Diaquabis(1H-1,2,4-triazole-3-carboxylato)cadmium(II)

In the title complex, [Cd(C3H2N3O2)2(H2O)2], the CdII atom is coordinated by two N and two O atoms from two deprotonated 1H-1,2,4-triazole-3-carboxylic acid ligands (TRIA) and two water molecules. The Cd atom is located on an inversion centre. In the crystal structure, molecules are linked together via O—H⋯O and N—H⋯O hydrogen bonds, forming a three-dimensional network.

In the title complex, [Cd(C 3 H 2 N 3 O 2 ) 2 (H 2 O) 2 ], the Cd II atom is coordinated by two N and two O atoms from two deprotonated 1H-1,2,4-triazole-3-carboxylic acid ligands (TRIA) and two water molecules. The Cd atom is located on an inversion centre. In the crystal structure, molecules are linked together via O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds, forming a three-dimensional network.
As shown in Fig. 1, the title compound consists of a centrosymmetric mononuclear cadmium(II) complex cation. In the cation the Cd atom is six-coordinated by two N and two O atoms from two TRIA ligands and two O atoms from two water molecules. The Cd II atom is in a slightly distorted octahedral environment. The Cd-O distances range from 2.315 (2) to 2.321 (3) Å, and the Cd-N bond length is 2.293 (3) Å, i.e. normal values. The C1-C2 bond length is 1.495 (5) Å, being in the normal C-C ranges in cadmium carboxylate complexes. The angles around Cd II atom are from 73.57 (9) to linear.
The TRIA molecule acts as a bidentate ligand.
In the title compound, the water molecules contribute to the formation of intermolecular hydrogen bonds involving carboxylate O atoms. Additional hydrogen bonds exist between the N-H groups of the triazole and carboxylate O atoms.

Experimental
1H-1,2,4-triazole-3-carboxylic acid and CdCl 2 ·2.5H 2 O were available commercially and were used without further purification. 1H-1,2,4-triazole-3-carboxylic acid (1 mmol, 113 mg) was dissolved in distilled water (15 ml) and CdCl 2 ·2.5H 2 O (0.5 mmol, 114.2 mg) was added in distilled water (5 ml) with stirring at 323 K. The resulting colorless solution was allowed to react for 5 h and was then filtered. Colorless crystals suitable for X-ray analysis were obtained by slow evaporation of a water solution over a period of one month (yield 75%

Refinement
All the H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with O-H, N-H and C-H distances of 0.85 Å, 0.86 Å and 0.93 Å, respectively, and U iso (H) = 1.2U eq (O), U iso (H) = 1.2U eq (N) and U iso (H) = 1.2U eq (C).
H atoms of the water molecules were located in a difference Fourier map and refined using a riding method. The highest peak in the difference map is 1.21 (1) Å from Cd1 and the largest hole is 0.60 (2) Å from Cd1. Diaquabis(1H-1,2,4-triazole-3-carboxylato)cadmium(II) Crystal data [Cd(C 3