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In the title complex, poly[triaquabis(dimethylformamide)di-
3-oxalato-
2-oxalato-dilanthanum(III)], [La
2(C
2O
4)
3(C
3H
7NO)(H
2O)
3]
n, both La ions are coordinated by nine O atoms, forming slightly distorted tricapped trigonal prisms. The two La ions, the terminal water O atom, and the O and N atoms of the dimethylformamide molecule reside on twofold rotation axes, giving the two La-centered coordination geometries twofold or pseudo-twofold symmetries. The two oxalate ligands, one of which rests on a center of inversion at the mid-point of the C-C bond, adopt different bridging modes, connecting with the La ions to form two types of lanthanide oxalate chains,
i.e. anionic {[La(C
2O
4)
2(DMF)(H
2O)
2]
n-}
n (DMF is dimethylformamide) and cationic zigzag {[La(C
2O
4)(H
2O)]
n+}
n, respectively. Each zigzag cationic chain is linked to four adjacent anionic chains
via the bridging oxalate anions, and each anionic chain connects with four zigzag cationic chains, constructing a three-dimensional neutral framework.
Supporting information
CCDC reference: 672406
A mixture of lanthanum nitrate hexahydrate [La(NO3)3·6H2O], oxalic
acid (H2C2O4·2H2O), dimethylamine (C2H6NH), dimethylformamide
and ethanol (molar ratio 1:1:2.5:130:500) was placed in a 15 ml Teflon-lined
steel bomb and heated at 368 K for 96 h under autogenous pressure. Upon
cooling to room temperature, colorless crystals of (I) were filtered off,
washed with distilled water and dried in air.
The C and H atoms of the DMF molecule are disordered over two twofold axis
symmetry-related positions and the DMF H atoms were refined in the rigid-model
approximation with distance constraints of C—H = 0.96 Å. H atoms of the
coordinated water molecules were located in difference Fourier maps and
refined with restraints on O—H bond lengths and the H—O—H angle.
Data collection: RAPID-AUTO (Rigaku Corporation, 1998); cell refinement: RAPID-AUTO (Rigaku Corporation, 1998); data reduction: RAPID-AUTO (Rigaku Corporation, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1993); software used to prepare material for publication: SHELXL97-2 (Sheldrick, 1997).
poly[triaquabis(dimethylformamide)di-µ
3-oxalato-µ
2-oxalato-dilanthanum(III)]
top
Crystal data top
[La2(C2O4)3(C3H7NO)(H2O)3] | F(000) = 632 |
Mr = 669.02 | Dx = 2.547 Mg m−3 |
Monoclinic, P2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yc | Cell parameters from 7311 reflections |
a = 10.392 (2) Å | θ = 3.2–27.6° |
b = 10.224 (2) Å | µ = 4.92 mm−1 |
c = 8.7073 (17) Å | T = 298 K |
β = 109.43 (3)° | Block, colorless |
V = 872.4 (3) Å3 | 0.20 × 0.19 × 0.18 mm |
