Poly[sodium(I)-μ₆-hydrogen benzene-1,4-dicarboxylato]

Alkali metal salts of terephthalic acid are common reagents in the preparation of metal–ligand coordination complexes containing terephthalate anions. In the title compound, sodium hydrogen terephthalate, [Na(C₈H₅O₄)]_n, the cations occupy crystallographic inversion centres, and each bridging anion coordinates to six octahedral cations and vice versa. As seen in the known potassium derivative [Kaduk (2000). Acta Cryst. B56, 474–485; Miyakubo, Takeda & Nakamura (1994). Bull. Chem. Soc. Jpn, 67, 2301–2303], sodium hydrogen terephthalate contains short O—H...O hydrogen bonds between anions [O...O = 2.4734 (17) Å]. The structure is centrosymmetric and exhibits disorder of the H-atom position in the hydrogen bond and of the non-bridging ring C atoms in the terephthalate ion.

S1. Comment

While it bears desirable para-distributed carboxylic acid groups, the insolubility of terephthalic acid (benzene-1,4-dicarboxylic acid, hereinafter H₂TA) in many organic solvents could limit its use in coordination chemistry. However, many chemists employ its alkali metal salts in the preparation of complexes of other metals, for example TA²⁻ anions are often utilized as bridging anions, linking metal centres together in the solid state to produce functional magnetic materials (Kurmoo et al., 2001). The use of coordinating anions such as TA²⁻ aids the creation of supramolecular arrays, as the neutral networks no longer need to be interrupted by uncoordinated anions (Groeneman & Atwood, 1999), and such networks have been shown to have both solvent inclusion (Li, Davis et al., 1998) and gas sorption (Li, Eddaoudi et al., 1998) properties.

A search of the Cambridge Structural Database (Version 5.24, July 2003 update; Allen, 2002) highlights a paper by Kaduk (2000), which studies the Li⁺, Na⁺ and K⁺ salts of H₂TA (all three having the stoichiometry M₂TA) and gives an additional redetermination of the K⁺ salt of the monodeprotonated hydrogen terephthalate (HTA⁻) anion, KHTA [previously studied by Miyakubo et al. (1994)]. We have now synthesized and characterized the related title compound, (I), NaHTA, and report its structure here. \sch

The asymmetric unit of (I) contains half a formula unit, with the octahedral Na⁺ cation occupying a crystallographic inversion centre. The cation is six-coordinate and bonds to six different HTA⁻ anions (Table 1 and Fig. 1), with each anion bonding to six cations through monodentate bonds in all cases.

The aromatic ring of the HTA⁻ anion in (I) is disordered and has been modelled over two sets of positions (in a 50:50 ratio due to the centrosymmetric nature of the structure), with the substituted ring atoms coincident in the two alternative ring positions, which lie at 24.6 (2)° with respect to each other. The geometry of the anion is unsurprizing (Miyakubo et al., 1994).

The carboxyl group deviates from the planes of the two alternative aromatic ring positions by 8.2 (3) and 18.8 (3)°. Although an electron-density peak was clearly observed on an inversion centre in the difference Fourier map, displacing the H atom away from the centre of symmetry [as suggested by Miyakubo et al. (1994) and Kaduk (2000) in their characterizations of KHTA] resulted in a further lowering of the R factor. This produced more reasonable O—H and H···O bond lengths within the short O—H···O hydrogen bond (Table 2), and removed the electron-density peak from the inversion centre. The carboxyl H atom was therefore modelled as half-weight, having two equivalent positions disordered symmetrically across the inversion centre.

The combination of Na—O coordination bonds and O—H···O hydrogen bonds results in the formation of R₁¹(6) graph-set motifs (Etter, 1990; Etter & MacDonald, 1990; Bernstein et al., 1995), with each Na⁺ centre being incorporated into two such rings, and this therefore leads to a three-dimensional structure. While (I) and KHTA are not isostructural, the K⁺ cations in KHTA also participate in two R₁¹(6) motifs each. However, these motifs are distributed cis around the psuedo-octahedral K⁺ cations in KHTA, while in (I) the two motifs are trans with respect to one another.

S2. Experimental

Terephthalic acid (H₂TA; 2 equivalents) was refluxed with Na₂CO₃ (1 equivalent) in H₂O overnight, producing a colourless solution which was evaporated to dryness in vacuo. The resulting white solid was recrystallized from dimethylformamide and H₂O (hot, 1:1), and slow cooling yielded colourless X-ray quality crystals of (I) in quantitative yield. Analysis calculated for NaC₈H₅O₄: C 51.08, H, 2.68%; found: C 50.82, H 2.56%; IR (KBr, ν_max, cm⁻¹): 3437 (br, OH), 2956 and 2924 (aromatic C—H), 1671 (C═O, acid), 1506 (asymmetric CO₂⁻), 1370 (symmetric CO₂⁻), 1297, 1207, 1145 and 1090 (C—O), 878, 778 and 740 (aromatic C—H), 509, 482.

