For PMDETA, a 1.05:1.00 HCO3 -: amine molar ratio is obtained (see SI), which validates the formation of catalytic amounts of biprotonated PMDETA, named 2c-PMDETA (see Figure and discussion below). At the working potential of -1.35 V, the hydride complex HMn is reduced to its corresponding electronrich radical anion HMn -, which is the real catalyst for CO2 to formate conversion. DFT calculations indicate that the irreversible reduction potential of HMn is less negative by ~65 mV than that of the corresponding Mn dimer. By using Mn -as model, DFT calculation performed at high level def2-TZVP basis set allowed us to elucidate the two mechanisms depicted in Scheme 2, in MeOH as solvent. The path leading to CO passes through the coordination of the weak electrophile CO2 to the strong nucleophile Mn -(described in the SI), whereas the formate production in MeOH proceed via the hydride HMn and its reduced form HMn -. Table summarizes the relevant intermediates and Transition States found for this system. The first step consists into the weak coordination of CO2 to the HMn -radical anion. The adduct (Mn-