205Tl, 14N, and 1H NMR Studies of Salt Solutions in Liquid Methylamine

Article abstract of DOI:10.1021/j100256a059

205Tl, 14N, and 1H NMR techniques were used to investigate thallium(I) salt solutions in liquid methylamine from 1 mM to 7.2 M.Essentially complete association was observed between Tl⁺ and NO^-₃ or HCO^-₂ at 1 mM.Thermodynamic parameters for the ion association of Tl⁺ and ClO^-₄ were found to be ΔH_A = +10.3 +/- 4 kcal mol^-1 and ΔS_A = +50 +/- 15 eu.Due to its lower dielectric constant, more extensive ion association occurs in liquid methylamine than in liquid ammonia.Ion pairs in liquid methylamine appear to be of solvent-shared or solvent-separeted type, as opposed to contact ion pairs previously found to exist in liquid ammonia.Relative anion and solvent donicities, as determined from 205Tl chemical shifts, were strongly temperature dependent.At high concentrations, no evidence for a structural rearangement of the solvated TlNO₃ species was found.However, the anomalous behavior of the 205Tl chemical shift observed at TlNO₃ concentrations below 0.5 M may results from such rearrangements.Two methylamine molecules were determined to be the minimum number necessary to saturate the associated ionic species at very high concentrations.