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The molecule of the title compound, [Zn(C2H3O2)2(H2O)2], is located on a twofold axis in the crystal structure. The displacement parameters and the thermal expansion of the crystal show significant anisotropy. This is explained by the two-dimensional hydrogen-bonded structure, with only very weak interactions perpendicular to it. Besides the overall molecular motion, there are internal vibrations, which cause the Zn—O(carboxylate) bonds to fail the Hirshfeld rigid-bond test. It is shown that this can be interpreted in terms of the steric strain in the four-membered chelate ring due to the bidentate carboxylate coordination.
Supporting information
CCDC references: 724184; 724185
Crystals of (I) were unintentionally obtained by slow evaporation of an aqueous
solution of zinc acetate in the presence of urea in a molar ratio of 1:2 at
room temperature.
Because many effects discussed in this paper might be influenced by the
correctness of the absorption correction, special care was taken to index the
crystal faces and measure their distances. This information was used for the
numerical absorption correction in the program SADABS (Sheldrick,
2008a), which additionally refines spherical harmonics functions
based
on multiple measured reflections to improve further the reliability of the
data.
The O-bound H atoms of the water molecule were located in a difference Fourier
map and refined freely with isotropic displacement parameters. The difference
density map in the plane of the methyl H atoms does not show distinct maxima.
The methyl H atoms were therefore introduced in calculated positions and
refined with an AFIX 137 card (SHELXL97; Sheldrick, 1998b) using
a large number of refinement cycles [Please give specific constraints
used].
For both compounds, data collection: COLLECT (Nonius, 1999); cell refinement: PEAKREF (Schreurs, 2008); data reduction: PIXEL15 (Xian et al., 2006) and SADABS (Sheldrick, 2008a); program(s) used to solve structure: initial coordinates from Ishioka et al. (1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: manual editing of SHELXL97 (Sheldrick, 2008b) output.
(Ia) bis(acetato-
κ2O,O')diaquazinc(II)
top
Crystal data top
[Zn(C2H3O2)2(H2O)2] | F(000) = 448 |
Mr = 219.49 | Dx = 1.807 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 3489 reflections |
a = 13.8556 (2) Å | θ = 1.9–27.5° |
b = 5.38096 (7) Å | µ = 3.03 mm−1 |
c = 10.92487 (14) Å | T = 110 K |
β = 97.942 (1)° | Plate, colourless |
V = 806.71 (2) Å3 | 0.42 × 0.30 × 0.06 mm |
Z = 4 | |
Data collection top
Nonius KappaCCD area-detector diffractometer | 925 independent reflections |
Radiation source: rotating anode | 898 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.015 |
ϕ and ω scans | θmax = 27.5°, θmin = 3.0° |
Absorption correction: numerical (SADABS; Sheldrick, 2008a) | h = −18→18 |
Tmin = 0.408, Tmax = 0.856 | k = −6→6 |
6788 measured reflections | l = −14→14 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.016 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.045 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0247P)2 + 1.0186P] where P = (Fo2 + 2Fc2)/3 |
925 reflections | (Δ/σ)max = 0.004 |
60 parameters | Δρmax = 0.35 e Å−3 |
