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 first structural characterization of the text-book tetraammineberyllium(II) cation [Be(NH(3))(4)](2+), obtained in the compounds [Be(NH(3))(4)](2)Cl(4)⋅17NH(3) and [Be(NH(3))(4)]Cl(2), is reported. Through NMR spectroscopic and quantum chemical studies, its hydrolysis products in liquid ammonia were identified. These are the dinuclear [Be(2)(μ-OH)(NH(3))(6)](3+) and the cyclic [Be(2)(μ-OH)(2)(NH(3))(4)](2+) and [Be(3)(μ-OH)(3)(NH(3))(6)](3+) cations. The latter species was isolated as the compound [Be(3)(μ-OH)(3)(NH(3))(6)]Cl(3)⋅7NH(3). NMR analysis of solutions of BeF(2) in liquid ammonia showed that the [BeF(2)(NH(3))(2)] molecule was the only dissolved species. It acts as a strong fluoride-ion acceptor and forms the [BeF(3)(NH(3))](-) anion in the compound [N(2)H(7)][BeF(3)(NH(3))]. The compounds presented herein were characterized by single-crystal X-ray structure analysis, (9)Be, (17)O, and (19)F NMR, IR, and Raman spectroscopy, deuteration studies, and quantum chemical calculations. The extension of beryllium chemistry to the ammine system shows similarities but also decisive differences to the aquo system.

The use of acoustic levitation in the fields of analytical chemistry and in the containerless processing of materials requires a good stability of the levitated particle. However, spontaneous oscillations and rotation of the levitated particle have been reported in literature, which can reduce the applicability of the acoustic levitation technique. Aiming to reduce the particle oscillations, this paper presents the analysis of the particle stability in a new acoustic levitator device. The new acoustic levitator consists of a piezoelectric transducer with a concave radiating surface and a concave reflector. The analysis is conducted by determining numerically the axial and lateral forces that act on the levitated object and by measuring the oscillations of a sphere particle by a laser Doppler vibrometer. It is shown that the new levitator design allows to increase the lateral forces and reduce significantly the lateral oscillations of the levitated object.

By reaction of the tetrafluorides MF4 or the ternary silver fluorides Ag3M2F14 (M = Zr, Hf) with dry liquid ammonia at –40 °C, the pentaammoniates [M(NH3)4F4]·NH3 (1, M = Zr; 2, M = Hf) were obtained, and these compounds represent hitherto unknown molecular inorganic Zr and Hf compounds that simultaneously bear nitrogen and fluorine ligands. The compounds crystallize isotypically in the shape of colorless needles in the tetragonal space group P4/ncc. As a further product [NH4(NH3)]F (3) was isolated in the form of colorless cubes in the orthorhombic space group Pca21. It is the first ammoniate of ammonium fluoride. Ag(NH3)2F·2NH3 (4) can be synthesized either from AgF or AgF2 in liquid ammonia. The compound crystallizes merohedrally twinned in the orthorhombic space group Pnna and represents the first crystallographically characterized diamine silver(I) halide complex. In the latter two structures, free fluoride anions are encountered. The ammoniates are highly temperature‐sensitive and decompose at temperatures above –30 °C due to their ammonia pressure.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

From the reaction of uranium hexafluoride UF6 with dry liquid ammonia, the [UF7(NH3)]3- anion and the [UF4(NH3)4] molecule were isolated and identified for the first time. They are found in signal-green crystals of trisammonium monoammine heptafluorouranate(IV) ammonia (1:1; [NH4]3[UF7(NH3)].NH3) and emerald-green crystals of tetraammine tetrafluorouranium(IV) ammonia (1:1; [UF4(NH3)4].NH3). [NH4]3[UF7(NH3)].NH3 features discrete [UF7(NH3)]3- anions with a coordination geometry similar to a bicapped trigonal prism, hitherto unknown for U(IV) compounds. The emerald-green [UF4(NH3)4].NH3 contains discrete tetraammine tetrafluorouranium(IV) [UF4(NH3)4] molecules. [UF4(NH3)4].NH3 is not stable at room temperature and forms pastel-green [UF4(NH3)4] as a powder that is surprisingly stable up to 147 degrees C. The compounds are the first structurally characterized ammonia complexes of uranium fluorides.