Hexaaqua­zinc(II) dipicrate

S Natarajan; K V Vijitha; S A Martin Britto Dhas; J Suresh; P L Nilantha Lakshman

doi:10.1107/S1600536808006624

. 2008 Mar 29;64(Pt 4):m581. doi: 10.1107/S1600536808006624

Hexaaquazinc(II) dipicrate

S Natarajan ^a, K V Vijitha ^a, S A Martin Britto Dhas ^a, J Suresh ^b, P L Nilantha Lakshman ^c,^*

PMCID: PMC2961002 PMID: 21202030

Abstract

In the title compound, [Zn(H₂O)₆](C₆H₂N₃O₇)₂, the Zn^II ion is located on an inversion center and is coordinated by six water molecules in an octahedral geometry. The picrate anions have no coordination interactions with the Zn^II atom. The three nitro groups are twisted away from the attached benzene ring by19.8 (3), 6.5 (4) and 28.6 (3)°. There are numerous O—H⋯O hydrogen bonds in the crystal structure.

Related literature

For related literature, see: Gartland et al. (1974 ▶); Herbstein et al. (1977 ▶); Liu et al. (2008 ▶); Maartmann-Moe (1969 ▶); Yang et al. (2001 ▶).

Experimental

Crystal data

[Zn(H₂O)₆](C₆H₂N₃O₇)₂
M _r = 629.68
Triclinic,
a = 7.8571 (4) Å
b = 8.3311 (6) Å
c = 8.9897 (7) Å
α = 89.8350 (11)°
β = 83.097 (1)°
γ = 72.8370 (9)°
V = 557.84 (7) Å³
Z = 1
Mo Kα radiation
μ = 1.22 mm⁻¹
T = 293 (2) K
0.13 × 0.11 × 0.10 mm

Data collection

Nonius MACH-3 diffractometer
Absorption correction: ψ scan (North et al., 1968 ▶) T _min = 0.854, T _max = 0.886
2441 measured reflections
1971 independent reflections
1908 reflections with I > 2σ(I)
R _int = 0.006
2 standard reflections frequency: 60 min intensity decay: none

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.087
S = 1.14
1971 reflections
196 parameters
4 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.42 e Å⁻³
Δρ_min = −0.71 e Å⁻³

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1996 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808006624/ci2563sup1.cif

e-64-0m581-sup1.cif^{(17.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808006624/ci2563Isup2.hkl

e-64-0m581-Isup2.hkl^{(95KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3W—H3WB⋯O1ⁱ	0.82 (2)	2.02 (2)	2.781 (2)	153 (3)
O3W—H3WB⋯O2ⁱ	0.82 (2)	2.38 (3)	2.972 (3)	130 (3)
O3W—H3WA⋯O2ⁱⁱ	0.84 (2)	2.07 (2)	2.880 (3)	164 (3)
O2W—H2WB⋯O3ⁱⁱ	0.82 (2)	2.48 (3)	3.083 (3)	131 (3)
O1W—H1WA⋯O6ⁱⁱⁱ	0.83 (4)	1.99 (4)	2.799 (3)	164 (3)
O1W—H1WB⋯O1^iv	0.80 (4)	1.99 (4)	2.705 (2)	149 (3)
O1W—H1WB⋯O6^iv	0.80 (4)	2.24 (4)	2.839 (2)	132 (3)
O2W—H2WB⋯O4^v	0.82 (2)	2.22 (3)	2.931 (3)	144 (3)
O2W—H2WA⋯O5^v	0.82 (2)	2.57 (3)	3.097 (3)	123 (3)
O2W—H2WA⋯O7^vi	0.82 (2)	2.46 (2)	3.223 (3)	154 (3)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

Acknowledgments

The authors thank the UGC for the SAP programme and the DST for the FIST programme.

supplementary crystallographic information

Comment

Picric acid forms salts with many organic and metallic cations (Gartland et al., 1974). Picrates with various degrees of hydration are formed by metals (e.g. Li, Na), the alkaline earths (e.g. Cd, Hg) and various transition metals (e.g. Al, Y). Crystal structures have been reported for isomorphous NH₄ and K picrates (Maartmann-Moe, 1969), thallium picrate (Herbstein et al., 1977) and recently for manganese picrate (Liu et al., 2008). The present work reports the crystal structure of the title compound, a zinc picrate. This work is part of a systematic investigation on the structures of the metal complexes of picric acid.

In the crystal structure of the title compound, each Zn^II ion is coordinated by the O atoms of six water molecules and not by the O atoms from the picrate anions. The Zn—O distances range from 2.0297 (16) to 2.1126 (17) Å. The coordination polyhedra around the Zn^II ion can be described as a distorted octahedron. The picrate anion adopts a keto form with a C1—O1 bond distance of 1.242 (3) Å; the C6—C1 [1.457 (3) Å] and C2—C1 [1.456 (3) Å] bond distances are longer than the other C—C bond lengths of the benzene ring. The three nitro groups are twisted out of the attached benzene ring by 19.8 (3)° [N1/O2/O3], 6.5 (4)° [N2/O4/O5] and 28.6 (3)° [N3/O6/O7]. The twisting of the nitro groups may be attributed to the O—H···O hydrogen bonding interactions taking place between water and picrate O atoms. The C2—C1—C6 bond angle of 111.20 (18)° is narrower than the corresponding angle in picric acid (116.4 (5)°; Yang et al., 2001).

The packing of molecules is governed by large number of O—H···O hydrogen bonds (Table 1). π···π interactions are observed between the benzene rings of inversion related picrate ions, with a centroid to centroid distance of 3.6268 (11) Å (Fig. 2).

Experimental

Colourless needle shaped single crystals of the title compound were grown from a saturated aqueous solution containing picric acid and zinc chloride in a 1:1 stoichiometric ratio.