The title ligand (MAMI) was prepared by reaction of 2-ethyl-4-methylimidazole and diethanolamine under basic (pH 11) Mannich conditions and treatment of the resultant alcohol with thionyl chloride. The nitrogen mustard formed was derivatized with thiourea to afford a bis(isothiuronium) salt. Hydrolysis of this material to a dimercaptide could only be accomplished efficiently in the presence of transition-metal salts. Treatment of the isothiuronium salt with NiCl2 under basic conditions afforded an incompletely characterized derivative in which, by IR spectroscopy and C:N ratio, the ligand had been completely hydrolyzed to a dimercaptide. Oxidation of this material by I2 and extraction into HCCl3 afforded the title ligand. Changes in the 13C NMR spectrum of MAMI in Me2SO-d6 as a function of added Cd(NO3)2 revealed the formation of a 1:1 complex with Kf ∼ 60 M-1. The coordinated and free ligand are in fast exchange on the 13C NMR scale, and the assessement of the groups involved in complex formation was unclear. However, 113Cd NMR is consistent with coordination by the two N donors in MAMI. The 1:1 complex is in slow exchange on the 113Cd NMR time scale. Crystalline complexes of MAMI with CdCl2 and CdBr2 were isolated. The CdBr2 complex was investigated by X-ray methods. Crystal data: P21/n, a = 12.988 (4) Å, b = 10.899 (3) Å, c = 13.148 (3) Å, β = 108.74 (2)°, Z = 4, R = 0.0235 for 1474 independent reflections. The complex is a highly distorted trigonal bipyramid with 2 Br, 2 N (from imidazole and the tertiary amine functions), and a disulfide S in the coordination sphere. The Cd-S bond is very long (2.938 Å).
|Original language||English (US)|
|Number of pages||5|
|State||Published - 1984|
ASJC Scopus subject areas
- Inorganic Chemistry