Crystal structure of rhombohedral MCd(NO2)3 [M = K, Rb, Cs, Tl] from X-ray powder diffraction data

Crystal structure of double nitrites MCd(NO2)3 [M=K, Rb, Cs, Tl] at room temperature was ab initio determined from X-ray powder diffraction data. The compounds are isostructural and can be described as rhombohedrally distorted perovskites: space group R3 (no. 146); Z=1; M=K: a=7.5887(1), c=9.1285(2) إ; M=Rb: a=7.6290(1), c=9.2355(2) إ; M=Cs: a=7.7305(1), c=9.4170(3) إ; M=Tl: a=7.6219(1), c=9.2300(2) إ. The coordination polyhedra of cadmium and M cations are the distorted tricapped trigonal prism [(3O+3N)+3O] and cuboctahedron, respectively.