Structural characterization and Raman spectrum of Cs[OCN]

The compound Cs[OCN] has been synthesized and its crystal structure and Raman spectrum were determined on selected single crystals. As postulated in earlier work, the title compound crystallizes isopointal to KN3 exhibiting the space group I4/mcm (no. 140, Z = 4) with the lattice parameters a = 653.79(2) and c = 799.42(5) pm. The Raman spectrum verified the nature of the triatomic moiety and shows the frequencies typical for an [OCN]− anion with Fermi resonance between the 2δ and the νsym vibrations. The undisturbed frequencies and the resulting force constants have been calculated and compared to those of other alkali metal compounds containing comparable linear triatomic anions.

Aluminates with Fluorinated Schiff Bases: Influence of the Alkali Metal–Fluorine Interactions in Structure Stabilization

New heterometallic aluminium-alkali metal compounds have been prepared using Schiff bases with electron withdrawing substituents as ligands. The synthesis of these new species was achieved via the reaction of AlMe3 with the freshly prepared alkali-metallated ligand. The derivatives formed were characterized by NMR in solution and by single crystal X-ray diffraction in the solid state. Aluminate derivatives with lithium and sodium were prepared and a clear influence of the alkali metal in the final outcome is observed. The presence of a Na···F interaction in the solid state has a stabilization effect and the species [NaAlMe3L]2 can de isolated for the first time, which was not possible when using Schiff bases without electron withdrawing substituents as ligands.

Structural Chemistry of Halide including Thallides A8Tl11X1−n (A = K, Rb, Cs; X = Cl, Br; n = 0.1–0.9)

A8Tl11 (A = alkali metal) compounds have been known since the investigations of Corbett et al. in 1995 and are still a matter of current discussions as the compound includes one extra electron referred to the charge of the Tl117− cluster. Attempts to substitute this additional electron by incorporation of a halide atom succeeded in the preparation of single crystals for the lightest triel homologue of the group, Cs8Ga11Cl, and powder diffraction experiments for the heavier homologues also suggested the formation of analogous compounds. However, X-Ray single crystal studies on A8Tl11X to prove this substitution and to provide a deeper insight into the influence on the thallide substructure have not yet been performed, probably due to severe absorption combined with air and moisture sensitivity for this class of compounds. Here, we present single crystal X-Ray structure analyses of the new compounds Cs8Tl11Cl0.8, Cs8Tl11Br0.9, Cs5Rb3Tl11Cl0.5, Cs5.7K2.3Tl11Cl0.6 and K4Rb4Tl11Cl0.1. It is shown that a (partial) incorporation of halide can also be indirectly determined by examination of the Tl-Tl distances, thereby the newly introduced cdd/cdav ratio allows to evaluate the degree of distortion of Tl117− clusters.

Single Crystal X-ray Structure Analyses of Thallides: Halide Incorporation and Mixed Alkali Sites in A8Tl11X (A = K, Rb, Cs; X = Cl, Br)

A8Tl11 (A = alkali metal) compounds have been known since the investigations of Corbett et al. in 1995 and still are matter of current discussions as the compound includes one extra electron referred to the charge of the Tl117− cluster. Attempts to substitute the charge by incorporation of a halide atom succeeded for the lightest homologue of the group, Cs8Ga11Cl, and powder diffraction experiments for the heavier homologues also suggested the formation of analogous compounds. However, X-ray single crystal studies on A8Tl11X to prove this substitution and to provide a deeper insight into the influence on the thallide substructure have not yet been performed, probably due to severe absorption combined with air and moisture sensitivity for this class of compounds. In our contribution we present single crystal X-ray analyses of the new compounds Cs8Tl11Cl0.8, Cs8Tl11Br0.9 and Cs5Rb3Tl11Cl0.5. It is shown that a (partial) incorporation of halide can also be indirectly determined by examination of the Tl-Tl distances for low resolved data sets, e.g., for Cs5.7K2.3Tl11Cl?. Mixed occupied sites by two different alkali metals indicate a dependence on the cesium content, the systems K/Rb–Tl–Br and K/Rb–Tl–Cl only gave rise to the formation of the higher reduced (K/Rb)8Tl11 and the less reduced by-product (K/Rb)15Tl27. We have not been able to prove the formation of halide including thallides in the absence of cesium.

Sila-polyethers as innocent crystallization reagents for heavy alkali metal compounds

Sila-polyethers are used as innocent crystallization reagents for the formation of single crystals of different elusive rubidium and cesium salts.

The alkali metals: 200 years of surprises

Alkali metal compounds have been known since antiquity. In 1807, Sir Humphry Davy surprised everyone by electrolytically preparing (and naming) potassium and sodium metals. In 1808, he noted their interaction with ammonia, which, 100 years later, was attributed to solvated electrons. After 1960, pulse radiolysis of nearly any solvent produced solvated electrons, which became one of the most studied species in chemistry. In 1968, alkali metal solutions in amines and ethers were shown to contain alkali metal anions in addition to solvated electrons. The advent of crown ethers and cryptands as complexants for alkali cations greatly enhanced alkali metal solubilities. This permitted us to prepare a crystalline salt of Na − in 1974, followed by 30 other alkalides with Na − , K − , Rb − and Cs − anions. This firmly established the −1 oxidation state of alkali metals. The synthesis of alkalides led to the crystallization of electrides, with trapped electrons as the anions. Electrides have a variety of electronic and magnetic properties, depending on the geometries and connectivities of the trapping sites. In 2009, the final surprise was the experimental demonstration that alkali metals under high pressure lose their metallic character as the electrons are localized in voids between the alkali cations to become high-pressure electrides!