Aqua(2,2′-bipyridine-κ2 N,N′)[2-(3-thienyl)malonato-κ2 O,O′]zinc(II) dihydrate

In the crystal structure of the title compound, [Zn(C7H4O4S)(C10H8N2)(H2O)]·2H2O, the ZnII ion assumes a trigonal–bipyramidal coordination geometry completed by two N atoms from a 2,2′-bipyridine ligand, two O atoms from a 2-(3-thienyl)malonate anion and a water molecule. The S atom of the 2-(3-thienyl)malonate ligand is disordered over two sites with an occupancy ratio of 0.701 (5):0.299 (5). Intermolecular O—H⋯O hydrogen bonding is present in the crystal structure.

In the crystal structure of the title compound, [Zn(C 7 H 4 O 4 S)-(C 10 H 8 N 2 )(H 2 O)]Á2H 2 O, the Zn II ion assumes a trigonalbipyramidal coordination geometry completed by two N atoms from a 2,2 0 -bipyridine ligand, two O atoms from a 2-(3thienyl)malonate anion and a water molecule. The S atom of the 2-(3-thienyl)malonate ligand is disordered over two sites with an occupancy ratio of 0.701 (5):0.299 (5). Intermolecular O-HÁ Á ÁO hydrogen bonding is present in the crystal structure.
This work was supported financially by the Natural Science Foundation of Shaanxi Provinces of China (SJ08B11).

Comment
The nature of organic heterocycles are special enough to attract a lot of scientific researches (Lin et al., 2008;Jin et al., 2001).
Because of the big radius of the S atom, its lone pair of electrons can be more easily delocalized with in the heterocycle, and the ligand exhibits good charge-transfer ability (He et al., 2009). However, its reaction mechanism is rather complicated to study, a small quantity of literatures about thiophenemalonic are reported, with thiophenemalonic acid researched even less (Murray et al., 2008;Huang et al., 2009;Lim et al., 2006). In this paper, we report the hydrothermal synthesis and structure of a new compound incorporating the thiophene-containing ligand3-thiophenecarboxylate with two kinds of hydrogen bond rings (Nichol et al., 2009;Etter, 1990;Eppel et al., 2009).
The molecular structure of the title complex is shown in Fig.1. The coordination geometry around Zn 2+ ion is five-coordinated, with two N atoms from 2,2'-bipyridine ligand (N1, N2), two O atom from 3-thiophenecarboxylate ligand (O1,O3), and a coordinated water(O5). The equatorial positions are occupied by N2, O1 and O5, while N1, O3 are in axial positions, so the local coordination environment of Zn(II) can be described as a distorted trigonal bipyramidal environment (Table 1).
The S1 and C6 atoms of the 3-thiophenemalonate ligand are disordered over two sites with refined occupancies of 0.701 (5) and 0.299 (5). The units are interconnected by two kinds of O-H···O hydrogen bonds rings (R 3 3 (12), R 4 3 (12)) to form a two-dimensional supramolecular network, in which the lattice water molecule acts as both hydrogen-bond donor and acceptor (Table 2). These hydrogen bonds rings contributes to the additional stability of the structure.

Refinement
All H atoms were positioned geometrically (C-H = 0.93 and O-H = 0.85 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (C) or 1.5U eq (O). The S1 and C6 atoms of the 3-thiophenemalonate ligand are disordered over two sites, occupancies were refined to 0.701 (5):0.299 (5).
supplementary materials sup-2 Figures Fig. 1. The structure of title complex,with the atom-numbering scheme for the asymmetric unit, showing displacementellipsoids at the 50% probability level.