Hexa­aqua­trioxalatodierbium(III) tetrahydrate: [{Er(H₂O)₃}₂(C₂O₄)₃]·4H₂O

In the layered structure of the title compound, [Er₂(C₂O₄)₃(H₂O)₆]·4H₂O, the Er atoms are bridged by oxalate ligands. Each Er atom coordinates to six O atoms from three oxalate ligands, and three water mol­ecules. The layers are parallel to the ac plane and four disordered water mol­ecules of crystallization are situated between the layers.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.004 Å
• H-atom completeness 61%
• R factor = 0.028
• wR factor = 0.070
• Data-to-parameter ratio = 28.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT201_ALERT_2_B Isotropic non-H Atoms in Main Residue(s) ..... =          1
PLAT420_ALERT_2_B D-H Without Acceptor       O1M    -   H1M1   ...          ?
PLAT430_ALERT_2_B Short Inter D...A Contact  O1W    ..  O2       =       2.73 Ang.
PLAT430_ALERT_2_B Short Inter D...A Contact  O2     ..  O2W      =       2.73 Ang.
PLAT430_ALERT_2_B Short Inter D...A Contact  O2     ..  O5W      =       2.84 Ang.

Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.99
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT043_ALERT_1_C Check Reported Molecular Weight ................     778.74
PLAT044_ALERT_1_C Calculated and Reported Dx Differ ..............          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       2.00 Ratio
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT301_ALERT_3_C Main Residue  Disorder .........................       4.00 Perc.
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....       >O1W
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....       <O2W
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....       <O3W
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....       <O4W
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....       <O5W
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C12    -   C12_c    =       1.54 Ang.
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C34    -   C34_b    =       1.53 Ang.
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C56    -   C56_a    =       1.55 Ang.
PLAT432_ALERT_2_C Short Inter X...Y Contact  O1W    ..  C12      =       2.98 Ang.
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          6
PLAT764_ALERT_4_C Overcomplete CIF Bond list Detected (Rep/Expd) .       1.28 Ratio

Alert level G
FORMU01_ALERT_2_G  There is a discrepancy between the atom counts in the
            _chemical_formula_sum and the formula from the _atom_site* data.
            Atom count from _chemical_formula_sum:C6 H20 Er2 O22
            Atom count from the _atom_site data:  C6 H12 Er2 O22
CELLZ01_ALERT_1_G Difference between formula and atom_site contents detected.
CELLZ01_ALERT_1_G WARNING: H atoms missing from atom site list. Is this intentional?
           From the CIF: _cell_formula_units_Z    2
           From the CIF: _chemical_formula_sum  C6 H20 Er2 O22
           TEST: Compare cell contents of formula and atom_site data

           atom    Z*formula  cif sites diff
           C         12.00     12.00    0.00
           H         40.00     24.00   16.00
           Er         4.00      4.00    0.00
           O         44.00     44.00    0.00
CHEMW03_ALERT_2_C The ratio of given/expected molecular weight as
            calculated from the _atom_site* data lies outside
            the range 0.99 <> 1.01
           From the CIF: _cell_formula_units_Z                    2
           From the CIF: _chemical_formula_weight           778.74
           TEST: Calculate formula weight from _atom_site_*
           atom     mass    num     sum
           C        12.01    6.00   72.07
           H         1.01   12.00   12.10
           O        16.00   22.00  351.98
           Er      167.26    2.00  334.52
           Calculated formula weight              770.66

   0 ALERT level A = In general: serious problem
   5 ALERT level B = Potentially serious problem
  21 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   8 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
  16 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   3 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

The lanthanoid elements all form hydrated oxalates of the composition M₂(C₂O₄)₃.nH₂O (M = lanthanoid). There are two large isomorphous series of lanthanide oxalates, one with n ~10 (monoclinic) and one with n = 6 (triclinic). In the isomorphous series with n ~10, the n value varies slightly, and it appears to be dependent on the crystallographic radius of the lanthanide ion and the method of preparation. Compounds with M = Y, La–Ho form a series of `decahydrates', while compounds with M = Sc, Tm–Lu form a series of `hexahydrates'. Only erbium oxalate can be synthesized both as a decahydrate and a hexahydrate (Hansson, 1973), and this is of special interest.

