A second monoclinic polymorph of caesium salicylate monohydrate

The structure of the title caesium salt with salicylic acid, poly[μ₂-aqua-μ₄-(salicylato-κ⁴O¹:O¹:O^1′:O²)caesium], [Cs(C₇H₅O₃)(H₂O)]_n, represents a second monoclinic polymorph of this compound. The two-dimensional coordination polymeric structure is based on a centrosymmetric dinuclear bridged repeat unit with each irregular CsO₆ coordination polyhedron comprising a μ₂-bridging water mol­ecule and μ₄-bridging O-atom donors, three from the carboxyl group and one from the phenolic group of the salicylate ligand. The Cs—O bond range is 3.023 (3)–3.368 (4) Å and the Cs⋯Cs separation within the dinuclear unit is 4.9265 (6) Å. The polymeric sheet structure lies parallel to (010) with the water mol­ecule and the phenol group involved in intra-polymer O—H⋯O_carbox­yl hydrogen-bonding inter­actions.

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Chemical scheme

Structure description

In the title complex salt, [Cs(C₇H₅O₃)(H₂O)]_n (polymorph 2) (Fig. 1), although polymorphic with the Wiesbrock & Schmidbaur (2003a) crystal and forming a two-dimensional coordination polymeric structure, apart from the very obvious cell-parameter differences, particularly the disparate values of the unique b axis, the mol­ecular structures are distinctly different. Polymorph 2 is based on a centrosymmetric dinuclear bridged repeat unit with each irregular CsO₆ coordination polyhedron comprising a μ₂-bridging water mol­ecule (O1W), and μ₄-bridging O-atom donors, three from the carboxyl group and one from the phenolic group of the salicylate ligand. The Cs—O bond-length range is 3.023 (3)–3.368 (4) Å (Table 1) and the Cs⋯Csⁱⁱⁱ separation within the dinuclear unit is 4.9265 (6) Å. With polymorph 1, the Cs—O range in the CsO₇ coordination sphere is given as 3.071 (3)–3.584 (2) Å (although stated incorrectly as eight-coordinate), this would be reduced to CsO₆ with the last value in the stated range being considered too long for a Cs—O bond (PLATON; Spek, 2009), with the sixth value being 3.341 (2) Å. The shortest Cs⋯Cs separation in polymorph 1 is also very different [4.1391 (3) Å].

Table 1
Selected bond lengths (Å)

Cs1—O12^i	3.023 (3)	Cs1—O11^ii	3.159 (4)
Cs1—O1W	3.108 (3)	Cs1—O12^iii	3.244 (3)
Cs1—O2	3.130 (4)	Cs1—O1W^iii	3.368 (4)
Symmetry codes: (i) x, y, z+1; (ii) x-1, y, z+1; (iii) -x+1, -y+1, -z+1.

Figure 1 The mol­ecular configuration and atom-numbering scheme for the centrosymmetric repeat unit in the title complex, with non-H atoms shown as 40% probability displacement ellipsoids. For symmetry codes, see Table 1. Hydrogen bonds are shown as dashed lines.

The polymeric sheet structure in the title complex lies parallel to (010) (Figs. 2 and 3) and in the crystal, intra-layer hydrogen-bonding inter­actions (Table 2) involving H-atom donors of the coordinating water mol­ecule and carboxyl O-atom acceptors are present (Fig. 3). Also present are short Cs1⋯C inter­actions to four of the salicylate ring C atoms [C1^v 3.838 (4) Å; C4^v 3.825 (5) Å; C5^v 3.648 (5) Å; C6^v 3.658 (5) Å; for symmetry code (v), see Table 2].

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O12	0.78 (6)	1.82 (6)	2.516 (5)	148 (8)
O1W—H11W⋯O11^iv	0.89 (4)	2.00 (5)	2.867 (5)	165 (6)
O1W—H11W⋯O12^iv	0.89 (4)	2.57 (5)	3.268 (5)	136 (5)
O1W—H12W⋯O11^v	0.89 (4)	2.04 (5)	2.848 (5)	151 (6)
Symmetry codes: (iv) -x+1, -y+1, -z; (v) x-1, y, z.

Figure 2 A partial extension of the polymeric structure of the title compound. [Symmetry code: (vi) −x + 2, −y + 1, −z; for other codes, see Tables 1 and 2.]

Figure 3 The hydrogen-bonded sheet structure viewed along the a axis. Non-associative H atoms are omitted and intra­molecular hydrogen bonds are shown as dashed lines.

