Water-Soluble α-Amino Acid Complexes of Molybdenum as Potential Antidotes for Cyanide Poisoning: Synthesis and Catalytic Studies of Threonine, Methionine, Serine, and Leucine Complexes.

Water-soluble complexes are desirable for the aqueous detoxification of cyanide. Molybdenum complexes with α-amino acid and disulfide ligands with the formula K[(L)MoO(μ-S)(S)] (L = leu (), met (), thr (), and ser ()) were synthesized in a reaction of [(DMF)MoO(μ-S)(S)] with deprotonated α-amino acids; leu, met, thr, and ser are the carboxylate anions of l-leucine, l-methionine, l-threonine, and l-serine, respectively. Potassium salts of α-amino acids (leu (), met (), thr (), and ser ()) were prepared as precursors for complexes -, respectively, by employing a nonaqueous synthesis route. The ligand exchange reaction of [MoO(μ-S)(DMF)](I) with deprotonated α-amino acids afforded -α-amino acid complexes, [(L)MoO(μ-S)] (-). A -α-amino acid complex, [(leu)MoO(μ-S)(μ-leu + H)] (; leu + H is the carboxylate anion of l-leucine with the amine protonated), formed in the reaction with leucine. crystallized from methanol with a third weakly bonded leucine as a bridging bidentate carboxylate. An adduct of with SCN coordinated, , crystallized and was structurally characterized. Complexes - are air stable and highly water-soluble chiral molecules. Cytotoxicity studies in the A549 cell line gave IC values that range from 80 to 400 μM. Cyclic voltammetry traces of - show solvent-dependent irreversible electrochemical behavior. Complexes - demonstrated the ability to catalyze the reaction of thiosulfate and cyanide to exhaustively transform cyanide to thiocyanate in less than 1 h.