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Acta Crystallogr Sect E Struct Rep Online. 2009 June 1; 65(Pt 6): m671.
Published online 2009 May 23. doi:  10.1107/S1600536809018649
PMCID: PMC2969650



The title compound, [K(C6H4N5)(H2O)2]n, was synthesized by hydro­thermal reaction of KOH with 4-(5-tetra­zolio)pyridine. The K atom has a distorted octa­hedral coordination environment and is coordinated by two axial N atoms from the organic ligand and by four water mol­ecules in the equatorial plane. The mol­ecules as a whole are located on crystallographic mirror planes; the K atom is also located on an inversion center. Both the water mol­ecules and the organic ligands act as bridges to link symmetrically the adjacent K atoms into polymeric chains parallel to the c axis. O—H(...)N hydrogen bonds involving the water O atoms and aromatic π–π inter­actions [centroid–centroid distance 3.80 (2) Å] between the pyridine and tetra­zole rings build up an infinite three-dimensional network.

Related literature

For applications of tetra­zole derivatives in coordination chemistry, see: Xiong et al. (2002 [triangle]); Wang et al. (2005 [triangle]). For the crystal structure of a related compound, see: Dai & Fu (2008 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-0m671-scheme1.jpg


Crystal data

  • [K(C6H4N5)(H2O)2]
  • M r = 221.27
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-0m671-efi1.jpg
  • a = 12.361 (3) Å
  • b = 12.281 (3) Å
  • c = 7.3431 (15) Å
  • β = 117.25 (3)°
  • V = 991.1 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.52 mm−1
  • T = 298 K
  • 0.25 × 0.15 × 0.10 mm

Data collection

  • Rigaku Mercury2 diffractometer
  • Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 [triangle]) T min = 0.913, T max = 1.000 (expected range = 0.867–0.949)
  • 5056 measured reflections
  • 1134 independent reflections
  • 928 reflections with I > 2σ(I)
  • R int = 0.027


  • R[F 2 > 2σ(F 2)] = 0.037
  • wR(F 2) = 0.096
  • S = 1.07
  • 1134 reflections
  • 67 parameters
  • 2 restraints
  • H-atom parameters constrained
  • Δρmax = 0.32 e Å−3
  • Δρmin = −0.19 e Å−3

Data collection: CrystalClear (Rigaku, 2005 [triangle]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809018649/zl2195sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809018649/zl2195Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report


This work was supported by a Start-up Grant from Southeast University to Professor Ren-Gen Xiong.

supplementary crystallographic information


In the past few years, more and more people have focused on the chemistry of tetrazole derivatives because of their multiple coordination modes as ligands to metal ions and for the construction of novel metal-organic frameworks (Wang, et al. 2005; Xiong, et al. 2002). We report here the crystal structure of the title compound, tetra-aqua-bis[4-(2H-tetrazol-5-yl)pyridine]potassium(I).

The K atom has a distorted octahedral geometry and is coordinated by two axial pyridyl N atoms from the organic ligand and four water molecules ligands in the equatorial plane. The molecules as a whole are located on crystallographic mirror planes, the potassium ion is also located on an inversion center. Both the water molecules and the organic ligands act as bridges linking adjacent K ions into polymeric chains parallel to the c axis by covalent bonds (K—N, and K—O). The pyridine and tetrazole rings are nearly coplanar and are twisted from each other by a dihedral angle of only 12.99 (0.13) ° (Fig.1). The bond distances and bond angles of the tetrazole rings are in the usual ranges (Wang, et al. 2005; Dai & Fu 2008).

The crystal packing (Fig. 2) is stabilized by aromatic π–π interactions between the pyridine and tetrazole rings of the neighbouring ligand systems. The centroid···centroid distance is 3.80 (2)Å (symmetry code: x, y, z+1 and x, y, z). The molecular packing is further stabilized by intermolecular O—H···N hydrogen bonds involving the aqueous O atoms. The π–π and hydrogen bonding interactions build up an infinite three-dimensional network. (Fig. 2 and Table 1).


A mixture of 4-(2H-tetrazol-5-yl)pyridine (0.4 mmol) and KOH (0.4 mmol), ethanol (1 ml) and a few drops of water sealed in a glass tube was maintained at 373 K. Colorless needle crystals suitable for X-ray analysis were obtained after 3 days.


