Poly[[diaquabis(mu2-1-oxo-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-4-carboxylato)copper(II)] dihydrate].

The asymmetric unit of the title complex, {[Cu(C(5)H(6)O(6)P)(2)(H(2)O)(2)] x 2 H(2)O}(n), consists of half a Cu atom, one complete 1-oxo-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-4-carboxylate anion ligand and two non-equivalent water molecules. The Cu atom lies on a crystallographic inversion centre and has an elongated axially distorted octahedral environment. A two-dimensional layer structure parallel to (100) is formed as a result of the connectivity brought about by each anion bonding to two different Cu atoms via a carboxylate O atom and a bridging O atom of a C-O-P group. The water molecules participate in extensive O-H...O hydrogen bonding. Neighbouring layers are linked together by intermolecular hydrogen-bonding interactions. The crystal structure is characterized by intra- and interlayer motifs of a hydrogen-bonded network. This study demonstrates the usefulness of carboxylates with caged phosphate esters in crystal engineering.