Crystal structure of catena-poly[calcium-di-μ3-benzoato-κ(6) O,O':O-μ2-(dimethyl sulfoxide)-κ(2) O:O].

In the title complex, [Ca(C7H5O2)2(C2H6OS)] n , the Ca(2+) ion (site symmetry m..) is surrounded by eight O atoms, six from two bridging-chelating tridentate benzoate carboxyl groups and two from a bridging dimethyl sulfoxide mol-ecule (point group symmetry m..), giving an irregular coordination geometry [Ca-O bond length range = 2.345 (2)-2.524 (2) Å]. One-dimensional coordination complex chains extending parallel to c are generated in which the triply μ2-O-bridged Ca(2+) cations are separated by 3.6401 (5) Å. In the crystal, weak intra-chain C-H⋯π hydrogen bonds are present between the methyl H atoms of the dimethyl sulfoxide mol-ecules as donors and the aromatic rings as acceptors [C-H⋯Cg = 3.790 (4) Å].

Chemical context

Compounds of benzoic acid with calcium are of special inter­est due to their wide-ranging applications, for example as a preservative in the food industry, in cosmetics and in medicine. In spite of that, the crystal structures of such compounds have been poorly investigated. Searches of the Cambridge Structural Database (CSD; Version 5.35, November 2013 + 2 updates; Groom & Allen, 2014 ▸) for simple calcium benzoate complexes revealed only three results: [Ca(benz)2(dmf)(H2O)] (Yano et al., 2001 ▸), {[Ca(benz)(H2O)3]+ (benz)−} (Senkovska & Thewalt, 2005 ▸) and [Ca(benz)2(Hbenz)(H2O)] (Azizov et al., 2011 ▸) (where benz = benzoate).

Here we report the synthesis of a new calcium benzoate–dimethyl sulfoxide complex, [Ca(benz)2(dmso)], which was obtained as a by-product of an attempted synthesis of an Mn/Cu heterometallic complex (in crystalline form available for X-ray analysis) from the system: Mn–Cu–(bhz–sal)–CaO–KSCN–dmso (in open air), where manganese and copper were used as unactivated metal powders, bhz = benzohydrazide and sal = salicyl­aldehyde. The investigation of the system was carried out as a part of systematic research on the elaboration the ‘direct synthesis’ approach to both homo- and heterometallic coordination compounds (Babich et al., 1996 ▸; Buvaylo et al., 2005 ▸; Vassilyeva et al., 1997 ▸). It is worth noting that an alternative method of synthesis using a classical reaction between calcium oxide and benzoic acid in dmso, affords the same complex in good yield (up to 90%), but does not give X-ray quality crystals. The crystal structure of the title complex, [Ca(benz)2(dmso)], is reported herein.

Structural commentary

The asymmetric unit of [Ca(benz)2(dmso)] comprises one Ca2+ cation (site symmetry m..), one benzoate ligand and half of a dmso mol­ecule, the other half being generated by mirror symetry. The irregular CaO8 coordination polyhedron consists of six O atom donors from two O,O′ chelating-bridging benzoate carboxyl groups with the same coordination modes, [2.11112] in the Harris notation (Coxall et al., 2000 ▸), and two from μ2-bridging dmso mol­ecules (Fig. 1 ▸). The coordination geometry deviates strongly from ideal, the Ca—O bond lengths varying from 2.345 (2) to 2.524 (2) Å (Table 1 ▸) and the O—Ca—O angles from 52.19 (7) to 156.06 (8)°. The bridging Ca1—O1i and Ca1—O1ii (carbox­yl) bond lengths are considerably shorter than the chelate ones, as is usually observed in polymeric benzoates. For the title complex, the bond-valence index [BVS (Ca)] (Allmann, 1975 ▸) is 2.03.

Figure 1

A fragment of the [Ca(benz)2(dmso)] chain with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms have been omitted for clarity. For symmetry codes, see Table 1 ▸.

