions towards oxidizing agents has been investigated. The mo nonuclear (CON3S3)-N-III complex [Co-III(L-1)] (2) (H3L1 represents the hex adentate ligand N,N',N " -Tris(2-thio-benzyl)-1,1,1-tris(aminomethyl)ethane ) featuring three terminal thiolate ligands, and the binuclear N3CoIII- (mu -S)(3)(CoN3)-N-III complex [Co-2(III)(L-2)](3+) (4) (H3L2 = N,N',N " -Tris -[2-thio-3-aminomethyl- butyl-benzyl] 1,1,1-tris(aminomethyl)ethane) featur ing three bridging thiolates were selected. Hydrogen peroxide was the oxidi zing agent. Whereas the thiolato-bridged complex 4 is resistant towards oxi dation by hydrogen peroxide 2 undergoes a ligand-based oxidation reaction t o give the amine-sulfinate complex [Co(L-1)] 5, where all three terminal th iolates have been oxidized to sulfinates without gross structural changes o f the parent complex 2. In contrast to 4, the cyclic voltammogram of 2 reve als an irreversible oxidation wave at E = +0.52 V vs SCE which can be attri buted to a ligand-centered oxidation reaction. 4 and 5 have been structural ly characterized by X-ray crystallography.