Crystal structure of CaSiF₆·2H₂O(mP2) and reevaluation of the Si^IV–F bond-valence parameter R₀

The crystal structure of a second polymorph of CaSiF₆·2H₂O featuring a layered structure connected by hydrogen bonds is presented.

Key indicators

Structure: I

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](i-F) = 0.001 Å
• R factor = 0.025
• wR factor = 0.070
• Data-to-parameter ratio = 10.0

checkCIF/PLATON results

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PLAT088_ALERT_3_C Poor Data / Parameter Ratio ....................       9.97 Note

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PLAT304_ALERT_4_G Non-Integer Number of Atoms in ..... (Resd  3  )       0.50 Check
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   2 ALERT level C = Check. Ensure it is not caused by an omission or oversight
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Computing details

Calcium hexafluoridosilicate dihydrate

Crystal data

CaSiF6·2H2O	F(000) = 216
Mr = 218.20	Dx = 2.492 Mg m^−3
Monoclinic, P2/c	Cu Kα radiation, λ = 1.54184 Å
a = 5.96605 (17) Å	Cell parameters from 5902 reflections
b = 5.13977 (12) Å	θ = 7.8–75.3°
c = 9.9308 (3) Å	µ = 12.29 mm^−1
β = 107.275 (3)°	T = 100 K
V = 290.78 (1) Å^3	Plate, colourless
Z = 2	0.15 × 0.08 × 0.02 mm

Data collection

XtaLAB Synergy-S, Dualflex, Eiger2 R CdTe 1M diffractometer	608 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Cu) X-ray Source	598 reflections with I > 2σ(I)
Mirror monochromator	Rint = 0.051
Detector resolution: 13.3333 pixels mm^-1	θmax = 75.4°, θmin = 7.8°
ω scans	h = −7→7
Absorption correction: gaussian (CrysalisPro; Rigaku OD, 2022)	k = −6→6
Tmin = 0.365, Tmax = 1.000	l = −12→12
8322 measured reflections

Refinement

Refinement on F^2	Primary atom site location: iterative
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.025	All H-atom parameters refined
wR(F^2) = 0.070	w = 1/[σ^2(Fo^2) + (0.0516P)^2 + 0.0488P] where P = (Fo^2 + 2Fc^2)/3
S = 1.14	(Δ/σ)max < 0.001
608 reflections	Δρmax = 0.32 e Å^−3
61 parameters	Δρmin = −0.37 e Å^−3
0 restraints

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ca1	0.000000	0.58252 (7)	0.250000	0.01360 (19)
Si1	0.000000	0.000000	0.500000	0.0135 (2)
F1	−0.06447 (16)	0.26688 (17)	0.39793 (9)	0.0187 (3)
F2	0.20424 (15)	0.17052 (18)	0.62125 (9)	0.0178 (2)
F3	−0.19861 (16)	0.09149 (15)	0.58239 (10)	0.0164 (3)
O1	0.3884 (2)	0.4033 (2)	0.36145 (15)	0.0190 (3)
H1	0.378 (5)	0.255 (6)	0.373 (3)	0.035 (7)*
H2B	0.469 (8)	0.483 (9)	0.441 (5)	0.016 (13)*	0.49 (5)
H2A	0.475 (8)	0.419 (7)	0.318 (5)	0.017 (13)*	0.51 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ca1	0.0176 (3)	0.0092 (3)	0.0144 (3)	0.000	0.00529 (18)	0.000
Si1	0.0181 (3)	0.0090 (3)	0.0140 (3)	0.0000 (2)	0.0059 (2)	0.0000 (2)
F1	0.0251 (5)	0.0124 (4)	0.0201 (5)	0.0025 (4)	0.0091 (4)	0.0041 (3)
F2	0.0189 (5)	0.0155 (4)	0.0190 (5)	−0.0010 (3)	0.0056 (4)	−0.0037 (3)
F3	0.0201 (5)	0.0120 (5)	0.0185 (5)	−0.0003 (3)	0.0080 (4)	−0.0020 (3)
O1	0.0199 (6)	0.0145 (6)	0.0224 (6)	−0.0008 (4)	0.0058 (5)	0.0006 (4)

Geometric parameters (Å, º)

