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The Reaction of S-methyl-S-cysteine (L-Smc) with racemic s-cis-[Co(dmedba)Cl 2 ] - 1 (H 2 dmedba = N,N'-dimethylethylenediamine-N,N'-di-α-butyric acid) yields A-s-cis-[Co(dmedba)(L-Smc)] 2 with N,O-chelation. Oxidation of sulfur of 2 with H 2 O 2 in a 1: 1 mole ratio gives Δ-s-cis-[Co(dmedba)(L-S(O)mc)] 3 having an uncoordinated sulfenate group. Oxidation of sulfur of L-Smc with H 2 O 2 in a 1: 1 mole ratio produces S-methyl-L-cysteinesulfenate (L-S(O)mc) 5. Direct reaction of 1 with 5 in basic medium gives an N,O-chelated Δ-s-cis-[Co(dmedba)(S-S(O)mc)-N,O], which turned out to be same as obtained by oxidation of 2, while an N, S-chelated Δ-s-cis-[Co(dmedba)(S-S(O)mc)-N,S] complex 4 is obtained in acidic medium from the reaction of 1 with 5. This is one of the rare [Co I I I (N 2 O 2 -type ligand)(amino acid)] type complex preparations, where the reaction conditions determine which mode of N, O and N, S chelation modes is favored. |
