Isomorphous phosphonoacetic acid salts with magnesium(II), manganese(II), cobalt(II), zinc(II) and copper(II)

All crystals of the title compounds, with general formula M2+(C2H4O5P-)(2)(H2O)(2), (MAP), are isomorphous and crystallize in the space group P (1) over bar with Z = 2. The two crystallographically independent M2+ cations are situated on a center of symmetry and are octahedrally coordinated by two phosphonate monoanions and two water molecules. In the case Of Cu2+ cation, Jahn-Teller effect causes strong extension of two Cu-O bonds. The monoanions coordinate the metal ions by one carboxylic and one phosphonate oxygen atom, which is facilitated by their specific overall conformation. In each morroanion, one of the phosphonate O atoms is nearly antiperiplanar ap to the carboxylic C atom, and the remaining phosphonate O atoms are nearly gauche (+sc and -sc) with respect to the mentioned C atom. The carboxylic O atoms are in positions close to +sc and -ac in relation to the phosphonate P atom. The complex molecules form well separated layers in all MAP compounds. The phosphonate and carboxylic groups act as donors in medium strong and weak intermolecular O-H...O hydrogen bonding and, as acceptors, in C-H...O hydrogen interactions in all structures. Additionally both crystallographically independent water molecules are donors of weak hydrogen bonding to phosphonate oxygen atoms from adjacent complex molecules.