Poly[diaqua-di-μ(4)-citrato-trizinc(II)].

The title compound, [Zn(3)(C(6)H(5)O(7))(2)(H(2)O)(2)](n), is a polymer in which the repeating unit contains three zinc atoms, two hepta-dentate Hcit ligands (Hcit = citric acid trianion) and two coordinated water mol-ecules, only half of which are independent due to one of the metal atoms lying on a centre of symmetry. The two independent cations both exhibit an octa-hedral geometry, but the way in which they are coordinate are different; while the Zn atom in a general position is bound to three Hcit ligands and one water mol-ecule, the one at the centre of symmetry is coordinated by six O atoms from two symmetry-related Hcit ligands through the (protonated) hydroxyl and carboxyl-ate groups. The three carboxyl-ate groups coordinate to the Zn centres in three different ways, viz. chelating, bridging and a mixture of both, in an unusual coordination mode for citrate. The result is a two-dimensional structure parallel to (010), built up by a square-grid motif. Intermolecular O-H⋯O hydrogen bonds are present in the crystal structure.

Related literature

For related literature, see: Albrecht et al. (2000 ▶); Dybtsev et al. (2004 ▶); Lightfoot & Sueddden (1999 ▶); Ma et al. (2000 ▶); Xie et al. (2004 ▶, 2005 ▶); Yaghi & Li (1996 ▶); Yaghi & Rowsell (2006 ▶); Zhao et al. (2006 ▶); Zou et al. (2006 ▶).

Experimental

Crystal data

[Zn3(C6H5O7)2(H2O)2]

M = 610.34

Monoclinic,

a = 6.1073 (5) Å

b = 15.3132 (12) Å

c = 9.7858 (8) Å

β = 102.79 (10)°

V = 892.48 (12) Å3

Z = 2

Mo Kα radiation

μ = 4.09 mm−1

T = 298 (2) K

0.20 × 0.18 × 0.18 mm

Data collection

Bruker APEXII area-detector diffractometer

Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ▶) T min = 0.46, T max = 0.48

4693 measured reflections

1749 independent reflections

1694 reflections with I > 2σ(I)

R int = 0.026

Refinement

R[F 2 > 2σ(F 2)] = 0.048

wR(F 2) = 0.233

S = 1.36

1648 reflections

143 parameters

1 restraint

H-atom parameters constrained

Δρmax = 1.18 e Å−3

Δρmin = −1.06 e Å−3

Data collection: APEX2 (Bruker, 2004 ▶); cell refinement: SAINT (Bruker, 2004 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and DIAMOND (Brandenburg, 2004 ▶); software used to prepare material for publication: SHELXTL.

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808007642/bg2172sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808007642/bg2172Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

[Zn3(C6H5O7)2(H2O)2]	F000 = 608
Mr = 610.34	Dx = 2.271 Mg m−3
Monoclinic, P21/c	Mo Kα radiation λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1749 reflections
a = 6.1073 (5) Å	θ = 2.5–26.0º
b = 15.3132 (12) Å	µ = 4.09 mm−1
c = 9.7858 (8) Å	T = 298 (2) K
β = 102.7910 (10)º	Block, colourless
V = 892.48 (12) Å3	0.20 × 0.18 × 0.18 mm
Z = 2

Bruker APEXII area-detector diffractometer	1749 independent reflections
Radiation source: fine-focus sealed tube	1694 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.026
T = 298(2) K	θmax = 26.0º
φ and ω scan	θmin = 2.5º
Absorption correction: multi-scan(SADABS; Sheldrick, 2004)	h = −4→7
Tmin = 0.46, Tmax = 0.48	k = −18→18
4693 measured reflections	l = −12→11

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)] = 0.048	H-atom parameters constrained
wR(F2) = 0.233	w = 1/[σ2(Fo2) + (0.160P)2 + 1.0412P] where P = (Fo2 + 2Fc2)/3
S = 1.36	(Δ/σ)max < 0.001
1648 reflections	Δρmax = 1.18 e Å−3
143 parameters	Δρmin = −1.06 e Å−3
1 restraint	Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.021 (6)

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.Some reflections data are omiited may attributted to their bad reflections.

