Rb[SbO(OH)₄]—A Novel Structural Setup for the Anion in Alkali Metal Hydroxidoantimonates(V)

Abstract

Rb[SbO(OH)<inf>4</inf>] was prepared under hydrothermal conditions at pH (Formula Presented.) 10. The crystal structure was determined at −173 °C on basis of X-ray data from a twinned crystal (P2<inf>1</inf>, Z = 2, a = 5.6579(4), b = 7.2961(5), c = 5.6472(5) Å, β= 92.032(6)°; R1 = 0.0309, wR2 = 0.0903 for all data). In comparison with the crystal structures of other alkali hydroxidoantimonates(V), a novel polymeric anion (Formula presented.) [SbO<inf>2/2</inf>(OH)<inf>4/1</inf>]⁻ is present, which is made up of [SbO<inf>2</inf>(OH)<inf>4</inf>] octahedra vertex-sharing the trans-aligned O atoms. All OH groups act as donor and acceptor groups of inter- and intra-chain hydrogen bonds of moderate strengths. The Rb⁺ cations are situated between the chains and are bound to twelve O atoms from two O²⁻ and ten OH groups. The dehydration process of Rb[SbO(OH)<inf>4</inf>] starts at ≈280 °C and yields RbSbO<inf>3</inf> as the final product at 900 °C. Vibrational spectra (infrared and Raman) show characteristic bands for the O-H and Sb-O(H) vibrations.