Hydratisierte Cyanoelpasolithe: Bis(tetramethylammonium)diaquaIithium-hexacyanometallate(III) des Mangans, Eisens und Cobalts / Hydrated Cyanoelpasolites: Bis(tetramethylammonium)diaqualithium-hexacyanometallates(III) of Manganese, Iron and Cobalt

Abstract

The crystal structures of three isotypic hexacyanometallates(III) (NMe4)2LiM(CN)6·2H2O have been determined and refined in the monoclinic space group C2/c, Z = 4, to wR = 0.053 (M = Mn, 959 independent single crystal reflections), 0.041 (M =Fe, 2002 reflections) and 0.037 (M = Co, 1881 reflections). The stucture is elpasolite-related by its face-centered pseudocubic arrangement of M atoms within nearly undistorted M(CN)6 3- octahedra, six of which form strongly distorted octahedral N6 cavities occupied by dihydrated lithium ions. The resulting average distances for the M(CN)6 3- octahedra are Mn-C = 201, Fe-C = 194.7, Co-C = 190.3, and C-N = 114 pm. The lithium coordination is distorted tetrahedral, consisting of LiO2N2 units with distances of about Li-O = 194, Li -N = 209 pm (for M = Fe, Co). The remaining four N atoms of the N6 cavity are bound by hydrogen bridges from the two aqua ligands, O-H···N = 283 and 295 pm. The relations to the hydrated elpasolite structure of (NMe4)2NaFe(CN)6·H2O are discussed.