Organomercury Compounds Containing Three-Coordinate Mercury. Synthesis and Spectroscopic Studies of Cationic Complexes of Methylmercury(II) with Neutral Donor Ligands

Synthetic and spectroscopic studies of cationic complexes of methylmercury(II), [MeHgL][N03], are reported. The complexes [MeHgL][NO3] (L = pyridine; 2-methyl-, 3-methyl-, 4-methyl-, 2-benzyl-, 2,4-dimethyl-, and 2,6-dimethylpyridine; 2,2'-bipyridyl; 3,3'-dimethyl-, 4,4'-dimethyl-, 5,5'-dimethyl-, and 6,6'-dimethyl-2,2'-bipyridyl;, l0-phenanthroline; 2,9-dimethyl-, 4,7-dimethyl-, and 5,6-dimethyl-1,10-phenanthroline) are obtained from addition reactions in acetone. A complex of composition MeHgN03.1/2L is also formed by 3,3'-dimethyl-2,2'-bipyridyl. Infrared evidence for coordination of ligands in the solid complexes is presented. Proton magnetic resonance spectra indicate that the complexes of 2,2'-bipyridyls (except for those of 3,3'-dimethyl-2,2'-bipyridyl) and 1,10-phenanthrolines have three-coordinate mercury in solution. A linear correlation is observed between J(1H-199Hg) and protonation constants of the ligands, with separate relationships for complexes of unidentate ligands, bidentate 2,2'-bipyridyls, and 1,l0-phenanthrolines. Aspects of bonding in three-coordinate complexes are deduced from 1H and 13C NMR of the complexes and an X-ray structural determination of [MeHg(2,2'-bpy)][N03]. Bonding between mercury and carbon in the three-coordinate complexes is considered to be similar to that in the linear sp-hybridized complexes of pyridine ligands. Comparison of structural data for the 2,2'-bipyridyl and some amino acid complexes of methylmercury suggests that a similar sp hybridization bonding model is applicable for the latter complexes.