0 restraints | Δρmin = −0.47 e Å−3 |
Crystal data top
[Zn(C2H3O2)2(H2O)2] | V = 806.71 (2) Å3 |
Mr = 219.49 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 13.8556 (2) Å | µ = 3.03 mm−1 |
b = 5.38096 (7) Å | T = 110 K |
c = 10.92487 (14) Å | 0.42 × 0.30 × 0.06 mm |
β = 97.942 (1)° | |
Data collection top
Nonius KappaCCD area-detector diffractometer | 925 independent reflections |
Absorption correction: numerical (SADABS; Sheldrick, 2008a) | 898 reflections with I > 2σ(I) |
Tmin = 0.408, Tmax = 0.856 | Rint = 0.015 |
6788 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.016 | 0 restraints |
wR(F2) = 0.045 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | Δρmax = 0.35 e Å−3 |
925 reflections | Δρmin = −0.47 e Å−3 |
60 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Zn1 | 0.0000 | 0.11907 (4) | 0.2500 | 0.01426 (9) | |
O1 | −0.08735 (8) | −0.1237 (2) | 0.14848 (10) | 0.0180 (2) | |
H1O | −0.0966 (15) | −0.250 (5) | 0.175 (2) | 0.029 (6)* | |
H2O | −0.0823 (16) | −0.139 (4) | 0.081 (2) | 0.028 (6)* | |
O2 | 0.10704 (8) | 0.42204 (19) | 0.26068 (9) | 0.0191 (2) | |
O3 | 0.06989 (8) | 0.2111 (2) | 0.09043 (9) | 0.0195 (2) | |
C1 | 0.11449 (10) | 0.3916 (2) | 0.14763 (13) | 0.0152 (3) | |
C2 | 0.17317 (11) | 0.5694 (3) | 0.08262 (14) | 0.0209 (3) | |
H2A | 0.1334 | 0.7153 | 0.0559 | 0.031* | |
H2B | 0.1937 | 0.4878 | 0.0103 | 0.031* | |
H2C | 0.2308 | 0.6217 | 0.1391 | 0.031* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Zn1 | 0.02348 (14) | 0.00915 (13) | 0.01049 (12) | 0.000 | 0.00356 (8) | 0.000 |
O1 | 0.0309 (6) | 0.0123 (5) | 0.0110 (5) | −0.0039 (4) | 0.0040 (4) | 0.0004 (4) |
O2 | 0.0316 (6) | 0.0137 (5) | 0.0124 (5) | 0.0019 (4) | 0.0045 (4) | 0.0004 (4) |
O3 | 0.0290 (5) | 0.0159 (5) | 0.0142 (5) | −0.0061 (4) | 0.0048 (4) | −0.0012 (4) |
C1 | 0.0189 (6) | 0.0130 (7) | 0.0136 (6) | 0.0028 (5) | 0.0018 (5) | 0.0019 (5) |
C2 | 0.0253 (7) | 0.0201 (7) | 0.0176 (7) | −0.0056 (6) | 0.0040 (6) | 0.0016 (6) |
Geometric parameters (Å, º) top
Zn1—O1 | 2.0076 (11) | O1—H1O | 0.76 (2) |
Zn1—O1i | 2.0076 (11) | O1—H2O | 0.76 (2) |
Zn1—O3i | 2.1653 (10) | O2—C1 | 1.2641 (18) |
Zn1—O3 | 2.1653 (10) | O3—C1 | 1.2685 (17) |
Zn1—O2 | 2.1962 (11) | C1—C2 | 1.4970 (19) |
Zn1—O2i | 2.1962 (11) | C2—H2A | 0.9800 |
Zn1—C1i | 2.5313 (14) | C2—H2B | 0.9800 |
Zn1—C1 | 2.5313 (14) | C2—H2C | 0.9800 |
| | | |
O1—Zn1—O1i | 98.81 (7) | O3i—Zn1—C1 | 126.91 (4) |
O1—Zn1—O3i | 106.92 (4) | O3—Zn1—C1 | 30.07 (4) |
O1i—Zn1—O3i | 90.37 (4) | O2—Zn1—C1 | 29.96 (4) |
O1—Zn1—O3 | 90.37 (4) | O2i—Zn1—C1 | 90.36 (4) |
O1i—Zn1—O3 | 106.92 (4) | C1i—Zn1—C1 | 109.20 (6) |
O3i—Zn1—O3 | 153.57 (6) | Zn1—O1—H1O | 119.4 (16) |
O1—Zn1—O2 | 149.71 (4) | Zn1—O1—H2O | 118.7 (16) |
O1i—Zn1—O2 | 95.88 (4) | H1O—O1—H2O | 109 (2) |
O3i—Zn1—O2 | 99.29 (4) | C1—O2—Zn1 | 89.86 (8) |
O3—Zn1—O2 | 59.95 (4) | C1—O3—Zn1 | 91.15 (8) |
O1—Zn1—O2i | 95.88 (4) | O2—C1—O3 | 118.73 (13) |
O1i—Zn1—O2i | 149.71 (4) | O2—C1—C2 | 120.24 (13) |
O3i—Zn1—O2i | 59.95 (4) | O3—C1—C2 | 121.01 (13) |
O3—Zn1—O2i | 99.29 (4) | O2—C1—Zn1 | 60.18 (7) |
O2—Zn1—O2i | 84.14 (6) | O3—C1—Zn1 | 58.79 (7) |
O1—Zn1—C1i | 104.73 (4) | C2—C1—Zn1 | 174.02 (10) |
O1i—Zn1—C1i | 119.98 (5) | C1—C2—H2A | 109.5 |
O3i—Zn1—C1i | 30.07 (4) | C1—C2—H2B | 109.5 |
