Mechanistic studies of fluorinated cobaloximes

Abstract

In a previous work, a family of cobalt complexes derived from the fluorinated diphenylglyoxime ligand ("dAr^FgH_2") was synthesized. These complexes, [Co(dAr^FgH)_2(py)_2] (1 ) and [Co(dAr^FgH-BF_2)_2(py)_2] (2 ), are variations of the extensively studied diglyoxime systems [Co(dRgBF_2)_2L_2] (R = Me, phenyl), which have been shown to catalyze hydrogen evolution at low overpotentials. Like these catalysts, 2 minimizes energy losses by generating hydrogen at negligible thermodn. overpotentials in electrocatalysis expts. Through cyclic voltammetry, it was detd. that hydrogen evolution is occurring in protic solns. at the second redn. potential (-0.88 V vs. Its precursor, 1 , was also characterized and studied as a means of better understanding the hydrogen evolution pathway in 2 since both complexes possess a similar electronic structure. This complex exhibits a similar catalytic peak at E = -0.86 V vs. Nevertheless, the two complexes differ in their electrochem. and suggest that the asym. complex 2 is a better catalyst for hydrogen evolution.