Terminal Iron Carbyne Complexes Derived from Arrested CO Reductive Disproportionation.

The encumbered tetraisocyanide dianion Na [Fe(CNArMes2 ) ] reacts with two molecules of CO to effect reductive disproportionation to CO and carbonate ([CO ] ). When the reaction is performed in the presence of silyl triflates, reductive disproportionation is arrested by silylative esterification of a mono-CO 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 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.