Until the present study, no structurally characterized erbium(III) oxalates have been reported; only powder X-ray diffraction data have been measured and indexed (Hansson, 1973; Ollendorff & Weigel, 1969; Watanabe & Nagashima, 1971). We report here the crystal and molecular structure of erbium(III) oxalate decahydrate, (I).

Two crystallographically equivalent Er atoms, three centrosymmetric oxalate groups, and ten water molecules (six aqua ligands and four water molecules of crystallization) account for one structural unit of (I). Each Er atom coordinates six O atoms from three bidentate oxalates, and three aqua ligands (Fig. 1). The coordination polyhedron ErO₉ is a distorted three-capped trigonal prism. The Er—O distances are between 2.355 (2) and 2.522 (2) Å (average 2.406 Å), which is in a good agreement with the values found in the Cambridge Structural Database (CSD; Version of October 2002; Allen, 2002) of 2.348–2.450 Å, average 2.408 Å (5 hits, R < 0.1).

The oxalate ligands are planar with C—C distances between 1.530 (6) and 1.549 (6) Å (average 1.538 Å), and C—O distances between 1.246 (3) and 1.262 (4) Å (average 1.253 Å). All these values are in a good agreement with values found in the CSD: 1.426–1.669 Å (average 1.549 Å) and 1.076–1.435 Å (average 1.252 Å) for C—C and C—O distances, respectively (536 hits, R < 0.05).

The structure of (I) is composed of infinite erbium oxalate layers perpendicular to the b axis and situated around y = 0 and y = 1/2. The layers are held together by hydrogen bonds via the water molecules of crystallization situated between the layers. Fig. 2 shows part of the infinite layer around y = 1/2 projected along the b axis. Each oxalate ligand is coordinated to two metal atoms forming two chelates. Adjacent layers are related to each other by c glides. The four water molecules of crystallization, situated between the layers, are disordered over five positions.

S2. Experimental

Colourless crystals of the title compound were obtained from an aqueous solution containing HCl (0.1 M), K₄[Nb₂(S₂)₂(C₂O₄)₄] (0.01 g) (Sokolov et al., 2001) and Er(NO₃)₃ (0.02 g). Yield 70%.

S3. Refinement

The H atoms of the coordinated water molecules were located geometrically and refined with the O—H distances restrained to 0.98 (1) Å and the H···H distances restrained to 1.60 (3) Å. The isotropic displacement parameters of all the H atoms were fixed at 1.5U_eq of the parent O atom. The four water molecules of crystallization are disordered over five positions and were refined isotropically with equivalent displacement parameters. The largest difference peak is 0.99 Å from the disordered water molecule O4W and the deepest hole is 1.07 Å from the water molecule O1M, coordinated to the Er atom.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1998); program(s) used to refine structure: SHELXL97 (Sheldrick, 1998); molecular graphics: SHELXTL (Bruker, 2001); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The coordination environment of the Er atom. Displacement ellipsoids are plotted at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii.
	Fig. 2. Part of the erbium-oxalate layer around y = 1/2 projected on to (010).

(I)

Crystal data

[Er2(C2O4)3(H2O)6]·4H2O	F(000) = 736
Mr = 778.74	Dx = 2.753 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.9065 (6) Å	Cell parameters from 1006 reflections
b = 9.5339 (5) Å	θ = 3.1–38.9°
c = 9.8977 (5) Å	µ = 8.99 mm^−1
β = 114.125 (1)°	T = 173 K
V = 939.28 (9) Å^3	Block, colourless
Z = 2	0.26 × 0.18 × 0.11 mm

Data collection

Bruker SMART1000 CCD diffractometer	4504 independent reflections
Radiation source: fine-focus sealed tube	4077 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
Detector resolution: 8.33 pixels mm^-1	θmax = 36.3°, θmin = 3.0°
CCD scans	h = −18→18
Absorption correction: integration (SAINT-Plus; Bruker, 2001)	k = −8→15
Tmin = 0.204, Tmax = 0.470	l = −16→16
11931 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.028	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.070	w = 1/[σ^2(Fo^2) + (0.0212P)^2 + 2.9967P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max = 0.001
4504 reflections	Δρmax = 2.51 e Å^−3
158 parameters	Δρmin = −1.85 e Å^−3
10 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0011 (2)

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.

