In the title lanthanum complex, {[La(C4H4O5)(H2O)3]NO3}n, the lanthanum cation is immersed in a nine-coordinate environment provided by a tridentate oxydiacetate (oda) ligand (through two carboxylate and one ether O atoms), three carboxylate O atoms from neighbouring oda ligands and three aqua ligands. The LaO9 polyhedra are interlinked into a tight three-dimensional framework, which leaves holes where the nitrate anions lodge. The links to the polymeric framework are by an extensive hydrogen-bonding scheme utilizing all the water H atoms. Thermogravimetric analysis shows that the three coordinated water molecules leave the structure in two well differentiated steps.
Supporting information
CCDC reference: 237823
Compound (I) was obtained by treating an equimolar aqueous solution of lanthanum
nitrate and oxydiacetic acid in a refluxed system at 470 K for a period of 2 d; the pH of the solution was initially 2 but was adjusted to 5 using sodium
hydroxide. After cooling, the solution was filtered and single crystals of the
La complex were grown by slow evaporation at room temperature, in the form of
small colorless needles. In the thermal behavior study, the total weight loss
observed (57.9–58.1%, for repeated TGA measurements) is in good agreement
with the theoretical loss (57.8%) required to obtain the corresponding
La2O3 oxide.
H atoms attached to carbon were positioned geometrically and treated as riding
(C—H = 0.97 Å); those in the water molecules were found in a difference
Fourier map and refined with restrained O—H [0.85 (3) Å] and H···H [1.35 (4) Å] distances. In all cases, Uiso(H) was taken as
1.2Ueq(C,O).
Data collection: SMART-NT (Bruker, 2001); cell refinement: SAINT-NT (Bruker, 2001); data reduction: SAINT-NT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-NT (Bruker, 2001); software used to prepare material for publication: SHELXTL-NT and PLATON (Spek, 2003).
Poly[[triaqua(µ
4-oxydiacetato)lanthanum(III)] nitrate]
top
Crystal data top
[La(C4H4O5)(H2O)3]NO3 | F(000) = 744 |
Mr = 387.04 | Dx = 2.473 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 4908 reflections |
a = 7.0510 (5) Å | θ = 2.5–23.5° |
b = 14.5981 (11) Å | µ = 4.17 mm−1 |
c = 10.6214 (8) Å | T = 295 K |
β = 108.046 (1)° | Needles, colourless |
V = 1039.49 (13) Å3 | 0.28 × 0.08 × 0.08 mm |
Z = 4 | |
Data collection top
Bruker SMART CCD area-detector diffractometer | 2328 independent reflections |
Radiation source: fine-focus sealed tube | 2066 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.033 |
ϕ and ω scans | θmax = 27.9°, θmin = 2.5° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2001) | h = −9→9 |
Tmin = 0.50, Tmax = 0.72 | k = −19→18 |
8490 measured reflections | l = −13→13 |
