Synthesis and characterization of 1,10-phenantroline Ru(II) complexes and investigation of their catalytic activity in transfer hydrogenation reactions of aromatic ketones

There has been increasing interest in transition metals polypridine and phenanthroline complexes in recent years due to their chemical stability, redox and fluorescent properties. These complexes play an important role in the development of photochemistry, photophysics and photoelectrochemisty. The chemistry of nitrogen analogues of fluorene and fluorenone is of interest owing to high biological activity and the possibility of pharmaceutical application, as well as the syntetic importance of this less known class of compounds. 4,5-diazafluore-9-one and 4,5-diazafluoren, are a derivative of 1,10-phenanthroline, reported three decades ago have been expected to superior ligands with many coordination chemistry and have attracted a lot of research interest. Reduction of unsaturated organic substrates, catalyzed by complexes of transition metals can be accomplished by hydrogenation or by hydrogen transfer from a donor, has been one of useful method to obtain alcohols which are versatile synthetic precursors to give functionalized compounds. As catalysts for transfer hydrogenation Rh(I), Ru(II) and Ir(III) complexes have been widely used and proved to be effective catalysts. As shown by Noyori and co-workers Ru(II) complexes bearing 1,2-diamines are good catalysts for transfer hydrogenation of carbonyl compounds, various types of the Ru(II) complexes bearing N-donor ligands aimed to identify the best Ru(II) catalysts for transfer hydrogenation. For this purpose, polydentate ligands containing pyrdine nucleous recently led to significant success. Nonetheless, application of such Ru(II) complexes in homogeneous catalysis are relatively less studied. The aim of the present work has been to syntesize and characterize the Ru(II) complexes of rather little known ligands derived from 1,10-diazaphenanthrene and to examine their catalytic activities in transfer hydrogenation of ketones . Key Words: 1,10-phenanthroline, 4,5-diazafluoren, 4,5-diazafluore-9-one, Homogenous Catalysis, Ruthenium, Transfer Hydrogenation