Migratory Insertion of CO into a Au–C Bond

[Image: see text] A MeDalPhos-ligated gold(III) metallafluorene complex, generated via C–C oxidative addition of biphenylene, reacts with CO to produce 9-fluorenone. Experimental and computational studies show that this proceeds via a hitherto unknown migratory insertion of CO into a Au(III)–C bond. This process is more energetically challenging compared to other M–C bonds, but once achieved, the product is comparatively stable with respect to retro-carbonylation. Exploiting migratory insertion of CO into Au–C bonds may extend the range of products that are accessible using gold chemistry.