An orthorhombic modification of lithium chloride monohydrate

The structure of the title compound, LiCl·H₂O, has already been determined three times. Interestingly, the different authors found different cell parameters and space groups. We present here an orthorhombic modification.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](Please check) = 0.000 Å
• R factor = 0.019
• wR factor = 0.047
• Data-to-parameter ratio = 14.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level A:



DIFF_019  Alert A _diffrn_standards_number is missing
          Number of standards used in measurement.

Author response: The data were measured on an area-detector.

DIFF_020  Alert A _diffrn_standards_interval_count and
          _diffrn_standards_interval_time are missing. Number of measurements
          between standards or time (min) between standards.

Author response: The data were measured on an area-detector.

DIFF_022  Alert A _diffrn_standards_decay_% is missing
          Percentage decrease in standards intensity.

Author response: The data were measured on an area-detector.

 Alert Level B:



CHEMS_01  Alert B The sum formula contains elements in the wrong order.
          H  precedes Cl
          Sequence must be C, H, then alphabetical.

Author response: The elements are in alphabetical order. There is no C in the formula.

 3 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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S1. Comment

The structure of the title compound, LiCl·H₂O, has already been determined three times: Ott (1926) determined the structure by powder diffraction and stated a cubic cell with a = 3.830 Å and V = 56.2 ų in Pm3 m; Datt et al. (1971) investigated LiCl·D₂O and found similar cell parameters (a = b = 3.810 Å, c = 3.880 Å and V = 56.3 ų) but the tetragonal space group P4/m; Weiss et al. (1969) employed powder diffraction and ended up with a bigger cell (a = b = 7.669 Å, c = 7.742 Å and V = 455.3 ų) and a different tetragonal space group (P4₂/nmc). We report here an orthorhombic modification of LiCl·H₂O (Fig. 1) with the space group Cmcm.

The asymmetric unit comprises half a Cl anion on a mirror plane perpendicular to the c axis, half an O atom on a mirror plane perpendicular to the a axis, one H atom on a general position and two Li cations with s.o.f. = 0.25 on 2/m.. [please verify the two dots] (Li1) and m2m (Li2). The Cl anion is approximately octahedrally coordinated with Li2 and its symmetry equivalent in axial positions and Li1 and H1 and their symmetry equivalents in the equatorial plane. The Li cations are also octahedrally coordinated with Cl anions in the equatorial plane and two water molecules in axial positions. Apart from coordinating to Li the water molecules link two Cl anions by hydrogen bonds.

Unfortunately, Ott (1926) has not given the coordinates of the Li atom and Weiss et al. (1969) stated that the Li atom is disordered over three sites. Therefore, these two structures cannot be compared directly with the one we have determined. The fact that the cell parameters of Weiss et al. are so similar to those we have determined let us assume that the structure of Weiss et al. is wrong. The cell parameter of Ott is approximately half as long as what we determined for the three axes. Since the structure determination of Ott has also been done by powder diffraction, we assume that this structure is also wrong. The third determination, by Datt et al. (1971), gives a dubious position for the D atom leading to an Li···D distance of just 1.570 Å. Whereas the coordination of their Li atom is similar to the one we found (the Li atom is hexacoordinated by four Cl atoms and two water molecules), their Cl atom is coordinated by eight Li atoms (Cl···Li = 2.708 Å) and eight water molecules (Cl···O = 3.317 Å). For the same reasons which we have stated for the structure of Ott, we assume that the structure of Datt et al. is also incorrect.

S2. Experimental

X-ray quality crystals of the title compound were obtained after recrystallization from water at ambient temperature.

S3. Refinement

The H atom was located by difference Fourier synthesis and was refined isotropically.

Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 1991).

Figures

	Fig. 1. Perspective view of the title compound with the atom numbering; displacement ellipsoids are at the 50% probability level. [Symmetry code: (i) x, −y + 1/2, z.]
	Fig. 2. Perspective view of the title compound, showing the octahedral coordination of the Cl and Li ions. Colour scheme: Li pink, Cl green, O red, and H gray.

