Poly[[diaqua-μ2-hydroxido-(μ7-2-phosphonatoethanesulfonato)dicopper(II)] trihydrate]

The crystal structure of the title compound, [Cu2(C2H4O6PS)(OH)(H2O)2]·3H2O, consists of two Cu2+ ions, one (O3PC2H4SO3)3− ion and one OH− ion, as well as five water molecules, two of which are coordinated to Cu2+. The Cu2+ ions are coordinated by six O atoms. The CuO6 polyhedra are connected by μ- and μ3-O atoms into zigzag chains along the b axis. These chains are further connected by –CH2CH2– groups to form layers, in turn building a three-dimensional framework via hydrogen bonding.

A. Sonnauer, A. Lieb and N. Stock Comment Inorganic-organic hybrid materials based on metal carboxylates, sulfonates and phosphonates are intensively investigated due to their potential application in the field of gas separation, storage, as well as catalysis, or as sensor materials. We are interested in the use of organic ligands containing two or more different functional groups for the synthesis of functionalized hybrid compounds. Although a large number of metal phosphonates and metal sulfonates have been reported in the literature, compounds based on ligands containing simultaneously a phosphonic as well as a sulfonic acid group have only recently been investigated. These few studies are limited to the use of linker molecules based on rigid phosphonoarylsulfonic acids.
Our group has started a systematic investigation using the flexible linker 2-phosphonoethansulfonic acid, which has been reported in the literature (Sonnauer et al., 2007;Sonnauer & Stock, 2008a,b The title compound consists of two crystallographic independent copper(II) ions, one fully deprotonated (O 3 PC 2 H 4 SO 3 ) 3anion, one hydroxide ion, as well as five water molecules (two coordinated to the copper ions) (Fig. 1). The copper ions are coordinated by six oxygen atoms and form CuO 6 polyhedra. These polyhedra are connected by µ-O and µ 3 -O atoms. Thus, Cu-O-Cu zigzag chains of edge-sharing polyhedra are observed (Fig. 2), which are connected by the organic group -C 2 H 4 -to form layers. These layers are connected via hydrogen bonds into a three-dimensional framework (Fig. 3).
Experimental H 2 O 3 PC 2 H 4 SO 3 H was synthesized as previously reported (Sonnauer & Stock, 2008b). All other reagents were of analytical grade (Aldrich and Fluka) and were used without further purification. The synthesis was performed in a glass reactor

Refinement
The hydrogen atoms of the C-H groups were positioned with idealized geometry and were refined using a riding model.
The hydrogen atoms of the O-H groups were located in the Fourier difference map, their bond lengths were set to ideal values and afterwards the atom positions were refined using a riding model with U(H) = 1.2U eq (C) or U(H) = 1.5U eq (O). Fig. 1. Asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.