Abstract
The reaction of [NiIII(P(o-C6H3-3-SiMe3-2-S)3)]2 and NaBEt3H in 1:1 molar ratio and excess 18-crown-6-ether in THF led to the formation of complex [Na-18-crown-6 -ether][Ni2(P(o-C6H3-3-SiMe3-2-S)3)2] (1). The [PPN]2[NiCl4] and NaSEt in 1:4 molar ratio were dissolved in CH3CN and then added the P(o-C6H3-3-SiMe3-2-SH)3 ligand into solution to yield [PPN]2[Ni2(P(o-C6H3-3-SiMe3-2-S)3)2] (2). The core of complexes 1 and 2 were mixed-valence [Ni(II)-Ni(III)] and localized [Ni(II)-Ni(II)], respectively. The reaction of [NiIII(PPh3)(P(o-C6H4S)3)], KC8, and 18-crown-6-ether in 1:1:2 molar ratio in THF yielded the five-coordinated complex, [K-18-crown-6][NiII(PPh3) (P(C6H4-2-S)3)] (3). The interaction between potassium and sulfur decreasing electronic density of metal center may play a key role in stabilizing complex 3. The five-coordinated complex [PPN][NiIII(O-C6H5)(P(o-C6H3-3-SiMe3-2-S)3)] (4) was prepared by the reaction of [PPN][NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)] and [Na][O-C6H5] in 1:3 molar ratio in THF-CH3CN. In a similar fashion, the reaction of [PPN][NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)] and [Na][S-C6H5] in 1:1 molar ratio in THF-CH3CN produced the five-coordinated complex [PPN][NiIII(S-C6H5)(P(o-C6H3 -3-SiMe3-2-S)3)] (5). Complex 4 was the first nickel(III)-thiolate-OR model compound mimicking the oxidized-state active site structure of the [NiFe] hydrogenase. The series of structural and spectral data were compared among those NiIII-X (X = O, S, Se) bond lengths of complexes 4, 5 and [PPN][NiIII(Se-C6H5)(P(o -C6H3-3-SiMe3-2-S)3)].