A polymorph structure of copper(II) hydrogenphosphite dihydrate

The title compound, poly[[diaqua­copper(II)]-μ(3)-hydrogenphosphito], [Cu(HPO(3))(H(2)O)(2)](n), (I), has been prepared by hydro­thermal synthesis at 393 K. Its non-centrosymmetric polymorph structure, (II), was known previously and has been redetermined at 193 (2) K [El Bali & Massa (2002 ▶). Acta Cryst. E58, i29–i31]. The Cu atoms in (I) and (II) are square-pyramidal coordinated. A distorted octa­hedral geometry around the Cu atoms is considered by including the strongly elongated apical distances of 2.8716 (15) Å in (I) and 3.000 (1) Å in (II). The Cu⋯Cu separation of the dimeric unit is 3.1074 (3) Å. The secondary building units (SBU) (the Cu(2)O(2) dimer and two HPO(3) units) in (I) are inversion related and form a two-dimensional layered structure, with sheets parallel to the bc plane, whereas in the structure of (II), the chain elements are connected via screw-axis symmetry to form a three-dimensional microporous framework. In both polymorph structures, strong O—H⋯O hydrogen bonds are observed.