(I)

Crystal data

LiCl·H2O	F(000) = 240
Mr = 60.41	Dx = 1.782 Mg m^−3
Orthorhombic, Cmcm	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2c 2	Cell parameters from 11303 reflections
a = 7.6259 (13) Å	θ = 3.1–29.4°
b = 7.7107 (16) Å	µ = 1.27 mm^−1
c = 7.6592 (13) Å	T = 173 K
V = 450.37 (14) Å^3	Block, colourless
Z = 8	0.25 × 0.23 × 0.21 mm

Data collection

Stoe IPDS-II two-circle diffractometer	349 independent reflections
Radiation source: fine-focus sealed tube	325 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.049
ω scans	θmax = 29.2°, θmin = 4.6°
Absorption correction: multi-scan (MULABS; Spek, 1990; Blessing, 1995)	h = −10→10
Tmin = 0.742, Tmax = 0.777	k = −10→10
3852 measured reflections	l = −10→10

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.019	Hydrogen site location: difference Fourier map
wR(F^2) = 0.047	All H-atom parameters refined
S = 1.13	w = 1/[σ^2(Fo^2) + (0.0329P)^2] where P = (Fo^2 + 2Fc^2)/3
349 reflections	(Δ/σ)max < 0.001
25 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.43 e Å^−3

Special details

Experimental.

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
O1	0.0000	0.23543 (9)	0.00561 (8)	0.0159 (2)
H1	0.0868 (16)	0.1994 (15)	0.0598 (18)	0.040 (3)*
Cl1	0.26205 (3)	0.02380 (4)	0.2500	0.01605 (15)
Li1	0.5000	0.0000	0.0000	0.0270 (7)
Li2	0.5000	0.3138 (4)	0.2500	0.0308 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0156 (5)	0.0205 (4)	0.0117 (5)	0.000	0.000	0.0022 (3)
Cl1	0.01580 (19)	0.0200 (2)	0.01235 (18)	0.00075 (7)	0.000	0.000
Li1	0.0357 (19)	0.0168 (10)	0.0284 (15)	0.000	0.000	−0.0040 (10)
Li2	0.0454 (18)	0.0332 (13)	0.0138 (12)	0.000	0.000	0.000

Geometric parameters (Å, º)

