In combination, the cross-over experiments, calculations, solvent effects, and EPR data suggest that while heterolytic fragmentation of 2a is unlikely under the reaction conditions, homolytic cleavage leading to a radical pathway remains a distinct mechanistic possibility for H2 activation. Following homolysis of the metal-metal bond, the addition of H2 could potentially occur through either a single-site mechanism involving addition at the Fe fragment to generate a Fe-dihydride radical, which recombines with the zinc radical or a radical pair mechanism in which both metal radicals react with H2 in a concerted manner (Scheme 2C). The thermodynamics for these options were calculated by DFT, both are exergonic and feasible.