As Cp2Zr III Cl species was proven to be a strong single-electron reductant , it has the potential to reduce the NHPI esters instead of low-valent Ni . To determine the actual reductant, the initial-rate method was employed to determine the kinetics of 1a, ethyl gem-borazirconecene and Ni catalyst under standard conditions. Zero-order rate dependences on NHPI ester 1a and the Ni catalyst (Supplementary Figure ), and a first order dependence on gem-borazirconocene (Supplementary Figure ) were observed. To further elucidate the mechanistic details of the radical decarboxylative process, the conversion rate of NHPI ester 1a was monitored under varying loading of the Ni catalyst and the ethyl gem-borazirconocene reagent . The results showed that the conversion of 1a was independent of Ni catalyst loading (Supplementary Figure ). A positive correlation between the consuming rate of 1a and borazirconocene alkanes concentration was observed (Supplementary Figure ). According to the kinetics results, we proposed that the reduction of NHPI esters was independent of the Ni catalyst, suggesting the Cp2Zr III Cl mediated reduction might be a major pathway.