NEW INSIGHTS INTO THE CONSTITUTION OF SOLUTIONS CONTAINING LABILE, POLYNUCLEAR COMPOUNDS - AN ELECTROSPRAY MASS-SPECTROMETRIC STUDY OF MERCURY-RICH AND CADMIUM-RICH DITHIOCARBAMATO CATIONS

Electrospray mass spectrometry (ESMS) has been used to study the constitution of mercury and mixed mercury/cadmium dithiocarbamato cations in dichloromethane and methanol solutions. In all cases the ions observed are of the form {[M(R2dtc)]+ + nM(R2dtc)2} (n = 1-3, M = Hg, Cd), e.g. [Hg2(R2dtC)3] + (n = 1). Addition of M(R2dtc)2 favours formation of the higher oligomers. Ligand exchange between different mercury dithiocarbamato cations is fast on the NMR timescale, but ESMS shows the individual ions with various ligand combinations. Similarly, reaction of a mercury-rich dithiocarbamato cation with a neutral Cd(R2dtc), complex of a different dithiocarbamate gives global exchange between ligands and metals and ESMS observes individual ions in the complex mixture. Exploratory experiments show that a similar chemistry exists for metal-rich dithiophosphate cationic systems. The order observed in these solutions leads to the suggestion that the M(R2dtc), groups act as ligands towards the [M(R2dtc)]+ cations and analogies are proposed between these ligand properties and those of the [MS4]2- (M = Mo, W) anions.