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, beta = 98.864(2)degrees; Sr[N(CN)(2)](2), a = 1279.63(2), b = 624.756(8), and c = 817.56(1) pm, beta = 99.787(1)degrees; 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. (C) 2001 Academic Press.