Synthesis, characterization, and crystal structure of two novel 3D cadmium organotriphosphonates complexes

Reactions of nitrilotris(methylenephosphonic acid), [N(CH2PO3H2)3] (NTP) with cadmium acetates under different hydrothermal conditions result in two novel 3D cadmium organotriphosphonates complexes: Na|Cd2[N(CH2PO3H)(CH2PO3)2(H2O)] (1) and Na2|Cd5[N(CH2PO3)3]2(H2O)2| (2). Single-crystal X-ray diffraction analysis reveals that complex 1 crystallizes in monoclinic P21/c (No. 14), with a = 11.9730(3) Å, b = 10.5928(3) Å, c = 9.4435(2) Å, β = 97.881(2)°, V = 1186.38(5) Å3, and Z = 4. Complex 2 is monoclinic C2/c (No. 15) having unit cell parameters a = 25.377(5) Å, b = 10.543(2) Å, c = 9.7160(19) Å, β = 107.22(3)°, V = 2482.9(9) Å3, and Z = 4. The structures of complexes 1 and 2 both feature 3D coordination networks built from cadmium octahedral linked together by bridging phosphonate groups from NTP, sodium cations are deposited in the free volume of the structures. Hydrogen bonds are existed in structures. Notably, SBU-1 (Cd2(NTP)) and SBU-2 (Cd3(NTP)), formed by deprotonated NTP chelating with cadmium atoms, are present in the structure of complexes 1 and 2, respectively. The effect of the extent of deprotonation of phosphonic acids on the type of complex formed is discussed. Further characterizations of the two complexes have been performed, including X-ray powder diffraction, ICP, CHN, IR and TG–DTA analyses.