Synthesis and Characterization of Ca2(PO2NH)4•8H2O

Ca2(PO2NH)4 center dot 8H2O was obtained as single-phase crystalline powder starting from aqueous solution of K4(PO2NH)4 center dot 4H2O and Ca(NO3)2 center dot 4H2O. A small fiber-like specimen has been used for single-crystal X-ray structure determination. In the structure of Ca2(PO2NH)4 center dot 8H2O (Pbcn (no. 60), a = 1700.6(3), b = 1069.3(2), c = 963.2(2) pm, Z = 4) there are (PO2NH)44 ions in saddle conformation which are interconnected by NH center dot center dot center dot O hydrogen bonds forming infinite columns running along [001]. These columns are hold together by a complex hydrogen bonding network with crystal water molecules involved. The FTIR spectrum of the title compound has been measured and the relevant bands were assigned. 31P solid-state NMR investigations yielded three resolved resonances with chemical shift values of 3.1, 4.9 and 7.9 ppm. DTA / TG data are also discussed.