Li₂PtF₆ revisited

In comparison with previous stucture determinations of Li₂PtF₆, dilithium hexa­fluorido­platinate(IV) [Graudejus et al. (2000). Inorg. Chem. 39, 2794–2800; Henkel & Hoppe (1968). Z. Anorg. Allg. Chem. 359, 160–177], the current study revealed the Li atom to be refined with anisotropic displacement parameters, thus allowing for a higher overall precision of the model. Li₂PtF₆ adopts the trirutile structure type with site symmetries of 2.mm, m.mm, ..m and m.2m for the Li, Pt and the two F sites. The Pt—F distances in the slightly distorted PtF₆ octa­hedron are essentially similar with 1.936 (4) and 1.942 (6) Å, and the equatorial F—Pt—F angles range from 82.2 (2) to 97.8 (2)°. The Li—F distances in the somewhat more distorted LiF₆ octa­hedron are 1.997 (15) and 2.062 (15) Å, with equatorial F—Li—F angles ranging from 76.3 (7) to 99.71 (17)°.

Related literature

Henkel & Hoppe (1968) reported on the synthesis of Li₂PtF₆ by direct fluorination of (NH₄)₂PtCl₆ and Li₂CO₃. The obtained yellow Li₂PtF₆ was characterized by powder X-ray diffraction and reported to crystallize in the monoclinic crystal system. Graudejus et al. (2000) obtained Li₂PtF₆ in the form of yellow and air-stable crystals from the reaction of LiF with Pt in anhydrous HF under UV-photolysis of F₂. The reported space group and unit cell parameters are in accordance with the current redetermination. However, a low precision of the Pt—F bond lengths of only ±0.01 Å was obtained due to many unobserved reflections even at the 2σ level. For synthetic details for the preparation of PtF₄, see: Müller & Serafin (1992).

Experimental

Crystal data

• Li₂PtF₆

• M_r = 322.97

• Tetragonal, P 4₂ /m n m

• a = 4.6427 (1) Å

• c = 9.1234 (2) Å

• V = 196.65 (1) ų

• Z = 2

• Mo Kα radiation

• μ = 35.71 mm⁻¹

• T = 150 K

• 0.05 × 0.05 × 0.04 mm

Data collection

• Oxford Diffraction Xcalibur3 diffractometer

• Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007) T_min = 0.148, T_max = 1.000

• 5829 measured reflections

• 257 independent reflections

• 184 reflections with I > 2σ(I)

• R_int = 0.062

Refinement

• R[F² > 2σ(F²)] = 0.019

• wR(F²) = 0.052

• S = 1.17

• 257 reflections

• 19 parameters

• Δρ_max = 2.51 e Å⁻³

• Δρ_min = −1.33 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2007); software used to prepare material for publication: SHELXL97.

Supporting information

Related literature

Henkel & Hoppe (1968) reported on the synthesis of Li₂PtF₆ by direct fluorination of (NH₄)₂PtCl₆ and Li₂CO₃. The obtained yellow Li₂PtF₆ was characterized by powder X-ray diffraction and reported to crystallize in the monoclinic crystal system. Graudejus et al. (2000) obtained Li₂PtF₆ in the form of yellow and air-stable crystals from the reaction of LiF with Pt in anhydrous HF under UV-photolysis of F₂. The reported space group and unit cell parameters are in accordance with the current redetermination. However, a low precision of the Pt—F bond lengths of only ±0.01 Å was obtained due to many unobserved reflections even at the 2σ level. For synthetic details for the preparation of PtF₄, see: Müller & Serafin (1992).

S1. Experimental

Single-crystalline Li₂PtF₆ was obtained by the reaction of LiF and PtF₄ in platinum tubes. LiF was purified and dried in a stream of F₂:Ar 1:1 at 573 K for 24 hours. PtF₄ was synthesized according to literature procedures (Müller & Serafin, 1992). A stoichiometric mixture of the compounds was heated in a sealed platinum ampoule (jacketed in an evacuated fused silica tube) to 973 K with a rate of 30 K/d. After three weeks the ampoule was slowly cooled to room temperature and opened in an argon filled glove box. Yellow crystals of Li₂PtF₆ were obtained.

S2. Refinement

The highest residual electron density is 0.85 Å from atom Pt1. Structure data have also been deposited at the Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen (Germany), with depository number CSD-414496.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2007); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. View of the coordination polyhedra around Pt and Li. Displacement ellipsoids are shown at the 70% probability level. [Symmetry codes: (iii) -x, -y, z; (viii) x + 1, y, z; (ix) -x + 1, -y + 1, z; (xiv) y, x, -z; (xv) -y, -x, -z; (xvi) -x, 1 - y, z; (xvii) x + 1/2, -y + 1/2, -z + 1/2; (xviii) -x + 1/2, y + 1/2, -z + 1/2.]
	Fig. 2. The unit cell of Li2PtF6 viewed along [100], with all atoms displayed as spheres with arbitrary radii.

