Diholmium(III) tris­ulfate tetra­hydrate

The single-crystal structure of the title compound {systematic name: poly[tetra­aqua­tri-μ₂-sulfato-diholmium(III)]}, [Ho₂(SO₄)₃(H₂O)₄]_n, features two-dimensional holmium(III) sulfate layers constructed by eight-coordinate holmium and sulfate groups. The coordination about Ho includes four O atoms from bridging sulfate ions. One S atom makes three S—O—Ho linkages through bridging O atoms, while a second S atom lies on a twofold axis and makes two S—O—Ho linkages. The coordination of each Ho atom is completed by four water mol­ecules, which act as terminal ligands of Ho³⁺.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](S-O) = 0.003 Å
• R factor = 0.047
• wR factor = 0.130
• Data-to-parameter ratio = 12.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.98
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.91

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.913
            Tmax scaled      0.487 Tmin scaled      0.389
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT794_ALERT_5_G Check Predicted Bond Valency for Ho1         (3)       3.28
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......         13

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

Over the past decades, the synthesis of new two and three dimensional inorganic materials have received great attention, due to their functional applications. As the building elements of open-frameworks, not only silicon and germanium have been chosen to synthesize new frameworks (Li et al., 1998; Plévert et al., 2001; Xu et al., 2004a; Xu et al.,2004b), but also rare–earth elements. In the last few years, an important advance in solid inorganic materials has been achieved by study of lanthanide sulfates (Zhang et al.,2004; Yuan et al., 2004; Xu et al., 2006a; Xu et al., 2006b; Doran et al., 2002, Xu et al., 2007). In this work, we designed and synthesized the title compound, holmium(3+) sulfate octahydrate, which features a two–dimensional layered framework.

Similar to Eu₂(SO₄)₃(H₂O)₈ (Xu et al.,2007) and Gd₂(SO₄)₃(H₂O)₈ (Hummel et al.,1993), the layer of the title compound is constructed from HoO₈ polyhedra and SO₄ tetrahedra. The asymmetric unit contains 12 crystallographic independent non–hydrogen atoms, all of which belong to the inorganic framework. As show in Fig. 1, the coordination about Ho is achieved by four O atoms from bridging sulfate ions. S1 makes three S–O–Ho linkages through bridging O atoms, while S2 lies on a two fold axis and makes two S–O–Ho linkages. The coordination sphere of each Ho is completed by four water molecules, which act as terminal ligands of Ho³⁺. To the best of our knowledge, although many lanthanide sulfates are known, this is the first example of holmium sulfate.

The bond distances and bond angles are in agreement with those found in the reported rare-earth compounds (Xu et al., 2007). The geometry of the sulfate ions is unexceptional. Fig. 2 shows the two-dimensional arrangement in the unit cell, displaying the way the different Ho ions are connected by bridging sulfates and water molecules.

Related literature

For related literature, see: Doran et al. (2002); Hummel et al. (1993); Li et al. (1998); Plévert et al. (2001); Xu, Fan, Chino et al. (2004); Xu, Fan, Elangovan et al. (2004); <unl>Xu, Ding, Feng et al. (2006)</unl>; Xu, Ding, Zhou & Liu (2006); Yuan et al. (2004); Zhang et al. (2004); Xu et al. (2007).

S2. Experimental

Colorless block crystals were synthesized hydrothermally from a mixture of Ho₂O₃, H₂SO₄, H₂O and ethylenediamine. In a typical synthesis, Ho₂O₃(0.2584 g) was dissolved in a mixture of 5 ml water, ethylenediamine (0.3651 g) and H₂SO₄ (98%) (0.2148 g) with constant stirring. Finally, the mixture was kept in a 25 ml Teflon-lined steel autoclave at 453 K for 6 days. The autoclave was slowly cooled to room temperature, and then the product was filtered, washed with distilled water, and dried at room temperature. Colorless block crystals of the title compound were obtained.

S3. Refinement

The highest peak in the difference map is 4.55 e/ų, and 0.94 (2) Å from Ho₁, while the minimum peak is 0.83 (2) Å from Ho₁. The H atom was located from a difference-Fourier map. Because the refinement for H atoms is not stable, the distances for H—O are restrained in the final refinement. All the H—O bond lengths are fixed as 0.85 (2) Å.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL (Sheldrick, 1997b.

Figures

	Fig. 1. The molecular structure for title compound. Displacement ellipsoids at the 70% probability level.
	Fig. 2. The crystal packing in the unit cell of Ho2(SO4)3(H2O)8.

