Nuclear magnetic resonance study of the stoichiometry and stability of several HgX2- CH3COCHP (p-tolyl)3 complexes in various ionic liquid – methanol mixtures

The reaction of phosphorus ylide, CH3COCHP (p-tolyl)3 (L) with HgX2 (X = Cl, Br and I) in equimolar ratios using Ionic liquid [BMIM][PF6] and methanol (Me) as solvent leads to binuclear and mononuclear products, respectively [1,2]. 31P NMR spectroscopy was used to investigate the stoichiometry and stability of the HgX2 complex with p-methylbenzoyle methylentriparatolylphosphorane (L) in binary [BMIM][PF6] and Me mixtures of varying composition. In all cases studied, the variation of 31P NMR chemical shift with the [HgX2]/[ylide] mole ratio indicated the formation of 1:1 complexes (Scheme 1). The formation constants of the resulting complexes were evaluated from computer fitting of the mole ratio data to an equation that relates the observed chemical shifts to the formation constant. In all mercuric salts used, the stabilities of the resulting 1:1 complexes varied in the order HgCl2 HgBr2 HgI2. It was found that, in the case of all complexes, an increase in the percentage of Ionic liquid in the solvent mixtures significantly decreased the stability of the complexes.