Dilithium hexafluoridoplatinate(IV)

Crystal data

Li2PtF6	Dx = 5.454 Mg m^−3
Mr = 322.97	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P42/mnm	Cell parameters from 3453 reflections
Hall symbol: -P 4n 2n	θ = 4.4–34.6°
a = 4.6427 (1) Å	µ = 35.71 mm^−1
c = 9.1234 (2) Å	T = 150 K
V = 196.65 (1) Å^3	Cuboid, yellow
Z = 2	0.05 × 0.05 × 0.04 mm
F(000) = 276

Data collection

Oxford Diffraction Xcalibur3 diffractometer	257 independent reflections
Radiation source: Enhance (Mo) X-ray Source	184 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.062
Detector resolution: 16.0238 pixels mm^-1	θmax = 34.7°, θmin = 4.5°
ϕ and ω scans	h = −7→7
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007)	k = −7→7
Tmin = 0.148, Tmax = 1.000	l = −14→14
5829 measured reflections

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	w = 1/[σ^2(Fo^2) + (0.0246P)^2 + 2.1946P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.052	(Δ/σ)max < 0.001
S = 1.17	Δρmax = 2.51 e Å^−3
257 reflections	Δρmin = −1.33 e Å^−3
19 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.041 (3)

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
Pt1	0.0000	0.0000	0.0000	0.0056 (2)
F1	0.1939 (6)	0.1939 (6)	0.1599 (4)	0.0149 (7)
F2	−0.2958 (10)	0.2958 (10)	0.0000	0.0164 (11)
Li1	0.5000	0.5000	0.162 (2)	0.019 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt1	0.0054 (2)	0.0054 (2)	0.0061 (2)	0.00022 (14)	0.000	0.000
F1	0.0170 (11)	0.0170 (11)	0.0105 (13)	−0.0029 (15)	−0.0009 (10)	−0.0009 (10)
F2	0.0165 (18)	0.0165 (18)	0.016 (2)	0.004 (2)	0.000	0.000
Li1	0.024 (6)	0.024 (6)	0.010 (7)	−0.006 (7)	0.000	0.000

Geometric parameters (Å, º)

Pt1—F1^i	1.936 (4)	F1—Li1^iv	2.062 (15)
Pt1—F1^ii	1.936 (4)	F2—Li1^vi	1.997 (15)
Pt1—F1^iii	1.936 (4)	F2—Li1^vii	1.997 (15)
Pt1—F1	1.936 (4)	Li1—F2^vi	1.997 (15)
Pt1—F2^i	1.942 (6)	Li1—F2^viii	1.997 (15)
Pt1—F2	1.942 (6)	Li1—F1^ix	2.010 (4)
Pt1—Li1^iv	3.081 (19)	Li1—F1^x	2.062 (15)
Pt1—Li1^v	3.081 (19)	Li1—F1^xi	2.062 (15)
F1—Li1	2.010 (4)	Li1—Li1^xii	2.96 (4)
F1^i—Pt1—F1^ii	82.2 (2)	F2^vi—Li1—F2^viii	84.3 (8)
F1^i—Pt1—F1^iii	97.8 (2)	F2^vi—Li1—F1^ix	89.5 (4)
F1^ii—Pt1—F1^iii	180.0 (3)	F2^viii—Li1—F1^ix	89.5 (4)
F1^i—Pt1—F1	180.0	F2^vi—Li1—F1	89.5 (4)
F1^ii—Pt1—F1	97.8 (2)	F2^viii—Li1—F1	89.5 (4)
F1^iii—Pt1—F1	82.2 (2)	F1^ix—Li1—F1	178.8 (11)
F1^i—Pt1—F2^i	90.0	F2^vi—Li1—F1^x	176.0 (7)
F1^ii—Pt1—F2^i	90.0	F2^viii—Li1—F1^x	99.71 (17)
F1^iii—Pt1—F2^i	90.0	F1^ix—Li1—F1^x	90.5 (4)
F1—Pt1—F2^i	90.0	F1—Li1—F1^x	90.5 (4)
F1^i—Pt1—F2	90.0	F2^vi—Li1—F1^xi	99.71 (17)
F1^ii—Pt1—F2	90.0	F2^viii—Li1—F1^xi	176.0 (7)
F1^iii—Pt1—F2	90.0	F1^ix—Li1—F1^xi	90.5 (4)
F1—Pt1—F2	90.0	F1—Li1—F1^xi	90.5 (4)
F2^i—Pt1—F2	180.00 (19)	F1^x—Li1—F1^xi	76.3 (7)

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