Poly[tetraaquatri-µ₂-sulfato-diholmium(III)]

Crystal data

[Ho2(SO4)3(H2O)4]	F(000) = 1432
Mr = 762.17	Dx = 3.155 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1579 reflections
a = 13.466 (3) Å	θ = 2.8–27.0°
b = 6.6966 (15) Å	µ = 10.29 mm^−1
c = 18.183 (4) Å	T = 293 K
β = 101.875 (3)°	Block, colorless
V = 1604.6 (6) Å^3	0.10 × 0.08 × 0.07 mm
Z = 4

Data collection

Bruker APEX2 CCD diffractometer	1725 independent reflections
Radiation source: fine-focus sealed tube	1579 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
ω scans	θmax = 27.0°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	h = −15→17
Tmin = 0.426, Tmax = 0.533	k = −8→8
4131 measured reflections	l = −21→23

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)] = 0.047	Only H-atom coordinates refined
wR(F^2) = 0.130	w = 1/[σ^2(Fo^2) + (0.0925P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max = 0.009
1725 reflections	Δρmax = 4.55 e Å^−3
139 parameters	Δρmin = −2.86 e Å^−3
13 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997a), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00497 (16)

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
Ho1	0.833712 (14)	0.02050 (3)	0.607964 (10)	0.01160 (7)
S1	0.78096 (8)	−0.02655 (15)	0.41069 (6)	0.0116 (3)
S2	1.0000	0.3197 (2)	0.7500	0.0125 (3)
O1	0.9155 (2)	0.1928 (5)	0.71260 (17)	0.0239 (8)
O2	0.8377 (2)	−0.0344 (5)	0.3506 (2)	0.0219 (9)
O3	0.8517 (2)	−0.0730 (5)	0.48430 (16)	0.0153 (7)
O4	1.0348 (2)	0.4445 (5)	0.69329 (18)	0.0192 (8)
O5	0.6988 (2)	−0.1760 (5)	0.39806 (16)	0.0184 (8)
O6	0.7382 (2)	0.1712 (5)	0.41740 (17)	0.0211 (8)
O1W	0.9839 (2)	−0.1652 (5)	0.6397 (2)	0.0307 (10)
H1A	0.989 (3)	−0.2916 (17)	0.641 (3)	0.046*
H1B	1.0392 (12)	−0.101 (3)	0.646 (3)	0.046*
O2W	0.6576 (3)	−0.0171 (4)	0.5448 (2)	0.0199 (9)
H2A	0.6163 (18)	0.076 (3)	0.528 (3)	0.030*
H2B	0.6365 (12)	−0.106 (3)	0.5116 (12)	0.030*
O3W	0.7442 (3)	−0.0132 (5)	0.7027 (2)	0.0272 (11)
H3A	0.6826 (11)	−0.045 (6)	0.6842 (17)	0.041*
H3B	0.7534 (16)	0.023 (5)	0.7492 (6)	0.041*
O4W	0.9593 (2)	0.2333 (5)	0.56423 (16)	0.0183 (8)
H4A	1.0001 (11)	0.172 (4)	0.5433 (12)	0.028*
H4B	0.992 (2)	0.309 (4)	0.5977 (15)	0.028*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ho1	0.00961 (13)	0.00923 (12)	0.01614 (14)	−0.00108 (5)	0.00306 (11)	−0.00041 (6)
S1	0.0102 (5)	0.0092 (5)	0.0160 (5)	−0.0012 (3)	0.0039 (4)	0.0008 (3)
S2	0.0096 (5)	0.0116 (7)	0.0159 (6)	0.000	0.0015 (5)	0.000
O1	0.0205 (14)	0.0269 (19)	0.0239 (16)	−0.0132 (14)	0.0032 (13)	−0.0038 (14)
O2	0.0153 (18)	0.0308 (18)	0.0211 (17)	−0.0025 (12)	0.0069 (15)	−0.0044 (13)
O3	0.0124 (12)	0.0193 (15)	0.0151 (13)	0.0017 (13)	0.0053 (11)	0.0023 (13)
O4	0.0172 (15)	0.0214 (16)	0.0212 (16)	−0.0008 (13)	0.0092 (13)	0.0067 (14)
O5	0.0136 (13)	0.0121 (15)	0.0287 (16)	−0.0049 (13)	0.0022 (12)	0.0002 (13)
O6	0.0250 (14)	0.0083 (14)	0.0299 (17)	0.0019 (13)	0.0052 (13)	0.0025 (13)
O1W	0.0127 (13)	0.0118 (16)	0.063 (2)	0.0014 (13)	−0.0016 (16)	0.0069 (17)
O2W	0.0170 (17)	0.0108 (15)	0.0287 (19)	0.0009 (11)	−0.0027 (17)	−0.0013 (12)
O3W	0.0206 (19)	0.045 (2)	0.0180 (19)	−0.0147 (13)	0.0087 (17)	−0.0067 (13)
O4W	0.0152 (13)	0.0208 (17)	0.0199 (15)	−0.0031 (13)	0.0058 (12)	−0.0043 (12)

