The Complexing of the Thallium(I) Ion with Other Solvents in Acetonitrile. Investigation Using a Cationsensitive Glass Electrode

The complexing of the thallium(I) ion with other common solvents has been studied in acetonitrile by using a univalent cation-sensitive glass electrode. A method similar to that developed to study the complexing of sodium and lithium ions was employed. Mono-, di-, and tri-solvated species were formed with DMF, SDMF, DMA, pyridine, formamide, and DMSO. Tetra-solvated species were also formed with N-methylformamide and HMPA. The complex formation constants for the mono-solvated thallium(I) ion were 4.1 with DMF, 5.6 with SDMF, 6.9 with DMA, 11 with pyridine and formamide, 12 with N-methylformamide, 15 with DMSO, and 1.0×102 with HMPA. Prior to these experiments, the cation-sensitive glass electrode was confirmed to respond to the thallium-(I)-ion activity in different solvents by comparing its behavior with that of a thallium-amalgam electrode. When water was the complexing solvent the potential of the glass electrode was not stable, and therefore, a thallium-amalgam electrode was used instead of a glass electrode to obtain the hydration constants of the thallium(I) ion in acetonitrile. Mono- and di-solvated species were formed with water and the hydration constant for the mono-solvated species was 1.1. The amalgam electrode and the glass electrode were used to obtain the constants with DMSO.