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)] = 0.028 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.063 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0301P)2 + 1.1025P] where P = (Fo2 + 2Fc2)/3 |
2328 reflections | (Δ/σ)max = 0.005 |
172 parameters | Δρmax = 1.05 e Å−3 |
9 restraints | Δρmin = −0.55 e Å−3 |
Crystal data top
[La(C4H4O5)(H2O)3]NO3 | V = 1039.49 (13) Å3 |
Mr = 387.04 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 7.0510 (5) Å | µ = 4.17 mm−1 |
b = 14.5981 (11) Å | T = 295 K |
c = 10.6214 (8) Å | 0.28 × 0.08 × 0.08 mm |
β = 108.046 (1)° | |
Data collection top
Bruker SMART CCD area-detector diffractometer | 2328 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2001) | 2066 reflections with I > 2σ(I) |
Tmin = 0.50, Tmax = 0.72 | Rint = 0.033 |
8490 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.028 | 9 restraints |
wR(F2) = 0.063 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | Δρmax = 1.05 e Å−3 |
2328 reflections | Δρmin = −0.55 e Å−3 |
172 parameters | |
Special details top
Experimental. The thermal behavior study was performed on single crystals by means of a
Shimadzu TG 50 equipment, in an air atmosphere and a heating rate of 10 K/min
in the range of 300 to 900 K. |
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 (Å2) top | x | y | z | Uiso*/Ueq | |
La1 | 0.72435 (3) | 0.611465 (14) | 0.49874 (2) | 0.01492 (8) | |
O11 | 0.3942 (4) | 0.55791 (18) | 0.5432 (3) | 0.0184 (6) | |
O21 | 0.0863 (4) | 0.59213 (19) | 0.5360 (3) | 0.0266 (7) | |
O31 | 0.5209 (4) | 0.72487 (19) | 0.5883 (3) | 0.0253 (6) | |
O41 | 0.9149 (4) | 0.85192 (19) | 0.8048 (3) | 0.0243 (6) | |
O51 | 0.9069 (4) | 0.7196 (2) | 0.6961 (3) | 0.0256 (6) | |
C11 | 0.2619 (5) | 0.6139 (3) | 0.5506 (4) | 0.0167 (7) | |
C21 | 0.3163 (6) | 0.7131 (3) | 0.5740 (4) | 0.0253 (9) | |
H21A | 0.2364 | 0.7494 | 0.4999 | 0.030* | |
H21B | 0.2891 | 0.7340 | 0.6534 | 0.030* | |
C31 | 0.6067 (6) | 0.8048 (3) | 0.6613 (4) | 0.0267 (10) | |
H31A | 0.5438 | 0.8171 | 0.7289 | 0.032* | |
H31B | 0.5849 | 0.8572 | 0.6025 | 0.032* | |
C41 | 0.8265 (6) | 0.7899 (3) | 0.7249 (4) | 0.0204 (8) | |
N12 | 1.1398 (7) | 0.9177 (3) | 0.4499 (5) | 0.0436 (11) | |
O12 | 1.0467 (5) | 0.8973 (2) | 0.5298 (3) | 0.0393 (8) | |
O22 | 1.0830 (11) | 0.8872 (4) | 0.3390 (5) | 0.110 (2) | |
O32 | 1.2924 (6) | 0.9634 (4) | 0.4855 (5) | 0.0840 (17) | |
O1W | 0.8328 (5) | 0.5154 (2) | 0.7126 (3) | 0.0276 (7) | |
H1WA | 0.843 (7) | 0.547 (2) | 0.783 (3) | 0.033* | |
H1WB | 0.764 (6) | 0.4677 (19) | 0.713 (4) | 0.033* | |
O2W | 0.7653 (5) | 0.7666 (2) | 0.4063 (3) | 0.0355 (8) | |
H2WA | 0.672 (5) | 0.783 (3) | 0.338 (3) | 0.043* | |
H2WB | 0.844 (5) | 0.811 (2) | 0.435 (4) | 0.043* | |
O3W | 0.7827 (5) | 0.5692 (2) | 0.2841 (3) | 0.0328 (7) | |
H3WA | 0.694 (5) | 0.580 (3) | 0.211 (2) | 0.039* | |
