Solution-state NMR and X-ray crystallography were used to investigate the complexation of Hg(II) by the tridentate ligand bis [(2-pyridyl)methyl]amine (BMPA). Mercury coordination compounds exhibiting rarely observed solutionstate NMR 1 H 199 Hg satellites were characterized. Temperature and concentration effects on solution-state NMR properties were investigated. The solution-state NMR were correlated with two solid-state structures. The distorted trigonal prismatic complex [Hg(BMPA) 2 ](ClO 4 ) 2 ‚0.5toluene (1) crystallizes in the triclinic space group P1 h with a ) 10.953(5) Å, b ) 12.812(5) Å, c ) 13.006(5) Å, R ) 67.50(3)°, β ) 82.74(3)°, γ ) 67.88(3)°, and Z ) 2. The Hg-N amine bonds are 2.404(4) and 2.350(4) Å and the Hg-N pyridyl bond lengths are similar, ranging from 2.352(4) to 2.557(5) Å. Solution NMR studies are consistent with rapid equilibrium between isomeric trigonal prismatic and facial octahedral forms of this complex. A twisting mechanism is proposed to mediate interconversion. The distorted square planar complex [Hg(BMPA)NCCH 3 ](ClO 4 ) 2 ( 7) crystallizes in the monoclinic space group P2 1 /c with a ) 12.987(2) Å, b ) 17.469(4) Å, c ) 8.886(2) Å, β ) 95.200(12)°, and Z ) 4. The Hg-N amine distance is 2.403 Å, the average Hg-N pyridyl distance is 2.23 Å, and the Hg-N nitrile distance is 2.229 Å. The BMPA ligand is bound to Hg(II) in a meridional fashion with a solvent molecule in the same plane and close associations to two axial perchlorates with Hg-O distances of 2.707(7) and 2.90(2) Å. Solution NMR studies support limited dynamics for a cation with similar interactions between BMPA and Hg(II).

The complexation of Hg(II) by the tripodal ligand tris[(2-pyridyl)methyl]amine (TMPA) was investigated by solution state NMR and X-ray crystallography. Mercury coordination compounds exhibiting rarely observed room-temperature solution state NMR 1H199Hg and 13C199Hg satellites were characterized. Solvent, counterion, temperature, and concentration effects on solution state NMR properties were investigated. The solution state NMR were correlated with two solid state structures. The eight-coordinate complex [Hg(TMPA)2](ClO4)2 (1) crystallizes in the monoclinic space group P21/n with a = 9.735(10) Å, b = 10.963(2) Å, c = 18.553(34) Å, β = 103.81(12)°, and Z = 2. The mercury is at the inversion center of a bicapped trigonal antiprism. The Hg−Namine distance is 2.560(3) Å, and the average Hg−Npyridyl distance is 2.58(2) Å. The five-coordinate complex [Hg(TMPA)Cl]2(HgCl4) (2) crystallizes in the triclinic space group P1̄ with a = 11.887(2) Å, b = 13.260(2) Å, c = 15.278(4) Å, α = 112.27(2)°, β = 109.39(2)°, γ = 90.670(10)°, and Z = 2. The two crystallographically unique cations are distorted trigonal bipyramids. The average Hg−Cl distance is 2.355(12) Å, the average Hg−Namine distance is 2.43(2) Å, and the average Hg−Npyridyl distance is 2.40(5) Å.

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)(ClO(4))(2), Cd(1)(2)(ClO(4))(2), and Zn(1)(2)(ClO(4))(2).CH(3)CN form mononuclear, six-coordinate species in the solid state with 1 binding in a tridentate coordination mode. Hg(1)(2)(ClO(4))(2) has a distorted trigonal prismatic coordination geometry while Cd(1)(2)(ClO(4))(2) and Zn(1)(2)(ClO(4))(2).CH(3)CN have distorted octahedral geometries. With chloride anions, the 1:1 metal to ligand complexes Hg(1)Cl(2), [Cd(1)Cl(2)](2), and Zn(1)Cl(2) are formed. A bidentate binding mode that lacks thioether coordination is observed for 1 in the four-coordinate, distorted tetrahedral complexes Zn(1)Cl(2) and Hg(1)Cl(2). [Cd(1)Cl(2)](2) is dimeric with a distorted octahedral coordination geometry and a tridentate 1. Hg(1)Cl(2) is comprised of pairs of loosely associated monomers and Zn(1)Cl(2) is monomeric. In addition, Hg(2)(1)Cl(4) 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 (1)H NMR spectra of [Hg(1)(2)](2+) and [Hg(1)(NCCH(3))(x)()](2+) reveal (3)(-)(5)J((199)Hg(1)H) due to slow ligand exchange found in these thioether complexes. Implications for use of Hg(II) as a metallobioprobe are discussed.

The coordination chemistry of Hg() with tris[(1-methylimidazol-2-yl)methyl]amine (TMIMA) was investigated. The structures of [Hg(TMIMA) 2 ](ClO 4 ) 2 (1), [Hg(TMIMA)(NCCH 3 )](ClO 4 ) 2 (2) and [Hg(TMIMA)Cl] 2 (HgCl 4 ) (3) were characterized by X-ray crystallography. Complex 1 has six strong Hg-N imidazoyl bonds ranging from 2.257(5) to 2.631(6) Å. Ligand geometry suggests the Hg-N (NR 3 ) distances of 2.959(6) Å in 1 reflects weak bonding interactions. This complex has a 199 Hg chemical shift of Ϫ1496 ppm, significantly upfield from nitrogen coordination complexes with lower coordination numbers. The five-coordinate complex 2 has Hg-N (NR 3 ) , Hg-N imidazoyl and Hg-N acetonitrile bond lengths of 2.642(8), 2.198(5) and 2.264(11) Å, respectively. Complex 3 is also five coordinate, with Hg-N (NR 3 ) , Hg-Cl and average Hg-N imidazoyl distances in the cations of 2.758(7), 2.424(2) and 2.29(4) Å, respectively. Conditions for slow exchange on the J(HgH) coupling time-scale were found for both 1 : 1 metal-to-ligand complexes in acetonitrile-d 3 . Observed heteronuclear coupling constants were similar to those associated with Hg() substituted proteins with histidine-metal bonds. Solution and solid-state comparisons to the Hg() coordination chemistry of tetradenate pyridyl ligands are made. Relevance to development of 199 Hg NMR as a metallobioprobe is discussed.

Tridentate ligand N-(2-pyridylmethyl)-N-(2-(ethylthiolato)amine (L) forms the novel complex [Hg(5)(L)(6)](ClO(4))(4).toluene () with a bicyclo[3.3.3] Hg(5)S(6) core and 4-, 5- and 6-coordinate metal centers; characterization of a solution of by ESI-MS revealed elaborate speciation involving [Hg(n)L(n+1)(ClO(4))(n-2)](+), [Hg(n)L(n)(ClO(4))(n-1)](+) and [Hg(n)L(n-1)(ClO(4))(n)](+) ion families.

The complexation of Cd(II) by the tripodal ligand tris[(2-pyridyl)methyl]amine and dipodal ligand bis[(2-pyridyl)methyl]amine was investigated by solution-state NMR and X-ray crystallography. Cadmium coordination compounds exhibiting rarely observed solution-state NMR (1)H-(111/113)Cd satellites were characterized. The eight-coordinate complex [Cd(TMPA)(2)](ClO(4))(2).toluene (1) crystallizes in the triclinic space group P1 with a = 9.629(2) Å, b = 11.020(2) Å, c = 11.641(2) Å, alpha = 114.069(13) degrees, beta = 97.492(13) degrees, gamma = 91.034(14) degrees, and Z = 1. The average Cd-N(amine) distance is 2.53(4) Å and the average Cd-N(pyridyl) distance is 2.54(6) Å. The complex [Cd(BMPA)(NCCH(3))(OH(2))(OClO(3))][Cd(BMPA)(2)](ClO(4))(3).(CH(3)CN) (2) crystallizes in the triclinic space group P&onemacr; with a = 10.446(2) Å, b = 16.653(3) Å, c = 17.736(3) Å, alpha = 62.479(9) degrees, beta = 80.606(14) degrees, gamma = 84.66(2) degrees, and Z = 2. In the pseudo-octahedral monocation, the nitrogen-containing ligands occupy equatorial positions with Cd-N distances of 2.321(8), 2.283(7), and 2.263(8) Å for the amine, pyridyl (average) and acetonitrile nitrogens, respectively. Significant axial interactions occur with Cd-O bond distances of 2.313(7) Å (water) and 2.478(7) Å (perchlorate). In the pseudo-trigonal prismatic dication, the average Cd-N(amine) distances is 2.395(5) Å and the average Cd-N(pyridyl) distance is 2.362(8) Å. The solid-state structures and solution-state NMR trends were very similar to recently reported isovalent complexes of Hg(II), providing an exceptional opportunity to compare coupling constants of coordination compounds. Implications for the use of (111/113)Cd and (199)Hg NMR as metallobioprobes are discussed.