O3—Zn1—C1i | 126.91 (4) | H2A—C2—H2B | 109.5 |
O2—Zn1—C1i | 90.36 (4) | C1—C2—H2C | 109.5 |
O2i—Zn1—C1i | 29.96 (4) | H2A—C2—H2C | 109.5 |
O1—Zn1—C1 | 119.98 (5) | H2B—C2—H2C | 109.5 |
O1i—Zn1—C1 | 104.73 (4) | | |
| | | |
O1—Zn1—O2—C1 | −9.34 (13) | Zn1—O3—C1—O2 | 5.64 (13) |
O1i—Zn1—O2—C1 | 109.46 (8) | Zn1—O3—C1—C2 | −173.02 (12) |
O3i—Zn1—O2—C1 | −159.20 (8) | O1—Zn1—C1—O2 | 174.58 (8) |
O3—Zn1—O2—C1 | 3.30 (8) | O1i—Zn1—C1—O2 | −75.88 (9) |
O2i—Zn1—O2—C1 | −100.99 (9) | O3i—Zn1—C1—O2 | 26.00 (10) |
C1i—Zn1—O2—C1 | −130.35 (8) | O3—Zn1—C1—O2 | −174.30 (13) |
O1—Zn1—O3—C1 | 170.38 (9) | O2i—Zn1—C1—O2 | 77.57 (9) |
O1i—Zn1—O3—C1 | −90.29 (9) | C1i—Zn1—C1—O2 | 53.80 (7) |
O3i—Zn1—O3—C1 | 38.55 (8) | O1—Zn1—C1—O3 | −11.12 (10) |
O2—Zn1—O3—C1 | −3.28 (8) | O1i—Zn1—C1—O3 | 98.42 (9) |
O2i—Zn1—O3—C1 | 74.35 (8) | O3i—Zn1—C1—O3 | −159.70 (6) |
C1i—Zn1—O3—C1 | 61.54 (12) | O2—Zn1—C1—O3 | 174.30 (13) |
Zn1—O2—C1—O3 | −5.56 (13) | O2i—Zn1—C1—O3 | −108.13 (8) |
Zn1—O2—C1—C2 | 173.11 (12) | C1i—Zn1—C1—O3 | −131.90 (9) |
Symmetry code: (i) −x, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···O2ii | 0.76 (2) | 1.91 (3) | 2.6663 (15) | 174 (2) |
O1—H2O···O3iii | 0.76 (2) | 1.94 (2) | 2.6956 (15) | 175 (2) |
Symmetry codes: (ii) −x, y−1, −z+1/2; (iii) −x, −y, −z. |
(Ib) bis(acetato-
κ2O,O')diaquazinc(II)
top
Crystal data top
[Zn(C2H3O2)2(H2O)2] | F(000) = 448 |
Mr = 219.49 | Dx = 1.767 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 3506 reflections |
a = 14.2904 (5) Å | θ = 1.9–27.5° |
b = 5.34245 (11) Å | µ = 2.96 mm−1 |
c = 10.9616 (2) Å | T = 250 K |
β = 99.590 (1)° | Plate, colourless |
V = 825.17 (4) Å3 | 0.42 × 0.30 × 0.06 mm |
Z = 4 | |
Data collection top
Nonius KappaCCD area-detector diffractometer | 940 independent reflections |
Radiation source: rotating anode | 888 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.017 |
ϕ and ω scans | θmax = 27.5°, θmin = 2.9° |
Absorption correction: numerical (SADABS; Sheldrick, 2008a) | h = −18→18 |
Tmin = 0.405, Tmax = 0.864 | k = −6→6 |
6929 measured reflections | l = −14→14 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.020 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.056 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0338P)2 + 0.4592P] where P = (Fo2 + 2Fc2)/3 |
940 reflections | (Δ/σ)max = 0.005 |
60 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.30 e Å−3 |
Crystal data top
[Zn(C2H3O2)2(H2O)2] | V = 825.17 (4) Å3 |
Mr = 219.49 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 14.2904 (5) Å | µ = 2.96 mm−1 |
b = 5.34245 (11) Å | T = 250 K |
c = 10.9616 (2) Å | 0.42 × 0.30 × 0.06 mm |
β = 99.590 (1)° | |
Data collection top
Nonius KappaCCD area-detector diffractometer | 940 independent reflections |
Absorption correction: numerical (SADABS; Sheldrick, 2008a) | 888 reflections with I > 2σ(I) |
Tmin = 0.405, Tmax = 0.864 | Rint = 0.017 |
6929 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.020 | 0 restraints |
wR(F2) = 0.056 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | Δρmax = 0.29 e Å−3 |
940 reflections | Δρmin = −0.30 e Å−3 |
60 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Zn1 | 0.0000 | 0.12885 (4) | 0.2500 | 0.03453 (12) | |
O1 | −0.08474 (11) | −0.1154 (2) | 0.14588 (13) | 0.0419 (3) | |