H3WB | 0.864 (5) | 0.528 (3) | 0.276 (4) | 0.039* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
La1 | 0.01046 (12) | 0.01568 (13) | 0.01862 (13) | −0.00023 (8) | 0.00449 (8) | 0.00032 (9) |
O11 | 0.0165 (14) | 0.0136 (13) | 0.0271 (15) | 0.0015 (10) | 0.0096 (11) | −0.0018 (11) |
O21 | 0.0146 (14) | 0.0262 (16) | 0.0391 (18) | −0.0028 (12) | 0.0083 (12) | −0.0032 (13) |
O31 | 0.0150 (14) | 0.0204 (15) | 0.0419 (18) | −0.0032 (11) | 0.0110 (12) | −0.0134 (13) |
O41 | 0.0231 (15) | 0.0223 (15) | 0.0236 (15) | −0.0062 (12) | 0.0015 (12) | −0.0084 (12) |
O51 | 0.0196 (15) | 0.0266 (16) | 0.0272 (16) | 0.0007 (12) | 0.0024 (12) | −0.0075 (13) |
C11 | 0.0142 (18) | 0.022 (2) | 0.0147 (18) | 0.0005 (15) | 0.0055 (14) | 0.0004 (16) |
C21 | 0.0133 (19) | 0.027 (2) | 0.037 (2) | 0.0002 (16) | 0.0085 (17) | −0.0058 (19) |
C31 | 0.020 (2) | 0.020 (2) | 0.038 (3) | −0.0025 (16) | 0.0053 (18) | −0.0129 (18) |
C41 | 0.019 (2) | 0.021 (2) | 0.021 (2) | −0.0024 (16) | 0.0052 (15) | −0.0015 (16) |
N12 | 0.049 (3) | 0.036 (2) | 0.047 (3) | 0.004 (2) | 0.016 (2) | 0.012 (2) |
O12 | 0.043 (2) | 0.042 (2) | 0.037 (2) | −0.0090 (16) | 0.0183 (16) | 0.0010 (16) |
O22 | 0.192 (7) | 0.104 (5) | 0.050 (3) | −0.050 (4) | 0.060 (4) | −0.016 (3) |
O32 | 0.033 (2) | 0.114 (5) | 0.096 (4) | −0.017 (3) | 0.007 (2) | 0.039 (3) |
O1W | 0.0336 (17) | 0.0282 (17) | 0.0210 (16) | 0.0009 (13) | 0.0085 (13) | −0.0005 (13) |
O2W | 0.0346 (19) | 0.0275 (18) | 0.038 (2) | −0.0081 (14) | 0.0010 (14) | 0.0080 (15) |
O3W | 0.0313 (18) | 0.045 (2) | 0.0234 (17) | 0.0134 (15) | 0.0103 (13) | 0.0035 (14) |
Geometric parameters (Å, º) top
La1—O21i | 2.475 (3) | C11—C21 | 1.500 (5) |
La1—O3W | 2.516 (3) | C21—H21A | 0.9700 |
La1—O2W | 2.521 (3) | C21—H21B | 0.9700 |
La1—O41ii | 2.550 (3) | C31—C41 | 1.502 (5) |
La1—O31 | 2.559 (3) | C31—H31A | 0.9700 |
La1—O1W | 2.576 (3) | C31—H31B | 0.9700 |
La1—O11iii | 2.604 (3) | N12—O22 | 1.206 (6) |
La1—O51 | 2.622 (3) | N12—O32 | 1.222 (6) |
La1—O11 | 2.633 (2) | N12—O12 | 1.259 (5) |
O11—C11 | 1.261 (4) | O1W—H1WA | 0.86 (5) |
O21—C11 | 1.240 (5) | O1W—H1WB | 0.85 (4) |
O31—C21 | 1.414 (5) | O2W—H2WA | 0.85 (4) |
O31—C31 | 1.428 (5) | O2W—H2WB | 0.85 (5) |
O41—C41 | 1.266 (5) | O3W—H3WA | 0.84 (4) |
O51—C41 | 1.254 (5) | O3W—H3WB | 0.84 (4) |
| | | |
O21i—La1—O3W | 70.53 (10) | La1iii—O11—La1 | 120.40 (9) |
O21i—La1—O2W | 85.86 (10) | C11—O21—La1iv | 158.6 (3) |
O3W—La1—O2W | 78.27 (12) | C21—O31—C31 | 113.8 (3) |
O21i—La1—O41ii | 137.28 (10) | C21—O31—La1 | 123.5 (2) |
O3W—La1—O41ii | 70.04 (10) | C31—O31—La1 | 122.6 (2) |
O2W—La1—O41ii | 70.70 (10) | C41—O41—La1v | 144.3 (3) |
O21i—La1—O31 | 133.12 (9) | C41—O51—La1 | 122.7 (2) |
O3W—La1—O31 | 139.78 (10) | O21—C11—O11 | 123.8 (4) |
O2W—La1—O31 | 73.06 (11) | O21—C11—C21 | 117.5 (3) |
O41ii—La1—O31 | 74.16 (9) | O11—C11—C21 | 118.7 (3) |
