Caging the mercurous ion:: a tetradentate tripodal nitrogen ligand enhances stability and J(1H199Hg)

The dimeric mercurous ion has been encapsulated by a pair of the tetradentate tripodal nitrogen ligands tris[(2-(6-methylpyridyl)) methyl] amine (TLA). The complex [Hg-2(TLA)(2)](ClO4)(2) (1) was isolated directly from an acetonitrile solution of Hg(ClO4)(2) . 3H(2)O and TLA. Complex 1 crystallizes in the triclinic space group (P) over bar1 with a = 10.537( 2) Angstrom, b = 10.751(2) Angstrom, c = 10.907(2) Angstrom, alpha = 75.20(3) degrees, beta = 73.73(3) degrees, gamma = 75.73(3) degrees, and Z = 1. The cation is located an inversion center. The Hg-Hg and Hg-N-amine bond distances are 2.5469(8) and 2.297(6) Angstrom, respectively, and the average Hg-N-pyridyl bond length is 2.75(7) Angstrom. Complex 1 was stable indefinitely in acetonitrile-d(3) solution, permitting detection of 13 and 22 Hz heteronuclear couplings between the Hg( I) ions and the methylene protons of the ligand. Comparisons with the structures and spectroscopic properties of related mercuric and mercurous complexes are made.