Cooperative Reactivity in Carbometalated Pincer-Type Complexes Possessing an Appended Functionality

Unlike traditional catalysis, where ligands only pass stereoelectronic information to the metal center, ligand-metal cooperative catalysis deals with noninnocent ligands that take an active part in facilitating reaction pathways. After the pioneering studies of Fryzuk, who described the noninnocent behavior of the amine-based aliphatic pincer ligands, and of Milstein, who discovered the dearomative cooperation mechanism in pyridine-based pincer systems, this concept also became prevalent in the context of pincer complexes. Many excellent reviews have dealt with these aspects of heteroatom-based pincer compounds. Nevertheless, this perspective aims to focus on recent developments in the chemistry and catalytic applications of the carbometalated pincer ligands for which noninnocent behavior is rarely observed, and especially those applications incorporating an appended functionality that can interact with the catalytic center. Combining the concepts of robust carbometalated pincer complexes and cooperative mechanisms highlighted by modulation of the secondary coordination sphere provides a "second wind" for this powerful family of organometallic compounds.