In a recent systematic study on the influence of the reaction temperature on the structure formation in the system CdCl2/H(HO3PCH2)(2)NH-CH2C6H4-COOH (H5L)/NaOH, [Cd-3(H2O)(3)((O3PCH2)(2)NH-CH2C6H4-COOH)(2)]center dot 11H(2)O was obtained as a microcrystalline compound. We have now been able to elucidate the structure from single-crystal data: triclinic, P (1) over tilde; a = 5.4503(9), b = 12.880(2), and c 16.417(3) angstrom; alpha = 67.841(6)degrees, beta = 80.633(6)degrees, gamma =87,688(8)degrees, V = 1052.9(3) angstrom(3); Z = 1; R-1 = 0.1143, R-2 0.2108 (all data); 0.0705, 0.1823 ((1 > 2 sigma(1)). The structure of [Cd-3(H2O)(3)((O3PCH2)(2)NH-CH2C6H4-COOH)(2)]center dot 11H20 is built up of cadmium phosphonate layers connected by water-mediated hydrogen bonds between aryl-carboxylic acid groups and water molecules coordinated to Cd2+ ions of adjacent layers (C-OH center dot center dot center dot H2O center dot center dot center dot H2O-Cd2+). The title compound was characterized by IR spectroscopy and energy dispersive X-ray, elemental, and thermogravimetric analyses. Furthermore, temperature-dependent X-ray diffraction data are presented. [Cd-3(H2O)(3)((O3PCH2)(2)NH-CH2C6H4-COOH)(2)]center dot 11H(2)O can be reversibly dehydrated, and mechanical stress and grinding in the presence of water leads to the intercalation of additional water molecules.