H1O | −0.0962 (18) | −0.229 (5) | 0.171 (2) | 0.055 (8)* | |
H2O | −0.0805 (17) | −0.136 (4) | 0.076 (2) | 0.051 (7)* | |
O2 | 0.10495 (11) | 0.4302 (2) | 0.26044 (11) | 0.0459 (3) | |
O3 | 0.07017 (10) | 0.2153 (3) | 0.09191 (11) | 0.0464 (3) | |
C1 | 0.11407 (13) | 0.3949 (3) | 0.14928 (15) | 0.0353 (3) | |
C2 | 0.17375 (15) | 0.5666 (4) | 0.08771 (18) | 0.0488 (4) | |
H2A | 0.1381 | 0.7172 | 0.0615 | 0.073* | |
H2B | 0.1916 | 0.4840 | 0.0162 | 0.073* | |
H2C | 0.2305 | 0.6105 | 0.1454 | 0.073* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Zn1 | 0.05210 (19) | 0.02247 (16) | 0.02942 (16) | 0.000 | 0.00798 (11) | 0.000 |
O1 | 0.0673 (9) | 0.0299 (7) | 0.0291 (6) | −0.0097 (6) | 0.0097 (6) | −0.0005 (5) |
O2 | 0.0757 (9) | 0.0321 (6) | 0.0319 (6) | 0.0065 (6) | 0.0151 (6) | 0.0012 (5) |
O3 | 0.0667 (8) | 0.0389 (7) | 0.0354 (6) | −0.0148 (6) | 0.0140 (6) | −0.0033 (5) |
C1 | 0.0444 (9) | 0.0301 (8) | 0.0316 (8) | 0.0057 (6) | 0.0068 (6) | 0.0032 (6) |
C2 | 0.0573 (11) | 0.0470 (10) | 0.0431 (10) | −0.0132 (9) | 0.0114 (8) | 0.0008 (8) |
Geometric parameters (Å, º) top
Zn1—O1 | 2.0027 (13) | O1—H1O | 0.69 (3) |
Zn1—O1i | 2.0027 (13) | O1—H2O | 0.78 (3) |
Zn1—O2i | 2.1904 (15) | O2—C1 | 1.261 (2) |
Zn1—O2 | 2.1904 (15) | O3—C1 | 1.257 (2) |
Zn1—O3i | 2.1910 (12) | C1—C2 | 1.489 (2) |
Zn1—O3 | 2.1911 (12) | C2—H2A | 0.9700 |
Zn1—C1i | 2.5488 (17) | C2—H2B | 0.9700 |
Zn1—C1 | 2.5489 (17) | C2—H2C | 0.9700 |
| | | |
O1—Zn1—O1i | 98.70 (8) | O2i—Zn1—C1 | 92.82 (5) |
O1—Zn1—O3i | 105.96 (6) | O2—Zn1—C1 | 29.65 (5) |
O1i—Zn1—O3i | 89.97 (5) | O3i—Zn1—C1 | 129.43 (5) |
O1—Zn1—O3 | 89.97 (5) | O3—Zn1—C1 | 29.53 (5) |
O1i—Zn1—O3 | 105.96 (6) | C1i—Zn1—C1 | 112.20 (7) |
O3i—Zn1—O3 | 155.68 (8) | Zn1—O1—H1O | 120 (2) |
O1—Zn1—O2 | 148.47 (5) | Zn1—O1—H2O | 120.5 (17) |
O1i—Zn1—O2 | 96.05 (6) | H1O—O1—H2O | 109 (2) |
O2i—Zn1—O3 | 101.74 (5) | C1—O2—Zn1 | 91.13 (11) |
O2—Zn1—O3 | 59.13 (5) | C1—O3—Zn1 | 91.22 (10) |
O1—Zn1—O2i | 96.05 (6) | O3—C1—O2 | 118.33 (16) |
O1i—Zn1—O2i | 148.48 (5) | O3—C1—C2 | 121.31 (16) |
O2i—Zn1—O3i | 59.13 (5) | O2—C1—C2 | 120.34 (16) |
O2—Zn1—O3i | 101.74 (5) | O3—C1—Zn1 | 59.25 (9) |
O2i—Zn1—O2 | 85.37 (7) | O2—C1—Zn1 | 59.23 (10) |
O1—Zn1—C1i | 103.92 (6) | C2—C1—Zn1 | 174.93 (13) |
O1i—Zn1—C1i | 119.09 (6) | C1—C2—H2A | 109.5 |
O2i—Zn1—C1i | 29.65 (5) | C1—C2—H2B | 109.5 |
O2—Zn1—C1i | 92.82 (5) | H2A—C2—H2B | 109.5 |
O3i—Zn1—C1i | 29.53 (5) | C1—C2—H2C | 109.5 |
O3—Zn1—C1i | 129.43 (5) | H2A—C2—H2C | 109.5 |
O1—Zn1—C1 | 119.08 (6) | H2B—C2—H2C | 109.5 |
O1i—Zn1—C1 | 103.92 (6) | | |
| | | |
O1—Zn1—O2—C1 | −9.98 (17) | Zn1—O2—C1—O3 | −4.47 (17) |
O1i—Zn1—O2—C1 | 107.63 (11) | Zn1—O2—C1—C2 | 174.14 (15) |
O2i—Zn1—O2—C1 | −104.00 (11) | O1—Zn1—C1—O3 | −10.53 (13) |
O3i—Zn1—O2—C1 | −161.14 (10) | O1i—Zn1—C1—O3 | 97.90 (11) |
O3—Zn1—O2—C1 | 2.63 (10) | O2i—Zn1—C1—O3 | −109.05 (11) |
C1i—Zn1—O2—C1 | −132.72 (10) | O2—Zn1—C1—O3 | 175.42 (17) |
O1—Zn1—O3—C1 | 170.81 (11) | O3i—Zn1—C1—O3 | −160.39 (8) |
O1i—Zn1—O3—C1 | −90.15 (11) | C1i—Zn1—C1—O3 | −132.16 (12) |
O2i—Zn1—O3—C1 | 74.64 (11) | O1—Zn1—C1—O2 | 174.05 (10) |
O2—Zn1—O3—C1 | −2.64 (10) | O1i—Zn1—C1—O2 | −77.52 (11) |
O3i—Zn1—O3—C1 | 39.01 (10) | O2i—Zn1—C1—O2 | 75.53 (12) |
