Freed from iron: easy release of a stable ketene from the reaction of CO with di-iron bis-μ2-alkylidenes

Abstract

Iron bis-μ²-alkylidene complexes were shown to perform CO/alkylidene coupling and liberate a stable ketene derivative. The easy release of the ketene formed from CO incorporation is usually the prerogative of terminal iron carbene complexes, while dimetallic, bridging carbenes tend to retain bridging acyl ligands after 1,1 migratory insertion of CO. Observations at −40 °C showed that an acyl intermediate could evolve into a ketene and form a stable μ²-alkylidene di-iron hexacarbonyl complex. Ketene release was shown to depend on the redox state of the iron byproducts. The CC bond formation is reversible, with instant hydration–decarboxylation upon water addition at room temperature.