Latent Porosity in Potassium Dodecafluoro-closo-dodecaborate(2-). Structures and Rapid Room Temperature Interconversions of Crystalline K2B12F12, K2(H2O)2B12F12, and K2(H2O)4B12F12 in the Presence of Water Vapor. -Recrystallization of K2B12F12 (I) in water yields two different hydrates, K2(H2O)2B12F12 (II) and K2(H2O)4B12F12 (III), whose structures are determined by single crystal XRD. (II) crystallizes in the space group P2 1 /c with Z = 2 and (III) in the space group P1 with Z = 2. The structures of (II) and (III) contain [K(ΞΌ-H2O)2K] 2+ and [(H2O)K(ΞΌ-H2O)2K(H2O)] 2+ dimers, respectively, which interact with superweak B12 anions via multiple Kβ’β’β’F-B interactions and O-Hβ’β’β’F-B hydrogen bonds. The three compounds (I), (II), and (III) are related by a series of remarkably rapid solid state hydration and/or dehydration reactions.
It is concluded that permanent porosity is not required for rapid and reversible gas absorption and for rapid gas diffusion in crystalline solids at ordinary temperatures, but can be achieved in an all-inorganic system with the large, symmetric, rigid, and robust superweak anion B12
. -(PERYSHKOV, D. V.; POPOV, A. A.; STRAUSS*,