O21i—La1—O1W | 77.72 (10) | O31—C21—C11 | 109.6 (3) |
O3W—La1—O1W | 125.33 (10) | O31—C21—H21A | 109.8 |
O2W—La1—O1W | 142.59 (10) | C11—C21—H21A | 109.8 |
O41ii—La1—O1W | 140.57 (10) | O31—C21—H21B | 109.8 |
O31—La1—O1W | 94.11 (10) | C11—C21—H21B | 109.8 |
O21i—La1—O11iii | 100.35 (8) | H21A—C21—H21B | 108.2 |
O3W—La1—O11iii | 75.28 (10) | O31—C31—C41 | 109.3 (3) |
O2W—La1—O11iii | 148.87 (10) | O31—C31—H31A | 109.8 |
O41ii—La1—O11iii | 84.93 (9) | C41—C31—H31A | 109.8 |
O31—La1—O11iii | 119.38 (8) | O31—C31—H31B | 109.8 |
O1W—La1—O11iii | 68.03 (9) | C41—C31—H31B | 109.8 |
O21i—La1—O51 | 73.40 (9) | H31A—C31—H31B | 108.3 |
O3W—La1—O51 | 134.01 (10) | O51—C41—O41 | 125.6 (4) |
O2W—La1—O51 | 71.55 (10) | O51—C41—C31 | 119.4 (3) |
O41ii—La1—O51 | 127.23 (9) | O41—C41—C31 | 115.0 (4) |
O31—La1—O51 | 60.40 (9) | O22—N12—O32 | 119.9 (6) |
O1W—La1—O51 | 71.61 (10) | O22—N12—O12 | 119.1 (5) |
O11iii—La1—O51 | 139.53 (9) | O32—N12—O12 | 120.9 (5) |
O21i—La1—O11 | 149.61 (9) | La1—O1W—H1WA | 113 (3) |
O3W—La1—O11 | 119.45 (10) | La1—O1W—H1WB | 116 (3) |
O2W—La1—O11 | 123.44 (10) | H1WA—O1W—H1WB | 109 (3) |
O41ii—La1—O11 | 67.96 (9) | La1—O2W—H2WA | 116 (3) |
O31—La1—O11 | 59.79 (8) | La1—O2W—H2WB | 134 (3) |
O1W—La1—O11 | 73.59 (9) | H2WA—O2W—H2WB | 109 (3) |
O11iii—La1—O11 | 59.60 (9) | La1—O3W—H3WA | 120 (3) |
O51—La1—O11 | 106.11 (8) | La1—O3W—H3WB | 125 (3) |
C11—O11—La1iii | 114.9 (2) | H3WA—O3W—H3WB | 111 (3) |
C11—O11—La1 | 122.1 (2) | | |
| | | |
O21i—La1—O11—C11 | 145.3 (3) | O11iii—La1—O31—C31 | 154.8 (3) |
O3W—La1—O11—C11 | −112.8 (3) | O51—La1—O31—C31 | 21.6 (3) |
O2W—La1—O11—C11 | −17.4 (3) | O11—La1—O31—C31 | 156.1 (3) |
O41ii—La1—O11—C11 | −63.5 (3) | O21i—La1—O51—C41 | 154.8 (3) |
O31—La1—O11—C11 | 20.5 (3) | O3W—La1—O51—C41 | 115.3 (3) |
O1W—La1—O11—C11 | 125.5 (3) | O2W—La1—O51—C41 | 63.7 (3) |
O11iii—La1—O11—C11 | −160.8 (3) | O41ii—La1—O51—C41 | 17.4 (3) |
O51—La1—O11—C11 | 60.8 (3) | O31—La1—O51—C41 | −16.9 (3) |
O21i—La1—O11—La1iii | −53.9 (2) | O1W—La1—O51—C41 | −122.9 (3) |
O3W—La1—O11—La1iii | 47.96 (15) | O11iii—La1—O51—C41 | −118.6 (3) |
O2W—La1—O11—La1iii | 143.30 (12) | O11—La1—O51—C41 | −56.9 (3) |
O41ii—La1—O11—La1iii | 97.30 (13) | La1iv—O21—C11—O11 | −164.8 (5) |
O31—La1—O11—La1iii | −178.73 (15) | La1iv—O21—C11—C21 | 13.2 (10) |
O1W—La1—O11—La1iii | −73.78 (12) | La1iii—O11—C11—O21 | −1.7 (5) |
O11iii—La1—O11—La1iii | 0.0 | La1—O11—C11—O21 | 160.0 (3) |
O51—La1—O11—La1iii | −138.47 (11) | La1iii—O11—C11—C21 | −179.7 (3) |
O21i—La1—O31—C21 | −167.3 (3) | La1—O11—C11—C21 | −18.0 (5) |
O3W—La1—O31—C21 | 79.1 (3) | C31—O31—C21—C11 | −156.1 (4) |
O2W—La1—O31—C21 | 125.6 (3) | La1—O31—C21—C11 | 22.1 (5) |
O41ii—La1—O31—C21 | 51.4 (3) | O21—C11—C21—O31 | 179.9 (3) |
O1W—La1—O31—C21 | −90.3 (3) | O11—C11—C21—O31 | −1.9 (5) |
