Poly[bis­(μ-2-amino-4-nitro­benzoato)di-μ-aqua-dirubidium]

Graham Smith

doi:10.1107/S1600536814008861

. 2014 Apr 30;70(Pt 5):m192–m193. doi: 10.1107/S1600536814008861

Poly[bis(μ-2-amino-4-nitrobenzoato)di-μ-aqua-dirubidium]

Graham Smith ^a,^*

PMCID: PMC4011243 PMID: 24860320

Abstract

In the structure of the title salt, [Rb₂(C₇H₅N₂O₄)₂(H₂O)₂]_n, the asymmetric unit comprises two independent and different seven-coordinate Rb⁺ cations, one forming an RbO₇ polyhedron, the other a RbO₆N polyhedron, each of which is considerably distorted. The RbO₇ polyhedron comprises bridging O-atom donors from two water molecules, three carboxylate groups, and two nitro groups. The RbO₆N polyhedron comprises the two bridging water molecules, one monodentate amine N-atom donor, one carboxyl O-atom donor and three O-atom donors from nitro groups (one from the chelate bridge). The extension of the dinuclear unit gives a three-dimensional polymeric structure which is stabilized by both intra- and intermolecular amine N—H⋯O and water O—H⋯O hydrogen bonds to carboxyl and water O-atom acceptors, as well as a number of inter-ring π–π interactions [minimum centroid–centroid separation = 3.364 (2) Å]. The title salt is isostructural with the analogous caesium salt.

Related literature

For the structures of some rubidium salts of substituted benzoic acids, see: Wiesbrock & Schmidbaur (2003 ▶); Dinnebier et al. (2002 ▶); Hu et al. (2005 ▶); Miao et al. (2011 ▶). For the structures of caesium 4-nitroanthranilate and caesium 3,5-dinitrosalicylate, see: Smith & Wermuth (2011 ▶) and Meng (2011 ▶), respectively. For the structures of the sodium and potassium 4-nitroanthranilates, see: Smith (2013 ▶).

Experimental

Crystal data

[Rb₂(C₇H₅N₂O₄)₂(H₂O)₂]
M _r = 569.23
Monoclinic,
a = 15.2938 (9) Å
b = 6.8601 (3) Å
c = 17.8075 (10) Å
β = 99.996 (5)°
V = 1839.95 (17) Å³
Z = 4
Mo Kα radiation
μ = 5.39 mm⁻¹
T = 200 K
0.30 × 0.18 × 0.08 mm

Data collection

Oxford Diffraction Gemini-S CCD diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2013 ▶) T _min = 0.691, T _max = 0.980
6954 measured reflections
3634 independent reflections
2708 reflections with I > 2σ(I)
R _int = 0.046

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.075
S = 1.03
3634 reflections
295 parameters
8 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.61 e Å⁻³
Δρ_min = −0.51 e Å⁻³

Data collection: CrysAlis PRO (Agilent, 2013 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶) within WinGX (Farrugia, 2012 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: PLATON.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536814008861/wm5020sup1.cif

e-70-0m192-sup1.cif^{(34.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814008861/wm5020Isup2.hkl

e-70-0m192-Isup2.hkl^{(178.2KB, hkl)}

CCDC reference: 998206

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Rb1—O1W	3.041 (3)
Rb1—O2W	3.006 (3)
Rb1—O42A	3.064 (3)
Rb1—O42A ⁱ	3.092 (3)
Rb1—O12A ⁱⁱ	3.074 (3)
Rb1—O11B ⁱⁱⁱ	3.059 (3)
Rb1—O12A ^iv	2.998 (3)
Rb2—O1W	2.994 (3)
Rb2—O2W	2.897 (3)
Rb2—O41A	2.992 (3)
Rb2—N2B	3.177 (4)
Rb2—O42B ^v	2.984 (3)
Rb2—O12B ^vi	2.947 (3)
Rb2—O42B ^iv	3.069 (3)

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

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2A—H21A⋯O12A	0.91 (2)	1.97 (3)	2.686 (5)	134 (3)
N2A—H21A⋯O1W ^vii	0.91 (2)	2.58 (4)	3.149 (5)	122 (3)
N2A—H22A⋯O11B ^v	0.94 (3)	2.46 (3)	3.206 (5)	136 (3)
N2B—H21B⋯O11A ^viii	0.90 (3)	2.01 (3)	2.831 (5)	151 (3)
N2B—H22B⋯O12B	0.90 (3)	1.88 (3)	2.644 (6)	142 (4)
O1W—H11W⋯O11B ^vi	0.88 (3)	1.92 (4)	2.783 (4)	167 (4)
O1W—H12W⋯O12A ^viii	0.89 (3)	1.96 (4)	2.847 (4)	176 (2)
O2W—H21W⋯O11A ⁱⁱ	0.89 (4)	1.93 (4)	2.823 (4)	178 (7)
O2W—H22W⋯O12B ⁱⁱⁱ	0.88 (4)	1.95 (5)	2.812 (5)	166 (5)

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Symmetry codes: (ii) Inline graphic ; (iii) ; (v) ; (vi) ; (vii) ; (viii) .