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Er1	0.191404 (11)	0.456295 (12)	−0.669046 (12)	0.00793 (4)
O1M	0.2120 (3)	0.6856 (3)	−0.5707 (3)	0.0213 (5)
H1M1	0.269 (4)	0.756 (4)	−0.587 (6)	0.032*
H1M2	0.133 (3)	0.734 (5)	−0.568 (6)	0.032*
O2M	0.1667 (3)	0.2191 (3)	−0.6175 (3)	0.0247 (6)
H2M1	0.108 (5)	0.151 (4)	−0.688 (4)	0.037*
H2M2	0.221 (5)	0.167 (5)	−0.528 (3)	0.037*
O3M	0.2955 (2)	0.3191 (3)	−0.7993 (3)	0.0179 (4)
H3M1	0.3934 (11)	0.322 (5)	−0.752 (5)	0.027*
H3M2	0.262 (4)	0.223 (2)	−0.821 (6)	0.027*
O1	0.6108 (2)	0.6089 (2)	−0.5352 (2)	0.0128 (4)
O2	0.3906 (2)	0.5737 (2)	−0.6662 (2)	0.0122 (4)
C12	0.5008 (3)	0.5531 (3)	−0.5580 (3)	0.0101 (4)
O3	−0.1636 (2)	0.5629 (3)	−0.5710 (3)	0.0183 (5)
O4	−0.0260 (2)	0.5246 (3)	−0.6842 (3)	0.0136 (4)
C34	−0.0550 (3)	0.5248 (3)	−0.5732 (3)	0.0126 (5)
O5	−0.1283 (2)	0.3960 (2)	−1.1227 (2)	0.0144 (4)
O6	0.0141 (2)	0.3541 (2)	−0.8878 (2)	0.0119 (3)
C56	−0.0330 (3)	0.4274 (3)	−1.0035 (3)	0.0100 (4)
O1W	0.4246 (8)	−0.1872 (9)	−0.7979 (9)	0.0444 (10)*	0.577 (4)
O2W	0.4431 (10)	−0.2877 (11)	−0.8780 (11)	0.0444 (10)*	0.428 (9)
O3W	0.3386 (10)	−0.0884 (11)	−0.6556 (11)	0.0444 (10)*	0.442 (9)
O4W	0.4210 (15)	0.0125 (16)	−0.5761 (16)	0.0444 (10)*	0.298 (9)
O5W	0.4183 (17)	−0.1448 (19)	−0.7429 (19)	0.0444 (10)*	0.255 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Er1	0.00658 (6)	0.00993 (6)	0.00659 (6)	0.00003 (4)	0.00198 (4)	0.00012 (3)
O1M	0.0176 (10)	0.0208 (11)	0.0241 (12)	0.0035 (9)	0.0071 (9)	−0.0074 (9)
O2M	0.0357 (14)	0.0168 (11)	0.0111 (9)	−0.0117 (10)	−0.0011 (9)	0.0012 (8)
O3M	0.0136 (9)	0.0183 (10)	0.0206 (10)	−0.0005 (8)	0.0057 (8)	−0.0082 (9)
O1	0.0087 (8)	0.0156 (9)	0.0131 (8)	−0.0007 (7)	0.0033 (7)	0.0038 (7)
O2	0.0076 (7)	0.0154 (9)	0.0105 (8)	−0.0012 (7)	0.0004 (7)	0.0027 (7)
C12	0.0086 (9)	0.0121 (10)	0.0090 (10)	0.0000 (8)	0.0029 (8)	−0.0008 (8)
O3	0.0146 (9)	0.0276 (12)	0.0160 (10)	0.0099 (9)	0.0097 (8)	0.0070 (9)
O4	0.0119 (8)	0.0181 (10)	0.0117 (9)	0.0036 (7)	0.0058 (7)	0.0024 (7)
C34	0.0122 (10)	0.0149 (11)	0.0123 (11)	0.0040 (9)	0.0067 (9)	0.0041 (9)
O5	0.0131 (9)	0.0150 (9)	0.0098 (8)	−0.0049 (7)	−0.0007 (7)	0.0020 (7)
O6	0.0123 (8)	0.0132 (9)	0.0093 (8)	−0.0015 (7)	0.0037 (7)	0.0015 (7)
C56	0.0097 (10)	0.0114 (10)	0.0079 (9)	−0.0022 (8)	0.0027 (8)	−0.0001 (8)

Geometric parameters (Å, º)