C1i—Zn1—O3—C1 | 62.69 (15) | O3i—Zn1—C1—O2 | 24.19 (13) |
Zn1—O3—C1—O2 | 4.47 (17) | O3—Zn1—C1—O2 | −175.42 (17) |
Zn1—O3—C1—C2 | −174.12 (16) | C1i—Zn1—C1—O2 | 52.42 (9) |
Symmetry code: (i) −x, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···O2ii | 0.69 (3) | 1.98 (3) | 2.6702 (19) | 169 (3) |
O1—H2O···O3iii | 0.78 (3) | 1.92 (3) | 2.7023 (18) | 175 (2) |
Symmetry codes: (ii) −x, y−1, −z+1/2; (iii) −x, −y, −z. |
Experimental details
| (Ia) | (Ib) |
Crystal data |
Chemical formula | [Zn(C2H3O2)2(H2O)2] | [Zn(C2H3O2)2(H2O)2] |
Mr | 219.49 | 219.49 |
Crystal system, space group | Monoclinic, C2/c | Monoclinic, C2/c |
Temperature (K) | 110 | 250 |
a, b, c (Å) | 13.8556 (2), 5.38096 (7), 10.92487 (14) | 14.2904 (5), 5.34245 (11), 10.9616 (2) |
β (°) | 97.942 (1) | 99.590 (1) |
V (Å3) | 806.71 (2) | 825.17 (4) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 3.03 | 2.96 |
Crystal size (mm) | 0.42 × 0.30 × 0.06 | 0.42 × 0.30 × 0.06 |
|
Data collection |
Diffractometer | Nonius KappaCCD area-detector diffractometer | Nonius KappaCCD area-detector diffractometer |
Absorption correction | Numerical (SADABS; Sheldrick, 2008a) | Numerical (SADABS; Sheldrick, 2008a) |
Tmin, Tmax | 0.408, 0.856 | 0.405, 0.864 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6788, 925, 898 | 6929, 940, 888 |
Rint | 0.015 | 0.017 |
(sin θ/λ)max (Å−1) | 0.650 | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.016, 0.045, 1.10 | 0.020, 0.056, 1.10 |
No. of reflections | 925 | 940 |
No. of parameters | 60 | 60 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.35, −0.47 | 0.29, −0.30 |
Selected geometric parameters (Å, º) for (Ia) topZn1—O1 | 2.0076 (11) | O2—C1 | 1.2641 (18) |
Zn1—O3 | 2.1653 (10) | O3—C1 | 1.2685 (17) |
Zn1—O2 | 2.1962 (11) | | |
| | | |
O1—Zn1—O1i | 98.81 (7) | O1—Zn1—O2i | 95.88 (4) |
O1—Zn1—O3i | 106.92 (4) | O3—Zn1—O2i | 99.29 (4) |
O1—Zn1—O3 | 90.37 (4) | O2—Zn1—O2i | 84.14 (6) |
O3i—Zn1—O3 | 153.57 (6) | C1—O2—Zn1 | 89.86 (8) |
O1—Zn1—O2 | 149.71 (4) | C1—O3—Zn1 | 91.15 (8) |
O3—Zn1—O2 | 59.95 (4) | O2—C1—O3 | 118.73 (13) |
Symmetry code: (i) −x, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) for (Ia) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···O2ii | 0.76 (2) | 1.91 (3) | 2.6663 (15) | 174 (2) |
O1—H2O···O3iii | 0.76 (2) | 1.94 (2) | 2.6956 (15) | 175 (2) |
Symmetry codes: (ii) −x, y−1, −z+1/2; (iii) −x, −y, −z. |
Selected geometric parameters (Å, º) for (Ib) topZn1—O1 | 2.0027 (13) | O2—C1 | 1.261 (2) |
Zn1—O2 | 2.1904 (15) | O3—C1 | 1.257 (2) |
Zn1—O3 | 2.1911 (12) | | |
| | | |
O1—Zn1—O1i | 98.70 (8) | O1—Zn1—O2i | 96.05 (6) |
O1—Zn1—O3i | 105.96 (6) | O2—Zn1—O3i | 101.74 (5) |
O1—Zn1—O3 | 89.97 (5) | O2i—Zn1—O2 | 85.37 (7) |
O3i—Zn1—O3 | 155.68 (8) | C1—O2—Zn1 | 91.13 (11) |
O1—Zn1—O2 | 148.47 (5) | C1—O3—Zn1 | 91.22 (10) |
O2—Zn1—O3 | 59.13 (5) | O3—C1—O2 | 118.33 (16) |
Symmetry code: (i) −x, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) for (Ib) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···O2ii | 0.69 (3) | 1.98 (3) | 2.6702 (19) | 169 (3) |
O1—H2O···O3iii | 0.78 (3) | 1.92 (3) | 2.7023 (18) | 175 (2) |
Symmetry codes: (ii) −x, y−1, −z+1/2; (iii) −x, −y, −z. |
Hirshfeld rigid-bond test (Hirshfeld, 1976) of the Zn—O(carboxylate)
bonds.
