Polymeric bis(phosphonomethylcarboxylato)calcium(II) at 85 K

In the crystal structure of the title compond, alternatively called poly[calcium(II)-di-mu-carboxymethylphosphonato], [Ca(C(2)H(4)O(5)P)(2)](n) or [Ca(H(2)AP)(2)](n), one of the phosphonate O atoms of the phosphonocarboxylate monoanion lies nearly antiperiplanar (ap) to the carboxylic acid C atom. The phosphonate P atom is located -sc and +ac relative to the carboxylic acid O atoms. The overall structure has a layered architecture. The Ca(2+) cations lie on a twofold axis and are bridged by the phosphonate O atoms to form chains along the c axis, giving layers parallel to (100). There are medium-strength O-H...O and C-H...O hydrogen-bonding interactions stabilizing the layers, and O-H...O hydrogen bonds connect adjacent layers.