With the salicylate anion, the carboxyl group is rotated slightly out of the benzene plane [torsion angle C2—C1—O11—C11 = −167.4 (4)°], comparing with −168.2 (3)° in polymorph 1 and 179.3 (1)° in the structure of the parent salicylic acid (Munshi & Guru Row, 2006). In all of the salicylate structures, including those of the anhydrous Li salt (Smith et al., 2013), the Li monohydrate salt (Wiesbrock & Schmidbaur, 2003b) and the K and Rb salt (Dinnebier et al., 2002) or salt adducts (Downie & Speakman, 1953), a short intra­molecular phenolic O—H⋯O_carbox­yl hydrogen bond is present.

Synthesis and crystallization

The title compound was formed in the attempted synthesis of a Cs–aspirinate complex by the dropwise addition of cold 50 wt% aqueous caesium hydroxide solution to a solution containing 100 mg of acetyl­salicylic acid in 10 ml of 10 wt% ethanol/water. Room temperature evaporation resulted in a change in the colour of the solution to dark brown, finally giving colourless crystal plates of the title compound from which a specimen was cleaved for the X-ray analysis.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3.

Table 3
Experimental details

Crystal data
Chemical formula	[Cs(C7H5O3)(H2O)]
Mr	288.04
Crystal system, space group	Monoclinic, P21/n
Temperature (K)	200
a, b, c (Å)	6.3365 (4), 21.5911 (18), 6.6167 (6)
β (°)	100.661 (7)
V (Å^3)	889.62 (12)
Z	4
Radiation type	Mo Kα
μ (mm^−1)	4.13
Crystal size (mm)	0.35 × 0.25 × 0.12
Data collection
Diffractometer	Oxford Diffraction Gemini-S CCD-detector
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2014)
Tmin, Tmax	0.758, 0.980
No. of measured, independent and observed [I > 2σ(I)] reflections	3528, 1747, 1466
Rint	0.034
(sin θ/λ)max (Å^−1)	0.617
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.033, 0.067, 1.02
No. of reflections	1747
No. of parameters	109
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å^−3)	0.76, −0.78
Computer programs: CrysAlis PRO (Agilent, 2014), SIR92 (Altomare et al., 1993), SHELXL97 (Sheldrick, 2008) within WinGX (Farrugia, 2012), and PLATON (Spek, 2009).

Structural data

Computing details

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: SIR92 (Altomare et al., 1993); 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 (Spek, 2009).

Poly[(µ₂-aqua-µ₄-(salicylato-κ⁴O¹:O¹:O^1':O²)-caesium]

Crystal data

[Cs(C7H5O3)(H2O)]	F(000) = 544
Mr = 288.04	Dx = 2.151 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1068 reflections
a = 6.3365 (4) Å	θ = 3.4–27.7°
b = 21.5911 (18) Å	µ = 4.13 mm^−1
c = 6.6167 (6) Å	T = 200 K
β = 100.661 (7)°	Plate, colourless
V = 889.62 (12) Å^3	0.35 × 0.25 × 0.12 mm
Z = 4

Data collection

Oxford Diffraction Gemini-S CCD-detector diffractometer	1747 independent reflections
Radiation source: Enhance (Mo) X-ray source	1466 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
Detector resolution: 16.077 pixels mm^-1	θmax = 26.0°, θmin = 3.3°
ω scans	h = −4→7
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2014)	k = −25→26
Tmin = 0.758, Tmax = 0.980	l = −7→8
3528 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.033	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.067	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0209P)^2] where P = (Fo^2 + 2Fc^2)/3
1747 reflections	(Δ/σ)max = 0.001
109 parameters	Δρmax = 0.76 e Å^−3
0 restraints	Δρmin = −0.78 e Å^−3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

