catena-Poly[[tetrakis(1H-pyrazole-κN 2)copper(II)]-μ-hexafluoridosilicato-κ2 F:F′]

In the title one-dimensional coordination polymer, [Cu(SiF6)(C3H4N2)4]n, the CuII atom is coordinated by two hexafluoridosilicate F atoms and four pyrazole N atoms in a distorted trans-CuF2N4 octahedral environment. The dihedral angle between the planes of the pyrazlole rings in the asymmetric unit is 74.4 (3)°. The hexafluoridosilicate dianion acts as a bridging ligand, connecting the CuII atoms into a [1-10] chain. The Cu and Si atoms lie on special positions with 2/m site symmetry. In the crystal, intrachain N—H⋯F hydrogen bonds occur and weak C—H⋯F interactions link the chains.

In the title one-dimensional coordination polymer, [Cu(SiF 6 )-(C 3 H 4 N 2 ) 4 ] n , the Cu II atom is coordinated by two hexafluoridosilicate F atoms and four pyrazole N atoms in a distorted trans-CuF 2 N 4 octahedral environment. The dihedral angle between the planes of the pyrazlole rings in the asymmetric unit is 74.4 (3) . The hexafluoridosilicate dianion acts as a bridging ligand, connecting the Cu II atoms into a [110] chain. The Cu and Si atoms lie on special positions with 2/m site symmetry. In the crystal, intrachain N-HÁ Á ÁF hydrogen bonds occur and weak C-HÁ Á ÁF interactions link the chains.

Related literature
For background to coordination polymers with nitrogencontaining ligands, see: Li et al. (2011).
Single-crystal X-ray diffraction analysis reveals that the title compound (I) crystallizes in the monoclinic space group C2/c. For the title compound, the geometry of the Cu(II) ion is bound by four pyrazole ligands and two hexafluoridosilicate dianions, which illustrates a distorted octahedral coordination environment (Fig 1). The dihedral angle between the pyrazole rings is 105.6°.

Experimental
A buffer layer of a solution (8 ml) of methanol and chloroform (1:1) was carefully layered over the chloroform solution of pyrazole (0.06 mmol, 6 ml). Then a methanol solution of CuSiF 6 (0.02 mmol, 6 ml) was layered over the buffer layer.
The resultant reaction was left to stand at room temperature. After ca three weeks, colorless blocks appeared at the boundary. Yield: ~20% (based on pyrazole).

Refinement
C-bound H atoms were positioned geometrically and refined in the riding-model approximation, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).
The N-bound H atoms were located in a difference map and their positions were freely refined with U iso (H) = 1.2U eq (N).

catena-Poly[[tetrakis(1H-pyrazole-κN 2 )copper(II)]µ-hexafluoridosilicato-κ 2 F:F′]
Crystal data 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq