CRYSTAL-STRUCTURE OF N,N-DIMETHYLTHIOFORMAMIDE SOLVATES OF THE DIVALENT GROUP-12 IONS WITH LINEAR COORDINATION GEOMETRY FOR MERCURY(II), TETRAHEDRAL FOR ZINC(II), AND OCTAHEDRAL FOR CADMIUM(II)

The crystalline solvates of the divalent group 12 metal ions with the soft sulfur donor N,N-dimethylthioformamide display an unusual variati on in coordination number and geometry with two, four, and six ligands attached to the mercury(ll), zinc(II), and cadmium(II), ions, respect ively. Bis(N,N-dimethylthioformamide)mercury(II) perchlorate precipita tes from acetonitrile solution when adding less than 2 equiv of N,N-di methylthioformamide, while the zinc and cadmium solvates crystallize f rom saturated N,N-dimerhylthioformamide solutions. The disolvate [Hg-( SCHN(CH3)(2))(2)](ClO4)(2) crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 6.208(1) Angstrom, b = 15.239(7) Angstrom, c = 8.681(2) Angstrom, beta = 99.30(3)degrees, and Z = 2. Centrosymmetr ic mercury(II) complexes with strong collinear bonds to two N,N-dimeth ylthioformamide molecules, Hg-S 2.350(2) Angstrom, are joined by doubl e bridges of perchlorate ions in chains along the a-axis by four weak interactions between the mercury and the perchlorate oxygen atoms, mea n Hg-O distance 2.84 Angstrom. Tetrakis(N,N-dimethylthioformamide)zinc trifluoromethanesulfonate, [Zn(SCHN(CH3)(2))(4)](CF3SO3)(2), crystall izes in the triclinic space group P (1) over bar (No. 2) with a = 10.4 87(3) Angstrom, b = 13.489(5) Angstrom, c = 68.800(4)degrees, beta = 6 9.260(4)degrees, gamma = 74.05(1)degrees, and Z = 2, with the zinc ion s tetrahedrally surrounded by four N,N-dimethylthioformamide ligands, mean Zn-S distance 2.34 Angstrom. Also the cadmium solvate of correspo nding composition, [Cd(SCHN(CH3)(2))(4)(CF3SO3)(2)], crystallizes in t he space group P (1) over bar, with a = 8.670(1) Angstrom, b = 9.529(1 ) Angstrom, c = 10.685(1) Angstrom, alpha = 75.20(1)degrees, beta = 66 .97(1)degrees gamma = 65.31(1)degrees, and Z = 1, although the structu re comprises centrosymmetric tetrakis(N, ormamide)bis(trifluoromethane sulfonato)cadmium(II) complexes in which four Cd-S bonds (mean 2.65 An gstrom) and two weaker Cd-O bonds at 2.470(2) Angstrom to the trifluor omethanesulfonate ions give rise to a pseudo-octahedral coordination a round the cadmium ion. When using perchlorate instead as counterion, h exakis(N, N-dimethylthioformamide)cadmium perchlorate, [Cd(SCHN(CH3)(2 ))(6)](ClO4)(2), crystallizes in the space group P2(1)/n with a 12.757 (1) Angstrom, b = 7.4681-(6) Angstrom, c = 19.732(2) Angstrom, beta = 96.31(1)degrees, and Z = 2. The mean Cd-S bond distance increases to 2 .715 Angstrom in the fully solvated cadmium ion with almost regular oc tahedral coordination geometry to its six centrosymmetrically related ligands. The effect of the weak internal hydrogen bonding occuring bet ween the hydrogen atom of a -CHS group and the sulfur atom of neighbor ing N,N-dimethylthioformamide ligands is discussed.