Redox Reactions of Nickel, Copper, and Cobalt Complexes with 'Noninnocent' Dithiolate Ligands:Combined in Situ Spectroelectrochemical and Theoretical Study

摘要

The redox properties of copper, nickel, and cobalt complexes (MePh_3P)[M(bdt)_2] with the ligand benzene-1,2-dithiolate (bdt) and synthesized complexes (MePh_3P)[M(bdtCl_2)_2] with the ligand 3,6-dichlorobenzene- 1,2-dithiolate (bdtCl_2) have been studied by cyclic voltammetry and in situ EPR-UV/vis/NIR spectroelectrochemistry. The addition of chlorine substituents to the 3- and 6-positions of the benzene ring not only facilitates the reduction of [M(bdtCl_2)_2]~- complexes but also leads to the remarkable stabilization of [M(bdtCl_2)_2]~(2-) dianions in solution. In contrast to the EPR-silent copper complexes, the solutions of nickel samples exhibit a broad singlet EPR signal at room temperature which becomes anisotropic at 100 K with a characteristic rhombic pattern. Cathodic reduction of copper and cobalt complexes leads to paramagnetic species having an EPR signal with splitting from ~(63/65)Cu for copper and from ~(59)Co for cobalt samples, confirming a strong contribution of the central atom with substantial delocalization of the unpaired spin onto the central atom. B3LYP/6-311g~ */pcm calculations of the monoanions as well as of their oxidized and reduced forms were performed. The spin density of all open-shell ground states calculated for the investigated complexes in different redox states corresponds well to the experimental spectroelectrochemical data.