Crystal structure determinations of Cs2NaCr(CN)6 and further compounds A2BM(CN)6 (A = Rb, Cs; B=Na, K, Rb, NH4; M = Cr, Mn, Fe, Co):: Tilting of octahedra and tolerance factor of cyano cryolites

The crystal structures of Cs2NaCr(CN)(6) (space group P2(1)/n, Z = 2; a = 763.2(1), b = 789.8(1), c = 1102.4(1) pm. beta = 90.09(1)degrees) and of 9 isostructural cyano cryolites A(2)BM(CN)(6) of the elements M = Cr, Mn, Fe, Co were determined by X-rays at single crystals. The results, including data from the literature, were studied with respect to the interdependence of radii resp, bond lengths and cyano bridge angles M-CN-B resp. tilting of [M(CN)(6)] and [BN6] octahedra: The average tilt angles kappa of the latter are within the range 13 degrees less than or equal to kappa less than or equal to 23 degrees and increase linearly if the modified tolerance factor t (of range 0,87 greater than or equal to t greater than or equal to 0,78) decreases.