O11iii—La1—O31—C21 | −23.2 (3) | C21—O31—C31—C41 | 153.7 (4) |
O51—La1—O31—C21 | −156.4 (3) | La1—O31—C31—C41 | −24.5 (5) |
O11—La1—O31—C21 | −22.0 (3) | La1—O51—C41—O41 | −168.6 (3) |
O21i—La1—O31—C31 | 10.8 (4) | La1—O51—C41—C31 | 11.3 (5) |
O3W—La1—O31—C31 | −102.8 (3) | La1v—O41—C41—O51 | −20.9 (7) |
O2W—La1—O31—C31 | −56.4 (3) | La1v—O41—C41—C31 | 159.2 (3) |
O41ii—La1—O31—C31 | −130.6 (3) | O31—C31—C41—O51 | 7.9 (6) |
O1W—La1—O31—C31 | 87.8 (3) | O31—C31—C41—O41 | −172.2 (3) |
Symmetry codes: (i) x+1, y, z; (ii) x−1/2, −y+3/2, z−1/2; (iii) −x+1, −y+1, −z+1; (iv) x−1, y, z; (v) x+1/2, −y+3/2, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1WA···O32vi | 0.86 (5) | 2.29 (5) | 3.015 (6) | 141 (3) |
O1W—H1WB···O41vii | 0.85 (4) | 2.08 (4) | 2.929 (4) | 175 (4) |
O2W—H2WA···O51ii | 0.85 (4) | 2.00 (4) | 2.813 (4) | 158 (4) |
O2W—H2WB···O12 | 0.85 (5) | 1.93 (5) | 2.773 (5) | 169 (4) |
O3W—H3WA···O12ii | 0.84 (4) | 1.91 (4) | 2.742 (5) | 166 (4) |
O3W—H3WB···O1Wviii | 0.84 (4) | 2.20 (4) | 2.969 (4) | 151 (4) |
Symmetry codes: (ii) x−1/2, −y+3/2, z−1/2; (vi) x−1/2, −y+3/2, z+1/2; (vii) −x+3/2, y−1/2, −z+3/2; (viii) −x+2, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | [La(C4H4O5)(H2O)3]NO3 |
Mr | 387.04 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 295 |
a, b, c (Å) | 7.0510 (5), 14.5981 (11), 10.6214 (8) |
β (°) | 108.046 (1) |
V (Å3) | 1039.49 (13) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 4.17 |
Crystal size (mm) | 0.28 × 0.08 × 0.08 |
|
Data collection |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2001) |
Tmin, Tmax | 0.50, 0.72 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8490, 2328, 2066 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.659 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.063, 1.06 |
No. of reflections | 2328 |
No. of parameters | 172 |
No. of restraints | 9 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 1.05, −0.55 |
Selected bond lengths (Å) topLa1—O21i | 2.475 (3) | La1—O11iii | 2.604 (3) |
La1—O3W | 2.516 (3) | La1—O51 | 2.622 (3) |
La1—O2W | 2.521 (3) | La1—O11 | 2.633 (2) |
La1—O41ii | 2.550 (3) | N12—O22 | 1.206 (6) |
La1—O31 | 2.559 (3) | N12—O32 | 1.222 (6) |
La1—O1W | 2.576 (3) | N12—O12 | 1.259 (5) |
Symmetry codes: (i) x+1, y, z; (ii) x−1/2, −y+3/2, z−1/2; (iii) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1WA···O32iv | 0.86 (5) | 2.29 (5) | 3.015 (6) | 141 (3) |
O1W—H1WB···O41v | 0.85 (4) | 2.08 (4) | 2.929 (4) | 175 (4) |
O2W—H2WA···O51ii | 0.85 (4) | 2.00 (4) | 2.813 (4) | 158 (4) |
O2W—H2WB···O12 | 0.85 (5) | 1.93 (5) | 2.773 (5) | 169 (4) |
O3W—H3WA···O12ii | 0.84 (4) | 1.91 (4) | 2.742 (5) | 166 (4) |
O3W—H3WB···O1Wvi | 0.84 (4) | 2.20 (4) | 2.969 (4) | 151 (4) |
