A polymorph structure of copper(II) hydrogenphosphite dihydrate

The title compound, poly[[diaquacopper(II)]-μ3-hydrogenphosphito], [Cu(HPO3)(H2O)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 Cu2O2 dimer and two HPO3 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.

The title compound, poly [[diaquacopper(II)]-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 squarepyramidal 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 CuÁ Á ÁCu 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-HÁ Á ÁO hydrogen bonds are observed.

Comment
Cu atoms in the asymmetric unit are pentahedrally coordinated and link three P atoms via phosphite O atoms (O1, O2, O3) with shorter distances and two water molecules (O4, O5) with longer distances ( Fig. 1 and Table 1). A distorted octahedral geometry around the Cu atoms are considered when the strongly elongated apical Cu-O distances of 3.036 (14) Å (Handlovič, 1969), 3.000 (1) Å in II (El Bali & Massa, 2002), and 2.8716 (15) in I are included. The P atoms form the centers of a pseudo pyramid with the hydrogen phosphite groups, and each P links to three Cu via P-O-Cu bonds. The P-O bonds are in the range of 1.5178 (14) -1.5337 (14) Å. The two-dimensional structure (Fig. 2) is built up from SBU (Biradha, 2007) (secondary building units, Fig.1), the corner sharing of tetra-meric units. One Cu atom links two P atom via O1 and O2. Two pentahedra Cu(H 2 O) 2 O 3 , and two pseudopyramids HPO 3 form a dinucleus unit, noted as SBU. The Cu···Cu distance in the dimeric unit of I is 3.1074 (3) Å. The SBU and hydrogenphosphite polyhedra are connected into a one-dimensional chain by sharing the corner O3, and each chain links two other chains by sharing other atoms O3, forming a sheet along the bc-plane, containing 8-membered rings when the long Cu-O3c distance is neglected. In the structure of (CN 3 H 6 ) 2 .Zn(HPO 3 ) 2 , ZnO 4 and HPO 3 building units form a 12-ring framework (Harrison et al., 2001). In both polymorph structures strong O-H···O hydrogen bonds are observed (Table 2).

Experimental
All reagents were of analytical grade. The title sample was prepared by Cu(NO 3 ) 2 , H 2 O, H 3 (PO 3 ) and (C 2 H 5 ) 3 N triethylamine in the molar ratio 1:144:5:11 and heated at 393 K for 8 d. The blue single crystals were filtered, washed with distilled water and dried in air.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq