Die Kristallstruktur des Rubidium-TrihydrogenDiphthalat-Dihydrats, RbH3(C8O4H4)2 · 2H2O

Abstract

Abstract RbH3(C8O4H4)2 · 2H2O is monoclinic (space group C2/c) with a = 13.561(4), b = 21.185(6), c = 6.873(2) Å; β = 113.82(4)°; Z = 4. The structure was determined by direct methods and was refined to an R value of 2.0%. The Rb ion is coordinated to eight oxygen atoms. The hydrogen phthalate ion has no intramolecular hydrogen bond, but, two different ions are interconnected by a “very short” O–H–O hydrogen bond [2.447(2) Å]. Assuming space group C2/c, the connecting hydrogen atom is in a special position on a twofold axis and the hydrogen bond should be designated as symmetrical. The difference Fourier synthesis, however, reveals indications of a disordered asymmetrical location of this hydrogen atom which is confirmed also by refinement. The crystal under investigation is assumed to be identical with a crystal species which was formerly described as RbHC8O4H4 · 11H2O.