COMPARATIVE-STUDIES OF MONONUCLEAR NICKEL(II) COMPLEXES WITH N2SX (X=2-4) LIGANDS

The new ligands 1,12-bis(2-pyridyl)-2,5,8,11-tetrathiadecane (L3) and 1,13-bis(2-pyridyl)-2,5,9,12-tetrathiaundecane (L4) their complexes and those of 1,6-bis(2-pyridyl)-2, 5-dithiahexane (L1) and 1,9-bis(2-pyridyl)-2,5,8-trithianonane (L2) have been prepared as their perchlorate and tetrafluoroborate salts. Crystal data are as follows. For triclinic [Ni(L1)(CH3CN)(2)][ClO4](2): space group P (l) over bar; a = 11.269(3), b = 11.889(3), c = 10.624(2) Angstrom; alpha = 115.25(1), beta = 91.25(2), gamma = 99.68(2)degrees; Z = 2; R = 0.057, R(W) = 0.048 for 2207 reflections. For triclinic [Ni(L2)(H2O)][ClO4](2).CH3OH: space group Pl; a = 11.515(3), b = 11.869(2), c = 11.466(2) Angstrom; alpha = 98.72(2), beta 118.22(1), gamma = 73.00(2)degrees; Z = 2; R = 0.050, R(W) = 0.043 for 2907 reflections. For monoclinic [Ni(L3)][ClO4](2): space group C2/c; a = 18.126(9), b = 11.599(8), c = 14.506(4) Angstrom; beta = 124.42(1)degrees; Z = 4; R = 0.047, R(W) = 0.042 for 1531 reflections. All complexes are pseudooctahedral with coordination sites filled by donor atoms of ligands L1-L4 or solvent. There is no coordination of anions to the metal either in the solids or in solution, but evidence is presented for a second coordination sphere interaction in some cases. Electronic spectroscopic parameters are found to be sensitive to the number and nature of donors in the coordination sphere and to chain length between donor sites. Cyclic voltammetry reveals a sensitivity to anion in some cases but none to chain length, in contrast to the electronic spectroscopic results. Increasing the number of thioether donors increases the positive character of E(1/2).