[beta]-Sm(OH)₂Cl: a new lamellar variety

Crystals of dihydroxysamarium chloride were synthesized hydro­thermally at 473 K. The orthorhombic structure was determined by single-crystal X-ray diffraction analysis. [beta]-­Sm(OH)₂Cl exhibits a lamellar structure built up from the stacking of neutral slabs; all the atoms lie on crystallographic mirror planes. The structure is stabilized by strong hydrogen bonds between the OH groups and the Cl ions of adjacent layers.

S1. Comment

Research into field of compounds with microporous frameworks has been dramatically enhanced by use of a hydrothermal technique (Cheetham et al., 1999). Inside this large family of compounds, the hybrids whose structures are built up from the iono-covalent association of inorganic and organic moieties show great porosity with, for example, metallocarboxylates (Li et al., 1999) or metallophosphonates (Riou et al., 2000).

In our work with metallosulfonates with open-structures, we have obtained a by-product which corresponds to a new polymorph of bis(hydroxyl)samarium chloride denoted β-Sm(OH)₂Cl to distinguish from the already reported form (Klevtsova et al., 1969). β-Sm(OH)₂Cl is a bidimensional structure built up from the stacking along [100] of neutral layers (noted A on Fig. 1a) in strict alternation with their equivalent (noted B) from an n-mirror glide. Inside the layers, each Sm atom is eight-coordinated, with six Sm—O distances in the range 2.383 (5)–2.452 (4) Å and two longer Sm···Cl distances of 2.930 (2) Å (Table 1). The edge-connections of these polyhedra form corrugated layers (Fig. 1 b) whose mean plane is parallel to (100).

The stabilization of the structure is ensured via hydrogen bonds between the protons of the OH groups and the Cl ions from an adjacent layer. It is worth noting that two successive layers along [100] are arranged in such a way that the OH groups from one layer and the Cl ions of the other are face to face (Fig. 1a) resulting in short Cl···O distances (<3.5 Å) implying strong hydrogen bonds which stabilize the structure (Table 2). In a first examination, the structure of the previously reported variety of Sm(OH)₂Cl (Klevtsova et al., 1969) looks very different from the title compound (I) since it exhibits a three-dimensional framework with a larger density (4.991 versus 4.892 g cm^-3). Nevertheless, some correlations between the two structure types are observed. The coordination around Sm is similar with six Sm—O distances in the range 2.36 (2)–2.46 (1) Å and two longer Sm···Cl distances [3.176 (5) and 2.936 (5)]. Furthermore, the framework (Fig. 2) is built up from the connection via the OH groups of layers almost identical to the B layers drawn on Fig. 1a. In fact, just the relative location of the Cl ions in the Sm(OH)₆Cl₂ polyhedra differs. In (I) they are all located on the outer edges of the corrugated planes (Fig. 1 b) and point alternatively on each side of the layers whereas they constitute the internal edge-sharing of the similar planes in the other form. This difference prohibits any phase transition between the two forms without a complete rearrangement of the structure.

S2. Experimental

The title compound (I) was prepared from a mixture of samarium trichloride hexahydrate, ethylsulfonic acid and deionized water in the molar ratio 1:2:300. The initial pH was adjusted to 8 by adding dropwise a concentrated NaOH solution. The resulting mixture was sealed in a teflon-lined autoclave (Parr) then heated for two days at 473 K under autogenous pressure. After cooling to room temperature, the pH was measured to 4 (?? what was added, or had the ph changed to 4??), the solid was separated from the solution by filtration, washed with water and dried in air. β-Sm(OH)₂Cl was obtained pure in the form of ??colorless?? rhombic platelets. Attempts to synthesize β-Sm(OH)₂Cl without ethylsulfonic acid have failed leading to a mixture of the two varieties of Sm(OH)₂Cl. A suitable single-crystal for X-ray diffraction study was choosen by optical microscopy and glued on a glass fiber.

The data set is complete to 98.2% at θ=28.96°. The OH groups were defined both from electroneutrality and bond-valence calculations (O'Keeffe et al., 1992).

H atoms were refined with constraints on the O—H distances.

Computing details

Data collection: SMART (Bruker, 199?); cell refinement: SMART (Bruker, 199?); data reduction: SMART (Bruker, 199?); program(s) used to solve structure: SHELXTL (Sheldrick, 1994); program(s) used to refine structure: SHELXTL (Sheldrick, 1994); molecular graphics: DIAMOND (Brandenburg, 1996); software used to prepare material for publication: SHELXTL (Sheldrick, 1994).

