Calcium tartrate esahydrate, CaC₄H₄O₆·6H₂O: a structural and spectroscopic study

The crystal structure of calcium tartrate esahydrate, CaC₄H₄O₆·6H₂O, has been solved by the charge-flipping method from single-crystal X-ray diffraction data and refined to R = 0.021, based on 1700 unique observed diffractions. Salient crystallographic data are: a = 7.7390 (1), b = 12.8030 (2), c = 5.8290 (1) Å, Z = 2, and space group P2₁2₁2. During the refinement step it was possible to locate all H atoms by difference Fourier synthesis. The tartrate molecule has a (-)-gauche conformation and is coordinated to two calcium ions to form infinite chains along the a axis which alternate Ca polyhedra with tartrate molecules. The chains are interlinked by a three-dimensional network of hydrogen bonds from four water molecules surrounding the Ca ion, reinforced by hydrogen bonds from one interstitial water molecule. Micro-Raman and FT-IR spectroscopic data are provided.

S1. Experimental

S1.1. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

S2. Results and discussion

Computing details

Program(s) used to refine structure: SHELXL2013 (Sheldrick, 2013).

Figures

(I)

Crystal data

C4H16CaO12	Z = 2
Mr = 296.25	F(000) = 312
Orthorhombic, P21212	Dx = 1.704 Mg m^−3
a = 7.7390 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 12.8030 (2) Å	µ = 0.60 mm^−1
c = 5.8290 (1) Å	T = 293 K
V = 577.55 (2) Å^3	0.22 × 0.20 × 0.07 mm

Data collection

Bruker APEXII diffractometer	θmax = 30.5°, θmin = 3.1°
8303 measured reflections	h = −10→11
1759 independent reflections	k = −17→18
1700 reflections with I > 2σ(I)	l = −8→6
Rint = 0.025

Refinement

Refinement on F^2	Hydrogen site location: difference Fourier map
Least-squares matrix: full	Only H-atom coordinates refined
R[F^2 > 2σ(F^2)] = 0.021	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.075	(Δ/σ)max < 0.001
S = 0.68	Δρmax = 0.29 e Å^−3
1759 reflections	Δρmin = −0.19 e Å^−3
102 parameters	Absolute structure: Flack x determined using 679 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons and Flack (2004), Acta Cryst. A60, s61).
8 restraints	Absolute structure parameter: −0.173 (15)

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
Ca1	0.0000	0.5000	0.31079 (6)	0.01632 (12)
O1	−0.01771 (16)	0.37975 (10)	−0.00915 (19)	0.0242 (2)
O2	0.18578 (15)	0.53433 (11)	0.6286 (2)	0.0263 (3)
O3	0.42004 (16)	0.60400 (11)	0.7860 (2)	0.0287 (3)
O4	0.31487 (15)	0.53668 (11)	0.2164 (2)	0.0267 (3)
O5	0.1153 (3)	0.32751 (12)	0.4185 (3)	0.0450 (4)
O6	0.22163 (16)	0.79013 (10)	0.1646 (3)	0.0325 (3)
C1	0.34089 (18)	0.56254 (11)	0.6220 (2)	0.0177 (3)
C2	0.43903 (19)	0.54806 (11)	0.3954 (2)	0.0178 (2)
H1	0.079 (3)	0.3486 (18)	−0.059 (5)	0.029*
H2	−0.065 (3)	0.4106 (17)	−0.129 (4)	0.029*
H3	0.166 (4)	0.311 (3)	0.551 (5)	0.054*
H4	0.141 (4)	0.275 (2)	0.323 (6)	0.054*
H5	0.132 (3)	0.833 (2)	0.165 (6)	0.039*
H6	0.188 (4)	0.7346 (19)	0.092 (5)	0.039*
H7	0.508 (3)	0.6119 (16)	0.376 (4)	0.021*
H8	0.359 (3)	0.560 (2)	0.085 (4)	0.032*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ca1	0.01416 (17)	0.02106 (19)	0.01374 (18)	−0.00108 (12)	0.000	0.000
O1	0.0233 (5)	0.0320 (5)	0.0173 (5)	0.0057 (4)	−0.0001 (4)	0.0006 (4)
O2	0.0159 (4)	0.0431 (6)	0.0198 (5)	−0.0054 (5)	0.0036 (4)	−0.0066 (4)
O3	0.0235 (5)	0.0429 (6)	0.0198 (5)	−0.0088 (5)	−0.0012 (4)	−0.0071 (5)
O4	0.0165 (4)	0.0488 (7)	0.0149 (4)	0.0020 (5)	−0.0017 (4)	0.0060 (5)
O5	0.0694 (11)	0.0289 (6)	0.0368 (8)	0.0064 (7)	−0.0244 (8)	−0.0017 (6)
O6	0.0222 (5)	0.0302 (6)	0.0452 (8)	−0.0029 (4)	−0.0006 (5)	−0.0055 (6)
C1	0.0160 (6)	0.0219 (6)	0.0152 (5)	0.0009 (4)	0.0009 (4)	−0.0014 (5)
C2	0.0135 (5)	0.0255 (6)	0.0144 (5)	0.0009 (5)	−0.0001 (4)	0.0010 (5)