Z = 2 | |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 1779 reflections with I > 2σ(I) |
Radiation source: rotating-anode X-ray tube | Rint = 0.046 |
Graphite monochromator | θmax = 27.5°, θmin = 3.2° |
Oscillation scans | h = −13→13 |
8351 measured reflections | k = −13→13 |
2011 independent reflections | l = −11→11 |
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)] = 0.026 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.058 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0157P)2 + 1.7609P] where P = (Fo2 + 2Fc2)/3 |
2008 reflections | (Δ/σ)max = 0.001 |
143 parameters | Δρmax = 1.52 e Å−3 |
2 restraints | Δρmin = −1.10 e Å−3 |
Crystal data top
[La2(C2O4)3(C3H7NO)(H2O)3] | V = 872.4 (3) Å3 |
Mr = 669.02 | Z = 2 |
Monoclinic, P2/c | Mo Kα radiation |
a = 10.392 (2) Å | µ = 4.92 mm−1 |
b = 10.224 (2) Å | T = 298 K |
c = 8.7073 (17) Å | 0.20 × 0.19 × 0.18 mm |
β = 109.43 (3)° | |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 1779 reflections with I > 2σ(I) |
8351 measured reflections | Rint = 0.046 |
2011 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.026 | 2 restraints |
wR(F2) = 0.058 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | Δρmax = 1.52 e Å−3 |
2008 reflections | Δρmin = −1.10 e Å−3 |
143 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 | Occ. (<1) |
La1 | 0.0000 | 0.43195 (3) | 0.7500 | 0.01358 (9) | |
La2 | 0.5000 | 0.23575 (3) | 0.7500 | 0.01326 (9) | |
O2 | 0.0753 (2) | 0.4019 (3) | 0.4929 (3) | 0.0176 (5) | |
O3 | 0.2023 (3) | 0.4179 (3) | 0.2753 (3) | 0.0220 (6) | |
O4 | 0.2542 (3) | 0.3054 (3) | 0.6688 (3) | 0.0211 (6) | |
O5 | 0.3917 (3) | 0.3333 (3) | 0.4536 (3) | 0.0246 (6) | |
O6 | 0.6121 (3) | 0.1322 (3) | 0.5644 (3) | 0.0219 (6) | |
O7 | 0.6213 (3) | −0.0386 (3) | 0.4094 (3) | 0.0276 (6) | |
C1 | 0.2714 (4) | 0.3709 (3) | 0.4111 (4) | 0.0171 (7) | |
C2 | 0.1953 (4) | 0.3574 (3) | 0.5353 (4) | 0.0151 (7) | |
C3 | 0.5676 (4) | 0.0273 (4) | 0.4920 (4) | 0.0195 (7) | |
O1 | 0.0000 | 0.1954 (4) | 0.7500 | 0.0492 (13) | |
C4 | 0.0542 (9) | 0.0987 (9) | 0.7277 (12) | 0.034 (2) | 0.50 |
H4A | 0.1331 | 0.1051 | 0.6942 | 0.041* | 0.50 |
N1 | 0.0000 | −0.0212 (5) | 0.7500 | 0.0544 (19) | |
C5 | −0.1175 (9) | −0.0462 (12) | 0.7838 (14) | 0.050* | 0.50 |
H5D | −0.1638 | 0.0310 | 0.8003 | 0.060* | 0.50 |
H5E | −0.1775 | −0.0962 | 0.6955 | 0.060* | 0.50 |
H5F | −0.0909 | −0.0981 | 0.8812 | 0.060* | 0.50 |
C6 | 0.0886 (11) | −0.1238 (10) | 0.7164 (13) | 0.050* | 0.50 |
H6A | 0.0513 | −0.2082 | 0.7256 | 0.060* | 0.50 |
H6B | 0.0932 | −0.1134 | 0.6088 | 0.060* | 0.50 |
H6C | 0.1786 | −0.1167 | 0.7949 | 0.060* | 0.50 |
OW1 | 0.2120 (3) | 0.3442 (4) | 0.9791 (3) | 0.0350 (8) | |
H1W1 | 0.225 (6) | 0.358 (5) | 1.076 (2) | 0.052* | |
