C-H bond chlorination and bromination using water soluble nickel(II) guanidine complexes.

Water-soluble nickel(II)-guanidine-based complexes successfully catalyzed the C-H chlorination of a series of hydrocarbons in the presence of NaOCl and acetic acid in water-chloroform (7 : 3, biphasic condition) at room temperature. Majorly chlorinated products (TON ∼680 for cyclohexane) were obtained. Furthermore, C-H bond bromination of cyclohexane, n-hexane, and toluene was also carried out using in situ generation of NaOBr. These putative formations of Ni(III) species were characterized by electron paramagnetic resonance (EPR) spectroscopy, and the plausible mechanism for chlorination was confirmed by DFT calculations.