31P NMR study of the stoichiometry and stability of several mercury(II) halides with a phosphorus ylide in different solvents

31P NMR measurements were employed to monitor the stoichiometry and stability of complexes between HgCl2, HgBr2 and HgI2 with 4-methylbenzoylmethylenetriphenylphosphorane (L) in acetonitrile (AN), dimethylsulfoxide (DMSO), dimethylformamide (DMF) and tetrahydrofuran (THF) solvents of varying composition. In all cases studied, the variation of 31P chemical shift with the [M]/[L] mole ratio indicated the formation of 1:1 complexes. 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 solvents used, the stabilities of the resulting 1:1 complexes varied in the order HgCl2 > HgBr2 > HgI2.