Comparison of (Ia), (Ib) and ZNAQAC03 (Ishioka et al., 1997)
with zinc
carboxylate structures extracted from Acta Crystallographica. The structures
are identified by their refcode in the Cambridge Structural Database (Allen,
2002). Only the maximum m.s.d.a. values are given. Structures FAXPEA
and UMIBIB
have been omitted because of disorder topCSD refcode | Site symmetry Zn | T (K) | Δ m.s.d.a. (Å2) | Δ m.s.d.a./σ |
(Ia) | 2 | 110 | 0.0080 (5) | 16.06 |
(Ib) | 2 | 250 | 0.0221 (7) | 31.62 |
ZNAQAC03 | 2 | 292 | 0.0272 (25) | 10.87 |
ACOGIJ01 | 1 | 298 | 0.0141 (12) | 11.72 |
CEHCAT01 | 2 | 160 | 0.0047 (9) | 5.18 |
CICHOM | 2 | 293 | 0.0276 (12) | 22.99 |
EDUNOH | 2 | 292 | 0.0050 (9) | 5.61 |
EXOZUM | 1 | 293 | 0.0260 (27) | 9.62 |
EYOVOD | 1 | 293 | 0.0276 (19) | 14.55 |
EYOVUJ | 1 | 293 | 0.0102 (17) | 6.01 |
FERQID | 1 | 293 | 0.0244 (8) | 30.48 |
GAVPAV | 1 | 295 | 0.0350 (37) | 9.47 |
GETZOV | 1 | 293 | 0.0134 (24) | 5.58 |
GIMHUG | 1 | 263 | 0.0133 (30) | 4.43 |
HAMMOY | 1 | 293 | 0.0368 (14) | 26.30 |
HAYTOR | 1 | 295 | 0.0357 (14) | 25.49 |
HAYXIP | 1 | 234 | 0.0120 (14) | 8.57 |
HIQDIV | 1 | 295 | 0.0046 (8) | 5.81 |
HIQSUW | 1 | 293 | 0.0174 (14) | 12.44 |
KIWNOU | 2 | 294 | 0.0109 (27) | 4.04 |
KIWNUA | 1 | 294 | 0.0448 (16) | 27.97 |
KIYSEQ | 2 | 299 | 0.0151 (17) | 8.91 |
JEWDIZ | 1 | 293 | 0.0090 (8) | 11.19 |
NEQLIF | 1 | 298 | 0.0122 (34) | 3.59 |
NIWNOX | 1 | 295 | 0.0101 (14) | 7.22 |
PAHSOH | 1 | 293 | 0.0289 (18) | 16.03 |
PESKEE | 1 | 153 | 0.0208 (50) | 4.16 |
REHDIS | 1 | 292 | 0.0191 (23) | 8.29 |
VAVFUU02 | 1 | 298 | 0.0279 (34) | 8.21 |
VIQLEN | 1 | 293 | 0.0275 (17) | 16.20 |
WEJMOO | 1 | 292 | 0.0103 (17) | 6.07 |
WIZRAZ | 1 | 293 | 0.0596 (20) | 29.80 |
XIYJAR | 1 | 298 | 0.0104 (18) | 5.80 |
XIYJEV | 1 | 296 | 0.0125 (15) | 8.32 |
XIYNOJ | 1 | 296 | 0.0251 (14) | 17.94 |
YASMOV | 1 | 295 | 0.0211 (16) | 13.19 |
Tensor components of the thermal expansion (10 -6 K-1) in the
cartesian xyz coordinate system (α12, α23 = 0) topT (K) | α11 | α22 | α33 | α13 |
290-270 | 171.83 | -25.03 | 26.38 | -66.61 |
270-250 | 169.18 | -33.16 | 23.65 | -71.36 |
250-230 | 174.96 | -26.40 | 25.26 | -88.10 |
230-210 | 177.31 | -44.72 | 27.88 | -93.61 |
210-190 | 178.82 | -33.66 | 19.71 | -98.09 |
190-170 | 174.93 | -29.99 | 41.78 | -80.03 |
170-150 | 189.30 | -75.00 | 18.95 | -143.43 |
150-130 | 199.49 | -71.55 | 37.89 | -146.19 |
130-110 | 228.14 | -79.43 | 7.33 | -178.73 |
Eigenvalues (10 -6 K-1) of the thermal expansion tensor and angles of
the eigenvectors with the crystallographic axes topT (K) | Principal axis | Eigenvalue | Angle with a | Angle with b | Angle with c |
290-270 | α1 | 198 (3) | 11.5 (5) | 90 | 111.2 (5) |
| α2 | 0(3) | 78.5 (5) | 90 | 21.2 (5) |
| α3 | -25 (4) | 90 | 180 | 90 |
270-250 | α1 | 198 (3) | 12.6 (5) | 90 | 112.2 (5) |
| α2 | -6(2) | 77.4 (5) | 90 | 22.2 (5) |
| α3 | -33 (4) | 90 | 180 | 90 |
250-230 | α1 | 216 (4) | 15.4 (5) | 90 | 114.8 (5) |
| α2 | -15 (3) | 74.6 (5) | 90 | 24.8 (5) |
| α3 | -26 (4) | 90 | 180 | 90 |
230-210 | α1 | 222 (4) | 16.4 (6) | 90 | 115.7 (6) |
| α2 | -17 (4) | 73.6 (6) | 90 | 25.7 (6) |
| α3 | -44 (4) | 90 | 180 | 90 |
210-190 | α1 | 226 (4) | 16.4 (5) | 90 | 115.5 (5) |
| α2 | -27 (4) | 73.6 (5) | 90 | 25.5 (5) |
| α3 | -34 (4) | 90 | 180 | 90 |
190-170 | α1 | 213 (4) | 16.2 (7) | 90 | 115.1 (7) |
| α2 | 4(4) | 73.8 (7) | 90 | 25.1 (7) |
| α3 | -30 (5) | 90 | 180 | 90 |
170-150 | α1 | 271 (3) | 21.0 (5) | 90 | 119.7 (5) |
| α2 | -62 (4) | 69.0 (5) | 90 | 29.7 (5) |
| α3 | -75 (4) | 90 | 180 | 90 |
150-130 | α1 | 286 (3) | 22.2 (5) | 90 | 120.5 (5) |
| α2 | -48 (4) | 67.8 (5) | 90 | 30.5 (5) |
| α3 | -72 (4) | 90 | 180 | 90 |
130-110 | α1 | 328 (4) | 21.2 (4) | 90 | 119.2 (4) |
| α2 | -79 (4) | 90 | 0 | 90 |
| α3 | -92 (4) | 68.8 (4) | 90 | 29.2 (4) |
Scale factor K = [mean(Fo2)/mean(Fc2)] versus intensity for (Ia) topFc/Fc(max) | No. refl. | K |
<0.039 | 94 | 1.050 |
<0.076 | 91 | 1.020 |
<0.110 | 94 | 0.996 |
<0.140 | 91 | 0.985 |
<0.170 | 94 | 0.999 |
<0.200 | 92 | 0.999 |
<0.241 | 91 | 1.006 |
<0.304 | 94 | 1.000 |
<0.413 | 91 | 1.004 |
<1.000 | 93 | 1.000 |
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The room-temperature structure of the title compound, (I), is known from the literature (van Niekerk et al., 1953; Semenenko & Kurdyumov, 1958; Kaduk & Chen, 1996; Ishioka et al., 1997) to form a two-dimensional network by hydrogen bonding, with only very weak interactions in the third direction. The displacement ellipsoids show a large anisotropy and the Zn—O2 bond (Ishioka et al., 1997) fails the Hirshfeld rigid-bond test (Hirshfeld, 1976) by 11σ, as calculated using PLATON (Spek, 2003). To investigate further the anisotropy of this compound, we performed temperature-dependent cell determinations and two complete crystal structure determinations at 110 and 250 K, (Ia) and (Ib), respectively.
