Polymer-pendant ligand chemistry, 2: Reactions of vanadyl acetylacetonate with catechol ligands bonded to polystyrene-divinylbenzene resins and structural determination of the vanadium catecholates on the polymer

Abstract

Abstract The reactions of catechol ligands, bonded to either 2% or 20% crosslinked methylated polystyrene-divinylbenzene resins (CAT-PS-DVB), with vanadyl acetylacetonate [VO(AcAc)2] were studied. Vanadyl ion removal from solution at equilibrium was 0.104 mmol V/g of resin and 0.075 mmol V/g of resin for the 2% and 20% CAT-PS-DVB resins, respectively. It was found that the 20% crosslinked modified resin was limited in the vanadyl ion ligand exchange reaction by diffusion into the resin, while this was not the case for the 2% crosslinked modified resin. The effect of the base, triethylamine, dramatically increased the amount of vanadyl ion removed from solution, via ligand exchange; this is thought to occur by deprotonation of the catechol ligand. The bidentate ligand, bipyridine, had no effect on the removal of vanadyl ion in the ligand exchange reaction and thus apparently does not form a 1 : 1 complex with the vanadium catecholate bonded complex. The structures of the vanadium catecholates on the resin were tentatively established by infrared and electron paramagnetic resonance (EPR) spectroscopy to include two vanadium (4 +) complexes - a vanadyl bis(catecholate) complex, , and a distorted tris(catecholate) complex of octahedral geometry, . Scanning electron microscopy (SEM) and energy dispersive analysis (EDX) studies were also performed on the 2% and 20% cross-linked vanadium-containing CAT-PS-DVB resins to show clearly a uniform distribution of vanadium throughout both the resins.