Er1—O1M	2.366 (3)	O1—C12	1.246 (3)
Er1—O2M	2.357 (3)	O2—C12	1.256 (3)
Er1—O3M	2.420 (2)	C12—C12^i	1.536 (6)
Er1—O1^i	2.359 (2)	O3—C34	1.247 (4)
Er1—O2	2.434 (2)	O4—C34	1.262 (4)
Er1—O3^ii	2.522 (2)	C34—C34^ii	1.530 (6)
Er1—O4	2.404 (2)	O5—C56	1.249 (3)
Er1—O5^iii	2.355 (2)	O6—C56	1.257 (3)
Er1—O6	2.440 (2)	C56—C56^iii	1.549 (6)
O1M—H1M1	0.97 (5)	O1W—O2W	1.311 (12)
O1M—H1M2	0.99 (4)	O1W—O5W	0.704 (17)
O2M—H2M1	0.98 (4)	O3W—O4W	1.332 (18)
O2M—H2M2	0.98 (4)	O3W—O5W	1.55 (2)
O3M—H3M1	0.98 (3)	O4W—O4W^iv	1.78 (3)
O3M—H3M2	0.98 (3)
O1M—Er1—O2M	142.85 (10)	O5^iii—Er1—O3^ii	139.76 (8)
O1M—Er1—O3M	137.06 (9)	O5^iii—Er1—O4	81.68 (8)
O1M—Er1—O2	68.67 (9)	O5^iii—Er1—O6	67.64 (7)
O1M—Er1—O3^ii	72.97 (10)	O6—Er1—O3^ii	116.76 (8)
O1M—Er1—O4	72.58 (9)	Er1—O1M—H1M1	122 (3)
O1M—Er1—O6	129.89 (8)	Er1—O1M—H1M2	121 (3)
O2M—Er1—O3M	73.56 (10)	H1M1—O1M—H1M2	108 (3)
O2M—Er1—O1^i	72.96 (9)	Er1—O2M—H2M1	126 (3)
O2M—Er1—O2	128.24 (10)	Er1—O2M—H2M2	127 (3)
O2M—Er1—O3^ii	70.00 (9)	H2M1—O2M—H2M2	107 (3)
O2M—Er1—O4	94.38 (10)	Er1—O3M—H3M1	113 (3)
O2M—Er1—O6	71.95 (8)	Er1—O3M—H3M2	114 (3)
O3M—Er1—O2	69.13 (8)	H3M2—O3M—H3M1	112 (3)
O3M—Er1—O3^ii	136.54 (9)	C12—O1—Er1^i	121.21 (18)
O3M—Er1—O6	71.69 (8)	C12—O2—Er1	118.43 (19)
O1^i—Er1—O1M	89.50 (9)	O1—C12—O2	127.0 (3)
O1^i—Er1—O3M	81.39 (8)	O1—C12—C12^i	116.8 (3)
O1^i—Er1—O2	67.17 (7)	O2—C12—C12^i	116.2 (3)
O1^i—Er1—O3^ii	66.01 (8)	C34—O3—Er1^ii	118.4 (2)
O1^i—Er1—O4	131.17 (8)	C34—O4—Er1	122.56 (19)
O1^i—Er1—O6	140.44 (8)	O3—C34—O4	126.4 (3)
O2—Er1—O3^ii	118.24 (8)	O3—C34—C34^ii	117.2 (3)
O2—Er1—O6	125.00 (7)	O4—C34—C34^ii	116.4 (3)
O4—Er1—O3M	141.15 (8)	C56—O5—Er1^iii	121.12 (19)
O4—Er1—O2	136.82 (8)	C56—O6—Er1	117.83 (18)
O4—Er1—O3^ii	65.35 (8)	O5—C56—O6	126.9 (3)
O4—Er1—O6	69.46 (8)	O5—C56—C56^iii	116.6 (3)
O5^iii—Er1—O1M	75.67 (9)	O6—C56—C56^iii	116.5 (3)
O5^iii—Er1—O2M	138.12 (8)	O5W—O1W—O2W	167.4 (19)
O5^iii—Er1—O3M	83.67 (9)	O4W—O3W—O5W	100.6 (11)
O5^iii—Er1—O1^i	138.22 (8)	O3W—O4W—O4W^iv	126.1 (15)
O5^iii—Er1—O2	71.06 (7)	O1W—O5W—O3W	152 (2)

Symmetry codes: (i) −x+1, −y+1, −z−1; (ii) −x, −y+1, −z−1; (iii) −x, −y+1, −z−2; (iv) −x+1, −y, −z−1.