	x	y	z	Uiso*/Ueq
Zn1	0.5000	0.0000	1.0000	0.0150 (5)
Zn2	0.11561 (9)	0.09674 (4)	0.31681 (6)	0.0129 (5)
O1W	−0.1974 (13)	0.0915 (4)	0.4010 (8)	0.0543 (17)
H1WA	−0.2908	0.0542	0.3686	0.081*
H1WB	−0.1748	0.0841	0.4860	0.081*
O1	0.3216 (12)	0.0872 (4)	0.5521 (7)	0.0506 (17)
O2	0.3258 (10)	0.2105 (4)	0.4410 (7)	0.0473 (14)
O3	0.4296 (10)	0.1275 (4)	0.8697 (6)	0.0427 (13)
H3	0.3866	0.1764	0.8859	0.064*
O4	0.8310 (11)	0.0722 (5)	1.0802 (7)	0.0504 (16)
O5	1.0418 (12)	0.1871 (5)	1.1333 (7)	0.0566 (19)
O6	0.8360 (11)	0.0532 (4)	0.6858 (6)	0.0471 (15)
O7	0.6177 (11)	−0.0177 (4)	0.7974 (7)	0.0464 (15)
C1	0.3868 (13)	0.1633 (5)	0.5492 (8)	0.0383 (17)
C2	0.5471 (15)	0.2027 (5)	0.6762 (9)	0.0408 (19)
H2A	0.4776	0.2546	0.7046	0.049*
H2B	0.6825	0.2210	0.6478	0.049*
C3	0.6146 (12)	0.1423 (6)	0.8041 (8)	0.0349 (17)
C4	0.8172 (15)	0.1853 (6)	0.9036 (9)	0.0419 (19)
H4A	0.9423	0.1854	0.8574	0.050*
H4B	0.7793	0.2458	0.9168	0.050*
C5	0.8961 (12)	0.1437 (5)	1.0478 (8)	0.0356 (16)
C6	0.6918 (13)	0.0533 (5)	0.7569 (8)	0.0360 (17)

	U11	U22	U33	U12	U13	U23
Zn1	0.0192 (7)	0.0147 (7)	0.0113 (7)	−0.0059 (3)	0.0041 (4)	0.0027 (3)
Zn2	0.0151 (6)	0.0123 (6)	0.0095 (6)	0.0008 (2)	−0.0014 (4)	0.0000 (2)
O1W	0.066 (4)	0.056 (4)	0.044 (4)	−0.001 (3)	0.018 (3)	−0.004 (3)
O1	0.061 (4)	0.038 (3)	0.044 (4)	−0.009 (3)	−0.008 (3)	0.005 (3)
O2	0.054 (4)	0.047 (3)	0.036 (3)	−0.007 (3)	0.000 (3)	0.002 (2)
O3	0.049 (3)	0.037 (3)	0.042 (3)	0.007 (3)	0.009 (3)	−0.003 (3)
O4	0.053 (4)	0.051 (4)	0.043 (4)	−0.015 (3)	−0.001 (3)	0.011 (3)
O5	0.060 (4)	0.055 (4)	0.046 (4)	−0.012 (3)	−0.007 (3)	0.008 (3)
O6	0.048 (3)	0.048 (4)	0.047 (3)	0.001 (3)	0.016 (3)	−0.002 (3)
O7	0.059 (4)	0.039 (3)	0.042 (3)	−0.005 (3)	0.012 (3)	0.003 (3)
C1	0.039 (4)	0.040 (4)	0.036 (4)	0.006 (3)	0.008 (3)	0.006 (3)
C2	0.047 (5)	0.033 (4)	0.040 (5)	−0.003 (3)	0.005 (4)	−0.001 (3)
C3	0.035 (4)	0.037 (4)	0.031 (4)	0.002 (3)	0.003 (3)	0.001 (3)
C4	0.045 (5)	0.041 (4)	0.038 (5)	−0.006 (3)	0.006 (4)	−0.003 (3)
C5	0.035 (4)	0.034 (4)	0.035 (4)	−0.002 (3)	0.002 (3)	−0.004 (3)
C6	0.036 (4)	0.041 (4)	0.029 (4)	−0.001 (3)	0.003 (3)	0.001 (3)