H2W1 | 0.251 (6) | 0.276 (3) | 0.973 (6) | 0.052* | |
OW2 | 0.5000 | 0.4956 (4) | 0.7500 | 0.0317 (9) | |
H1W2 | 0.531 (5) | 0.544 (3) | 0.695 (5) | 0.048* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
La1 | 0.01620 (15) | 0.01392 (15) | 0.01110 (13) | 0.000 | 0.00517 (10) | 0.000 |
La2 | 0.01272 (14) | 0.01437 (15) | 0.01210 (13) | 0.000 | 0.00333 (10) | 0.000 |
O2 | 0.0170 (12) | 0.0211 (12) | 0.0169 (11) | 0.0041 (10) | 0.0085 (10) | 0.0027 (11) |
O3 | 0.0239 (13) | 0.0297 (15) | 0.0136 (11) | 0.0084 (11) | 0.0080 (10) | 0.0049 (11) |
O4 | 0.0207 (13) | 0.0293 (15) | 0.0154 (11) | 0.0025 (11) | 0.0085 (10) | 0.0059 (12) |
O5 | 0.0202 (13) | 0.0367 (16) | 0.0192 (12) | 0.0090 (12) | 0.0096 (10) | 0.0086 (12) |
O6 | 0.0230 (13) | 0.0190 (13) | 0.0252 (12) | −0.0060 (11) | 0.0099 (11) | −0.0091 (12) |
O7 | 0.0239 (14) | 0.0292 (15) | 0.0345 (15) | −0.0097 (12) | 0.0159 (12) | −0.0158 (14) |
C1 | 0.0203 (17) | 0.0177 (17) | 0.0153 (15) | 0.0020 (14) | 0.0087 (13) | −0.0001 (15) |
C2 | 0.0172 (16) | 0.0133 (15) | 0.0158 (14) | 0.0007 (13) | 0.0069 (13) | −0.0015 (14) |
C3 | 0.0185 (17) | 0.0204 (18) | 0.0194 (16) | −0.0014 (15) | 0.0059 (14) | −0.0021 (16) |
O1 | 0.049 (3) | 0.018 (2) | 0.086 (4) | 0.000 | 0.028 (3) | 0.000 |
C4 | 0.026 (4) | 0.021 (4) | 0.052 (5) | 0.005 (3) | 0.007 (4) | −0.002 (4) |
N1 | 0.066 (4) | 0.015 (3) | 0.057 (4) | 0.000 | −0.013 (3) | 0.000 |
OW1 | 0.0452 (19) | 0.0434 (19) | 0.0159 (12) | 0.0242 (16) | 0.0095 (13) | 0.0033 (13) |
OW2 | 0.041 (3) | 0.019 (2) | 0.043 (2) | 0.000 | 0.026 (2) | 0.000 |
Geometric parameters (Å, º) top
La1—O1 | 2.418 (5) | O7—La2v | 2.532 (3) |
La1—O3i | 2.553 (3) | C1—C2 | 1.544 (5) |
La1—O3ii | 2.553 (3) | C3—C3v | 1.562 (7) |
La1—OW1iii | 2.591 (3) | O1—C4 | 1.185 (9) |
La1—OW1 | 2.591 (3) | O1—C4iii | 1.185 (9) |
La1—O2i | 2.621 (2) | C4—C4iii | 1.308 (19) |
La1—O2ii | 2.621 (2) | C4—N1 | 1.389 (10) |
La1—O2 | 2.624 (2) | C4—C5iii | 1.638 (14) |
La1—O2iii | 2.624 (2) | C4—H4A | 0.9600 |
La2—O4iv | 2.516 (3) | N1—C5iii | 1.372 (8) |
La2—O4 | 2.516 (3) | N1—C5 | 1.372 (8) |
La2—O6 | 2.518 (3) | N1—C4iii | 1.389 (10) |
La2—O6iv | 2.518 (3) | N1—C6 | 1.488 (8) |
La2—O7v | 2.532 (3) | N1—C6iii | 1.488 (8) |
La2—O7vi | 2.532 (3) | C5—C6iii | 0.848 (14) |
La2—O5iv | 2.644 (3) | C5—C4iii | 1.638 (14) |
La2—O5 | 2.644 (3) | C5—H5D | 0.9601 |
La2—OW2 | 2.657 (4) | C5—H5E | 0.9600 |
O2—C2 | 1.262 (4) | C5—H5F | 0.9601 |
O2—La1ii | 2.621 (2) | C6—C5iii | 0.848 (14) |
O3—C1 | 1.257 (4) | C6—H6A | 0.9600 |
O3—La1ii | 2.553 (3) | C6—H6B | 0.9601 |
O4—C2 | 1.239 (4) | C6—H6C | 0.9600 |
O5—C1 | 1.242 (4) | OW1—H1W1 | 0.818 (10) |
O6—C3 | 1.252 (5) | OW1—H2W1 | 0.818 (10) |