The solution state coordination chemistry of Hg(ClO 4 ) 2 with tris [(2-(6-methylpyridyl))methyl] amine (TLA) was investigated in acetonitrile-d 3 by proton NMR. Although Hg(II) is a d 10 metal ion commonly associated with notoriously rapid exchange between coordination environments, as many as six ligand environments were observed to be in slow exchange on the chemical shift time scale at select metal-to-ligand ratios. One of these ligand environments was associated with extensive heteronuclear coupling between protons and 199 Hg and was assigned to the complex [Hg(TLA)] 2+ . The 5 J( 1 H 199 Hg) = 8 Hz associated with this complex is the first example of five-bond coupling in a nitrogen coordination compound of Hg(II). The spectral complexity of related studies conducted in acetone-d 6 precluded analysis of coordination equilibria. Crystallographic characterization of the T-shaped complex [Hg(TLAH)(CH 2 COCH 3 )](ClO 4 ) 2 (1) in which two pyridyl rings are pendant suggested that the acidity of acetone combined with the poor coordinating abilities of the neutral solvent adds additional complexity to solution equilibria. The complex crystallizes in the triclinic space group P1 with a = 9.352(2) Å, b = 12.956(2) Å, c = 14.199(2) Å, α = 115.458(10)°, β = 90.286 (11)°, γ = 108.445(11)°, and Z = 2. The HgN amine , Hg-N pyridyl , and Hg-C bond lengths in the complex are 2.614(4), 2.159(4), and 2.080(6) Å, respectively. Relevance to development of 199 Hg NMR as a metallobioprobe is discussed.

Solution-state NMR and X-ray crystallography were used to investigate the complexation of HgCl(2) by the potentially tetradentate ligand tris[(6-methyl-2-pyridyl)methyl]amine (TLA) in acetonitrile. A change in the ligand conformation as a function of the metal-to-ligand ratio could be indirectly monitored through large changes in (3)J((1)H(199)Hg) to the methylene protons at -40 degrees C. The solution-state NMR were correlated with two solid-state structures. The five-coordinate complex [Hg(TLA)Cl(2)] (1) crystallizes in the triclinic space group P&onemacr; with a = 8.663(3) Å, b = 11.539(4) Å, c = 13.739(3) Å, alpha = 80.81(2) degrees, beta = 75.84(2) degrees, gamma = 80.97(3) degrees, and Z = 2. The Hg-N(amine) distance of 2.505(7) Å for the tridentate ligand is the same as the average Hg-N(lutidyl) distance of 2.50(3) Å for the two bound lutidyl nitrogens. [Hg(TLA)Cl](2)(Hg(2)Cl(6)) (2) also crystallizes in P&onemacr; with a = 10.606(2) Å, b = 15.104(3) Å, c = 17.785(4) Å, alpha = 67.46(3) degrees, beta = 83.52(3) degrees, gamma = 80.29(3) degrees, and Z = 2. The ligand is tetradentate in the two crystallographically unique cations which are arranged in a dimer-like orientation. The average Hg-Cl distance is 2.37 (1) Å, and the average interionic Hg-Cl distance is 3.51(1) Å. The Hg- N(lutidyl) distances are of two types: two have an average distance of 2.36(3) Å, nearly the same as the Hg-N(amine) distance of 2.35(2) Å. The remaining four N(lutidyl) distances have an average distance of 2.56(5) Å.