Poly[di-μ2-aqua-μ4-chlorido-μ4-(2-mercaptopyrimidine-4,6-diolato-κ4 O:O:O′:O′)-disodium(I)]

In the title coordination polymer, [Na2(C4H3N2O2S)Cl(H2O)2]n, the NaI ion lies on a twofold rotation axis and the chloride anion on an inversion center. The NaI ion is six-coordinated by two O atoms from two zwitterionic 2-mercaptopyrimidine-4,6-diolate ligands (mm2 symmetry), two water O atoms (m symmetry) and two Cl atoms in a distorted octahedral geometry. Adjacent NaI ions are bridged by an olate group, a water molecule and a chloride anion into a three-dimensional network. The crystal structure is further stabilized by N—H⋯Cl, O—H⋯O and O—H⋯S hydrogen bonds.

In the title coordination polymer, [Na 2 (C 4 H 3 N 2 O 2 S)Cl-(H 2 O) 2 ] n , the Na I ion lies on a twofold rotation axis and the chloride anion on an inversion center. The Na I ion is sixcoordinated by two O atoms from two zwitterionic 2mercaptopyrimidine-4,6-diolate ligands (mm2 symmetry), two water O atoms (m symmetry) and two Cl atoms in a distorted octahedral geometry. Adjacent Na I ions are bridged by an olate group, a water molecule and a chloride anion into a three-dimensional network. The crystal structure is further stabilized by N-HÁ Á ÁCl, O-HÁ Á ÁO and O-HÁ Á ÁS hydrogen bonds.
Comment 2-Mercaptopyrimidine-4,6-diol and its derivatives have been used widely to build organic-inorganic hybrids due to their diverse properties (Carballo et al. 1996). During the course of on-going crystal engineering studies on nickel salts, we obtained two types of crystals different in color, green and colorless. We herein report the crystal structure of the colorless one, the title compound.
The coordination environment around Na I ion is shown in Fig. 1, with atom numbering scheme. The Na I ion is six-coordinated in a distorted octahedral geometry by two O atoms from two 2-mercaptopyrimidine-4,6-diolate ligands, two water O atoms and two Cl atoms. The 2-mercaptopyrimidine-4,6-diolate anion serving as a bridging ligand coordinates to four Na I ions. The crystal structure is stabilized by N-H···Cl, O-H···O and O-H···S hydrogen bonds (Table 1).
Experimental 2-Mercaptopyrimidine-4,6-diol (1.44 g, 10 mmol) and NiCl 2 .6H2O (3.28 g, 10 mmol) were dissolved in hot water (20 ml) and the pH value was adjusted to about 5 by using dilute NaOH solution with stirring. The mixture was heated for one hour and then cooled to room temperature. The precipitate was washed by dilute HCl and the filtrate was allowed to evaporate at room temperature for two weeks, generating two types of block crystals, one was colorless and the other was green.

Refinement
C-and N-bound H atoms were positioned geometrically (C-H = 0.93, N-H = 0.86 Å) and refined as riding atom, with U iso (H) = 1.2U eq (C,N). Water H atoms were located in a difference Fourier map and refined as riding, with U iso (H) = 1.5U eq (O). Fig. 1. The asymmetric unit of the title compound, with symmetry-related atoms to complete the ligand and Na coordination. Displacement ellipsoids are drawn at the 30% probability level.   (3)