O7—C3 | 1.246 (5) | OW2—H1W2 | 0.818 (10) |
| | | |
O1—La1—O3i | 126.96 (7) | C2—O2—La1 | 109.8 (2) |
O1—La1—O3ii | 126.96 (7) | La1ii—O2—La1 | 121.26 (10) |
O3i—La1—O3ii | 106.07 (13) | C1—O3—La1ii | 120.5 (2) |
O1—La1—OW1iii | 69.74 (8) | C2—O4—La2 | 121.6 (2) |
O3i—La1—OW1iii | 137.69 (9) | C1—O5—La2 | 117.9 (2) |
O3ii—La1—OW1iii | 71.14 (11) | C3—O6—La2 | 120.8 (2) |
O1—La1—OW1 | 69.74 (8) | C3—O7—La2v | 120.7 (2) |
O3i—La1—OW1 | 71.14 (11) | O5—C1—O3 | 127.0 (3) |
O3ii—La1—OW1 | 137.69 (9) | O5—C1—C2 | 117.6 (3) |
OW1iii—La1—OW1 | 139.49 (17) | O3—C1—C2 | 115.3 (3) |
O1—La1—O2i | 130.39 (6) | O4—C2—O2 | 124.2 (3) |
O3i—La1—O2i | 61.59 (8) | O4—C2—C1 | 119.1 (3) |
O3ii—La1—O2i | 72.33 (8) | O2—C2—C1 | 116.7 (3) |
OW1iii—La1—O2i | 142.65 (10) | O7—C3—O6 | 126.4 (4) |
OW1—La1—O2i | 69.75 (9) | O7—C3—C3v | 116.6 (4) |
O1—La1—O2ii | 130.39 (6) | O6—C3—C3v | 117.0 (4) |
O3i—La1—O2ii | 72.33 (8) | C4—O1—C4iii | 67.0 (10) |
O3ii—La1—O2ii | 61.59 (8) | C4—O1—La1 | 146.5 (5) |
OW1iii—La1—O2ii | 69.75 (9) | C4iii—O1—La1 | 146.5 (5) |
OW1—La1—O2ii | 142.65 (10) | O1—C4—C4iii | 56.5 (5) |
O2i—La1—O2ii | 99.21 (11) | O1—C4—N1 | 118.4 (8) |
O1—La1—O2 | 83.28 (6) | C4iii—C4—N1 | 61.9 (4) |
O3i—La1—O2 | 70.93 (8) | O1—C4—C5iii | 170.8 (9) |
O3ii—La1—O2 | 117.87 (8) | C4iii—C4—C5iii | 114.9 (5) |
OW1iii—La1—O2 | 73.80 (9) | N1—C4—C5iii | 53.1 (5) |
OW1—La1—O2 | 101.42 (9) | O1—C4—H4A | 119.6 |
O2i—La1—O2 | 132.11 (8) | C4iii—C4—H4A | 176.1 |
O2ii—La1—O2 | 58.74 (10) | N1—C4—H4A | 121.9 |
O1—La1—O2iii | 83.28 (6) | C5iii—C4—H4A | 69.0 |
O3i—La1—O2iii | 117.87 (8) | C5iii—N1—C5 | 158.5 (12) |
O3ii—La1—O2iii | 70.93 (8) | C5iii—N1—C4 | 72.8 (7) |
OW1iii—La1—O2iii | 101.42 (9) | C5—N1—C4 | 128.7 (7) |
OW1—La1—O2iii | 73.80 (9) | C5iii—N1—C4iii | 128.7 (7) |
O2i—La1—O2iii | 58.74 (10) | C5—N1—C4iii | 72.8 (6) |
O2ii—La1—O2iii | 132.11 (8) | C4—N1—C4iii | 56.1 (8) |
O2—La1—O2iii | 166.57 (12) | C5iii—N1—C6 | 34.2 (6) |
O4iv—La2—O4 | 147.13 (13) | C5—N1—C6 | 124.3 (9) |
O4iv—La2—O6 | 69.89 (8) | C4—N1—C6 | 106.8 (6) |
O4—La2—O6 | 125.57 (8) | C4iii—N1—C6 | 162.9 (7) |
O4iv—La2—O6iv | 125.57 (8) | C5iii—N1—C6iii | 124.3 (9) |
O4—La2—O6iv | 69.89 (8) | C5—N1—C6iii | 34.2 (6) |
O6—La2—O6iv | 130.28 (12) | C4—N1—C6iii | 162.9 (7) |
O4iv—La2—O7v | 130.78 (9) | C4iii—N1—C6iii | 106.8 (6) |
O4—La2—O7v | 78.30 (9) | C6—N1—C6iii | 90.3 (10) |
O6—La2—O7v | 64.28 (9) | C6iii—C5—N1 | 80.4 (9) |
O6iv—La2—O7v | 76.39 (9) | C6iii—C5—C4iii | 134.1 (11) |
O4iv—La2—O7vi | 78.30 (9) | N1—C5—C4iii | 54.1 (5) |
O4—La2—O7vi | 130.78 (9) | C6iii—C5—H5D | 164.7 |
O6—La2—O7vi | 76.39 (9) | N1—C5—H5D | 113.9 |
O6iv—La2—O7vi | 64.28 (9) | C4iii—C5—H5D | 59.7 |
O7v—La2—O7vi | 74.54 (14) | C6iii—C5—H5E | 68.7 |