Figures

	Fig. 1. (a) β-Sm(OH)2Cl, projection along [010] showing the bidimensional feature of the structure (black and white circles for Cl and O atoms, respectively, small circles for H atoms) and (b) the perspective view of one corrugated plane of β-Sm(OH)2Cl.
	Fig. 2. Sm(OH)2Cl (Klevtsova et al., 1969), projection along [010] showing the three-dimensional feature of the structure (black and white circles for Cl and OH groups respectively).

(I)

Crystal data

H2ClO2Sm	Dx = 4.892 Mg m^−3
Mr = 219.5	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 1259 reflections
a = 12.6014 (14) Å	θ = 3.2–29.9°
b = 3.7706 (4) Å	µ = 20.32 mm^−1
c = 6.2740 (7) Å	T = 296 K
V = 298.11 (6) Å^3	Rhombohedral, light yellow
Z = 4	0.04 × 0.04 × 0.04 mm
F(000) = 388

Data collection

CCD area-detector diffractometer	454 independent reflections
Radiation source: fine-focus sealed tube	347 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.028
ω scans	θmax = 29.9°, θmin = 3.2°
Absorption correction: semi-empirical (using intensity measurements) SADABS (Sheldrick, 1996)	h = −15→17
Tmin = 0.497, Tmax = 0.497	k = −4→5
1935 measured reflections	l = −3→8

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)] = 0.025	Only H-atom coordinates refined
wR(F^2) = 0.060	w = 1/[σ^2(Fo^2) + (0.0325P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.12	(Δ/σ)max < 0.001
454 reflections	Δρmax = 1.13 e Å^−3
30 parameters	Δρmin = −1.11 e Å^−3
2 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0034 (8)

Special details

Experimental. 'Blessing (1995). Acta Cryst. A51, 33–38'

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
Sm	0.06096 (3)	0.7500	0.24830 (6)	0.00993 (19)
Cl	0.21914 (14)	1.2500	0.4122 (3)	0.0171 (4)
O1	0.0813 (4)	0.2500	0.0018 (9)	0.0121 (10)
O2	−0.0437 (3)	0.2500	0.3660 (8)	0.0118 (11)
H1	0.146 (3)	0.2500	−0.057 (13)	0.020*
H2	−0.108 (3)	0.2500	0.311 (14)	0.020*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sm	0.0126 (2)	0.0068 (3)	0.0104 (2)	0.000	−0.00185 (14)	0.000
Cl	0.0143 (7)	0.0155 (8)	0.0217 (9)	0.000	−0.0024 (8)	0.000
O1	0.008 (2)	0.014 (3)	0.014 (2)	0.000	0.0010 (19)	0.000
O2	0.011 (2)	0.015 (3)	0.009 (3)	0.000	0.0005 (19)	0.000

Geometric parameters (Å, º)

