Cyclometallated nitrogen heterocycles

The cyclometallation of four different classes of nitrogen heterocycle (pyridazine, tetrazines, pyrazines and pyrimidines) by palladium and platinum has been studied. Pyridazines readily form singly and doubly cyclometallated compounds, whilst pyrazines only metallate once. Both tetrazines and pyrimidines readily metallate once and doubly metallated species have been identified in solution. The use of trans-cyclometallating reagents based on benzylamine and Schiffʹs base ligands was also studied: considerable promise was shown by a benzylamine compound.