Triclinic modification of diaqua­bis­(5-carb­oxy-1H-imidazole-4-carboxyl­ato-κ2 N 3,O 4)iron(II)

Eriko Ohshima; Kazuki Yoshida; Kazumasa Sugiyama; Hidehiro Uekusa

doi:10.1107/S1600536812031753

. 2012 Jul 21;68(Pt 8):m1093–m1094. doi: 10.1107/S1600536812031753

Triclinic modification of diaquabis(5-carboxy-1H-imidazole-4-carboxylato-κ² N ³,O ⁴)iron(II)

Eriko Ohshima ^a, Kazuki Yoshida ^a, Kazumasa Sugiyama ^b,^*, Hidehiro Uekusa ^c

PMCID: PMC3414146 PMID: 22904753

Abstract

The title compound, [Fe(C₅H₃N₂O₄)₂(H₂O)₂], is a triclinic modification of a monoclinic form recently reported by Du et al. [Acta Cryst. (2011) ▶, E67, m997]. The Fe^II ion lies at an inversion center and is coordinated by two N and two O atoms from two 5-carboxy-1H-imidazole-4-carboxylate ligands in trans positions, together with two water molecules, completing a slightly distorted octahedral coordination. Intermolecular N—H⋯O hydrogen bonding between the N—H group of the imidazole ring and the deprotonated carboxylate group builds a chain of 5-carboxy-1H-imidazole-4-carboxylate anions along the [101] direction. The water molecules form intermolecular hydrogen bonds to O—C and O=C sites of the carboxylate group in adjacent layers.

Related literature

For the structural diversity of the coordination architecture of the metal complexes of 4,5-imidazoledicarboxylic acid, see Shimizu et al. (2004 ▶); Fang & Zhang (2006 ▶). For the isotypic Co analog, see: Li et al. (2011 ▶). For the coexisting phase, see Yakubovich et al. (1995 ▶). For the monoclinic form, see: Du et al. (2011 ▶).

Experimental

Crystal data

[Fe(C₅H₃N₂O₄)₂(H₂O)₂]
M _r = 402.08
Triclinic,
a = 4.9290 (5) Å
b = 6.4258 (6) Å
c = 12.2812 (10) Å
α = 78.161 (3)°
β = 85.175 (3)°
γ = 72.776 (4)°
V = 363.52 (6) Å³
Z = 1
Mo Kα radiation
μ = 1.10 mm⁻¹
T = 298 K
0.15 × 0.13 × 0.10 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: empirical (using intensity measurements) (ABSCOR; Higashi, 1995 ▶) T _min = 0.852, T _max = 0.898
3655 measured reflections
1668 independent reflections
1066 reflections with I > 2σ(I)
R _int = 0.050

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.075
S = 0.92
1668 reflections
122 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.34 e Å⁻³

Data collection: RAPID-AUTO (Rigaku, 1998 ▶); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812031753/fj2571sup1.cif

e-68-m1093-sup1.cif^{(16.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812031753/fj2571Isup2.hkl

e-68-m1093-Isup2.hkl^{(80.5KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812031753/fj2571Isup6.mol

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
O5—H1W⋯O3ⁱ	0.86 (3)	1.86 (3)	2.705 (3)	165 (3)
O5—H2W⋯O4ⁱⁱ	0.79 (3)	1.95 (3)	2.702 (3)	158 (3)
N2—H2A⋯O1ⁱⁱⁱ	0.86	1.95	2.767 (3)	157
O2—H2⋯O3	0.82	1.85	2.665 (3)	174

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

Acknowledgments

This study was supported financially by the Inter-University Cooperative Research Program of the Institute for Materials Research, Tohoku University (proposal No. 11 K0091).

supplementary crystallographic information

Comment

A number of studies on transition metal complexes with carboxylate ligands are reported in the literature. Recently, imidazole dicarboxylate has been recognized as an efficient building block, since it shows two different coordination modes to bridge or chelate metals through the carboxyl oxygen atoms and heterocyclic nitrogen donor. The crystal of diaquabis(5-carboxy-1H-imidazole-4-carboxylato-κ²N³,O)iron(II) is isostructural with Co analog 4,5-dicarboxyimidazole complexes (Li et al., 2011). Iron(II) ion lies at the inversion center that is coordinated by two 1H-imidazole-4,5-dicarboxylate monoanionic ligands at the trans positions and two water molecules in a distorted octahedral geometry. A previous report described a monoclinic metal complex with a similar chemical composition (Du et al., 2011). This structural diversity is attributed to the different types of coordination architectures of hydrogen bonding between molecules. The intermolecular hydrogen bonding between the N—H site of an imidazole ring and C═O site of a deprotonated carboxylate in the title compound builds a unique chain of 5-carboxy-1H- imidazole-4-carboxylate anion. The chain structures are further linked into a three-dimensional supermolecular framework through O—H···O hydrogen bonding interactions. The average distance of Fe—O agrees well with that of the monoclinic phase. Nevertheless, the average distance of Fe—N (2.165 Å) is longer than that in the monoclinic analog (2.147 Å).

Experimental

A mixture of FeSO₄. 7H₂O (13.33 mmol), 4,5-imidazoledicarboxamide (22.21 mmol), 85.0% H₃PO₄ (8.89 mmol), and H₂O (8 ml) was placed in a 30 ml Teflon beaker. It was sealed in a stainless-steel reactor, heated to 453 K for 96 h under autogenous pressure, and then, slowly cooled to room temperature. Pale-yellow block crystals of the title complex were isolated, washed with distilled water, and dried in air. It may be added that NH₄FePO₄.H₂O: see Yakubovich et al. (1995), Pale-green plate crystals were also crystallized in the present synthetic condition. This supports the hydrolysis of the 4,5-imidazoledicarboxamide during the synthesis.