Solid-State and Solution-State Coordination Chemistry of the Zinc Triad with the Mixed N,S Donor Ligand Bis(2-methylpyridyl) Sulfide

The binding of group 12 metal ions to bis(2-methylpyridyl) sulfide (1) was investigated by X-ray crystallography and
NMR. Seven structures of the chloride and perchlorate salts of Hg(II), Cd(II), and Zn(II) with 1 are reported. Hg(1)2(ClO4)2, Cd(1)2(ClO4)2, and Zn(1)2(ClO4)2·CH3CN form mononuclear, six-coordinate species in the solid state
with 1 binding in a tridentate coordination mode. Hg(1)2(ClO4)2 has a distorted trigonal prismatic coordination geometry
while Cd(1)2(ClO4)2 and Zn(1)2(ClO4)2·CH3CN have distorted octahedral geometries. With chloride anions, the 1:1
metal to ligand complexes Hg(1)Cl2, [Cd(1)Cl2]2, and Zn(1)Cl2 are formed. A bidentate binding mode that lacks
thioether coordination is observed for 1 in the four-coordinate, distorted tetrahedral complexes Zn(1)Cl2 and Hg(1)Cl2. [Cd(1)Cl2]2 is dimeric with a distorted octahedral coordination geometry and a tridentate 1. Hg(1)Cl2 is
comprised of pairs of loosely associated monomers and Zn(1)Cl2 is monomeric. In addition, Hg2(1)Cl4 is formed
with alternating chloride and thioether bridges. The distorted square pyramidal Hg(II) centers result in a supramolecular
zigzagging chain in the solid state. The solution 1H NMR spectra of [Hg(1)2]2+ and [Hg(1)(NCCH3)x]2+ reveal
3-5J(199Hg1H) due to slow ligand exchange found in these thioether complexes. Implications for use of Hg(II) as a
metallobioprobe are discussed.