Zur Chemie und Strukturchemie von Phosphiden und Polyphosphiden. 36. Tetrakaliumhexaphosphid: Darstellung,Struktur und Eigenschaften von α-K4P6 und β-K4P6

Chemistry and Structural Chemistry of Phosphides and Polyphosphides. 36. Tetrapotassiumhexaphosphide: Preparation, Structure, and Properties of α-K₄P₆ and β-K₄P₆ Tetrapotassiumhexaphosphide has been prepared quantitatively by reaction of the elements at 870 K in sealed Nb and Ta ampoules, respectively. Two crystalline modifications are formed: α-K₄P₆ is stable below 850 K, β-K₄P₆ is stable above this temperature. Both compounds are black semiconductors (E_G(α) = 0.55 eV) with metallic lustre. The orthorhombic structures are defect variants of the hexagonal AlB₂ type structures (K₄P₆□₂) and of a different stacking sequence of this type. Characteristic building units are planar isometric P₆ rings, formed by a specific ordering of defects in the partial structure of the major component. The short P? P distances (215.5 pm and 215.0 pm, respectively) are about 30 pm shorter than the distances compared with a single bond (221 pm). They represent one double bond which is delocalized about six bonds or an aromatic 2π-system. The thermal decomposition in tantalum crucibles, the reaction with quartz walls as well as the reaction with benzophenone in monoglyme yields quantitatively K₃P₇. The reaction with RCl ? Me₃SnCl in monoglyme at 223 K results in the formation of P₇R₃ with high yield (75%). Very probably the valence fluctuating hexaphosphene(4) system is formed at 195 K in the primary reaction step (³¹P-NMR, singulett at 473 ppm downfield).     

Beiträge zur Chemie der Uranfluoride und -oxidfluoride. II. Darstellung und Schwingungsspektren von α- und β-Uranpentafluorid

On the Chemistry of Uranium Fluorides and Oxide Fluorides. II. Preparation and Vibrational Spectra of α- and β-Uranium Pentafluoride By reaction of a saturated solution of UF₆ in anhydrous HF with HBr β-UF₅ was prepared in a simple manner. β-UF₅ was changed into α-UF₅ by heating in the presence of UF₆. The IR and RAMAN spectra of the dimorphs are reported and discussed.