Controlled cis Labilization of CO from Manganese(I) Mixed Carbonyl/Isocyanide Complexes: An Entry Point to Coordinatively Unsaturated Metallo-Lewis Acids

Presented herein is a general design strategy for the formation of coordinatively unsaturated Mn(I) fragments via the cis labilization of CO using metal carboxylates and subsequent deprotection by a range of abstraction agents. A consistent trend is observed in the ability of carboxylate ligands to facilitate CO dissociation as a function of the electron-releasing properties of the carboxylate R group. This is in agreement with previous theoretical work on cis-labilizing ligands. A variety of K-2-coordinated carboxylates function as site-protection ligands for the [Mn(CO)(2)(CNArDIPP2)(2)](+) scaffold and can be liberated using a range of synthetic techniques. The coordinatively unsaturated species thus formed are shown to be strong metal-based Lewis acids and can engage in agostic-type interactions; in addition, they can be trapped as the corresponding solvento complexes by ethereal solvents.