Geometric parameters (Å, º)

Ca1—O1	2.4222 (12)	Ca1—O4	2.5419 (12)
Ca1—O1^i	2.4222 (12)	O2—C1	1.2541 (18)
Ca1—O2	2.3858 (12)	O3—C1	1.2535 (18)
Ca1—O2^i	2.3858 (12)	O4—C2	1.4259 (18)
Ca1—O5	2.4631 (15)	C1—C2	1.535 (2)
Ca1—O5^i	2.4631 (15)	C2—C2^ii	1.551 (3)
Ca1—O4^i	2.5419 (12)
O1—Ca1—O1^i	79.30 (6)	O2^i—Ca1—O4^i	63.66 (4)
O1—Ca1—O2	138.50 (4)	O5—Ca1—O4^i	103.70 (5)
O1^i—Ca1—O2	116.53 (4)	O5^i—Ca1—O4^i	82.74 (6)
O1—Ca1—O2^i	116.53 (4)	O1—Ca1—O4	90.29 (4)
O1^i—Ca1—O2^i	138.50 (4)	O1^i—Ca1—O4	70.22 (4)
O2—Ca1—O2^i	78.13 (6)	O2—Ca1—O4	63.66 (4)
O1—Ca1—O5	69.32 (5)	O2^i—Ca1—O4	141.25 (4)
O1^i—Ca1—O5	138.21 (6)	O5—Ca1—O4	82.74 (6)
O2—Ca1—O5	75.46 (5)	O5^i—Ca1—O4	103.70 (5)
O2^i—Ca1—O5	81.68 (6)	O4^i—Ca1—O4	154.99 (5)
O1—Ca1—O5^i	138.21 (6)	C1—O2—Ca1	127.30 (10)
O1^i—Ca1—O5^i	69.32 (5)	C2—O4—Ca1	120.43 (9)
O2—Ca1—O5^i	81.68 (6)	O2—C1—O3	124.49 (14)
O2^i—Ca1—O5^i	75.46 (5)	O2—C1—C2	117.73 (13)
O5—Ca1—O5^i	150.47 (9)	O3—C1—C2	117.76 (13)
O1—Ca1—O4^i	70.22 (4)	O4—C2—C1	107.98 (12)
O1^i—Ca1—O4^i	90.29 (4)	O4—C2—C2^ii	109.20 (11)
O2—Ca1—O4^i	141.25 (4)	C1—C2—C2^ii	113.39 (9)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O6^iii	0.90 (2)	1.82 (2)	2.7180 (17)	178 (2)
O1—H2···O2^iv	0.88 (2)	1.83 (2)	2.7131 (16)	173 (3)
O4—H8···O3^v	0.89 (2)	1.89 (2)	2.7746 (18)	171 (2)
O5—H3···O6^vi	0.89 (2)	1.89 (2)	2.780 (2)	174 (3)
O5—H4···O3^vi	0.90 (2)	2.33 (3)	3.112 (2)	146 (3)
O6—H5···O3^vii	0.88 (2)	1.85 (2)	2.7143 (18)	165 (3)
O6—H6···O1^i	0.87 (2)	2.06 (2)	2.8717 (18)	156 (3)

Symmetry codes: (i) −x, −y+1, z; (iii) −x+1/2, y−1/2, −z; (iv) −x, −y+1, z−1; (v) x, y, z−1; (vi) −x+1/2, y−1/2, −z+1; (vii) x−1/2, −y+3/2, −z+1.