Ca1—Si1^i	3.2815 (3)	Si1—F1^vi	1.6808 (9)
Ca1—Si1^ii	3.2815 (3)	Si1—F1	1.6809 (9)
Ca1—F1	2.2965 (9)	Si1—F2^vi	1.6826 (9)
Ca1—F1^iii	2.2965 (9)	Si1—F2	1.6827 (9)
Ca1—F2^iv	2.3783 (9)	Si1—F3	1.6942 (9)
Ca1—F2^v	2.3783 (9)	Si1—F3^vi	1.6942 (9)
Ca1—F3^iv	2.4105 (9)	O1—H1	0.78 (3)
Ca1—F3^v	2.4105 (9)	O1—H2B	0.90 (5)
Ca1—O1	2.4331 (13)	O1—H2A	0.77 (5)
Ca1—O1^iii	2.4331 (13)
Si1^ii—Ca1—Si1^i	98.328 (10)	O1—Ca1—Si1^i	112.20 (3)
F1^iii—Ca1—Si1^i	86.58 (2)	O1^iii—Ca1—Si1^ii	112.20 (3)
F1—Ca1—Si1^i	169.60 (2)	O1^iii—Ca1—Si1^i	96.74 (3)
F1^iii—Ca1—Si1^ii	169.60 (2)	O1^iii—Ca1—O1	135.49 (6)
F1—Ca1—Si1^ii	86.58 (2)	Ca1^vii—Si1—Ca1^v	180.0
F1—Ca1—F1^iii	90.11 (4)	F1—Si1—Ca1^v	82.60 (3)
F1—Ca1—F2^iv	158.57 (3)	F1—Si1—Ca1^vii	97.40 (3)
F1—Ca1—F2^v	79.82 (3)	F1^vi—Si1—Ca1^v	97.40 (3)
F1^iii—Ca1—F2^iv	79.82 (3)	F1^vi—Si1—Ca1^vii	82.60 (3)
F1^iii—Ca1—F2^v	158.57 (3)	F1^vi—Si1—F1	180.0
F1—Ca1—F3^iv	142.32 (3)	F1^vi—Si1—F2^vi	89.65 (5)
F1—Ca1—F3^v	100.99 (3)	F1—Si1—F2^vi	90.35 (5)
F1^iii—Ca1—F3^v	142.32 (3)	F1—Si1—F2	89.65 (5)
F1^iii—Ca1—F3^iv	100.99 (3)	F1^vi—Si1—F2	90.35 (5)
F1—Ca1—O1	76.07 (4)	F1—Si1—F3	89.83 (4)
F1^iii—Ca1—O1^iii	76.07 (4)	F1—Si1—F3^vi	90.17 (4)
F1^iii—Ca1—O1	72.88 (4)	F1^vi—Si1—F3	90.17 (4)
F1—Ca1—O1^iii	72.88 (4)	F1^vi—Si1—F3^vi	89.83 (4)
F2^v—Ca1—Si1^ii	29.44 (2)	F2—Si1—Ca1^v	44.00 (3)
F2^v—Ca1—Si1^i	99.95 (3)	F2—Si1—Ca1^vii	136.00 (3)
F2^iv—Ca1—Si1^i	29.44 (2)	F2^vi—Si1—Ca1^v	136.00 (3)
F2^iv—Ca1—Si1^ii	99.95 (3)	F2^vi—Si1—Ca1^vii	44.00 (3)
F2^iv—Ca1—F2^v	115.49 (5)	F2^vi—Si1—F2	180.0
F2^iv—Ca1—F3^v	77.00 (3)	F2—Si1—F3^vi	91.63 (4)
F2^v—Ca1—F3^v	58.87 (3)	F2^vi—Si1—F3	91.63 (4)
F2^v—Ca1—F3^iv	77.00 (3)	F2—Si1—F3	88.37 (4)
F2^iv—Ca1—F3^iv	58.87 (3)	F2^vi—Si1—F3^vi	88.37 (4)
F2^v—Ca1—O1^iii	82.87 (4)	F3—Si1—Ca1^v	45.25 (3)
F2^iv—Ca1—O1^iii	121.89 (4)	F3^vi—Si1—Ca1^v	134.75 (3)
F2^iv—Ca1—O1	82.87 (4)	F3—Si1—Ca1^vii	134.75 (3)
F2^v—Ca1—O1	121.89 (4)	F3^vi—Si1—Ca1^vii	45.25 (3)
F3^v—Ca1—Si1^ii	29.94 (2)	F3—Si1—F3^vi	180.0
F3^v—Ca1—Si1^i	87.56 (2)	Si1—F1—Ca1	155.57 (5)
F3^iv—Ca1—Si1^i	29.94 (2)	Si1—F2—Ca1^v	106.56 (4)
F3^iv—Ca1—Si1^ii	87.56 (2)	Si1—F3—Ca1^v	104.81 (4)
F3^v—Ca1—F3^iv	91.93 (4)	Ca1—O1—H1	110 (2)
F3^v—Ca1—O1	75.09 (4)	Ca1—O1—H2B	115 (3)
F3^v—Ca1—O1^iii	141.61 (4)	Ca1—O1—H2A	114 (3)
F3^iv—Ca1—O1	141.61 (4)	H1—O1—H2B	111 (3)
F3^iv—Ca1—O1^iii	75.09 (4)	H1—O1—H2A	107 (3)
O1—Ca1—Si1^ii	96.74 (3)
Ca1^v—Si1—F1—Ca1	115.56 (12)	F2^vi—Si1—F1—Ca1	−108.01 (13)
Ca1^vii—Si1—F1—Ca1	−64.44 (12)	F2—Si1—F1—Ca1	71.99 (13)
Ca1^vii—Si1—F2—Ca1^v	180.000 (1)	F2^vi—Si1—F3—Ca1^v	−170.07 (5)
Ca1^vii—Si1—F3—Ca1^v	180.000 (1)	F2—Si1—F3—Ca1^v	9.93 (5)
F1^vi—Si1—F2—Ca1^v	−100.32 (4)	F3^vi—Si1—F1—Ca1	−19.64 (13)
F1—Si1—F2—Ca1^v	79.69 (4)	F3—Si1—F1—Ca1	160.36 (13)
F1—Si1—F3—Ca1^v	−79.72 (4)	F3^vi—Si1—F2—Ca1^v	169.84 (5)
F1^vi—Si1—F3—Ca1^v	100.28 (4)	F3—Si1—F2—Ca1^v	−10.16 (5)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···F3^vi	0.78 (3)	2.19 (3)	2.9042 (14)	153 (3)
O1—H2B···O1^viii	0.90 (5)	1.98 (5)	2.856 (3)	167 (4)
O1—H2A···O1^ix	0.77 (5)	2.17 (5)	2.902 (3)	159 (4)

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