Methimazole complexes of platinum(II): Synthesis, characterization and redox behavior

A variety of platinum(II) complexes of methimazole (2-mercapto-1-methylimidazole; HImS = neutral form and ImS = thiolate form), coordinated in both thione and thiolate forms, have been isolated by reacting methimazole with [PtCl(terpy)] Cl (terpy = 2,20: 60,200 terpyridine), [PtCl2(bipy)] (bipy = bipyridine), [PtCl2(o-phen)] (o-phen = o-phenanthroline), [PtCl2(CH3CN)(2)] and [PtCl2(COD)] (COD = 1,5-cyclooctadiene). These complexes were characterized by electronic absorption, IR and NMR (H-1, C-13, Pt-195) spectroscopies. Molecular structure of [Pt(bipy)(HImS)(2)]Cl-2 center dot 3H(2)O (3a center dot 3H(2)O) has been established by single crystal X-ray crystallography. Platinum thiolate complex, [Pt(ImS) 2(HImS) 2] (5), could be obtained by treatment of [Pt(HImS)(4)] Cl-2 with sodium methoxide in methanol. The solution of 5 in organic solvents yielded bi- and tri-nuclear platinum complexes. The effect of diimine ligands on oxidation of methimazole moiety in the complexes has been studied by electrochemical oxidation and pulse radiolytic oxidation employing specific one-electron oxidant, N-3(center dot) radical. (C) 2011 Elsevier B.V. All rights reserved.