Transition metal complexes of the zwitterionic amino acid DL-methylsulfoniummethioninate and of the amido acid derived from it by facile amine deprotonation

Abstract

The reaction of the zwitterionic dl-methylsulfoniummethioninate, (CH 3) 2SCH 2CH 2CH(NH 2)COO −, with chromium(III), cobalt(II), nickel(II), copper(II), and zinc(II) salts have been examined. These mostly give rise to formation of octahedral complexes containing either bidentate or tridentate aminocarboxylate coordination. Under facile conditions the metal ions catalyse the deprotonation of the amino nitrogen to yield complexes of the amido acid (CH 3) +SCH 2 CH 2CH(NH)COO −. The unusual reactions of these ligands and the unusual properties of some of the resulting complexes is thought to be due, at least in part, to the formal anionic and cationic centers which exist in these species. The complexes were characterized by magnetic measurements and by visible reflectance and infrared spectral measurements.