Table 1

Selected bond lengths ()

Ca1O1i	2.345(2)	Ca1O3	2.494(3)
Ca1O1ii	2.345(2)	Ca1O3iv	2.516(3)
Ca1O2iii	2.481(2)	Ca1O1iii	2.524(2)
Ca1O2	2.481(2)	Ca1O1	2.524(2)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Supra­molecular features

The triple-O-bridged CaO8 polyhedra form one-dimensional coordination polymeric chains which extend parallel to the c-axis direction (Figs. 2 ▸–4 ▸ ▸). The Ca⋯Cai and Ca1⋯Ca1iv separation in the chain is 3.6401 (5) Å [symmetry code (iv): −x + 1, −y, z − ]. To the best of our knowledge, this is the first Ca carboxyl­ate polymer based on non-centrosymmetric bridges (μ-η2:η1)2. For bridging modes in coordination polymeric structures, reference should be made to Deacon et al. (2007 ▸) and Busskamp et al. (2007 ▸). The polymer chains in the title compound are additionally stabilized by weak C—H⋯π inter­actions between the methyl groups of the dmso mol­ecule and the benzoate rings (centroid Cg) (Table 2 ▸, Figs. 3 ▸ and 4 ▸).

Figure 2

Bridging inter­actions observed in the title complex polymer which extends along the c- axis direction. Phenyl rings and H atoms have been omitted for clarity.

Figure 3

C—H⋯π hydrogen bonds involving a dmso donor as found in the title complex. For symmetry codes, see Table 1 ▸).

Figure 4

Packing of the mol­ecular chains viewed down the chain direction (the crystallographic c axis). C—H⋯π bonds are shown as dashed lines.

Table 2

CH interactions (, )

Cg is the centroid of the benzoate ring.

DHA	DH	HA	D A	DHA
C8H8A Cg	0.96	2.84	3.790(4)	169

Synthesis and crystallization

Calcium oxide (0.056 g, 1 mmol) and benzoic acid (0.244 g, 2 mmol) were added to 20 ml of dmso and stirred magnetically for ca 5 h at 323 K, after which the solution was filtered. The white precipitate which formed after one day was collected and dried in air; yield: 0.4 g (90%). Elemental analysis for C16H16CaO5S (M r = 360.43). Calculated: Ca, 11.12%; found: Ca, 11.0%. IR (KBr, cm−1): 1603 (s), 1562 (s), 1405 (s), 1024 (s), 721 (s). Crystals suitable for X-ray analysis were obtained by slow evaporation at room temperature of a solution which was the product from the reaction between manganese powder (0.05 g, 1 mmol), copper powder (0.06 g, 1 mmol), benzohydrazide (0.409 g, 3 mmol), salicyl­aldehyde (0.314 ml, 3 mmol), CaO (0.168 g, 3 mmol), KSCN (0.291 g, 3 mmol) and dmso (20 ml). The reaction was carried out at 353 K with magnetic stirring for eight hours, after which undissolved products were filtered off.

Refinement details

Crystal data, data collection and structure refinement details are given in Table 3 ▸. Hydrogen atoms were placed in calculated positions [C—Haromatic = 0.95; C—Hmeth­yl = 0.99 Å] and were allowed to ride in the refinements, with U iso(H) = 1.2U eq(aromatic C) or 1.5U eq(methyl C). Although not of relevance in this crystal involving achiral mol­ecules, the Flack absolute structure parameter (Flack, 1983 ▸) was determined as 0.04 (8) by classical fit to all intensities and 0.07 (3) from 557 selected quotients (Parsons et al., 2013 ▸).

Table 3

Experimental details

Crystal data
Chemical formula	[Ca(C7H5O2)2(C2H6OS)]
M r	360.43
Crystal system, space group	Orthorhombic, C m c21
Temperature (K)	200
a, b, c ()	25.531(2), 9.5351(8), 6.9330(4)
V (3)	1687.7(2)
Z	4
Radiation type	Mo K
(mm1)	0.52
Crystal size (mm)	0.22 0.15 0.11
Data collection
Diffractometer	Rigaku Mercury CCD
Absorption correction	Multi-scan (Blessing, 1995 ▸)
T min, T max	0.798, 0.951
No. of measured, independent and observed [I > 2(I)] reflections	3704, 1897, 1676
R int	0.025
(sin /)max (1)	0.683
Refinement
R[F 2 > 2(F 2)], wR(F 2), S	0.044, 0.103, 1.13
No. of reflections	1897
No. of parameters	109
No. of restraints	1
H-atom treatment	H-atom parameters constrained
max, min (e 3)	0.59, 0.39
Absolute structure	Flack x determined using 557 quotients [(I +)(I )]/[(I +)+(I )] (Parsons et al., 2013 ▸)
Absolute structure parameter	0.07(3)