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 > 2sigma(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 (Ų)

	x	y	z	Uiso*/Ueq
Cs1	0.29377 (5)	0.55788 (1)	0.71890 (4)	0.0318 (1)
O1W	0.2151 (7)	0.50214 (16)	0.2782 (5)	0.0436 (14)
O2	0.5730 (7)	0.61882 (17)	0.4290 (6)	0.0446 (12)
O11	0.9693 (6)	0.59022 (14)	0.0129 (5)	0.0405 (14)
O12	0.6439 (6)	0.58055 (16)	0.0887 (5)	0.0442 (12)
C1	0.8959 (8)	0.64355 (18)	0.3047 (7)	0.0230 (14)
C2	0.7624 (9)	0.64822 (19)	0.4513 (7)	0.0288 (16)
C3	0.8274 (10)	0.6841 (2)	0.6268 (8)	0.0418 (19)
C4	1.0173 (11)	0.7160 (2)	0.6525 (8)	0.045 (2)
C5	1.1508 (10)	0.7116 (2)	0.5083 (8)	0.0441 (19)
C6	1.0884 (8)	0.67583 (19)	0.3357 (7)	0.0307 (16)
C11	0.8343 (9)	0.6023 (2)	0.1204 (7)	0.0293 (16)
H2	0.547 (12)	0.605 (3)	0.318 (9)	0.0670*
H3	0.74190	0.68640	0.72660	0.0500*
H4	1.05740	0.74090	0.76780	0.0540*
H5	1.28100	0.73270	0.52850	0.0530*
H6	1.17670	0.67320	0.23820	0.0370*
H11W	0.183 (10)	0.4708 (19)	0.191 (7)	0.0650*
H12W	0.184 (11)	0.5353 (18)	0.199 (7)	0.0650*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cs1	0.0266 (2)	0.0422 (2)	0.0263 (2)	−0.0017 (2)	0.0041 (1)	−0.0004 (1)
O1W	0.041 (3)	0.051 (2)	0.034 (2)	0.006 (2)	−0.0055 (19)	−0.0114 (16)
O2	0.029 (2)	0.055 (2)	0.052 (2)	−0.0078 (19)	0.013 (2)	−0.005 (2)
O11	0.050 (3)	0.044 (2)	0.0298 (19)	0.0028 (19)	0.0131 (19)	−0.0068 (16)
O12	0.036 (2)	0.051 (2)	0.042 (2)	−0.0102 (19)	−0.0025 (19)	−0.0136 (17)
C1	0.025 (3)	0.021 (2)	0.021 (2)	0.004 (2)	−0.001 (2)	0.0025 (19)
C2	0.030 (3)	0.024 (2)	0.032 (3)	0.004 (2)	0.005 (2)	0.004 (2)
C3	0.051 (4)	0.042 (3)	0.035 (3)	0.006 (3)	0.015 (3)	−0.002 (2)
C4	0.066 (5)	0.033 (3)	0.031 (3)	−0.005 (3)	−0.005 (3)	−0.009 (2)
C5	0.050 (4)	0.035 (3)	0.044 (3)	−0.014 (3)	0.000 (3)	0.000 (3)
C6	0.030 (3)	0.030 (2)	0.033 (3)	−0.004 (2)	0.008 (2)	0.003 (2)
C11	0.036 (3)	0.027 (2)	0.024 (3)	0.003 (2)	0.003 (2)	0.007 (2)

Geometric parameters (Å, º)

