Electron-Triggered Imine Coupling: Synthesis and Characterization of Three Redox States (0,-1,-2) of a Ni(N 2 S 2 ) Complex.

Metal imine-thiolate complexes, M(NS) 2 are known to undergo imine C-C bond formation to give M(N 2 S 2 ) complexes (M=Co, Ni) containing a redox-active ligand. Although these transfor-mations are not typically quantitative, we demonstrate here that the one-electron reduction of a related Ni bis(imine-thiolate) complex affords the corresponding paramagnetic [Ni(N 2 S 2 )] - anion (2⋅ - ) exclusively; subsequent oxidation with [Cp 2 Fe]BF 4 then affords a high yield of neutral 2 (Cp=η 5 -cyclopentadienyl). Moreover, electrochemical studies indicate that a second one-electron reduction affords the diamagnetic dianion. Both anionic products were isolated and characterized by SC-XRD and their electronic structures were investigated by UV-vis spectro-electrochemistry, EPR and NMR spectroscopy, and DFT studies. These studies show that reduction proceeds primarily on the ligand, with (N 2 S 2 ) 4- containing both thiolate and ring-delocalized anions.