Christof Suchentrunk

Ge52− Zintl anions: synthesis and crystal structures of [K([2.2.2]-crypt)]2Ge5·4NH3 and [Rb([2.2.2]-crypt)]2Ge5·4NH3

The new compounds [K(C18H36N2O6)]2Ge5·4NH3 (1) and [Rb(C18H36N2O6)]2Ge5·4NH3 (2) were prepared by the extraction of a binary phase of the nominal composition KGe1.67 and a ternary phase of the composition Rb0.5Cs0.5Ge2.25 with liquid ammonia in the presence of cryptand [2.2.2]. The resulting crystalline materials were characterized by low temperature X-ray structure analysis. Compounds 1 and 2 contain isolated trigonal-bipyramidal Ge52− cage anions, the symmetries of which were investigated and compared to the previously reported pentagermanide anion. Despite the nearly identical formulae, the two compounds are not isotypic, as the space group type changes from the acentric group P1 (no. 1) for the potassium compound to P (no. 2) for the rubidium compound.

Dissolving Silicides: Syntheses and Crystal Structures of New Ammoniates Containing Si5 2– and Si9 4– Polyanions and the Role of Ammonia of Crystallisation

The dissolution of the ternary material K6Rb6Si17 in liquid ammonia yields the solvate compound Rb4Si9 ・ 5NH3, which contains fourfold negatively charged nine atom silicon clusters Si94−. Using additionally the [2.2.2] cryptand during the dissolution results in the solvate [K(2.2.2- crypt)]2Si5 ・ 4NH3 , in which the Si52− anion is present in the crystal structure. The Si52− anion has the shape of a nearly ideal trigonal bipyramid. The starting material K6Rb6Si17 contains both Si44− and Si94− Zintl anions. In ammoniate crystal structures, Si94− anions are accessible independently of Si44− anions, and ammonia of crystallisation plays a major role in the observed crystal symmetry. For the cryptate structures of Si52− and Ge52− anions ammonia of crystallisation is obligatory despite the loss of crystal symmetry compared to the crystal structures of the heavier homologues Pb52− and Sn52−. Graphical Abstract Dissolving Silicides: Syntheses and Crystal Structures of New Ammoniates Containing Si5 2– and Si9 4– Polyanions and the Role of Ammonia of Crystallisation

Crystal structures of the [18]-crown-6 ammoniate C12H24O6 · 2 NH3 and the cryptand [2.2.2] ammoniate C18H36O6N2 · 2 NH3

Summary The crystal structures of the new polyether ligand-ammoniates C12H24O6 · 2 NH3 (1) and C18H36O6N2 · 2 NH3 (2) have been elucidated at 123 K by single crystal X-ray structure analysis. Compound 1 crystallizes as yellow plate-like crystals in the monoclinic space group P21/c (no. 14) with unit cell parameters a = 7.572(4) Å, b = 7.724(4) and c = 14.448(7) Å with an angle β = 91.79(6)°. It consists of a molecule of [18]-crown-6 to which two ammonia molecules of crystallisation are bound by three hydrogen bonds each. The ammonia molecules reside below and above the plane of the crown ether oxygen atoms. Compound 2 crystallizes as colourless isometric crystals in the space group P6322 (no. 182) with unit cell parameters a = 8.2568(5) Å and c = 18.992(2) Å. It consists of molecules of cryptand [2.2.2] which are connected by hydrogen bonds via ammonia molecules of crystallisation, resulting in two-dimensional layers parallel to the ab-plane.

Synthesis and Crystal Structures of the Polygermanide Ammoniates K4Ge9 · 9 NH3, Rb4Ge9 · 5 NH3 and Cs6Ge18 · 4 NH3

The new compounds K4Ge9 ·9 NH3 and Rb4Ge9 ·5 NH3 were prepared by the extraction of K4Ge9 and Rb4Ge9 with liquid ammonia and characterized by low temperature X-ray structure analysis. They both contain monocapped square antiprismatic Ge94− anions. Cs6Ge18 ·4 NH3 was prepared by the extraction of K2Cs2Ge9 with liquid ammonia in the presence of [(Bu)3MeN](Br2I) as an oxidizing agent, and contains a [Ge9-Ge9]6− dimer in which two Ge94− anions are linked by a single Ge-Ge bond

Coordination preferences of the alkali cations sodium and caesium in the mixed-cationic Zintl ammoniate Cs3.2Na0.8Ge9·5.3NH3

The involvement of two different alkali cations in the nonagermanide ammoniate Cs(3.2)Na(0.8)Ge9·5.3NH3 [tricaesium sodium nonagermanide-ammonia (1/5.3)] provides insights into the coordination behaviour of ammonia towards sodium and caesium cations within one compound and represents the first mixed-cationic solvate structure of nonagermanide tetraanions. The compound crystallizes in the monoclinic space group P2₁/m and, with the presence of pseudomerohedral twinning, mixed-cation sites and disordering of the nonagermanide cage anions, features a combination of crystallographic challenges which could all be resolved during the refinement.

Reduktion von Isochinolin und Indol mit Cäsium in flüssigem Ammoniak / Reduction of Isoquinoline and Indole with Cesium in Liquid Ammonia

Isoquinoline and indole were reduced with solutions of cesium in liquid ammonia and the resulting crystalline compounds isolated as ammonia-rich solvate crystals. The reduction of isoquinoline yields the anion bisisoquinoline-2,2’-diide in the compound Cs2C18H14N2 · (7/2) NH3 as the result of a coupling reaction. Indole is reduced to the 5,8-dihydroindolide anion in the ammoniate CsC8H8N · 3NH3. Both anions display interactions between their aromatic π-systems and the cesium cations.