An NMR study of thallium nitrate ion association in liquid ammonia

²⁰⁵Tl and¹H magnetic resonance frequencies have been determined for liquid ammonia solutions of TlClO₄ and TlNO₃ as a function of electrolyte concentration (5×10^–4 to 9.8 M) and temperature. The dependence of the resonance frequency on concentration suggests the presence of free, fully solvated thallium ions, ion pairs, and higher-order ion aggregates. Analysis of lowconcentration²⁰⁵Tl data between 0 and 30°C allowed the determination of TlNO₃ ion-pair association constants and thermodynamic parameters (H_A=+6.5 kcal-mole^–1, S_A=+36 e.u.). A preciptous decrease in²⁰⁵Tl resonance frequency was observed for NH₃ to TlNO₃ mole ratios below 3:1, suggesting the formula (NH₃)₃Tl⁺ NO₃^– for the fully solvated, contact ion pair.