Inorganic Chemistry, Vol.36, No.12, 2678-2681, 1997
Speciation of Main-Group Metal-Ions by Electrospray Mass-Spectrometry .1. Investigation of Aqueous Polyselenide Species and Effects of Cations and pH
Polyselenide anion speciation in aqueous solution has been investigated by electrospray mass spectrometry (ESMS). Two methods of control over this speciation are reported : countercation substitutions and pH adjustments. The countercation has been found to affect the degree of disproportionation or comproportionation. Solutions of sodium tetraselenide displayed numerous Se-n(2-) arid HSen- species in neutral and basic solutions. In potassium solutions, the dominant species was Se-4(2-).H2O. Solutions of cesium pentaselenide also showed preference for higher-order polyselenides. The pH dependence has been analyzed in terms of the percent Se-n(n = 2-5) present. Di-, tri-, tetra-, and pentaselenide species were present over the entire pH range investigated, and trends in selenide species versus pH were developed. For example, at pH > 9, tetraselenide species were dominant.
Keywords:LIQUID-AMMONIA;HYDROTHERMAL SYNTHESIS;CRYSTAL-STRUCTURE;POLYSULFIDE SOLUTIONS;ZINTL ANIONS;GAS-PHASE;CHEMICAL-REACTIONS;BUILDING-BLOCKS;POTENTIAL STEP;CHEMISTRY