O4iv—La2—O5iv | 63.66 (8) | N1—C5—H5E | 108.4 |
O4—La2—O5iv | 103.31 (9) | C4iii—C5—H5E | 126.8 |
O6—La2—O5iv | 130.36 (8) | H5D—C5—H5E | 109.5 |
O6iv—La2—O5iv | 70.71 (9) | C6iii—C5—H5F | 59.2 |
O7v—La2—O5iv | 143.88 (9) | N1—C5—H5F | 106.1 |
O7vi—La2—O5iv | 78.03 (10) | C4iii—C5—H5F | 123.4 |
O4iv—La2—O5 | 103.31 (9) | H5D—C5—H5F | 109.5 |
O4—La2—O5 | 63.66 (8) | H5E—C5—H5F | 109.5 |
O6—La2—O5 | 70.71 (9) | C5iii—C6—N1 | 65.4 (7) |
O6iv—La2—O5 | 130.36 (8) | C5iii—C6—H6A | 173.4 |
O7v—La2—O5 | 78.03 (10) | N1—C6—H6A | 108.9 |
O7vi—La2—O5 | 143.88 (9) | C5iii—C6—H6B | 76.2 |
O5iv—La2—O5 | 135.67 (14) | N1—C6—H6B | 110.4 |
O4iv—La2—OW2 | 73.57 (7) | H6A—C6—H6B | 109.5 |
O4—La2—OW2 | 73.57 (7) | C5iii—C6—H6C | 70.7 |
O6—La2—OW2 | 114.86 (6) | N1—C6—H6C | 109.1 |
O6iv—La2—OW2 | 114.86 (6) | H6A—C6—H6C | 109.5 |
O7v—La2—OW2 | 142.73 (7) | H6B—C6—H6C | 109.5 |
O7vi—La2—OW2 | 142.73 (7) | La1—OW1—H1W1 | 123 (4) |
O5iv—La2—OW2 | 67.83 (7) | La1—OW1—H2W1 | 124 (4) |
O5—La2—OW2 | 67.83 (7) | H1W1—OW1—H2W1 | 107 (4) |
C2—O2—La1ii | 118.1 (2) | La2—OW2—H1W2 | 127 (2) |
Symmetry codes: (i) x, −y+1, z+1/2; (ii) −x, −y+1, −z+1; (iii) −x, y, −z+3/2; (iv) −x+1, y, −z+3/2; (v) −x+1, −y, −z+1; (vi) x, −y, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
OW1—H1W1···O3vii | 0.82 (1) | 1.93 (2) | 2.721 (4) | 162 (5) |
OW1—H2W1···O6iv | 0.82 (1) | 2.15 (2) | 2.940 (4) | 164 (6) |
OW2—H1W2···O5viii | 0.82 (1) | 2.15 (1) | 2.966 (4) | 178 (5) |
Symmetry codes: (iv) −x+1, y, −z+3/2; (vii) x, y, z+1; (viii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | [La2(C2O4)3(C3H7NO)(H2O)3] |
Mr | 669.02 |
Crystal system, space group | Monoclinic, P2/c |
Temperature (K) | 298 |
a, b, c (Å) | 10.392 (2), 10.224 (2), 8.7073 (17) |
β (°) | 109.43 (3) |
V (Å3) | 872.4 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 4.92 |
Crystal size (mm) | 0.20 × 0.19 × 0.18 |
|
Data collection |
Diffractometer | Rigaku R-AXIS RAPID diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8351, 2011, 1779 |
Rint | 0.046 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.026, 0.058, 1.06 |
No. of reflections | 2008 |
No. of parameters | 143 |
No. of restraints | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 1.52, −1.10 |
Selected geometric parameters (Å, º) topLa1—O1 | 2.418 (5) | La2—O4 | 2.516 (3) |
La1—O3i | 2.553 (3) | La2—O6 | 2.518 (3) |
La1—OW1 | 2.591 (3) | La2—O7ii | 2.532 (3) |
La1—O2i | 2.621 (2) | La2—O5 | 2.644 (3) |
La1—O2 | 2.624 (2) | La2—OW2 | 2.657 (4) |
| | | |
O1—La1—O3i | 126.96 (7) | O2i—La1—O2 | 132.11 (8) |
O3i—La1—OW1 | 71.14 (11) | O6—La2—O7ii | 64.28 (9) |
OW1iii—La1—OW1 | 139.49 (17) | O6—La2—O7v | 76.39 (9) |
