Abstract
The reaction of [PPN][Ni(CO)(2-S-C4H3S)3] with 1 equiv of P(C6H3-3-SiMe3-2- SH)3 in THF leads to form the four-coordinated complex, [PPN][NiII(2-S-C4H3S)P- ((C6H3-3-SiMe3-2-S)2(C6H3-3-SiMe3-2-SH))] (1). In the same preparation way, the reaction of NiCl2(PPh3)2 with 1 equiv of P(C6H3-3-SiMe3-2-SH)3 in THF leads to yield another four-coordinated complex, [NiII(PPh3)P((C6H3-3-SiMe3-2-S)2(C6H3-3- SiMe3-2-SH))] (3). Complexes 1 and 3 display a similar structural geometry, distorted square planar with a S-H proton interacting with both nickel center and sulfur atom. The presence of intramolecular [Ni…H-S]/[Ni-S…H-S] interactions in complexes 1 and 3 were verified in the solid state by the observation of the lower IR vS－H band and further confirmed by X-ray study. Oxidation of complexes 1 and 3 by O2 results in the formation of a mononuclear, distorted triganol bipyramidal [PPN][NiIII(2-S-C4H3S)- P((C6H3-3-SiMe3-2-S)3)] (2) and [NiIII(PPh3)(P((C6H3-3-SiMe3-2-S)3)] (4), respectively. Complex 2 undergoes dechlorination of CH2Cl2 solution to generate [PPN][NiIII(Cl)P((C6H3-3-SiMe3-2-S)3)]. In addition, complex 2 reacts with exogenous CO to produce [PPN][NiII(CO)P((C6H3-3-SiMe3-2-S)3)]. In contrast to complex 2, complex 4 is inert in the presence of CH2Cl2 and CO. This results imply that PPh3 is a weaker donating ligand than thiolate ligand (2-S-C4H3S). This result is further confirmed by the result of the cyclic voltammograms of complex 2 and 4. Complexes 2 and 4 display a reversible NiIII/II redox processes with E1/2 = -1.16 V, -0.83 V (vs Cp2Fe/ Cp2Fe+), respectively. The structure, activity, and spectroscopic properties of these complexes may show some insight about the nickel site in bimetallic Ni-Fe active site of [NiFe] Hydrogenase.