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This article presents an overview of recent advancements in the field of uranium chemistry, paying special attention to the preparation of starting materials and to the chemistry of uranium halides in liquid ammonia. Where suitable, insights into the chemistry of thorium are also presented. Herein, we report upon the crystal structures of several ammine complexes as well as their deprotonation products. Specific examples of hydrolysis products in liquid ammonia are showcased. Additionally, advancements in the preparation of uranium cyanides are presented.

The aqueous chemistry of uranium is dominated by the linear uranyl cation [UO2] 2+ , yet the isoelectronic nitrogen-based analogue of this ubiquitous cation, molecular [UN2], has so far only been observed in an argon matrix. Here, we present three different complexes of [UN2] obtained by the reaction of the uranium pentahalides UCl5 or UBr5 with anhydrous liquid ammonia. The [UN2] moieties are linear, with the U atoms coordinated by five additional ligands (ammonia, chloride or bromide), resulting in a pentagonal bipyramidal coordination sphere that is also commonly adopted by the uranyl cation [UO2(L)5] 2+ . In all three cases, the nitrido ligands are further coordinated through their lone pairs by the Lewis acidic ligands [U(NH3)8] 4+ to form almost linear, trinuclear complex cations. Those were characterized by single crystal X-ray diffraction, Raman and IR spectroscopy, 14 N/ 15 N isotope studies, and quantum chemical calculations which support the presence of U≡N triple bonds within the [UN2] moieties.

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 (Ptrue1‾ ) 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+.

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Herein we describe a convenient lab scale synthesis for pure and solvent-free binary uranium(III) halides UCl 3 , UBr 3 , and UI 3 . This is achieved by the reduction of the respective uranium(IV) halides with elemental silicon in borosilicate ampoules at moderate temperature. The silicon tetrahalides SiX 4 formed as a side product are utilized for the removal of excess starting material via a chemical vapor transport reaction. The syntheses introduced herein avoid the need for pure metallic uranium and are based on uranium(IV) halides synthesized from UO 2 and the respective aluminum halides and purified by chemi-

Abstract. In this work we present a facile, lab scale synthesis for thorium tetrahalides ThX 4 (X = Cl, Br, and I). The reaction between the easily available ThO 2 and AlX 3 (X = Cl, Br, and I) and a subsequent in situ chemical vapor transport (CVT) leads to a product of high purity, which is obtained in the form of crystals or large aggregates of

Herein we present the crystal structure of lithium hexafluoridoplumbate(IV) determined from powder X‐ray diffraction data. The cell parameters are a = 5.01067(3), c = 4.66340(5) Å, V = 101.3969(13) Å3 at T = 293 K. Li2PbF6 is isotypic to Li2ZrF6, space group P31m (no. 162). The measured Raman spectrum is compared with the quantum chemically calculated spectrum. Furthermore, we determined the decomposition temperature of Li2PbF6. We also present the corrected space group and crystal structure for SrPbF6 which was previously reported as P42/mmc (no. 131) and could now be corrected to space group P42/mcm [no. 132, a = 5.21719(3), c = 8.92771(11) Å, V = 243.004(4) Å3, T = 293 K].