The Zn atom is located on a twofold rotation axis and has a distorted octahedral coordination environment, which is formed by four carboxylate O atoms and two water molecules (Fig. 1). The plane of the water molecule has an angle of 33 (2)° with the Zn1—O1 bond in (Ia). This is in contrast with the trigonal coordination with an angle of 0.2 (6)° reported in the literature (Ishioka et al., 1997, 1998). The Zn1—O1 bond to the coordinated water molecule is about 0.15 Å shorter than the Zn1—O2 and Zn1—O3 bonds to the carboxylate group (Tables 1 and 3). At 250 K, the latter Zn—O distances appear similar [(Ib) data set], but at 110 K the difference of about 0.03 Å is significant [(Ia) data set]. A large distortion from an ideal octahedron is found in the O—Zn—O angles, leading to angular distortions (Robinson et al., 1971) of 248.4 (4) and 260.1 (5)°2 for (Ia) and (Ib), respectively.
The bidentate mode, in which both carboxylate O atoms coordinate to the same Zn centre and form a four-membered Zn—O—C—O ring, thus leads to an extremely strained situation, with Zn—O—C angles close to 90° instead of the optimal 120° and O—Zn—O angles close to 60° instead of the octahedral 90° (Tables 1 and 3). The Cambridge Structural Database (CSD, August 2008 update; Allen, 2002) contains 1052 carboxylate complexes of six-coordinated Zn. Only 241 of them have this bidentate coordination mode, of which 225 are not additionally bridging between different metals. The range of Zn—O distances is between 1.9359 (16) Å (Dietzel et al., 2006) and 2.639 (4) Å (Tao et al., 2000). Crystal structures of bidentate carboxylate groups with tetrahedral Zn centres are unknown.
The coordinated water molecule acts as a donor of two intermolecular hydrogen bonds with the carboxylate atoms O2 and O3 as acceptors (Tables 2 and 4). This hydrogen bonding results in an infinite two-dimensional network in the crystallographic bc plane. Between the planes no strong interactions can be detected (van Niekerk et al., 1953). The hydrogen-bonded sheet-like structure is also reflected in the morphology of the crystals, which are shaped as plates where the form {100} has the smallest dimension.
A rigid-body analysis of the displacement parameters using the program THMA11 (Schomaker & Trueblood, 1998) results in a TLS model with weighted R values of 0.112 and 0.113 for (Ia) and (Ib) (R = {[Σ(wΔU)2]/[Σ(wUobs)2]}1/2). The main axes of the L and T tensors are in the ac plane (Fig. 2). In particular, the T tensor is very anisotropic and the T1 axis is close to the a axis. Translational motion in the b and c directions is restricted due to the hydrogen-bonding network, while no such restriction exists in the a direction. Consistent with the rigid-body analysis, the displacement parameters of the individual atoms have their largest components in the direction of the a axis. For Zn1, the anisotropicity, defined as the ratio of the main axes U3obs/U1obs, is 2.57 in (Ia) and 2.32 in (Ib). The average anisotropicity of the whole molecule is 2.15 in (Ia) and 1.94 in (Ib).
