Electrocatalytic Reduction of CO2 to Methanol by Iron Tetradentate Phosphine Complex Through Amidation Strategy

Abstract The iron complex of tetradentate tris[2‐(diphenylphosphino) ethyl]phosphine (PP 3 ), [Fe(PP 3 )(MeCN) 2 ](BF 4 ) 2 , was able to electrocatalytically reduce CO 2 to formate with a Faradaic efficiency (FE) of approximately 97.3 % in acetonitrile. Upon addition of diethylamine as a cocatalyst, electrocatalytic reduction to methanol was achieved with an FE of 68.5 %, and other products were formamide and formate. A mechanistic study suggested that the [FeH(PP 3 )](BF 4 ) hydride complex was the active species in the electrocatalysis. Added amine as cocatalyst could react with CO 2 to form carbamate, which could then be reduced to formamide and further to methanol. By contrast, free CO 2 could only be reduced to formate as the end‐product.