Syntheses, Vibrational Spectroscopy, and Crystal Structure Determination from X-Ray Powder Diffraction Data of Alkaline Earth Dicyanamides M[N(CN)2]2 with M=Mg, Ca, Sr, and Ba

The alkaline earth dicyanamides Mg[N(CN)2]2, Ca[N(CN)2]2, Sr[N(CN)2]2, and Ba[N(CN)2]2 were synthesized by ion exchange using Na[N(CN)2] and the respective nitrates or bromides as starting materials. The crystal structures were determined from X-ray powder diffractometry: Mg[N(CN)2]2, Pnnm, Z=2, a=617.14(3), b=716.97(3), and c=740.35(5) pm; Ca[N(CN)2]2 and Sr[N(CN)2]2, C2/c, Z=4; Ca[N(CN)2]2, a=1244.55(3), b=607.97(1), and c=789.81(1) pm, =98.864(2)°; Sr[N(CN)2]2, a=1279.63(2), b=624.756(8), and c=817.56(1) pm, =99.787(1)°; Ba[N(CN)2]2, Pnma, Z=4, a=1368.68(7), b=429.07(7), and c=1226.26(2) pm. The dicyanamides consist of the respective alkaline earth cations and bent planar [N(CN) 2]- ions. The structural features were correlated with vibrational spectroscopic data. The thermal behavior was studied by thermoanalytical experiments.