What is "diiminopyridine"

The diiminopyridine (DIP) class of ligands are pyridine derivative with imine sidearms appended to the 2,6–positions. The three nitrogen centres can bind metals in a tridentate fashion, forming pincer complexes. Diiminopyridines are notable as non-innocent ligand that can assume more than one oxidation state. Complexes of DIPs participate in a range of chemical reactions, including ethylene polymerization, hydrosilylation, and hydrogenation.