PENTACOORDINATED NICKEL(II) COMPLEXES WITH THIOLATO LIGATION - SYNTHETIC STRATEGY, STRUCTURES, AND PROPERTIES

Reaction of [Ni(terpy)Cl2] with 2 equiv of thiolates in methanol or acetonitrile affords, depending on the basicity and bulk of the thiolate, the thiolato-bridged dimer [Ni(terpy)(SPh)2]2.6CH3OH (1), solvated monomer [Ni(terpy)(SC6F5)2(CH3CN)]. 3CH3CN (2) and the desired pentacoordinated [Ni(terpy)(S-2,4,6-(i-Pr)3C6H2)2].1.5CH3CN (3). Complex 1 crystallizes in the monoclinic space group P2(1)/c, with a = 9.908 (2) angstrom, b = 20.441 (6) angstrom, c = 14.340 (4) angstrom, beta = 102.20 (2)-degrees, V = 2839 (1) angstrom, and Z = 2. The structure of 1 was refined to R = 5.2% on the basis of 2590 (I > 3-sigma-(I)) data. Complex 2 also crystallizes in the monoclinic space group P2(1)/c, with a = 10.197 (3) angstrom, b = 31.659 (7) angstrom, c = 11.431 (3) angstrom, beta = 105.58 (2)-degrees, V = 3554.6 (6) angstrom 3, and Z = 4. On the basis of 2618 (I > 4-sigma-(I)) data, the structure was refined to R = 7.85%. Complex 3 crystallizes in the triclinic space group P1BAR with a = 16.786 (6) angstrom, b = 17.266 (6) angstrom, c = 18.534 (7) angstrom, alpha = 68.34 (3)-degrees, beta = 64.57 (3)-degrees, gamma = 71.93 (3)-degrees, V = 4286 (3) angstrom 3, and Z = 4. The structure of 3 was refined to 8.06% by using 8587 (I > 4-sigma-(I)) data. In 1 and 2, the coordination geometry around nickel is distorted octahedral while that in 3 is distorted trigonal bipyramidal. In donor solvents, 1 splits into two solvated monomers. The NMR peaks corresponding to the protons of the thiolate ligands in 1-3 have been assigned. In DMF, complexes 2 and 3 are reduced by Na2S2O4 to generate [Ni(terpy)(SR)2]-, R = C6F5, 2,4,6-(i-Pr)3C6H2 (4), which are rather unstable. Binding of CO to 4 affords [Ni(terpy)(SR)2(CO)]-, R = C6F5, 2,4,6-(i-Pr)3C6H2 (5). These CO adducts are quite stable at low temperatures. The EPR spectra of 4 and 5 have been discussed. Evidence for binding of H- to the nickel center in [Ni(terpy)(S-2,4,6-(i-Pr)3C6H2)2] is also presented.