Reactions of ThX4 (X=F, Cl, Br, I) with Liquid Ammonia-Crystal Structures and a Theoretical Study of Ammine Thorium(IV) Halide Ammoniates

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)]X-4 . nNH(3) 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)(mu-O)]Cl-4 . 3NH(3) was observed when moisture was present within NH3. As expected, the Th and the previously reported U compounds [An(NH3)(10)]Br-4 . 8NH(3) (Pbca, An=Th, U), [An(NH3)(10)]I-4 . 9NH(3) (P4/n), and [An(2)Cl(2)(NH3)(14)(mu-O)]Cl-4 . 3NH(3) (P1? ) are isotypic, respectively. Surprisingly, ThCl4 formed the decaammine complex [Th(NH3)(10)]Cl-4 . 4NH(3) (P12(1)/n1), while UCl4 formed the octaammine chlorido complex [UCl(NH3)(8)]Cl-3 . 3NH(3) (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+).

Automated summary

Reactions of thorium tetrahalides with liquid ammonia at room temperature resulted in the formation of decaammine thorium(IV) halide ammoniates, with different compositions established by single crystal X-ray diffraction. In addition, the formation of a dinuclear Th complex compound was observed in the presence of moisture within NH3. The study also included quantum-chemical gas-phase calculations to study molecular structures and complex cations. However, the calculations could not explain the preferred formation of a specific complex over a hypothetical cation.