While the average anisotropicity is covered by the calculated rigid-body model with U3calc/U1calc of 2.11 in (Ia) and 1.87 in (Ib), the displacement parameters of the individual atoms deviate significantly from this overall model. In other words, there is clearly additional internal motion (Fig. 3). Most affected is atom O2 of the carboxylate group and the O2—Zn1 bonds, which have large differences of mean-square displacement amplitudes (Δ m.s.d.a.'s) along the bond (Hirshfeld, 1976) of 0.0080 (5) and 0.0221 (7) Å2 for (Ia) and (Ib). Internal motion also affects atom O3, but the effect is smaller than for atom O2, with Δ m.s.d.a.'s of 0.0026 (5) and 0.0017 (7) Å2 for (Ia) and (Ib), respectively. These values can be compared with recent bidentate carboxylate complexes of octahedral Zn extracted from Acta Crystallographica (Table 5). Interestingly, all structures have at least one Zn—O(carboxylate) bond where the Hirshfeld rigid-bond test fails, with Δ m.s.d.a. larger than 0.01 Å2 and/or Δ m.s.d.a./σ larger than 5. The similar bond lengths Zn1—O2 and Zn1—O3 observed by Ishioka et al. (1997) and also seen in (Ib) should therefore be considered as an effect of vibrational smearing. It should also be noted that the standard uncertainties for atomic positions and displacement parameters are much higher in Ishioka et al. (1997) compared with (Ia) and (Ib). If (Ia) is compared with (Ib), it can easily be seen that cooling of the crystal does considerably reduce the effect of vibrational smearing, but even the 110 K structure of (Ia) still fails the Hirshfeld test. This might be attributed to the severe strain in the four-membered chelate ring, with bond angles deviating from ideal values (see above). An inspection of the internal movements in the four-membered ring (Fig. 3) suggests that these motions tend to release the strain. In anhydrous zinc acetate (Clegg et al., 1986), there is no failure of the Hirshfeld test because the carboxylate group is bridging, with C—O—Zn angles in the normal range [113.0 (2)–134.6 (2)°], and the Zn is tetrahedral, with O—Zn—O angles also in the normal range [100.8 (1)–117.8 (1)]. The latter conclusion can be generalized on the basis of 25 recently published crystal structures: bridging carboxylate groups usually fulfil the Hirshfeld test for Zn—O bonds in zinc complexes.
The large difference in the intermolecular bonding situation should result in a large anisotropy of the thermal expansion tensor (Salud et al., 1998). We therefore performed a temperature-dependent study of the cell parameters by cooling the crystal from 290 to 110 K in steps of 20 K (Fig. 4). To minimize diffractometer errors in the cell determinations, we used the Phi/Phi-Chi routine (Duisenberg et al., 2000) and kept the position of the detector fixed. The largest change is found for the a axis, which is the direction of the weakest intermolecular interactions. More details are obtained from an analysis of the thermal expansion tensor. Usually, the thermal expansion tensor is expressed in a Cartesian coordinate system, resulting in a symmetric second-rank tensor. With monoclinic symmetry, two off-diagonal terms of this tensor become zero, with one eigenvector parallel to the crystallographic twofold axis. The program STRAIN (Ohashi, 1982) was used for the calculation of the tensors and the results are shown in Tables 6 and 7. The eigenvalue of α1 has the largest magnitude and is positive over the whole temperature range. α1 is nearly collinear with the a axis. This can also be graphically visualized by a plot of the strain ellipsoid of the thermal expansion (Fig. 5). α2 and α3 have much smaller magnitudes. α3 is parallel to the b axis by symmetry (see above) and has a negative sign over the whole temperature range. α2 is also negative for most temperature changes. We can therefore conclude that the crystal has a biaxial negative thermal expansion as a consequence of the hydrogen-bonding pattern.
An alternative explanation for large displacement parameters is the choice of a too high space group symmetry. The structure is then refined as an average and the corresponding increased displacement parameters are artefacts. Therefore, we performed a careful analysis of the symmetry. The crystal structure of (I) is best described in the centrosymmetric space group C2/c. In the literature there is a report of a refinement in Cc, which was unsuccessful due to abnormalities in the temperature factors and the bond distances, which caused the authors to choose C2/c (Ishioka et al., 1998). If the structure is solved in P1, the routine ADDSYM in PLATON (Spek, 2003) and the space group algorithm of SUPERFLIP (Palatinus & van der Lee, 2008) strongly suggest a transformation to C2/c. The correctness of C2/c is further proven by the least-squares refinement. The weakest reflections, which are most sensitive to the choice of the correct space group (Walker et al., 1999), have a scale factor K = [mean(Fo2)/mean(Fc2)] close to 1.0 (Table 8). If the real space group were noncentrosymmetric, a much higher value of K would be expected.
Nevertheless, the intensity statistics are noncentrosymmetric. <|E2-1|> for all reflections in (Ia), as calculated with SIR97 (Altomare et al., 1999), is 0.798, with theoretical values of 0.968 for centrosymmetric and 0.736 for noncentrosymmetric structures. A cumulative n(z) distribution is also indicative of a noncentrosymmetric structure (Fig. 6). A closer look shows that the Zn atoms on the special positions are the cause of the noncentrosymmetric intensity statistics. If <|E2-1|> is determined from calculated structure factors based only on Zn atoms, the result is 0.553, while calculated structure factors from only the C, H and O atoms lead to <|E2-1|> of 0.930.
Using the routine WTANAL of the WinGX package (Farrugia, 1999), it is possible to plot the mean intensities for the three principal directions of the crystal (Fig. 7). While similar behaviour is found for the b* and c* directions, the intensity decay with resolution is significantly stronger in the a* direction. This finding is consistent with the directions of the T tensor of the rigid-body analysis (see above). In accordance with this decay of Bragg intensities in the a* direction, we expect the presence of diffuse intensity in this direction. This diffuse intensity can indeed be detected, but the effect is very weak; it was necessary to collect overexposed diffraction images at 250 K, different from the images of (Ib), to make the streaks visible.