Crystal structure determinations of Cs2NaCr(CN)(6) and further compounds A(2)BM(CN)(6) (A = Rb, Cs; B=Na, K, Rb, NH4; M = Cr, Mn, Fe, Co): Tilting ofoctahedra and tolerance factor of cyano cryolites

The crystal structures of Cs2NaCr(CN)(6) (space group P2(1)/n, Z = 2; a = 7 63.2(1), b = 789.8(1), c = 1102.4(1) pm. beta = 90.09(1)degrees) and of 9 i sostructural 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 dat a 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 a re within the range 13 degrees less than or equal to kappa less than or equ al 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) dec reases.