Synthesis and characterization of novel rhodium and ruthenium based iminopyridyl complexes and their application in 1-octene hydroformylation

Abstract

Several novel iminopyridyl ligands ranging from monofunctional to tetra-functional analogues were prepared by reacting 4-((2-pyridylmethylene)amino)phenol with various benzyl bromide derivatives. These ligands were subsequently complexed to Ru and Rh using [{(η6-p-cymene)RuCl2}2] and [RhCl(COD)]2 as metal precursors respectively, leading to the formation of several novel ruthenium and rhodium complexes. The complexes obtained ranged from mononuclear to tetranuclear in nature. All complexes prepared were fully characterised using a range of analytical techniques which included infrared and nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis. The complexes prepared were then evaluated as catalyst precursors in the hydroformylation of alkenes using 1-octene as model substrate. The rhodium based catalysts were found to be much more active than their ruthenium counterparts, using much milder reaction conditions. The activity of the multinuclear complexes seem to correlate with the nuclearity of the complex in that an overall increase in activity is observed with increasing nuclearity of the complex.