Computer programs: CrystalClear (Rigaku, 1999 ▸), SIR92 (Altomare et al., 1993 ▸)., SHELXL97 (Sheldrick, 2008 ▸), DIAMOND (Brandenburg Putz, 2006 ▸) and WinGX (Farrugia, 2012 ▸).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989015012487/zs2334sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015012487/zs2334Isup2.hkl

CCDC reference: 1409468

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

[Ca(C7H5O2)2(C2H6OS)]	Dx = 1.418 Mg m−3
Mr = 360.43	Mo Kα radiation, λ = 0.71069 Å
Orthorhombic, Cmc21	Cell parameters from 1872 reflections
a = 25.531 (2) Å	θ = 2.3–28.7°
b = 9.5351 (8) Å	µ = 0.52 mm−1
c = 6.9330 (4) Å	T = 200 K
V = 1687.7 (2) Å3	Block, colorless
Z = 4	0.22 × 0.15 × 0.11 mm
F(000) = 752

Rigaku Mercury CCD (2x2 bin mode) diffractometer	1897 independent reflections
Graphite monochromator	1676 reflections with I > 2σ(I)
Detector resolution: 14.7059 pixels mm-1	Rint = 0.025
dtprofit.ref scans	θmax = 29.0°, θmin = 2.3°
Absorption correction: multi-scan (Blessing, 1995)	h = −34→26
Tmin = 0.798, Tmax = 0.951	k = −12→6
3704 measured reflections	l = −9→9

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044	H-atom parameters constrained
wR(F2) = 0.103	w = 1/[σ2(Fo2) + (0.040P)2 + 0.7932P] where P = (Fo2 + 2Fc2)/3
S = 1.13	(Δ/σ)max < 0.001
1897 reflections	Δρmax = 0.59 e Å−3
109 parameters	Δρmin = −0.39 e Å−3
1 restraint	Absolute structure: Flack x determined using 557 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.07 (3)

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.

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 > σ(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.

	x	y	z	Uiso*/Ueq
Ca1	0.5000	0.05825 (7)	0.36175 (11)	0.0325 (2)
O1	0.44205 (8)	0.06089 (19)	0.0668 (3)	0.0388 (5)
O2	0.43213 (9)	0.2334 (2)	0.2748 (4)	0.0509 (6)
O3	0.5000	0.1724 (3)	0.6855 (5)	0.0414 (7)
C1	0.41769 (12)	0.1682 (3)	0.1275 (5)	0.0375 (7)
C2	0.37045 (12)	0.2146 (3)	0.0171 (5)	0.0388 (7)
C3	0.35274 (13)	0.1367 (4)	−0.1381 (7)	0.0589 (10)
H3	0.3695	0.0533	−0.1704	0.071*
C4	0.31036 (16)	0.1818 (5)	−0.2452 (8)	0.0756 (13)
H4	0.2988	0.1289	−0.3495	0.091*
C5	0.28529 (14)	0.3044 (4)	−0.1984 (7)	0.0624 (11)
H5	0.2567	0.3340	−0.2707	0.075*
C6	0.30222 (15)	0.3831 (4)	−0.0461 (7)	0.0584 (11)
H6	0.2855	0.4669	−0.0160	0.070*
C7	0.34453 (12)	0.3375 (3)	0.0639 (6)	0.0464 (8)
H7	0.3555	0.3900	0.1695	0.056*
C8	0.44725 (16)	0.4090 (3)	0.6588 (6)	0.0560 (10)
H8A	0.4146	0.3721	0.7051	0.084*
H8B	0.4493	0.3964	0.5217	0.084*
H8C	0.4494	0.5071	0.6889	0.084*
S1	0.5000	0.31863 (10)	0.77164 (16)	0.0444 (3)

