Terminal Iron Carbyne Complexes Derived from Arrested CO 2 Reductive Disproportionation

The encumbered tetraisocyanide dianion Na 2 [Fe(CNArMes2) 4 ] reacts with two molecules of CO 2 to effect reductive disproportionation to CO and carbonate ([CO 3 ] 2− ). When the reaction is performed in the presence of silyl triflates, reductive disproportionation is arrested by silylative esterification of a mono‐CO 2 adduct. This results in the formation of four‐coordinate terminal iron carbynes possessing an aryl carbamate substituent owing to the direct attachment of an C(O)OSiR 3 group to an isocyanide nitrogen atom. Crystallographic, spectroscopic, and computational analyses of these iron–carbon multiply bonded species reveal electronic structure properties indicative of a conformationally locked iron carbyne unit.