Cs1—O12^i	3.023 (3)	C1—C11	1.502 (6)
Cs1—O1W	3.108 (3)	C1—C2	1.404 (7)
Cs1—O2	3.130 (4)	C1—C6	1.387 (7)
Cs1—O11^ii	3.159 (4)	C2—C3	1.393 (7)
Cs1—O12^iii	3.244 (3)	C3—C4	1.370 (9)
Cs1—O1W^iii	3.368 (4)	C4—C5	1.391 (9)
O2—C2	1.342 (7)	C5—C6	1.375 (7)
O11—C11	1.237 (6)	C3—H3	0.9300
O12—C11	1.275 (7)	C4—H4	0.9300
O1W—H11W	0.89 (4)	C5—H5	0.9300
O1W—H12W	0.89 (4)	C6—H6	0.9300
O2—H2	0.78 (6)
O1W—Cs1—O2	66.33 (10)	Cs1—O1W—H12W	103 (3)
O1W—Cs1—O11^ii	130.81 (10)	Cs1—O2—H2	112 (5)
O1W—Cs1—O12^i	142.02 (11)	C2—O2—H2	108 (6)
O1W—Cs1—O1W^iii	81.03 (10)	C2—C1—C6	119.2 (4)
O1W—Cs1—O12^iii	89.90 (9)	C2—C1—C11	120.3 (4)
O2—Cs1—O11^ii	142.24 (9)	C6—C1—C11	120.5 (4)
O2—Cs1—O12^i	90.83 (10)	C1—C2—C3	119.5 (5)
O1W^iii—Cs1—O2	62.53 (10)	O2—C2—C1	122.1 (4)
O2—Cs1—O12^iii	125.89 (10)	O2—C2—C3	118.4 (5)
O11^ii—Cs1—O12^i	85.96 (9)	C2—C3—C4	120.0 (5)
O1W^iii—Cs1—O11^ii	141.96 (8)	C3—C4—C5	120.8 (5)
O11^ii—Cs1—O12^iii	90.45 (9)	C4—C5—C6	119.4 (5)
O1W^iii—Cs1—O12^i	61.23 (9)	C1—C6—C5	121.0 (5)
O12^i—Cs1—O12^iii	79.27 (9)	O11—C11—O12	124.2 (4)
O1W^iii—Cs1—O12^iii	66.30 (9)	O11—C11—C1	119.2 (5)
Cs1—O1W—Cs1^iii	98.97 (11)	O12—C11—C1	116.6 (4)
Cs1—O2—C2	136.7 (3)	C2—C3—H3	120.00
Cs1^iv—O11—C11	177.0 (3)	C4—C3—H3	120.00
Cs1^v—O12—C11	136.3 (3)	C3—C4—H4	120.00
Cs1^iii—O12—C11	103.4 (3)	C5—C4—H4	120.00
Cs1^v—O12—Cs1^iii	100.74 (10)	C4—C5—H5	120.00
H11W—O1W—H12W	103 (4)	C6—C5—H5	120.00
Cs1^iii—O1W—H11W	79 (4)	C1—C6—H6	119.00
Cs1^iii—O1W—H12W	115 (4)	C5—C6—H6	120.00
Cs1—O1W—H11W	152 (3)
O2—Cs1—O1W—Cs1^iii	63.85 (11)	Cs1^v—O12—C11—C1	139.7 (3)
O11^ii—Cs1—O1W—Cs1^iii	−156.51 (8)	Cs1^iii—O12—C11—O11	79.6 (5)
O12^i—Cs1—O1W—Cs1^iii	6.24 (19)	Cs1^iii—O12—C11—C1	−98.6 (4)
O1W^iii—Cs1—O1W—Cs1^iii	−0.02 (13)	C6—C1—C2—O2	179.1 (4)
O12^iii—Cs1—O1W—Cs1^iii	−66.00 (10)	C6—C1—C2—C3	−1.3 (7)
O1W—Cs1—O2—C2	−153.6 (5)	C11—C1—C2—O2	−3.0 (7)
O11^ii—Cs1—O2—C2	79.6 (5)	C11—C1—C2—C3	176.6 (4)
O12^i—Cs1—O2—C2	−4.9 (4)	C2—C1—C6—C5	0.7 (7)
O1W^iii—Cs1—O2—C2	−61.6 (4)	C11—C1—C6—C5	−177.2 (4)
O12^iii—Cs1—O2—C2	−82.3 (4)	C2—C1—C11—O11	−167.4 (4)
O1W—Cs1—O12^i—C11^i	46.9 (5)	C2—C1—C11—O12	10.9 (6)
O2—Cs1—O12^i—C11^i	−3.8 (4)	C6—C1—C11—O11	10.5 (6)
O1W—Cs1—O1W^iii—Cs1^iii	0.00 (10)	C6—C1—C11—O12	−171.3 (4)
O2—Cs1—O1W^iii—Cs1^iii	−67.92 (11)	O2—C2—C3—C4	−178.4 (4)
O1W—Cs1—O12^iii—C11^iii	−73.3 (3)	C1—C2—C3—C4	2.0 (7)
O2—Cs1—O12^iii—C11^iii	−133.5 (3)	C2—C3—C4—C5	−2.1 (8)
Cs1—O2—C2—C1	147.1 (3)	C3—C4—C5—C6	1.5 (7)
Cs1—O2—C2—C3	−32.5 (7)	C4—C5—C6—C1	−0.8 (7)
Cs1^v—O12—C11—O11	−42.2 (7)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O12	0.78 (6)	1.82 (6)	2.516 (5)	148 (8)
O1W—H11W···O11^vi	0.89 (4)	2.00 (5)	2.867 (5)	165 (6)
O1W—H11W···O12^vi	0.89 (4)	2.57 (5)	3.268 (5)	136 (5)
O1W—H12W···O11^vii	0.89 (4)	2.04 (5)	2.848 (5)	151 (6)

Symmetry codes: (vi) −x+1, −y+1, −z; (vii) x−1, y, z.