RUBIDIUM DECAAMIDODICHROMATE(III), RB4CR2(NH2)(10) - SYNTHESIS AND CRYSTAL-STRUCTURE

The reaction of chromium(III) with rubidium amide in a molar ratio of Cr(NH2)(3)/RbNH2 = 1:1.75 at 140 degrees C and p(NH3) = 3 kbar in a hi gh-pressure autoclave results after 90 days in dark violet crystals of Rb4Cr2(NH2)(10). Structure determination was done by single crystal X -ray methods: Pna2(1) (No. 33), Z = 4, a = 12.244(3) Angstrom, b = 6.7 27(1) Angstrom, c = 19.775(5) Angstrom, N(F-o(2) > 3 sigma(F-o(2))) = 1046, N(Var.) = 94, R/R-w = 0,051/0,059 The structure of Rb4Cr2(NH2)(1 0) contains isolated, face-sharing N-octahedra around two Cr3+-ions gi ving [Cr(NH2)(3)(NH2)(3/2)](2)(3-). These are arranged to oneanother f ollowing the motif of a hexagonal closest packing. They are connected via Rb+- and one further amide ion not bound to Cr3+. The compound is characterized by thermoanalytical and IR-/Raman-spectroscopic measurem ents.