O1—La1—O2iv | 130.39 (6) | O4—La2—O5vi | 103.31 (9) |
O3iv—La1—O2iv | 61.59 (8) | O4—La2—O5 | 63.66 (8) |
O1—La1—O2 | 83.28 (6) | O4—La2—OW2 | 73.57 (7) |
O3i—La1—O2 | 70.93 (8) | O6—La2—OW2 | 114.86 (6) |
OW1—La1—O2 | 101.42 (9) | O5—La2—OW2 | 67.83 (7) |
Symmetry codes: (i) x, −y+1, z+1/2; (ii) −x+1, −y, −z+1; (iii) −x, y, −z+3/2; (iv) −x, −y+1, −z+1; (v) x, −y, z+1/2; (vi) −x+1, y, −z+3/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
OW1—H1W1···O3vii | 0.818 (10) | 1.931 (18) | 2.721 (4) | 162 (5) |
OW1—H2W1···O6vi | 0.818 (10) | 2.15 (2) | 2.940 (4) | 164 (6) |
OW2—H1W2···O5viii | 0.818 (10) | 2.148 (11) | 2.966 (4) | 178 (5) |
Symmetry codes: (vi) −x+1, y, −z+3/2; (vii) x, y, z+1; (viii) −x+1, −y+1, −z+1. |
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The use of multifunctional organic linker molecules to polymerize metal centers into open-framework materials has led to the development of a rich field of chemistry (Yaghi et al., 1998, 2003; Serre et al., 2004; James, 2003) owing to the potential applications in catalysis, separation, gas storage and molecular recognition. Among such novel open-framework materials, lanthanide oxalates are particularly noteworthy. The wide variety of coordination modes of the oxalate anion permits the use of metal–oxalate units as excellent building blocks to construct a great diversity of frameworks ranging from discrete oligomeric entities to one-, two- and three-dimensional networks. Lanthanide oxalates present generally a honey-comb layered structure in which the layers are separated by water or other molecules (Ollendorf & Weigel, 1969; Michaelides et al., 1988; Hansson, 1970, 1973; Trombe & Jaud, 2003). Generally, there are two developed routes to construct three-dimensional open-framework lanthanide oxalates. One is based on the employment of protonated organic amines, ammonium or alkali metal ions as counter-cations. By this method, some three-dimensional lanthanide–oxalate anionic frameworks, where the cations are suspended in the channels, have been prepared (Chapelet-Arab et al., 2005a, 2005b; Vaidhyanathan et al., 2002; Mohanu et al., 2006). The other method involves combining a second ligand and/or alkali metal ion into the framework, by which route several three-dimensional neutral frameworks have been created (Romero et al., 1996, 1997; Yuan et al., 2004; Zhang et al., 2007). Interestingly, only one example of a three-dimensional neutral framework constructed by lanthanide centers and oxalate anions alone, [{Er(H2O)3}2(C2O4)3].12H2O, (II), has been reported to date (Camara et al., 2003). In view of the limited number of lanthanide oxalates with three-dimensional neutral framework, we have attempted to synthesize new examples by introducing bulky solvent molecules to replace the coordinated water molecules under solvothermal conditions. A new DMF–lanthanum oxalate, [La2(C2O4)3(DMF)(H2O)3]n, (I), has been obtained and its structure is reported here.
