Nikolaus Korber

The shape of germanium clusters to come.

A different drummer: The existence of endohedral germanium clusters was predicted earlier by gas-phase experiments. The [Co@Ge(10)](3-) anion now synthesized is surprising, as it breaks with a long line of exclusively deltahedral structures found in the past. Instead, it has a regular pentagonal-prismatic structure (see picture; Co gray, Ge red).

Detection of the Elusive Highly Charged Zintl Ions Si44− and Sn44− in Liquid Ammonia by NMR Spectroscopy

Its detected! The existence of the prototypical Zintl ions Tt4 (4-) (Tt=Group 14 element), which are isoelectronic to the P4 molecule, used to be confined to the solid state. Recently, circumstantial evidence for a solution chemistry in liquid ammonia emerged. Direct spectroscopic observation of the dissolved anions has now been achieved. In the case of Si4 (4-) , this is the first solution detection of any homoatomic silicide.

Synthesis and crystal structure of (NEt3Me)2CsP11·5NH3

Abstract Two caesium cations of Cs 3 P 11 were exchanged for two NEt 3 Me + cations in liquid ammonia, yielding (NEt 3 Me) 2 CsP 11 ·5NH 3 . The crystal structure determination shows linear 1 ∞ [CsP 11 ] − chains along the crystallographic b axis, which are separated by NEt 3 Me + cations. Five ammonia molecules of crystallization complete the coordination sphere of the Cs cations. FT-IR frequencies in the region of the P 3− 11 molecular vibrations are in agreement with the values reported previously for the alkali metal undecaphosphides.

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.

PPh4+H2P7–—the first stable hydrogen polyphosphide salt

The tetraphenylphosphonium salt of the hydrogen polyphosphide H2P7– is synthesized from K3P11 and PPh4Cl in liquid ammonia and the nortricyclene topology of the anion is proven by X-ray crystal structure analysis.

Evidence of Solubility of the Acetylide Ion C22−: Syntheses and Crystal Structures of K2C2⋅2 NH3, Rb2C2⋅2 NH3, and Cs2C2⋅7 NH3

Carbon anions in solution: C(2)(2-) dumbbells are well-known in solid-state compounds. The crystallization of the title compounds now shows that acetylide ions are existent in solution and therefore chemistry with small dissolved carbon anions may be within reach.

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

Layers built from caesium cations and heptaphosphanortricyclane anions: synthesis and crystal structure of [NEt3Me][Cs2P7]·NH3 and [NEt4][Cs2P7]·4NH3

Exchange of one caesium cation of Cs3P7 for NEt3Me+ or NEt4+ in liquid ammonia gave [NEt3Me][Cs2P7]·NH31 and [NEt4][Cs2P7]·4NH32, respectively. The crystal structure of the compounds have been determined. They show the existence of corrugated ∞2[Cs2P7]– layers stacked along the crystallographic a axis in both compounds. The layers are topologically equivalent in 1 and 2. While the layers are repeated in the same orientation in 1, stacking mode AAA, they have two different orientations in 2, stacking mode ABAB, where B is related to A by a mirror plane. The space between the layers contains ammonia of solvation completing the co-ordination of caesium, and the tetraalkylammonium cations.

No aromaticity of P64− observed via solid state 31P-NMR spectroscopy

The solid state NMR spectra of the binary alkali hexaphosphides Rb4P6 and Cs4P6 unambiguously show the P(6)4- anion not to be aromatic.

Hydrogen Polyphosphides P3H23− and P3H32−: Synthesis and Crystal Structure of K3(P3H2)·2.3NH3, Rb3(P3H2)·NH3, [Rb(18-crown-6)]2(P3H3)·7.5NH3, and [Cs(18-crown-6)]2(P3H3)·7NH3

The incongruous solvation of polyphosphides and phosphanes or the direct reduction of white phosphorus in liquid ammonia leads to the hydrogen polyphosphides catena-dihydrogen triphosphide, P(3)H(2)(3-), and catena-trihydrogen triphosphide, P(3)H(3)(2-), in the crystalline compounds K(3)(P(3)H(2)).2.3NH(3) (1), Rb(3)(P(3)H(2)).NH(3) (2), [Rb(18-crown-6)](2)(P(3)H(3)).7.5NH(3) (3), and [Cs(18-crown-6)](2)(P(3)H(3)).7NH(3) (4).