Rubidium-diarsasilicat(IV) Rb2SiAs2, ein Derivat der SiS2-Struktur / Rubidium Diarsasilicate(IV) Rb2SiAs2, a Derivative of the SiS2 Structure Type

Abstract

Rb2SiAs2 was found as a byproduct in the course of the RbAs synthesis in a quartz container. The direct synthesis from the elements yields pure samples w-ithin 5 h at 925 K. Rb2SiAs2 forms transparent red needle-shaped crystals which split to bunches of golden, reflecting fibres. The compound is sensitive against moisture. Rb2SiAs2 is isotypic to K2SiP2 with a polyanionic chain [SiAs2]2- of edge-connected tetrahedra (isostructural and isoelectronic to SiS2) formed in a dis­torted cubic closed packed As arrangement, and with Rb in the octahedral holes (Ibam. No. 72; a = 726.6(5), b = 1377.1(6), c = 638.9(3) pm; Z = 4: Si−As = 238.1 pm; As−Si−As = 95.7° and Si−As−Si = 84.3° in the four membered Si2As2 rings).