Iridium complexes of quinone-based phosphine ligands

Abstract

This project was focused on the synthesis of iridium complexes containing Quinone-based phosphine ligands under dry and inert conditions. Iridium complexes with pincer-type ligands have been shown to serve as efficient catalysts in alkane dehydrogenation. However, to regenerate these compounds to their original states and maintain catalytic activity, a sacrificial hydrogen acceptor must be used which is costly and creates unnecessary by-products. Quinones may serve as a counter-balance to this inefficiency by acting as a catalytic hydrogen acceptor. Quinones may rapidly transition between their dehydrogenated and hydrogenated states through electron/proton transfers which may be driven electrochemically. The initial aim of this research was to produce iridium complexes bonded to a Quinone base in a pincer/tridentate framework. Two Quinone-based phosphine ligands (PCAQ and POAQ) were synthesized prior to being reacted with iridium-based catalysts. Synthesis reactions between Quinone-based ligands and iridium-based catalysts yielded a compound, which upon further investigation using 31P-NMR and 1H-NMR spectroscopy revealed a bidentate complex which was stabilized with a CO molecule. Further work is needed to characterize the compounds using X-ray crystallography and to compare the complexes to other iridium catalysts in efficiency of catalytic reactions.