Structure of the solvated thallium(I) ion in aqueous, dimethyl sulfoxide, N,N'-dimethylpropyleneurea, and N,N-dimethylthioformamide solution.

The structure of the solvated thallium(I) ion in aqueous, dimethyl sulfoxide, N,N'-dimethylpropyleneurea, and N,N-dimethylthioformamide solution has been studied by means of large-angle X-ray scattering (LAXS) and complemented by EXAFS studies on two systems. The first solvation shell around the thallium(I) ion comprises significantly different bond distances to the solvent molecules in solution, indicating a stereochemically active lone electron pair. The first hydration shell around the thallium(I) ion in aqueous solution can be modeled by two Tl-O bond distances at 2.73(2) A and about two more at 3.18(6) A. Thallium(I) ions solvated by dimethyl sulfoxide, N,N'-dimethylpropyleneurea, and N,N-dimethylthioformamide seem to have two short and four long Tl-solvent bond distances. The mean Tl-O bond distances of the two groups were 2.66(4) and 3.18(6) A for dimethyl sulfoxide and 2.73(4) and 3.27(8) A for N,N'-dimethylpropyleneurea. For the sulfur donor solvent N,N-dimethylthioformamide the corresponding groups of Tl-S bond distances were refined to 2.96(2) and 3.33(3) A.