	U11	U22	U33	U12	U13	U23
Ca1	0.0504 (4)	0.0257 (3)	0.0214 (4)	0.000	0.000	0.0005 (3)
O1	0.0472 (11)	0.0343 (11)	0.0349 (13)	0.0085 (8)	0.0000 (10)	−0.0033 (9)
O2	0.0720 (14)	0.0427 (12)	0.0381 (13)	0.0142 (11)	−0.0139 (13)	−0.0064 (11)
O3	0.069 (2)	0.0218 (12)	0.0333 (17)	0.000	0.000	−0.0020 (12)
C1	0.0515 (17)	0.0302 (14)	0.0307 (17)	0.0017 (13)	0.0019 (13)	0.0022 (12)
C2	0.0421 (15)	0.0389 (16)	0.0353 (17)	0.0002 (13)	0.0011 (13)	0.0042 (14)
C3	0.0556 (18)	0.060 (2)	0.061 (2)	0.0180 (16)	−0.014 (2)	−0.022 (2)
C4	0.067 (2)	0.086 (3)	0.074 (3)	0.020 (2)	−0.031 (2)	−0.022 (3)
C5	0.0483 (19)	0.069 (2)	0.070 (3)	0.0101 (19)	−0.0107 (18)	0.010 (2)
C6	0.0478 (19)	0.045 (2)	0.082 (3)	0.0097 (16)	0.0054 (19)	0.003 (2)
C7	0.0483 (17)	0.0390 (17)	0.052 (2)	0.0063 (14)	0.0025 (16)	−0.0028 (16)
C8	0.083 (3)	0.0357 (15)	0.049 (2)	0.0096 (17)	0.005 (2)	−0.0010 (17)
S1	0.0829 (8)	0.0257 (5)	0.0244 (6)	0.000	0.000	−0.0015 (4)