Symmetry codes: (ii) x−1/2, −y+3/2, z−1/2; (iv) x−1/2, −y+3/2, z+1/2; (v) −x+3/2, y−1/2, −z+3/2; (vi) −x+2, −y+1, −z+1. |
During the past few years, lanthanide manganese oxides have attracted scientific attention because of their unusual magnetic and transport properties and their technological importance as probable candidates for cathode materials in high-temperature solid oxide fuel cells (Fergus, 2006; Zhang et al., 2007; Piao et al., 2006). The interest in such ceramic materials has prompted a considerable growth in the development of alternative routes of synthesis, looking for the attainment of highly dispersed mixed oxides and oxide solid solutions with improved properties, low processing temperatures, better homogeneity and finer particles. LnIII carboxylate complexes have received much attention (Vanhoyland et al., 2005; Kumar et al., 2006; Grazyna & Przemyslaw, 2005) because they have been found to be convenient precursors for the thermal preparation of the corresponding oxides. In previous works, we investigated the crystal structure and thermal behavior of several copper and alkaline earth mixed formates, used as precursors in the chemical preparation of ceramic compounds (Polla et al., 1995, 2000; Perazzo et al., 1997). We also reported on the preparation and the thermal and magnetic properties of yttrium(III) and lanthanide(III) complexes with oxydiacetate as a connecting ligand in various mono- and heterometallic extended solids. Pursuing our interest in the obtainment and characterization of new lanthanide precursors, we report here the synthesis, crystal structure and thermal behaviour of {[La(oda)(H2O)3]+·NO3-}n, (I) (oda is oxydiacetate). Although some monocationic La complexes containing either oda or nitrate ions have been reported so far in the literature (see discussion below), (I) is the first compound to be associated with both anions simultaneously.
Fig. 1 shows the molecular structure of (I). The lanthanum cation is immersed in a nine-coordination environment provided by a tridentate oda ligand, through two carboxylate (O11 and O51) and one ether (O31) O atoms, three aqua ligands (O1W–O3W), and three carboxylate O atoms from three neighbouring oda ligands (O21i, O41ii and O11iii; symmetry codes as in Table 1). The resulting coordination polyhedron has the shape of a distorted monocapped square antiprism with a capping O3W atom, a first plane defined by O2W and the three carboxylate O atoms from neighbouring units, and a second plane by O1W and the tridentate oda bite, the angle between planes being 8.6 (1)°. The molecule forms a dimer around the symmetry centre at (1/2, 1/2, 1/2), through a double La—O—La bridge defined by the shared O11 atom and its symmetry-related atom. The dinuclear unit thus defined (Fig. 1) constitutes the real building block in the structure.
