Bis-tetradentate complexes of Cd(II) and Hg(II) with N8 coordination: structural and NMR comparisons.

Tripodal N4 ligands tris[(1-methylimidazol-2-yl)methyl]amine (L1), bis[(1-methylimidazol-2-yl)methyl][(2-pyridyl)methyl]amine (L2) and [(1-methylimidazol-2-yl)methyl]-bis-[(2-pyridyl)methyl]amine (L3) were used to prepare five new [ML2](ClO4)2 (M = Cd(II), Hg(II)) complexes. All complexes had N8 metal coordination and a trans-bicapped octahedral structure as determined by X-ray crystallography. Metal-nitrogen bond distances generally decreased in the order M-Namine > M-Npyridyl > M-Nimidazoyl, and the perchlorates were well separated from the metal ions. Variable temperature solution state (1)H NMR spectroscopy revealed conditions for slow intramolecular reorganization were more readily accessible for the Cd(II) complexes than for the Hg(II) complexes. Both protons of imidazoyl ring ligand components had large, comparable J((199)Hg(1)H) despite sizable differences in nuclear separation.