There are two crystallographically independent La3+ ions, two unique oxalate ligands, one DMF molecule, and two independent water molecules in the asymmetric unit (Fig. 1). Both the La centers, located on twofold rotation axes, are nine-coordinated by O atoms forming slightly distorted tricapped trigonal prisms, with the La—O distances ranging from 2.418 (4) to 2.658 (4) Å (Table 1). There is a distinct dissimilarity between the two oxalate ligands, both in their crystallographic positions and in their coordination modes. One oxalate ligand (containing C1 and C2, denoted ox1) adopting a (κ2)-(κ2-κ1-µ2)-µ3 bridging mode, sits in a general position. The other oxalate ligand (containing C3, denoted ox2) adopting a (κ2)-(κ2)-µ2 bridging mode, straddles an inversion center across the C—C bond.
The La1 center is coordinated by two ox1 ligands through atoms O2 and O3 in chelate mode, two water molecules (OW1), one DMF molecule, and two O2 atoms from other ox1 anions, which act as µ2-bridging atoms. Each La1–oxalate unit connects with two adjacent equivalent units, by sharing the two µ2-bridging O2 atoms, forming an edge-shared [{La(H2O)2(DMF)}(C2O4)2]nn- anionic chain along the c axis (Fig. 2a). Such an arrangement of the anionic chain has not been observed in previously reported lanthanide oxalates. The nine O atoms of the La2 coordination environment belong to two ox2 ligands (atoms O6 and O7), two ox1 ligands (atoms O4 and O5) from the neighboring [{La(H2O)2(DMF)}(C2O4)2]nn- anionic chain, and one water molecule (OW2). The {La2(H2O)} moieties and ox2 ligands connect with each other alternately, resulting in a zigzag cationic chain [{La(H2O)(C2O4)}]nn+ (Fig. 2b), along the c axis, which is identical to that of [Gd(C2O4){MeNH(CH2CO2)(CH2PO3H)}]·0.5H2O (Song & Mao, 2005). Each zigzag cationic chain is linked to four adjacent anionic chains via the bridging ox1 anions, and each anionic chain connects with four zigzag cationic chains, constructing a three-dimensional neutral framework (Fig. 3). There is a noticeable difference between complex (I) and the other three-dimensional neutral framework mentioned above, (II). In (II), the oxalate ligand adopts a (κ2)-(κ2)-µ2 bridging mode and each ErIII ion connects to three oxalate anions, resulting in the three-dimensional neutral framework. Furthermore, extended hydrogen bonds are found between the oxalate O atoms and the terminal water molecules (Table 2).