All H atoms attached to C atoms were fixed geometrically and treated as riding with C–H = 0.93 Å (aromatic) with Uiso(H) = 1.2Ueq(C). The H atoms of water molecules were located in difference Fourier maps and the O–H distances were restrained in the subsequent refinements to 0.85 Å with Uiso(H) =1.5Ueq(O). In the last stage of the refinement they were treated as riding on the O atom.


Fig. 1.
A view of the title compound with the atomic numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.
Fig. 2.
The crystal packing of the title compound viewed along the c axis showing the three dimensionnal network (dashed lines). Hydrogen atoms not involved in hydrogen bonding have been omitted for clarity.

Crystal data

[K(C6H4N5)(H2O)2]F(000) = 456
Mr = 221.27Dx = 1.483 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 1134 reflections
a = 12.361 (3) Åθ = 3.3–27.5°
b = 12.281 (3) ŵ = 0.52 mm1
c = 7.3431 (15) ÅT = 298 K
β = 117.25 (3)°Needle, colorless
V = 991.1 (3) Å30.25 × 0.15 × 0.10 mm
Z = 4

Data collection

Rigaku Mercury2 (2× 2 bin mode) diffractometer1134 independent reflections
Radiation source: fine-focus sealed tube928 reflections with I > 2σ(I)
graphiteRint = 0.027
Detector resolution: 13.6612 pixels mm-1θmax = 27.5°, θmin = 3.3°
ω scansh = −16→16
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)k = −15→15
Tmin = 0.913, Tmax = 1.000l = −9→9
5056 measured reflections


Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.096H-atom parameters constrained
S = 1.07w = 1/[σ2(Fo2) + (0.039P)2 + 0.7641P] where P = (Fo2 + 2Fc2)/3
1134 reflections(Δ/σ)max < 0.001
67 parametersΔρmax = 0.32 e Å3
2 restraintsΔρmin = −0.19 e Å3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 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 (Å2)

K10.50000.00000.50000.0467 (2)
C40.50000.5325 (2)0.75000.0365 (6)
C30.50000.4124 (2)0.75000.0358 (5)
N20.60000 (14)0.59305 (13)0.8162 (3)0.0468 (4)
C20.60283 (18)0.35391 (16)0.7821 (3)0.0459 (5)
N30.55965 (15)0.69599 (13)0.7896 (3)0.0530 (5)
N10.50000.18446 (19)0.75000.0522 (6)
C10.5980 (2)0.24208 (17)0.7797 (4)0.0534 (5)
O1W0.34559 (12)0.08972 (11)0.1308 (2)0.0516 (4)

Atomic displacement parameters (Å2)

K10.0545 (4)0.0460 (4)0.0403 (3)−0.0005 (3)0.0221 (3)−0.0025 (3)
C40.0345 (13)0.0344 (12)0.0323 (13)0.0000.0080 (11)0.000
C30.0381 (13)0.0334 (13)0.0296 (12)0.0000.0102 (10)0.000
N20.0383 (9)0.0337 (8)0.0522 (10)−0.0025 (7)0.0067 (7)−0.0016 (7)
C20.0392 (10)0.0406 (10)0.0536 (12)−0.0008 (8)0.0176 (9)−0.0029 (9)
N30.0503 (9)0.0340 (8)0.0541 (11)−0.0042 (7)0.0062 (8)−0.0020 (7)
N10.0602 (16)0.0343 (12)0.0524 (15)0.0000.0174 (13)0.000
C10.0514 (12)0.0416 (11)0.0596 (13)0.0090 (9)0.0189 (10)−0.0026 (9)
O1W0.0341 (7)0.0376 (7)0.0667 (10)0.0014 (6)0.0088 (7)0.0026 (6)

Geometric parameters (Å, °)

