Use of Tetradentate Monoanionic Ligands for Stabilizing Reactive Metal Complexes

Supporting ligand design has played a vital role in the development of coordination and organometallic chemistry. A myriad of ligands with varying charge, donor-type. and denticity have been explored in this realm. A ligand type that has garnered recent attention involves a tetradentate monoanionic (TDMA) framework. TDMA ligands have been used with p-, d-, and f-block elements to form an array of interesting new complexes with applications ranging from bioinorganic chemistry to catalysis. Complexes incorporating TDMA ligands have been shown to stabilize reactive low-valent and cationic species. Functionalized beta-diiminato and TACN derivatives as well as tripodal ligands featuring both hard sigma-donors as well as mixed-donors are covered in this review. The synthetic challenges associated with the implementation of each ligand set are discussed.