O1—Li2^i	1.9943 (9)	Li1—Cl1^vii	2.6444 (4)
O1—Li1^ii	2.0405 (8)	Li1—Cl1^viii	2.6444 (4)
O1—H1	0.829 (13)	Li1—Li2^viii	3.086 (2)
Cl1—Li2^iii	2.572 (2)	Li1—Li2	3.086 (2)
Cl1—Li1^iv	2.6444 (4)	Li2—O1^i	1.9943 (9)
Cl1—Li1	2.6444 (4)	Li2—O1^ix	1.9943 (9)
Cl1—Li2	2.880 (2)	Li2—Cl1^x	2.572 (2)
Li1—O1^i	2.0404 (8)	Li2—Cl1^xi	2.572 (2)
Li1—O1^v	2.0404 (8)	Li2—Cl1^vi	2.880 (2)
Li1—Cl1^vi	2.6444 (4)	Li2—Li1^iv	3.086 (2)
Li2^i—O1—Li1^ii	99.77 (9)	Cl1^vi—Li1—Li2	59.75 (2)
Li2^i—O1—H1	115.3 (9)	Cl1^vii—Li1—Li2	120.25 (2)
Li1^ii—O1—H1	110.2 (8)	Cl1^viii—Li1—Li2	120.25 (2)
Li2^iii—Cl1—Li1^iv	119.31 (3)	Li2^viii—Li1—Li2	180.00 (7)
Li2^iii—Cl1—Li1	119.31 (3)	O1^i—Li2—O1^ix	158.04 (17)
Li1^iv—Cl1—Li1	92.789 (16)	O1^i—Li2—Cl1^x	96.89 (5)
Li2^iii—Cl1—Li2	168.07 (9)	O1^ix—Li2—Cl1^x	96.89 (5)
Li1^iv—Cl1—Li2	67.76 (3)	O1^i—Li2—Cl1^xi	96.89 (5)
Li1—Cl1—Li2	67.76 (3)	O1^ix—Li2—Cl1^xi	96.89 (5)
O1^i—Li1—O1^v	180.0	Cl1^x—Li2—Cl1^xi	101.97 (11)
O1^i—Li1—Cl1	86.897 (14)	O1^i—Li2—Cl1^vi	81.49 (7)
O1^v—Li1—Cl1	93.103 (14)	O1^ix—Li2—Cl1^vi	81.49 (7)
O1^i—Li1—Cl1^vi	86.896 (14)	Cl1^x—Li2—Cl1^vi	89.96 (2)
O1^v—Li1—Cl1^vi	93.104 (14)	Cl1^xi—Li2—Cl1^vi	168.07 (9)
Cl1—Li1—Cl1^vi	86.659 (16)	O1^i—Li2—Cl1	81.49 (7)
O1^i—Li1—Cl1^vii	93.104 (14)	O1^ix—Li2—Cl1	81.49 (7)
O1^v—Li1—Cl1^vii	86.896 (14)	Cl1^x—Li2—Cl1	168.07 (9)
Cl1—Li1—Cl1^vii	93.341 (15)	Cl1^xi—Li2—Cl1	89.96 (2)
Cl1^vi—Li1—Cl1^vii	180.0	Cl1^vi—Li2—Cl1	78.11 (8)
O1^i—Li1—Cl1^viii	93.104 (14)	O1^i—Li2—Li1	40.67 (5)
O1^v—Li1—Cl1^viii	86.896 (14)	O1^ix—Li2—Li1	117.37 (12)
Cl1—Li1—Cl1^viii	180.0	Cl1^x—Li2—Li1	119.58 (2)
Cl1^vi—Li1—Cl1^viii	93.341 (16)	Cl1^xi—Li2—Li1	119.58 (2)
Cl1^vii—Li1—Cl1^viii	86.659 (16)	Cl1^vi—Li2—Li1	52.49 (5)
O1^i—Li1—Li2^viii	140.44 (4)	Cl1—Li2—Li1	52.49 (5)
O1^v—Li1—Li2^viii	39.56 (4)	O1^i—Li2—Li1^iv	117.37 (12)
Cl1—Li1—Li2^viii	120.25 (2)	O1^ix—Li2—Li1^iv	40.67 (5)
Cl1^vi—Li1—Li2^viii	120.25 (2)	Cl1^x—Li2—Li1^iv	119.58 (2)
Cl1^vii—Li1—Li2^viii	59.75 (2)	Cl1^xi—Li2—Li1^iv	119.58 (2)
Cl1^viii—Li1—Li2^viii	59.75 (2)	Cl1^vi—Li2—Li1^iv	52.49 (5)
O1^i—Li1—Li2	39.56 (4)	Cl1—Li2—Li1^iv	52.49 (5)
O1^v—Li1—Li2	140.44 (4)	Li1—Li2—Li1^iv	76.71 (7)
Cl1—Li1—Li2	59.75 (2)

Symmetry codes: (i) −x+1/2, −y+1/2, −z; (ii) x−1/2, y+1/2, z; (iii) x−1/2, y−1/2, z; (iv) −x+1, −y, z+1/2; (v) x+1/2, y−1/2, z; (vi) −x+1, y, z; (vii) x, −y, −z; (viii) −x+1, −y, −z; (ix) −x+1/2, −y+1/2, z+1/2; (x) x+1/2, y+1/2, z; (xi) −x+1/2, y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···Cl1	0.829 (13)	2.396 (14)	3.1875 (7)	159.9 (12)