Tridentate pyridine-pyrrolide chelate ligands: An under-appreciated ligand set with an immensely promising coordination chemistry

This review covers all aspects of the chemistry of metal complexes of tridentate κ3-N pyridine-pyrrolide ligands, from the syntheses of the ligands to what is known about the metal complexes - their structural and physical properties, and their reactivities, including use in catalytic processes. Applications of the complexes range from the switching elements in molecular devices, to luminophores in electroluminescent devices and photosensitisers in light-driven catalyses, to anticancer therapeutics and to efficient catalysts for organic transformations. The general properties of the ligands and metal complexes are deduced from the available literature, and areas of κ3-N pyridine-pyrrolide metal complex chemistry ripe for development are pinpointed.