Sm—O1^i	2.383 (5)	Sm—Sm^i	3.9525 (7)
Sm—O2	2.416 (3)	Sm—Sm^v	3.9525 (7)
Sm—O2^ii	2.416 (3)	Cl—Sm^ii	2.9301 (15)
Sm—O2^iii	2.430 (5)	O1—Sm^i	2.383 (5)
Sm—O1	2.452 (4)	O1—Sm^iv	2.452 (4)
Sm—O1^ii	2.452 (4)	O1—H1	0.90 (2)
Sm—Cl	2.9301 (15)	O2—Sm^iv	2.416 (3)
Sm—Cl^iv	2.9301 (15)	O2—Sm^iii	2.430 (5)
Sm—Sm^iv	3.7706 (4)	O2—H2	0.89 (2)
Sm—Sm^ii	3.7706 (4)
O1^i—Sm—O2	77.92 (13)	O1—Sm—Sm^ii	140.26 (10)
O1^i—Sm—O2^ii	77.92 (13)	O1^ii—Sm—Sm^ii	39.74 (10)
O2—Sm—O2^ii	102.57 (17)	Cl—Sm—Sm^ii	49.95 (2)
O1^i—Sm—O2^iii	126.05 (17)	Cl^iv—Sm—Sm^ii	130.05 (2)
O2—Sm—O2^iii	69.31 (14)	Sm^iv—Sm—Sm^ii	180.00 (2)
O2^ii—Sm—O2^iii	69.31 (14)	O1^i—Sm—Sm^i	35.74 (7)
O1^i—Sm—O1	70.32 (13)	O2—Sm—Sm^i	69.92 (12)
O2—Sm—O1	69.51 (14)	O2^ii—Sm—Sm^i	113.64 (11)
O2^ii—Sm—O1	148.19 (15)	O2^iii—Sm—Sm^i	138.61 (7)
O2^iii—Sm—O1	129.61 (10)	O1—Sm—Sm^i	34.58 (11)
O1^i—Sm—O1^ii	70.32 (13)	O1^ii—Sm—Sm^i	84.85 (11)
O2—Sm—O1^ii	148.19 (15)	Cl—Sm—Sm^i	148.00 (4)
O2^ii—Sm—O1^ii	69.51 (14)	Cl^iv—Sm—Sm^i	103.55 (3)
O2^iii—Sm—O1^ii	129.61 (10)	Sm^iv—Sm—Sm^i	61.511 (6)
O1—Sm—O1^ii	100.5 (2)	Sm^ii—Sm—Sm^i	118.489 (6)
O1^i—Sm—Cl	138.00 (5)	O1^i—Sm—Sm^v	35.74 (7)
O2—Sm—Cl	139.99 (13)	O2—Sm—Sm^v	113.64 (11)
O2^ii—Sm—Cl	76.23 (10)	O2^ii—Sm—Sm^v	69.92 (12)
O2^iii—Sm—Cl	73.22 (9)	O2^iii—Sm—Sm^v	138.61 (7)
O1—Sm—Cl	130.16 (11)	O1—Sm—Sm^v	84.85 (11)
O1^ii—Sm—Cl	69.85 (11)	O1^ii—Sm—Sm^v	34.58 (11)
O1^i—Sm—Cl^iv	138.00 (5)	Cl—Sm—Sm^v	103.55 (3)
O2—Sm—Cl^iv	76.23 (10)	Cl^iv—Sm—Sm^v	148.00 (4)
O2^ii—Sm—Cl^iv	139.99 (13)	Sm^iv—Sm—Sm^v	118.489 (6)
O2^iii—Sm—Cl^iv	73.22 (9)	Sm^ii—Sm—Sm^v	61.511 (6)
O1—Sm—Cl^iv	69.85 (11)	Sm^i—Sm—Sm^v	56.978 (12)
O1^ii—Sm—Cl^iv	130.16 (11)	Sm—Cl—Sm^ii	80.09 (5)
Cl—Sm—Cl^iv	80.09 (5)	Sm^i—O1—Sm	109.68 (13)
O1^i—Sm—Sm^iv	90.0	Sm^i—O1—Sm^iv	109.68 (13)
O2—Sm—Sm^iv	38.72 (8)	Sm—O1—Sm^iv	100.5 (2)
O2^ii—Sm—Sm^iv	141.28 (8)	Sm^i—O1—H1	115 (6)
O2^iii—Sm—Sm^iv	90.0	Sm—O1—H1	111 (3)
O1—Sm—Sm^iv	39.74 (10)	Sm^iv—O1—H1	111 (3)
O1^ii—Sm—Sm^iv	140.26 (10)	Sm—O2—Sm^iv	102.57 (17)
Cl—Sm—Sm^iv	130.05 (2)	Sm—O2—Sm^iii	110.69 (14)
Cl^iv—Sm—Sm^iv	49.95 (2)	Sm^iv—O2—Sm^iii	110.69 (14)
O1^i—Sm—Sm^ii	90.0	Sm—O2—H2	112 (3)
O2—Sm—Sm^ii	141.28 (8)	Sm^iv—O2—H2	112 (3)
O2^ii—Sm—Sm^ii	38.72 (8)	Sm^iii—O2—H2	108 (6)
O2^iii—Sm—Sm^ii	90.0

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···Cl^vi	0.90 (2)	2.54 (2)	3.193 (4)	130 (2)
O2—H2···Cl^vii	0.89 (2)	2.58 (3)	3.461 (5)	170 (8)

Symmetry codes: (vi) −x+1/2, −y+1, z−1/2; (vii) x−1/2, y−1, −z+1/2.