Poly[[aqua-μ3-2,2-dimethylmalonato-copper(II)] monohydrate] and poly[aqua-μ3-2,2-dimethylmalonato-copper(II)]

The coordination mode of the dimethylmalonate ligand in the two title CuII complexes, {[Cu(C5H3O4)(H2O)]·H2O}n, (I), and [Cu(C5H3O4)(H2O)]n, (II), is the same, with chelated six‐membered, bis‐monodentate and bridging bonding modes. However, the coordination environment of the CuII atoms, the connectivity of their metal–organic frameworks and their hydrogen‐bonding interactions are different. Complex (I) has a perfect square‐pyramidal CuII environment with the aqua ligand in the apical position, and only one type of square grid consisting of CuII atoms linked via carboxylate bridges to three dimethylmalonate ligands, with weak hydrogen‐bond interactions within and between its two‐dimensional layers. Complex (II) has a coordination geometry that is closer to square pyramidal than trigonal bipyramidal for its CuII atoms with the aqua ligand now in the basal plane. Its two‐dimensional layer structure comprises two alternating grids, which involve two and four different dimethylmalonate anions, respectively. There are strong hydrogen bonds only within its layers.