Stabilization of Simple Imines by Coordination to Ruthenium(II), and Aspects of Their Reactivity

The oxidation of a number of secondary amines coordinated to ruthenium(II) was investigated. Pyrrolidine (1) and piperidine (5) formed the corresponding 1-imines [1-pyrroline (2) and 2,3,4,5- tetrahydropyridine (6)]; these complexes were stable, although spectral and electrochemical properties show there to be only minor π-back- bonding between the RuII metal centre and the imine ligands. The analogous β-unsaturated amines [3-pyrroline (3) and 1,2,3,6- tetrahydropyridine (7)] complexes also underwent oxidative dehydrogenation reactions, and in these cases produced the corresponding aromatic species [pyrrole (4) and pyridine (8), respectively]. Coordinated N-methylallylamine (9) was oxidized to a mixture of the two possible 1-imine species (10) and (11), and preliminary studies indicated that the 1-aza 1,3-diene (11) product would undergo a Diels-Alder reaction while attached to the metal centre