Poly[di-μ-glycinato-copper(II)]: a two-dimensional coordination polymer

The title coordination polymer, [Cu(C2H4NO2)2]n, is two-dimensional and consists of a distorted octahedral copper coordination polyhedron with two bidentate glycine ligands chelating the metal through the O and N atoms in a trans-square-planar configuration. The two axial coordination sites are occupied by carbonyl O atoms of neighbouring glycine molecules. The Cu—O distances for the axial O atoms [2.648 (2) and 2.837 (2) Å] are considerably longer than both the Cu—O [1.9475 (17) and 1.9483 (18) Å] and Cu—N [1.988 (2) and 1.948 (2) Å] distances in the equatorial plane, which indicates a strong Jahn–Teller effect. In the crystal, the two-dimensional networks are arranged parallel to (001) and are linked via N—H⋯O hydrogen bonds, forming a three-dimensional arrangement.

The complexation of simple copper salts to amino acids is a well investigated reaction and various complexes and clusters have been reported (Low et al., 1959;Davies et al., 2003;Aromi et al., 2008;Bi et al., 2006;Zhang et al., 2005). A three-dimensional copper-glycinate coordination polymer has been reported on by (Chen et al., 2009).
In the crystal the two dimensional networks are linked via N-H···O hydrogen bonds to form a three-dimensional arrangement (Table 1 and Fig. 2).

Refinement
The NH-atoms were located in difference electron-density maps and were freely refined. The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.97 Å, with U iso (H) = 1.2U eq (C).

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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