AN ELECTROSPRAY MASS-SPECTROMETRIC STUDY OF SOME MERCURY PHOSPHINE COMPLEXES

Electrospray mass spectra have been obtained for a number of cationic mercury phosphine systems and mixtures thereof in methanol solution. Complexes of the type Hg(PR3)2X2 (PR3 = monodentate phosphine; X = ClO4, CF3COO) all give peaks in their electrospray mass spectra corresponding to the principal ion [Hg(PR3)2X]+, although with the perchlorates the base peak is due to [Hg(PR3)2(CH3COO)]+, the acetate being present in the mobile phase used in the spectrometer. Many of these systems are known to be labile on the NMR timescale at room temperature, but they all give good electrospray mass spectra at room temperature and for the rapidly exchanging mixtures all of the individual cationic species are observed. Addition of free phosphine leads to the formation of the tris(phosphine) complexes in solution and the principal ions [Hg(PR3)3X]+ are observed in the electrospray mass spectra. Collisionally activated decomposition (CAD) mass spectra, both within the ion source and in MS/MS experiments, show that the tris(phosphine) complexes very readily lose one phosphine, thus demonstrating the mechanism of phosphine exchange in these systems.