Synthesis and structure of R 2[UO2(NO3)2(NCS)2] (R = Rb or Cs)

Abstract

Crystals Rb2[UO2(NO3)2(NCS)2] (I) and Cs2[UO2(NO3)2(NCS)2] (II) have been synthesized and studied by IR spectroscopy and X-ray diffraction. Crystals I are monoclinic, with the following parameters: a = 12.2118(5) A, b = 10.2545(3) A, c = 11.8754(4) A, β = 110.287(1)°, sp. gr. C2/c, Z = 4, and R = 0.0523. Crystals II are orthorhombic, with a = 13.7309(3) A, b = 10.5749(2) A, c = 10.1891(2) A, sp. gr. Pnma, Z = 4, and R = 0.0411. The basic structural units of crystals I and II are one-core complexes [UO2(NO3)2(NCS)2]2−, which belong to the crystallochemical group cis-AB 2 01 M 2 1 (A = UO 2 2+ , B 01 = NO 3 − , M 1 = NCS−), which are combined into a framework via electrostatic interactions with ions of alkaline metals R (R = Rb or Cs). The structural features of crystals I and II, which condition the formation of [UO2(NO3)2(NCS)2]2− complexes with a cis rather than a trans position of isothiocyanate ions in the coordination sphere of uranyl ions, are discussed.