Characterization of HgCl2 Tridentate Amine Complexes by X-ray Crystallography, NMR and ESI–MS

Two new HgCl 2 complexes of tridentate nitrogen ligands were characterized by X-ray crystallography, proton NMR spectroscopy and ESI–MS. The five-coordinate complex [Hg(BMPA)Cl 2 ] ( 1 ) (BMPA = bis(2-pyridylmethyl)amine) crystallized from acetonitrile/ m -xylene by slow evaporation in the monoclinic space group P2 1 / n with a = 8.3896(8) Å, b = 12.8020(13) Å, c = 13.3526(13) Å, α = 90°, β = 90.480(2)°, γ = 90° and z = 4. The square pyramidal structure (τ = 0.009) has approximate C s symmetry. Despite comparable Hg–N bond lengths in 1 , inversion of the central nitrogen was rapid on the chemical shift time scale in dilute solution except at very low temperatures. The related complex [Hg(BEPA)Cl 2 ] ( 2 ) (BEPA = bis(2-{pyrid-2-yl}ethyl)amine) crystallized from acetonitrile/ethyl acetate/hexanes by slow diffusion in the orthorhombic space group Pnma with a = 13.424(3) Å, b = 14.854(3) Å, c = 8.118(2) Å, α = 90°, β = 90°, γ = 90° and z = 4. The mixed geometry structure (τ = 0.56) also has crystallographic mirror symmetry as well as C s point group symmetry. In dilute acetonitrile solution, 1 was stable while 2 slowly converted to a more thermodynamically stable complex. Graphical Abstract