Transition metal complexes with sulfur ligands Part CXLIV. Square planar nickel complexes with NiS4 cores in three different oxidation states: synthesis, X-ray structural and spectroscopic studies

The reaction of 'S-bu(2)'(2-) = 3,5-ditertiarybutyl-1,2-benzenedithiolate(2 -) with Ni(ac)(2). 4H(2)O and subsequently AsPh4Cl, yielded (AsPh4)(2)[Ni( 'S-bu(2)')(2)] (1). Complex 1 is extremely air sensitive and oxidized rapid ly to give (AsPh4)[Ni('S-bu(2)')(2)] (2). The anion of 2 could be further o xidized by iodine to give neutral [Ni('S-bu(2)')(2)] (3). Complexes 1, 2 an d 3 contain nickel in the formal oxidation states + 2, + 3 and + 4, and cou ld be completely characterized by X-ray structure determination and spectro scopic methods. The results indicate that the oxidation of 1-->2-->3 concer ns electrons residing in molecular orbitals having [NiS4] character. No evi dence could be obtained for an involvement of the benzene rings or an elect ron delocalization beyond the [NiS4] core. This conclusion corresponds with the reactivity of 3 versus 2 and 1 towards protons and CO. While 3 is iner t to the attack of H+ and CO, 2 and 1 exhibit rapid reactions to give 'S-bU (2)'-H-2 and either nickel-chioro complexes or Ni(CO)(4). (C) 2000 Elsevier Science S.A. All rights reserved.