Zn1—O7	2.270 (6)	O3—H3	0.82
Zn1—O7i	2.270 (6)	O4—C5	1.231 (10)
Zn1—O4i	2.285 (6)	O5—C5	1.266 (10)
Zn1—O4	2.285 (6)	O5—Zn2iv	2.232 (7)
Zn1—O3i	2.319 (6)	O6—C6	1.237 (9)
Zn1—O3	2.319 (6)	O6—Zn2iii	2.316 (6)
Zn2—O5ii	2.232 (7)	O7—C6	1.273 (10)
Zn2—O1W	2.244 (7)	O7—Zn2iii	2.485 (6)
Zn2—O6iii	2.316 (6)	C1—C2	1.526 (11)
Zn2—O2	2.338 (6)	C2—C3	1.538 (11)
Zn2—O1	2.371 (7)	C2—H2A	0.9700
Zn2—O7iii	2.485 (6)	C2—H2B	0.9700
O1W—H1WA	0.8200	C3—C4	1.543 (11)
O1W—H1WB	0.8200	C3—C6	1.546 (11)
O1—C1	1.233 (10)	C4—C5	1.526 (11)
O2—C1	1.268 (10)	C4—H4A	0.9700
O3—C3	1.435 (9)	C4—H4B	0.9700
O7—Zn1—O7i	180.000 (1)	C3—O3—H3	105.1
O7—Zn1—O4i	94.0 (2)	Zn1—O3—H3	133.7
O7i—Zn1—O4i	86.0 (2)	C5—O4—Zn1	130.9 (5)
O7—Zn1—O4	86.0 (2)	C5—O5—Zn2iv	101.2 (5)
O7i—Zn1—O4	94.0 (2)	C6—O6—Zn2iii	96.6 (5)
O4i—Zn1—O4	180.0	C6—O7—Zn1	111.9 (5)
O7—Zn1—O3i	108.9 (2)	C6—O7—Zn2iii	87.8 (5)
O7i—Zn1—O3i	71.1 (2)	Zn1—O7—Zn2iii	144.8 (3)
O4i—Zn1—O3i	79.9 (2)	O1—C1—O2	121.4 (8)
O4—Zn1—O3i	100.1 (2)	O1—C1—C2	120.5 (7)
O7—Zn1—O3	71.1 (2)	O2—C1—C2	118.1 (7)
O7i—Zn1—O3	108.9 (2)	C1—C2—C3	115.6 (7)
O4i—Zn1—O3	100.1 (2)	C1—C2—H2A	108.4
O4—Zn1—O3	79.9 (2)	C3—C2—H2A	108.4
O3i—Zn1—O3	180.000 (1)	C1—C2—H2B	108.4
O5ii—Zn2—O1W	106.3 (3)	C3—C2—H2B	108.4
O5ii—Zn2—O6iii	127.5 (3)	H2A—C2—H2B	107.4
O1W—Zn2—O6iii	95.1 (2)	O3—C3—C2	111.3 (6)
O5ii—Zn2—O2	86.9 (2)	O3—C3—C4	112.7 (6)
O1W—Zn2—O2	104.5 (2)	C2—C3—C4	106.8 (7)
O6iii—Zn2—O2	133.4 (2)	O3—C3—C6	108.5 (6)
O5ii—Zn2—O1	142.1 (2)	C2—C3—C6	109.4 (6)
O1W—Zn2—O1	87.3 (3)	C4—C3—C6	108.1 (6)
O6iii—Zn2—O1	84.7 (2)	C5—C4—C3	116.7 (7)
O2—Zn2—O1	55.2 (2)	C5—C4—H4A	108.1
O5ii—Zn2—O7iii	88.6 (3)	C3—C4—H4A	108.1
O1W—Zn2—O7iii	147.6 (2)	C5—C4—H4B	108.1
O6iii—Zn2—O7iii	54.1 (2)	C3—C4—H4B	108.1
O2—Zn2—O7iii	104.9 (2)	H4A—C4—H4B	107.3
O1—Zn2—O7iii	98.5 (2)	O4—C5—O5	121.1 (7)
Zn2—O1W—H1WA	117.3	O4—C5—C4	123.8 (7)
Zn2—O1W—H1WB	114.3	O5—C5—C4	115.1 (7)
H1WA—O1W—H1WB	104.0	O6—C6—O7	121.4 (8)
C1—O1—Zn2	91.4 (5)	O6—C6—C3	118.1 (7)
C1—O2—Zn2	92.0 (5)	O7—C6—C3	120.4 (7)
C3—O3—Zn1	108.1 (4)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O2v	0.82	1.88	2.691 (8)	172
O1W—H1WA···O7vi	0.82	2.35	3.071 (10)	148
O1W—H1WB···O6vii	0.82	2.00	2.811 (10)	171

Table 1

Selected bond lengths (Å)

Zn1—O7	2.270 (6)
Zn1—O4	2.285 (6)
Zn1—O3	2.319 (6)
Zn2—O5i	2.232 (7)
Zn2—O1W	2.244 (7)
Zn2—O6ii	2.316 (6)
Zn2—O2	2.338 (6)
Zn2—O1	2.371 (7)
Zn2—O7ii	2.485 (6)

Symmetry codes: (i) ; (ii) .

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O2iii	0.82	1.88	2.691 (8)	172
O1W—H1WA⋯O7iv	0.82	2.35	3.071 (10)	148
O1W—H1WB⋯O6v	0.82	2.00	2.811 (10)	171

Symmetry codes: (iii) ; (iv) ; (v) .