SEARCH

SEARCH BY CITATION

Keywords:

  • Ammonium;
  • rubidium;
  • caesium hydrogen sulfate;
  • crystal structure

Abstract

Aus den binären Systemen M2SO4/H2SO4 (M = Rb, Cs, NH4) konnten drei neue Hydrogensulfate des Typs M(HSO4)(H2SO4) synthetisiert und strukturell charakterisiert werden. Die Rubidium- und Caesiumverbindungen sind isotyp, während NH4(HSO4)(H2SO4) zu beiden topologisch verwandt ist. Alle drei Verbindungen kristallisieren mit nahezu identischen Gitterkonstanten [Rb: a = 7,382(1), b = 12,440(2), c = 7,861(2), β = 93,03(3); Cs: a = 7,604(1), b = 12,689(2), c = 8,092(2), β = 92,44(3); NH4: a = 7,521(3), b = 12,541(5), c = 7,749(3), β = 92,74(3)], Raumgruppe P21/c. Es liegen SO4-Tetraeder in Form von HSO4-Anionen (S1) und H2SO4-Molekülen (S2) vor, wobei die HSO4-Anionen über Wasserstoffbrückenbindungen Zick-Zack-Ketten ausbilden. In der Struktur der Rb- und Cs-Hydrogensulfat-Dihydrogensulfate verbinden H2SO4-Moleküle diese Ketten zu Doppelschichten. Die Metallatome sind von 9 O-Atomen mit den Abständen 2,97 – 3,39 Å (Rb) und 3,13 – 3,51 Å (Cs) koordiniert. In der Ammoniumverbindung liegen ausgehend von NH4+-Ionen zusätzliche Wasserstoffbrücken vor. Das führt zur Ausbildung von S2[BOND]NH4+-Ketten (parallel zu den S1-Ketten) sowie zur räumlichen Vernetzung beider Sorten von Ketten.

Synthesis and Structure of Hydrogen Sulfates of the Type M(HSO4)(H2SO4) (M = Rb, Cs and NH4)

From the binary systems M2SO4/H2SO4 (M = Rb, Cs, NH4), three new hydrogen sulfates of the type M(HSO4)(H2SO4) could be synthesized and structural characterized. The rubidium and caesium compounds are isotypic whereas NH4(HSO4)(H2SO4) is topologically very similar to both. All three compounds crystallize with nearly identical cell parameters [Rb: a = 7.382(1), b = 12.440(2), c = 7.861(2), β = 93.03(3); Cs: a = 7.604(1), b = 12.689(2), c = 8.092(2), β = 92.44(3); NH4: a = 7.521(3), b = 12.541(5), c = 7.749(3), β = 92.74(3)], in the monoclinic space group P21/c, There exist two kinds of SO4-tetrahedra: HSO4 anions (S1) and H2SO4-molecules (S2). The HSO4 anions form hydrogen bridged zigzag chains. In the case of the Rb and Cs compounds, the H2SO4 molecules connect these chains forming double layers. The metal atoms are coordinated by 9 O-atoms with M[BOND]O-distances of 2.97 – 3.39 Å (Rb) and 3.13 – 3.51 Å (Cs). In the ammonium compound additional hydrogen bonds are formed originating from the NH4+ cation. This finally leads to the formation of S2[BOND]NH4+ chains (parallel to the S1 chains) as well as to a three-dimensional connection of both kinds of chains.