Unsymmetrical Nickel (PCN) Pincer Complexes with a Benzothiazole Side-Arm: Synthesis, Characterization and Electrochemical Properties

The newly prepared unsymmetrical pincer ligand with a benzothiazole side-arm 2-(3-((di-tertbutylphosphino)methyl)phenoxy)benzo[d]thiazole [BzTz(H)PCN] has been reacted with anhydrous NiBr2 to get the corresponding NiII square planar bromo complex (BzTzPCN)NiBr (1) after HBr elimination and C-H activation on the pincer central phenyl ring. Starting from 1, reaction with AgF in toluene or with AgBF4 in THF led to bromide abstraction and formation of the fluoro complex (BzTzPCN)NiF (2) and the ionic aquo species [(BzTzPCN)Ni(H2O)]BF4 (3), respectively. All species have been characterized in solution (multinuclear 1H, 13C{1H}, 31P{1H} and 11B NMR spectroscopy) and in the solid state (singlecrystal X-ray diffraction analysis). Finally, comparative electrochemical measurements (CV and in situ EPR-spectroelectrochemistry) carried out on the halide complexes 1 and 2 revealed that the anodic oxidation process leads to the formation of stable NiIII species bearing a coordinated bromide ligand in case of 1 and a fluoride-free complex in case of 2.