K1—O1Wi2.7309 (16)C3—C2iv1.383 (2)
K1—O1Wii2.7309 (16)C3—C21.383 (2)
K1—O1W2.7330 (17)N2—N31.340 (2)
K1—O1Wiii2.7330 (17)C2—C11.375 (3)
K1—N1iii2.9159 (18)C2—H20.9300
K1—N12.9159 (18)N3—N3iv1.314 (3)
K1—C1iii3.499 (2)N1—C11.332 (3)
K1—C13.499 (2)N1—C1iv1.332 (3)
K1—K1ii3.6716 (7)N1—K1iv2.9159 (18)
K1—K1iv3.6716 (8)C1—H10.9300
K1—H1WB3.0780O1W—K1ii2.7309 (16)
C4—N21.329 (2)O1W—H1WA0.8412
C4—N2iv1.329 (2)O1W—H1WB0.8765
C4—C31.475 (3)
O1Wi—K1—O1Wii180.00 (3)C1iii—K1—K1iv115.36 (4)
O1Wi—K1—O1W103.20 (5)C1—K1—K1iv64.64 (4)
O1Wii—K1—O1W76.80 (5)K1ii—K1—K1iv180.0
O1Wi—K1—O1Wiii76.80 (5)O1Wi—K1—H1WB111.4
O1Wii—K1—O1Wiii103.20 (5)O1Wii—K1—H1WB68.6
O1Wi—K1—N1iii96.28 (4)O1Wiii—K1—H1WB164.0
O1Wii—K1—N1iii83.72 (4)N1iii—K1—H1WB96.4
O1W—K1—N1iii83.68 (4)N1—K1—H1WB83.6
O1Wiii—K1—N1iii96.32 (4)C1iii—K1—H1WB97.5
O1Wi—K1—N183.72 (4)C1—K1—H1WB82.5
O1Wii—K1—N196.28 (4)K1ii—K1—H1WB52.7
O1W—K1—N196.32 (4)K1iv—K1—H1WB127.3
O1Wiii—K1—N183.68 (4)N2—C4—N2iv112.0 (2)
N1iii—K1—N1180.0N2—C4—C3124.01 (11)
O1Wi—K1—C1iii75.74 (5)N2iv—C4—C3124.01 (11)
O1Wii—K1—C1iii104.26 (5)C2iv—C3—C2117.4 (2)
O1W—K1—C1iii82.15 (5)C2iv—C3—C4121.30 (12)
O1Wiii—K1—C1iii97.85 (5)C2—C3—C4121.30 (12)
N1iii—K1—C1iii21.60 (4)C4—N2—N3104.64 (16)
N1—K1—C1iii158.40 (4)C1—C2—C3119.1 (2)
O1Wi—K1—C1104.26 (5)C1—C2—H2120.5
O1Wii—K1—C175.74 (5)C3—C2—H2120.5
O1W—K1—C197.85 (5)N3iv—N3—N2109.38 (10)
O1Wiii—K1—C182.15 (5)C1—N1—C1iv115.8 (2)
N1iii—K1—C1158.40 (4)C1—N1—K1104.69 (11)
N1—K1—C121.60 (4)C1iv—N1—K1124.89 (11)
C1iii—K1—C1180.00 (9)C1—N1—K1iv124.89 (11)
O1Wi—K1—K1ii132.19 (4)C1iv—N1—K1iv104.69 (11)
O1Wii—K1—K1ii47.81 (4)K1—N1—K1iv78.04 (6)
O1W—K1—K1ii47.76 (3)N1—C1—C2124.3 (2)
O1Wiii—K1—K1ii132.24 (3)N1—C1—K153.71 (10)
N1iii—K1—K1ii50.98 (3)C2—C1—K1149.08 (16)
N1—K1—K1ii129.02 (3)N1—C1—H1117.8
C1iii—K1—K1ii64.64 (4)C2—C1—H1117.8
C1—K1—K1ii115.36 (4)K1—C1—H173.4
O1Wi—K1—K1iv47.81 (4)K1ii—O1W—K184.44 (4)
O1Wii—K1—K1iv132.19 (4)K1ii—O1W—H1WA111.4
O1W—K1—K1iv132.24 (3)K1—O1W—H1WA142.8
O1Wiii—K1—K1iv47.76 (3)K1ii—O1W—H1WB102.4
N1iii—K1—K1iv129.02 (3)K1—O1W—H1WB105.0
N1—K1—K1iv50.98 (3)H1WA—O1W—H1WB104.0

Symmetry codes: (i) x, −y, z+1/2; (ii) −x+1, y, −z+1/2; (iii) −x+1, −y, −z+1; (iv) −x+1, y, −z+3/2.

Hydrogen-bond geometry (Å, °)

O1W—H1WA···N2v0.842.012.852 (2)177
O1W—H1WB···N3vi0.881.972.831 (2)169

Symmetry codes: (v) x−1/2, y−1/2, z−1; (vi) −x+1, −y+1, −z+1.


Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZL2195).


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