Poly[diaqua(μ5-1H-imidazole-4,5-dicarboxylato)(μ4-1H-imidazole-4,5-dicarboxylato)trisilver(I)ytterbium(III)]

The asymmetric unit of the title compound, [Ag3Yb(C5HN2O4)2(H2O)2]n, contains three AgI ions, one YbIII ion, two imidazole-4,5-dicarboxylate ligands and two coordinating water molecules. The YbIII atom is eight-coordinated, in a bicapped trigonal prismatic coordination geometry, by six O atoms from three imidazole-4,5-dicarboxylate ligands and two coordinating water molecules. The two-coordinated AgI ions exhibit three types of coordination environments. One AgI atom is bonded to two N atoms from two different imidazole-4,5-dicarboxylate ligands. The other two AgI atoms are each coordinated by one O atom and one N atom from two different imidazole-4,5-dicarboxylate ligands. These metal coordination units are connected by bridging imidazole-4,5-dicarboxylate ligands, generating a two-dimensional heterometallic layer. These layers are stacked along the a axis via O—H⋯O hydrogen-bonding interactions to generate a three-dimensional framework.


Si-Ming Zhu Comment
In the past few years, lanthanide-transition metal heterometallic complexs with bridging multifunctionnal organic ligands are of increasing interest, not only because of their impressive topological structures, but also due to their versatile applications in ion exchange, magnetism, bimetallic catalysis and luminescent probe (Cheng et al., 2006;Kuang et al., 2007;Sun et al., 2006;Zhu et al., 2010). As an extension of this research, the structure of the title compound, a new heterometallic coordination polymer, has been determined which is presented in this artcle.
The asymmetric unit of the title compound ( Fig. 1), contains three Ag I ions, one Yb III ion, two imidazole-4,5-dicarboxylate ligands, and two coordinated water molecules. The Yb III are eight-coordinated, in a bicapped trigonal prismatic coordination geometry, by six O atoms from three imidazole-4,5-dicarboxylate ligands and two coordinated water molecules. The two-coordinated Ag I ions exhibit three types of coordination environment. One Ag I ion is linear bonded to two N atoms from two different imidazole-4,5-dicarboxylate ligands with N2 iv -Ag3-N3 angle 176.23 (17) (Table 1 and Fig. 2). Symmetry code: (iv) -x, y, -z+3/2.

Refinement
H atoms bonded to C atoms were positioned geometrically and refined as riding, with C-H = 0.93Å and U iso (H) = 1.2U eq (C). H atoms of water molecules were found from difference Fourier maps and refined isotropically with a restraint of O-H = 0.82Å and U iso (H) = 1.5U eq (O).

Figure 1
The molecular structure showing the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius. Symmetry codes: (i) -x, -y, 1-z; (ii) x, 1+y, z; (iv) -x, y,

Figure 2
A view of the three-dimensional structure of the title compound. The hydrogen bonding interactions showed as broken lines.

Poly[diaqua(µ 5 -1H-imidazole-4,5-dicarboxylato)(µ 4 -1H-imidazole-4,5-dicarboxylato)trisilver(I)ytterbium(III)]
Crystal data  Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 R-factors(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.