Reactions of thorium tetrahalides ThX4 (X=Cl, Br, I) with liquid ammonia at room temperature lead to the formation of decaammine thorium(IV) halide ammoniates. Their different compositions [Th(NH3)10]X4 ⋅ nNH3 were established by single crystal X-ray diffraction. While for the chloride the formation of a tetraammoniate is observed, the reaction of the bromide leads to an octaammoniate, whereas the iodide results in approximately a nonaammoniate. Additionally, the formation of the dinuclear Th complex compound [Th2Cl2(NH3)14(μ-O)]Cl4 ⋅ 3NH3 was observed when moisture was present within NH3. As expected, the Th and the previously reported U compounds [An(NH3)10]Br4 ⋅ 8NH3 (Pbca, An=Th, U), [An(NH3)10]I4 ⋅ 9NH3 (P4/n), and [An2Cl2(NH3)14(μ-O)]Cl4 ⋅ 3NH3 (P (Formula presented.)) are isotypic, respectively. Surprisingly, ThCl4 formed the decaammine complex [Th(NH3)10]Cl4 ⋅ 4NH3 (P121/n1), while UCl4 formed the octaammine chlorido complex [UCl(NH3)8]Cl3 ⋅ 3NH3 (Pnma) in ammonia. Quantum-chemical gas-phase calculations were carried out to study the molecular structures and the energetics of the complex cations. In addition, the localized molecular orbitals (LMO) and Intrinsic Bonding Orbitals (IBO) were analyzed. However, the calculations could not explain the preferred formation of the [Th(NH3)10]4+ complex over the hypothetical cation [ThCl(NH3)8]3+.
- Crystal structure