S3. Refinement

Aromatic H atoms were placed in geometric positions (C—H distance = 0.95 Å) using a riding model, while the coordinates of the O-bound H atom were freely refined. U_iso(H) values were set to 1.2U_eq(C) for aryl H (1.5U_eq for OH). Restraints were applied to the anisotropic displacement parameters of all the C atoms.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Figures

Fig. 1. A molecular view of (I), showing the atom-labelling scheme, the completed Na^+ coordination sphere and the hydrogen bonding. Displacement ellipsoids are drawn at the 50% probability level. Aromatic H atoms and one disorder component have been removed for clarity, and hydroxy H atoms are drawn as small spheres of arbitrary radii. The hydrogen bond is shown by dashed lines [symmetry codes: (i) x + 1, y, z; (ii) x + 1, 1 + y, z; (iii) 1 − x, 1 − y, 1 − z; (iv) 1 − x, −y, 1 − z; (v) 2 − x, 1 − y, 1 − z; (vi) 1 − x, −y, −z].

Fig. 2. A packing plot of (I) viewed along the a axis. Aromatic H atoms, one disorder component and hydrogen bonds have been omitted for clarity. Open circles denote C atoms, shaded circles O atoms and dotted circles Na atoms.

Poly[sodium(I)-µ₆-hydrogen benzene-1,4-dicarboxylato]

Crystal data

[Na(C8H5O4)]	Z = 1
Mr = 188.11	F(000) = 96
Triclinic, P1	Dx = 1.780 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 3.6204 (11) Å	Cell parameters from 1773 reflections
b = 5.7446 (17) Å	θ = 2.3–28.6°
c = 8.775 (3) Å	µ = 0.19 mm^−1
α = 90.271 (5)°	T = 150 K
β = 91.970 (5)°	Block, colourless
γ = 105.776 (5)°	0.29 × 0.17 × 0.09 mm
V = 175.50 (10) Å^3

Data collection

Bruker SMART 1000 CCD area-detector diffractometer	807 independent reflections
Radiation source: sealed tube	747 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.009
ω rotation with narrow frames scans	θmax = 28.8°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	h = −4→4
Tmin = 0.966, Tmax = 0.983	k = −7→7
1532 measured reflections	l = −11→11

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.028	Hydrogen site location: Geom except OH coords freely refined
wR(F^2) = 0.085	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0468P)^2 + 0.0676P] where P = (Fo^2 + 2Fc^2)/3
807 reflections	(Δ/σ)max = 0.001
82 parameters	Δρmax = 0.42 e Å^−3
40 restraints	Δρmin = −0.17 e Å^−3

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Na1	1.0000	0.5000	0.5000	0.0227 (2)
C1	0.4142 (3)	0.04548 (19)	0.14942 (12)	0.0131 (2)
C2	0.6462 (10)	0.2300 (7)	0.0644 (4)	0.0136 (6)	0.50
H2A	0.7484	0.3865	0.1088	0.016*	0.50
C3	0.7289 (10)	0.1857 (7)	−0.0859 (5)	0.0137 (7)	0.50
H3	0.8817	0.3124	−0.1442	0.016*	0.50
C2X	0.4013 (10)	−0.1900 (8)	0.1037 (5)	0.0151 (7)	0.50
H2XA	0.3325	−0.3193	0.1735	0.018*	0.50
C3X	0.4903 (10)	−0.2334 (7)	−0.0452 (4)	0.0148 (7)	0.50
H3X	0.4860	−0.3928	−0.0761	0.018*	0.50
C4	0.3087 (3)	0.1022 (2)	0.30726 (12)	0.0138 (2)
O1	0.4039 (2)	0.31521 (15)	0.35609 (9)	0.0195 (2)
O2	0.1094 (2)	−0.07760 (15)	0.38299 (9)	0.0179 (2)
H2	0.035 (11)	−0.018 (7)	0.466 (4)	0.027*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Na1	0.0226 (4)	0.0210 (4)	0.0244 (4)	0.0060 (3)	0.0017 (3)	−0.0093 (3)
C1	0.0131 (5)	0.0154 (5)	0.0109 (5)	0.0043 (4)	0.0009 (4)	−0.0019 (4)
C2	0.0143 (16)	0.0127 (11)	0.0136 (13)	0.0033 (13)	0.0005 (12)	−0.0029 (9)
C3	0.0149 (18)	0.0137 (12)	0.0124 (14)	0.0032 (14)	0.0041 (13)	0.0012 (9)
C2X	0.0172 (19)	0.0139 (12)	0.0144 (14)	0.0041 (14)	0.0025 (14)	0.0000 (9)
C3X	0.0153 (17)	0.0145 (12)	0.0149 (13)	0.0046 (14)	0.0010 (13)	−0.0037 (9)
C4	0.0138 (5)	0.0164 (5)	0.0119 (5)	0.0051 (4)	0.0001 (4)	−0.0021 (4)
O1	0.0261 (5)	0.0159 (4)	0.0152 (4)	0.0032 (3)	0.0038 (3)	−0.0047 (3)
O2	0.0230 (4)	0.0169 (4)	0.0128 (4)	0.0034 (3)	0.0057 (3)	−0.0019 (3)