Acknowledgments

The author acknowledges financial support from the Science and Engineering Faculty and the University Library, Queensland University of Technology.

supplementary crystallographic information

1. Comment

The structures of alkali metal salts derived from aromatic carboxylic acids are of interest (Smith, 2013), particularly with the heavier metals Rb and Cs, because of the expanded metals' coordination spheres and their ability to form coordination polymers. With 4-nitroanthranilic acid (4-NAA), a three-dimensional coordination polymeric structure [Cs₂(C₇H₅N₂O₄)₂(H₂O)₂] was described (Smith & Wermuth, 2011) and from the reaction of rubidium carbonate with 4-NAA, orange-red crystals of the title compound [Rb₂(C₇H₅N₂O₄)₂(H₂O)₂], were obtained, the structure of which is reported herein.

The Rb salt has the same formula as the Cs salt and has similar crystal data [comparative 200 K unit cell data for the Cs complex: a = 15.3615 (3), b = 6.9573 (2), c = 18.3714 (4) Å, β = 97.903 (2)°, V = 1944.79 (8) Å³, Z = 4, space group P2₁/n]. The X-ray analysis reported here confirms that the Rb and Cs analogues are isotypic.

In the structure of the Rb salt, the dinuclear asymmetric unit contains two independent and different seven-coordinate Rb⁺ cations, with both having irregular coordination environments (Fig. 1). The RbO₇ polyhedron about Rb1 comprises bridging oxygen donors from two water molecules, three carboxylate groups, and a nitro group, with one O atom doubly bridging [Rb—O range 2.998 (3)–3.092 (3) Å]. The RbO₆N polyhedron about Rb2 comprises the two bridging water atoms, one monodentate amine N donor, one carboxyl O donor and three O donors from nitro groups (one doubly bridging) [Rb—O range 2.897 (3)–3.069 (3) Å] (Table 1). The Rb1···Rb2 separation in this dinuclear unit is 4.1208 (7) Å. Extension of this unit gives an overall three-dimensional polymeric structure (Fig. 2) which is stabilized by both intra- and intermolecular amine N—H···O and water O—H···O hydrogen bonds to both carboxyl and water O-atom acceptors (Table 2). Also, there are several inter-ring π···π interactions involving both ring 1 (C1A–C6A) and ring 2 (C1B–C6B) with a minimum ring centroid separation 1···1^viii of 3.364 (2) Å and a maximum ring centroid separation: 2···2^ix of 3.556 (2) Å [for symmetry code (viii), see Table 1; for symmetry code (ix) -x + 3/2, y + 1/2, -z + 1/2].

The minor difference between the two isotypic Rb and Cs salt structures is that in the description of the Cs salt, the coordination about Cs1 includes two longer Cs—O bonds to O41B^iv [3.326 (2) Å] (see Fig. 1) and to O1W1ⁱ [3.414 (3) Å]. In the title Rb salt, the equivalent values [3.342 (3) and 3.495 (3) Å] preclude these as Rb—O bonds.

These structural features, including expanded metal coordination spheres and multiple bridging with polymeric extensions, are similar to those found in other Rb salts with substituted benzoic acids, e.g. rubidium 3,5-dinitrobenzoate (8-coordinate) (Miao et al., 2011), rubidium anthranilate (7-coordinate) (Wiesbrock & Schmidbaur, 2003), rubidium salicylate (8-coordinate) (Dinnebier et al., 2002) and rubidium 3,5-dinitosalicylate (10-coordinate) (Meng, 2011), this last Rb complex being isotypic with its Cs analogue (Hu et al., 2005).

2. Experimental

The title compound was synthesized by heating together for 5 minutes, 0.1 mmol of rubidium carbonate and 0.2 mmol of 4-nitroanthranilic acid in 10 ml of 1:8 (v/v) ethanol–water. Partial room temperature evaporation of the solution gave orange-red flat prisms of the title complex from which a suitable specimen was cleaved for the X-ray analysis.