According to our analysis, ethylene production is initiated by Co III -H, followed by HAT to acetylene to form a vinyl radical that may undergo a radical pair collapse to form a vinyl-cobalt species. Aided by density functional theory (DFT) calculations we note that the vinyl-cobalt intermediate contains a weak Co-C bond (46.1 kcal mol -1 ), which resembles diradicals. The strength of the Co III -H bond (49.9 kcal mol -1 ) matches the C-H bond of the vinyl radical (48.0 kcal mol -1 ), further supporting the thermodynamic feasibility of the HAT process. Calculations also support the thermodynamically favorable HAT process (ΔG = -17.9 kcal mol -1 , Figure and Figures ) that leads from Co-H to Co-vinyl formation. Consistently, the relatively weak Co-H (49.9 kcal mol -1 ) and Co-C (46.1 kcal mol -1 ) bond strengths in the Co-cobaloxime complexes indicate that a radical type of HAT pathway is probable.