The other two interactions have rather different, well defined, structural functions. Atom O41 links the reference dimer with its four nearest neighbours to form a two-dimensional structure parallel to the (-101) plane. These structures stack in a slanted fashion along [100], being in turn connected by O21 atoms into a three-dimensional array. Fig 2(a) shows the packing of (I) along [101], where the compact two-dimensional structures are clearly seen in projection (as horizontal compact zones in light lining), as is their linkage through atoms O21 (heavy lining). The [100] projection shown in Fig 2(b) clarifies the way in which the planes build up, though a four-nearest-neighbours interaction by way of atoms O41. The packing is quite compact along b and c, but leaves empty columnar spaces parallel to a, towards which the aqua ligands direct their H atoms. These hydrogen-padded channels are the locii where the nitrate anions locate. From this projection, and having the c axis as a reference, a conservative estimate of the internal H···H diameter of these channels would be some 0.4c, or about 4 Å. The simultaneous convergence of potentially good donors and acceptors for hydrogen bonding results in a complex interaction scheme building up, where all six aqua H atoms are involved (Table 2).
The nitrate O atoms enter into these types of interactions in a fairly uneven way, which correlates with the internal geometry of the anion as well as with its vibrational behaviour. Thus, atom O12, which is involved in stronger hydrogen bonds with two rather short O···H contacts towards two different dimers, has an (equivalent) isotropic displacement factor that is very small for an uncoordinated O atom (0.03 Å2) as well as the longest N—O distance. Atom O32, in turn, which interacts with a third binuclear unit through a single, medium-strength hydrogen bond, has a medium-size displacement parameter and an intermediate N—O bond length. Finally, atom O22, which makes a couple of very weak contacts with small interaction angles (O—H···O < 130°, not presented in Table 2), shows the largest ellipsoid, typical for a terminal, unbound O atom, and the shorter bond to the central n atom.
Two monocationic La(oda) complexes have already been reported in the literature, viz. La2oda3 (Baggio et al., 1998), which is isostructural to a whole lanthanide family of homologous compounds and contains two independent La units with coordination numbers 9 and 10, and (LaH2O)2(C2O4)oda2 (Trombe & Romero, 2000), where the oxalate anion is included in the coordination polyhedron and where the La atom has a coordination number of 10. Both complexes are [like (I)] three-dimensional polymers, confirming the unusual bridging capacity of the oda anion through its five O atoms. A search of the Cambridge Structural Database (CSD; Allen, 2002) for the different coordination modes known to oda confirms that almost all the reported cases share the chelating tridentate character of the anion towards some central cation (only four do not show coordination involving the central ether atom O31). The great diversity of binding modes arises from the extra bonds that the carboxylate O atoms can make, both those already involved in the central binding and the remaining `external' O atoms. In this respect, the binding mode adopted by oda in the present structure [one bridging `internal' (O11) and two monocoordinated `external' (O21 and O41) carboxylate O atoms] is a novel one.
Regarding the La—Ocarboxy distances, a search of the CSD for LaO9 cores with at least one O atom pertaining to a carboxylate group provided 316 entries with a mean La—Ocarboxy bond length of 2.51 (6) Å, slightly shorter (though not significantly different) than the value found here [2.57 (6) Å].
The dehydration process takes place in two well differentiated stages (Fig. 3). The first step, between 370 and 450 K, corresponds to the release of one water molecule (theoretical weigh loss: 5.0%; experimental: 4.9%), with an endothermic peak at about 420 K. After this, the two remaining water molecules are lost in the range 450–520 K, partially overlapping the decomposition of the nitrate ligand. Both simultaneous processes (the first slightly endothermic, the second largely exothermic) appear in the DTA curve as an integrated, exothermic peak centered at about 490 K and take place via an oxydiacetic acid intermediate; this is not uncommon, and similar cases can be found in the literature [e.g. the hydrazinium analogues reported by Yasodhai & Govindarajan (2000)].
It is worth mentioning that the splitting of the water loss process is in line with the difference in binding strength of the water molecules, as measured by their corresponding bond valence (Brown & Altermatt, 1985) [0.334 for O1W (first step), and 0.396 and 0.389 for O2W and O3W (second step)]. Finally, the very steep process beginning at about 520 K and continuing smoothly up to about 820 K (centered at the exothermic peak at 650 K) corresponds to the decomposition of the oda ligand, yielding La2O3 oxide in a pure phase.