Ca1—O1i	2.345 (2)	C1—C2	1.496 (4)
Ca1—O1ii	2.345 (2)	C2—C3	1.383 (5)
Ca1—O2iii	2.481 (2)	C2—C7	1.384 (4)
Ca1—O2	2.481 (2)	C3—C4	1.381 (5)
Ca1—O3	2.494 (3)	C3—H3	0.9300
Ca1—O3iv	2.516 (3)	C4—C5	1.371 (5)
Ca1—O1iii	2.524 (2)	C4—H4	0.9300
Ca1—O1	2.524 (2)	C5—C6	1.365 (6)
Ca1—C1iii	2.855 (3)	C5—H5	0.9300
Ca1—C1	2.855 (3)	C6—C7	1.392 (5)
Ca1—Ca1i	3.6401 (5)	C6—H6	0.9300
Ca1—Ca1iv	3.6401 (5)	C7—H7	0.9300
O1—C1	1.269 (3)	C8—S1	1.780 (4)
O1—Ca1iv	2.345 (2)	C8—H8A	0.9600
O2—C1	1.251 (4)	C8—H8B	0.9600
O3—S1	1.517 (3)	C8—H8C	0.9600
O3—Ca1i	2.516 (3)	S1—C8iii	1.780 (4)
O1i—Ca1—O1ii	78.22 (11)	C1iii—Ca1—Ca1i	130.82 (7)
O1i—Ca1—O2iii	91.88 (8)	C1—Ca1—Ca1i	130.82 (7)
O1ii—Ca1—O2iii	156.06 (8)	O1i—Ca1—Ca1iv	115.44 (6)
O1i—Ca1—O2	156.06 (8)	O1ii—Ca1—Ca1iv	115.44 (6)
O1ii—Ca1—O2	91.88 (8)	O2iii—Ca1—Ca1iv	88.51 (6)
O2iii—Ca1—O2	88.60 (12)	O2—Ca1—Ca1iv	88.51 (6)
O1i—Ca1—O3	70.48 (7)	O3—Ca1—Ca1iv	171.90 (7)
O1ii—Ca1—O3	70.48 (7)	O3iv—Ca1—Ca1iv	43.17 (8)
O2iii—Ca1—O3	85.70 (8)	O1iii—Ca1—Ca1iv	39.79 (5)
O2—Ca1—O3	85.70 (8)	O1—Ca1—Ca1iv	39.79 (5)
O1i—Ca1—O3iv	82.59 (8)	C1iii—Ca1—Ca1iv	64.56 (7)
O1ii—Ca1—O3iv	82.59 (8)	C1—Ca1—Ca1iv	64.56 (7)
O2iii—Ca1—O3iv	118.06 (7)	Ca1i—Ca1—Ca1iv	144.47 (4)
O2—Ca1—O3iv	118.06 (7)	C1—O1—Ca1iv	154.2 (2)
O3—Ca1—O3iv	144.93 (11)	C1—O1—Ca1	91.54 (19)
O1i—Ca1—O1iii	97.25 (7)	Ca1iv—O1—Ca1	96.69 (7)
O1ii—Ca1—O1iii	149.97 (5)	C1—O2—Ca1	94.01 (18)
O2iii—Ca1—O1iii	52.19 (7)	S1—O3—Ca1	139.05 (18)
O2—Ca1—O1iii	101.88 (8)	S1—O3—Ca1i	127.75 (19)
O3—Ca1—O1iii	136.43 (6)	Ca1—O3—Ca1i	93.19 (9)
O3iv—Ca1—O1iii	67.37 (7)	O2—C1—O1	121.8 (3)
O1i—Ca1—O1	149.97 (5)	O2—C1—C2	120.6 (3)
O1ii—Ca1—O1	97.25 (7)	O1—C1—C2	117.6 (3)
O2iii—Ca1—O1	101.88 (8)	O2—C1—Ca1	60.08 (16)
O2—Ca1—O1	52.19 (7)	O1—C1—Ca1	62.08 (16)
O3—Ca1—O1	136.43 (6)	C2—C1—Ca1	173.4 (2)
O3iv—Ca1—O1	67.37 (7)	C3—C2—C7	118.8 (3)
O1iii—Ca1—O1	71.78 (10)	C3—C2—C1	120.2 (3)
O1i—Ca1—C1iii	93.35 (8)	C7—C2—C1	121.1 (3)
O1ii—Ca1—C1iii	170.72 (8)	C4—C3—C2	120.4 (3)
O2iii—Ca1—C1iii	25.91 (8)	C4—C3—H3	119.8
O2—Ca1—C1iii	97.39 (9)	C2—C3—H3	119.8
O3—Ca1—C1iii	110.58 (8)	C5—C4—C3	120.3 (4)
O3iv—Ca1—C1iii	92.57 (8)	C5—C4—H4	119.9
O1iii—Ca1—C1iii	26.38 (7)	C3—C4—H4	119.9
O1—Ca1—C1iii	88.11 (8)	C6—C5—C4	120.2 (4)
O1i—Ca1—C1	170.72 (8)	C6—C5—H5	119.9
O1ii—Ca1—C1	93.35 (8)	C4—C5—H5	119.9
O2iii—Ca1—C1	97.39 (9)	C5—C6—C7	119.9 (3)
O2—Ca1—C1	25.91 (8)	C5—C6—H6	120.1
O3—Ca1—C1	110.58 (8)	C7—C6—H6	120.1
O3iv—Ca1—C1	92.57 (8)	C2—C7—C6	120.4 (3)
O1iii—Ca1—C1	88.11 (8)	C2—C7—H7	119.8
O1—Ca1—C1	26.38 (7)	C6—C7—H7	119.8
C1iii—Ca1—C1	94.77 (13)	S1—C8—H8A	109.5
O1i—Ca1—Ca1i	43.52 (5)	S1—C8—H8B	109.5
O1ii—Ca1—Ca1i	43.52 (5)	H8A—C8—H8B	109.5
O2iii—Ca1—Ca1i	115.90 (7)	S1—C8—H8C	109.5
O2—Ca1—Ca1i	115.90 (7)	H8A—C8—H8C	109.5
O3—Ca1—Ca1i	43.63 (7)	H8B—C8—H8C	109.5
O3iv—Ca1—Ca1i	101.29 (8)	O3—S1—C8iii	105.78 (14)
O1iii—Ca1—Ca1i	140.76 (5)	O3—S1—C8	105.78 (14)
O1—Ca1—Ca1i	140.76 (5)	C8iii—S1—C8	98.4 (3)

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8A···Cg	0.96	2.84	3.790 (4)	169