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.

Alkali and alkaline earth metal tetrafluorobromates M I BrF 4 , M II (BrF 4 ) 2 (M I = Na-Cs, M II = Sr, Ba) can be synthesized from the respective fluorides and BrF 3 . By the reaction of CsF with an excess of BrF 3 , the compound cesium tetrafluoridobromate(III) bromine trifluoride (1/1), CsBr 2 F 7 (1), was obtained in the form of a colorless powder and as single crystals. Shown by X-ray diffraction on single crystals, its Br 2 F 7 anion is neither planar, nor is its Br-μ-F-Br unit linear, as previously deduced by Raman spectroscopy. In stoichiomet-* Prof. Dr. R. Ostvald

Abstract. The reaction of K2Th(NO3)6 and UF4 with liquid ammonia as a solvent leads on air to planar colorless crystals of ditriakontaammine hexadeca‐μ‐fluorido tetra‐μ3‐oxido tetra‐μ4‐oxido decathorium(IV) octanitrate ammonia (1/19.6), [Th10F16O8(NH3)32](NO3)8·19.6 NH3 (1). The compound crystallizes in the tetragonal space group P$\bar{4}$21c (no. 114) with a = 18.4167(2), c = 14.7920(4) Å, and V = 5017.1(2) Å3 at 123 K with Z = 2. The crystal structure shows the presence of a decanuclear thorium core [Th10O4]32+ similar to an “inverse” P4O10 or like 1,3,5,7‐tetramethyladamantane. Such a complex seems to be the largest thorium complex reported so far – a finding that is of great importance for the knowledge of actinoid speciation in solutions.

Our attempts to synthesize the hitherto unknown binary copper(I) fluoride have led to first successes and a serendipitious result: By conproportionation of elemental copper and copper(II) fluoride in anhydrous liquid ammonia, two copper(I) fluorides were obtained as simple NH3 complexes. One of them presents an example of ligand-unsupported "cuprophilic" interactions in an infinite [Cu2 (NH3 )4 ](2+) chain with alternating Cu-Cu distances. We discovered that both copper(I) fluorides can easily be converted into Cu3 N at room temperature, just by applying a vacuum. Additionally, we investigated the formation mechanism of the classical synthesis route of Cu3 N that starts with CuF2 and flowing NH3 in the temperature range between ambient and 290 °C by means of thermal analysis and in situ neutron diffraction. The reaction proceeds at elevated temperatures through the formation of a blue and amorphous ammoniate Cu(NH3 )2 F2 , the reformation of CuF2 , and finally the redox reaction to form Cu3 N.

Additional Computational Details PCM and NBO calculations Starting from the gas-phase BLYP/SDD/6-311+G** equilibrium structures, [UO 2 L 5 ] 2+ (L = H 2 O, NH 3) were re-optimised using the polarisable continuum model in its integral equation formalism (IEF-PCM), 1 as implemented in Gaussian 09. 2 For L = H 2 O, standard solvent parameters of water were used, for ammonia we employed the static dielectric constant of liquid ammonia at 20ºC ( = 16.6), 3 the same dynamic dielectric constant as water, 4 and a solvent radius of 2.5 Å. 5 Natural bond orbital analyses 6 employed the Gaussian NBO version 3.1 as implemented in Gaussian 09. CPMD simulations The same methods and basis sets as in our previous studies of uranyl complexes 7 were employed. Car-Parrinello molecular dynamics (CPMD) 8 simulations were performed using the BLYP functional 9 and norm-conserving pseudopotentials that had been generated according to the Troullier and Martins procedure 10 and transformed into the Kleinman-Bylander form. 11 For uranium, the semicore (or small-core) pseudopotential was employed that had been generated and validated in reference 12. Periodic boundary conditions were imposed using cubic supercells with a lattice contant of 13.22 Å. Kohn-Sham orbitals were expanded in plane waves at the -point up to a kinetic energy cutoff of 80 Ry. Simulations were performed in the NVT ensemble using a single Nosé-Hoover thermostat set to 300 K (frequency 1800 cm 1), a fictitious electronic mass of 600 a.u., and a time step of 0.121 fs. The boxes contained uranyl and and a total of 42 ammonia molecules, affording a density of 0.71. The system has two positive charges, neutralised by a uniform background charge. In order to maintain the time step, hydrogen was substituted with deuterium. Long-range electrostatic interactions were treated with the Ewald method. No electro-static decoupling between replicated cells was included. Constrained CPMD simulations were performed along a predefined reaction coordinate  (a single U-N bond distance r), starting from the respective mean values for the five-coordinate minumum in gas and solution (as obtained from the unconstrained simulations. Changes in the Helmholtz free energes were evaluated by pointwise thermodynamic integration 13 of the mean constraint force f along this coordinate via      A ab =  a b f()d (1). Electronic Supplementary Material (ESI) for Dalton Transactions. This journal is