Reactivity of Cobalt(III) Amine-Thiolate Complexes with Terminal and Bridging Thiolate Functions towards Hydrogen Peroxide

Reprint requests to Dr. B. Kersting. E-mail: [email protected] Z. Naturforsch. 55 b, 1179-1187 (2000); received August 17, 2000 Cobalt Complexes, Amine-Thiolate Ligands, Sulfinate Complexes The reactivity of Co111 amine-thiolate complexes with terminal and bridging thiolate func­ tions towards oxidizing agents has been investigated. The mononuclear Co N3S3 complex [Coni(L1)] (2) (H3L 1 represents the hexadentate ligand /V,jV',./V"-Tris(2-thio-benzyl)-1,1,1 -tris(aminomethyl)ethane) featuring three terminal thiolate ligands, and the binuclear N3Com(Ai-S)3ComN3 complex [Coni2(L2)]3+ (4) (H3L2 = N, A^/V''-Tris-[2-thio-3-aminomethyl-5-terrbutyl-benzyl]-l,l,l-tris(aminomethyl)ethane) featuring three bridging thiolates were selected. Hydrogen peroxide was the oxidizing agent. Whereas the thiolato-bridged complex 4 is resis­ tant towards oxidation by hydrogen peroxide, 2 undergoes a ligand-based oxidation reaction to give the amine-sulfinate complex [Co(L'')] 5, where all three terminal thiolates have been oxidized to sulfinates without gross structural changes of the parent complex 2. In contrast to 4, the cyclic voltammogram of 2 reveals an irreversible oxidation wave at E = +0.52 V vs SCE which can be attributed to a ligand-centered oxidation reaction. 4 and 5 have been structurally characterized by X-ray crystallography.