Geometric parameters (Å, º)

Na1—O1^i	2.4120 (9)	C3—H3	0.9500
Na1—O1	2.4359 (10)	C2X—C3X	1.394 (6)
Na1—O2^ii	2.5745 (11)	C2X—H2XA	0.9500
C1—C3^iii	1.393 (4)	C3X—C1^iii	1.396 (4)
C1—C3X^iii	1.396 (4)	C3X—H3X	0.9500
C1—C2X	1.397 (4)	C4—O1	1.2470 (14)
C1—C2	1.398 (4)	C4—O2	1.2898 (14)
C1—C4	1.5067 (15)	O1—Na1^iv	2.4120 (9)
C2—C3	1.399 (5)	O2—Na1^v	2.5745 (11)
C2—H2A	0.9500	O2—H2	0.88 (3)
C3—C1^iii	1.393 (4)
O1^vi—Na1—O1	83.37 (4)	C3X—C2X—C1	119.4 (3)
O1^vi—Na1—O2^vii	103.71 (3)	C3X—C2X—H2XA	120.3
O1—Na1—O2^vii	84.09 (3)	C1—C2X—H2XA	120.3
C3X^iii—C1—C2X	119.8 (2)	C2X—C3X—C1^iii	120.8 (3)
C3^iii—C1—C2	120.0 (2)	C2X—C3X—H3X	119.6
C3^iii—C1—C4	120.7 (2)	C1^iii—C3X—H3X	119.6
C3X^iii—C1—C4	118.38 (17)	O1—C4—O2	123.60 (10)
C2X—C1—C4	121.8 (2)	O1—C4—C1	119.94 (10)
C2—C1—C4	119.26 (17)	O2—C4—C1	116.43 (10)
C1—C2—C3	120.4 (3)	C4—O1—Na1^iv	124.89 (7)
C1—C2—H2A	119.8	C4—O1—Na1	124.25 (7)
C3—C2—H2A	119.8	Na1^iv—O1—Na1	96.63 (4)
C1^iii—C3—C2	119.6 (3)	C4—O2—Na1^v	152.10 (7)
C1^iii—C3—H3	120.2	C4—O2—H2	108 (3)
C2—C3—H3	120.2	Na1^v—O2—H2	92 (3)
C3^iii—C1—C2—C3	1.5 (5)	O2—C4—O1—Na1	90.98 (12)
C4—C1—C2—C3	−176.1 (2)	C1—C4—O1—Na1	−91.39 (11)
C1—C2—C3—C1^iii	−1.5 (5)	O1^vi—Na1—O1—C4	−140.87 (10)
C3X^iii—C1—C2X—C3X	1.0 (5)	O1^i—Na1—O1—C4	39.13 (10)
C4—C1—C2X—C3X	178.0 (2)	O2^vii—Na1—O1—C4	−36.28 (8)
C1—C2X—C3X—C1^iii	−1.0 (5)	O2^ii—Na1—O1—C4	143.72 (8)
C3^iii—C1—C4—O1	−172.12 (18)	O1^vi—Na1—O1—Na1^iv	0.0
C2—C1—C4—O1	5.4 (2)	O1^i—Na1—O1—Na1^iv	180.0
C3^iii—C1—C4—O2	5.7 (2)	O2^vii—Na1—O1—Na1^iv	104.59 (3)
C2—C1—C4—O2	−176.80 (18)	O2^ii—Na1—O1—Na1^iv	−75.41 (3)
O2—C4—O1—Na1^iv	−39.18 (15)	O1—C4—O2—Na1^v	−126.48 (13)
C1—C4—O1—Na1^iv	138.44 (8)	C1—C4—O2—Na1^v	55.82 (19)

Symmetry codes: (i) x+1, y, z; (ii) x+1, y+1, z; (iii) −x+1, −y, −z; (iv) x−1, y, z; (v) x−1, y−1, z; (vi) −x+1, −y+1, −z+1; (vii) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O2^viii	0.88 (3)	1.59 (3)	2.4734 (17)	178 (4)

Symmetry code: (viii) −x, −y, −z+1.