Geometric parameters (Å, º)

Ho1—O6^i	2.287 (3)	S2—O1^iii	1.470 (3)
Ho1—O1	2.303 (3)	S2—O4	1.477 (4)
Ho1—O3W	2.308 (4)	S2—O4^iii	1.477 (4)
Ho1—O1W	2.344 (3)	O5—Ho1^ii	2.347 (3)
Ho1—O5^ii	2.347 (3)	O6—Ho1^i	2.287 (3)
Ho1—O3	2.394 (3)	O1W—H1A	0.849 (12)
Ho1—O2W	2.426 (4)	O1W—H1B	0.847 (14)
Ho1—O4W	2.466 (3)	O2W—H2A	0.849 (17)
S1—O2	1.457 (4)	O2W—H2B	0.855 (15)
S1—O6	1.459 (3)	O3W—H3A	0.855 (14)
S1—O5	1.474 (3)	O3W—H3B	0.866 (12)
S1—O3	1.507 (3)	O4W—H4A	0.839 (16)
S2—O1	1.470 (3)	O4W—H4B	0.845 (17)
O6^i—Ho1—O1	79.91 (11)	O2—S1—O6	111.8 (2)
O6^i—Ho1—O3W	88.51 (12)	O2—S1—O5	110.55 (19)
O1—Ho1—O3W	70.54 (12)	O6—S1—O5	109.45 (19)
O6^i—Ho1—O1W	146.85 (11)	O2—S1—O3	108.96 (19)
O1—Ho1—O1W	79.67 (12)	O6—S1—O3	107.54 (18)
O3W—Ho1—O1W	108.75 (13)	O5—S1—O3	108.37 (18)
O6^i—Ho1—O5^ii	144.18 (10)	O1—S2—O1^iii	109.4 (3)
O1—Ho1—O5^ii	125.75 (11)	O1—S2—O4	109.32 (18)
O3W—Ho1—O5^ii	79.48 (11)	O1^iii—S2—O4	108.85 (18)
O1W—Ho1—O5^ii	68.48 (10)	O1—S2—O4^iii	108.85 (18)
O6^i—Ho1—O3	99.64 (11)	O1^iii—S2—O4^iii	109.32 (18)
O1—Ho1—O3	141.59 (11)	O4—S2—O4^iii	111.0 (3)
O3W—Ho1—O3	147.65 (12)	S2—O1—Ho1	149.9 (2)
O1W—Ho1—O3	80.99 (12)	S1—O3—Ho1	127.75 (18)
O5^ii—Ho1—O3	75.70 (11)	S1—O5—Ho1^ii	143.27 (18)
O6^i—Ho1—O2W	70.48 (10)	S1—O6—Ho1^i	163.9 (2)
O1—Ho1—O2W	134.25 (12)	Ho1—O1W—H1A	127 (2)
O3W—Ho1—O2W	74.53 (14)	Ho1—O1W—H1B	117.0 (16)
O1W—Ho1—O2W	140.51 (11)	H1A—O1W—H1B	116 (3)
O5^ii—Ho1—O2W	73.80 (9)	Ho1—O2W—H2A	126.8 (19)
O3—Ho1—O2W	78.83 (12)	Ho1—O2W—H2B	123.8 (12)
O6^i—Ho1—O4W	72.75 (11)	H2A—O2W—H2B	99 (3)
O1—Ho1—O4W	74.56 (11)	Ho1—O3W—H3A	110 (2)
O3W—Ho1—O4W	142.73 (11)	Ho1—O3W—H3B	135.3 (16)
O1W—Ho1—O4W	76.79 (11)	H3A—O3W—H3B	113 (2)
O5^ii—Ho1—O4W	133.40 (11)	Ho1—O4W—H4A	114.7 (16)
O3—Ho1—O4W	68.87 (10)	Ho1—O4W—H4B	114 (2)
O2W—Ho1—O4W	125.16 (11)	H4A—O4W—H4B	109 (3)

Symmetry codes: (i) −x+3/2, −y+1/2, −z+1; (ii) −x+3/2, −y−1/2, −z+1; (iii) −x+2, y, −z+3/2.