1,1,1,5,5,5-Hexafluoro-2,4-dimeth­oxy­pentane-2,4-diol

The title compound, C₇H₁₀F₆O₄, was isolated as an unexpected product from a reaction of tantalum(V) methoxide with hexa­fluoro­acetyl­acetone in a methanol solution. The asymmetric unit consists of one half-mol­ecule with the middle C atom lying on a twofold axis. The crystal structure is stabilized by O—H...O and an array of C—H...F hydrogen-bonding inter­actions. These inter­actions link the mol­ecules into a stable supra­molecular three-dimensional network. The mol­ecules pack in a ribbon-like form in the ac plane as a result of these inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.030
• wR factor = 0.079
• Data-to-parameter ratio = 13.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT480_ALERT_4_C Long H...A H-Bond Reported H2     ..  O2      ..       2.64 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H4A    ..  F3      ..       2.74 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H3     ..  F2      ..       2.66 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H4A    ..  F1      ..       2.85 Ang.
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          2

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT063_ALERT_4_G Crystal Size Likely too Large for Beam Size ....       0.75 mm
PLAT153_ALERT_1_G The su's on the Cell Axes   are Equal ..........    0.00500 Ang.
PLAT764_ALERT_4_G Overcomplete CIF Bond List Detected (Rep/Expd) .       1.13 Ratio
PLAT793_ALERT_4_G The Model has Chirality at C2      (Verify) ....          R

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   5 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   5 ALERT level G = General information/check it is not something unexpected

   1 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
   1 ALERT type 3 Indicator that the structure quality may be low
   7 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

In continuation of our research on the formation kinetics of complexes derived from metals like hafnium, zirconium, etc., with different bidentate ligands (Viljoen et al., 2010; Steyn et al., 2008), an unexpected product, the title compound, was isolated after reacting tantalum(V) methoxide with hexafluoroacetylacetone in a methanol reaction solution.

The asymmetric unit of the title compound consists of a half molecule with C3 lying on a twofold axis (Figure 1). The bond angles and bond distances in the title compound are in accord with corresponding bond angles and distances reported for hexafluoroacetylacetone like derivatives (Cole et al., 2005).

The crystal structure is stabilized by O—H···O (O···O separation 2.6648 (14) and 3.073 (2) Å) and an array of C—H···F (C···F separation in the range 3.383 (2)-3.644 (2)Å) hydrogen bonding interactions. All of these interactions serve to link the molecules into a stable supramolecular three-dimensional network. In the ac plane, the molecules pack in a ribbon-like formation as a result of these interactions (Figure 2).

Related literature

For metal complexes with acetylacetone derivatives, see: Viljoen et al. (2010); Steyn et al. (2008); Cole et al. (2005).

S2. Experimental

The reaction was performed under modified Schlenk conditions under a nitrogen atmosphere. To a solution of Ta(OMe)₅ (0.5010 g, 1.40 x 10 ^-3 mol), a solution of hexafluoroacetylacetone (0.2912 g, 1.40 x 10 ^-3 mol) was added and was placed in a sonic bath for 1 h. The resultant mixture was then stored at 252 K. After two days colourless crystals of the title compound were formed.

S3. Refinement

All H atoms were located from differencee Fourier maps and refined isotropically.

Computing details

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. An ORTEP view of the title compound, showing the numbering scheme and displacement ellipsoids (50% probability). Symmetry code: ^i: 1 - x, y, 1/2 - z.
	Fig. 2. A partial packing diagram of the unit cell showing selected hydrogen bonding interactions of the title compound illustrating the ribbon-like formation across the ac plane.

1,1,1,5,5,5-Hexafluoro-2,4-dimethoxypentane-2,4-diol

Crystal data

C7H10F6O4	F(000) = 552
Mr = 272.15	Dx = 1.714 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 17.829 (5) Å	Cell parameters from 2123 reflections
b = 6.713 (5) Å	θ = 3.3–28.1°
c = 9.347 (5) Å	µ = 0.20 mm^−1
β = 109.509 (5)°	T = 100 K
V = 1054.5 (10) Å^3	Needle, colourless
Z = 4	0.75 × 0.28 × 0.19 mm

Data collection

Bruker APEXII CCD diffractometer	1049 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
φ and ω scans	θmax = 28°, θmin = 3.8°
Absorption correction: multi-scan (SADABS; Bruker, 2007)	h = −23→21
Tmin = 0.936, Tmax = 0.963	k = −8→8
5850 measured reflections	l = −11→12
1277 independent 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)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.079	All H-atom parameters refined
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0386P)^2 + 0.4659P] where P = (Fo^2 + 2Fc^2)/3
1277 reflections	(Δ/σ)max < 0.001
98 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
F1	0.67222 (4)	0.00201 (11)	0.36009 (8)	0.0251 (2)
F2	0.61085 (5)	−0.06716 (11)	0.12475 (8)	0.0263 (2)
F3	0.69105 (4)	0.18291 (12)	0.18451 (9)	0.0286 (2)
O1	0.59145 (5)	0.34897 (12)	0.35035 (9)	0.0176 (2)
O2	0.54269 (5)	0.31437 (13)	0.08511 (9)	0.0192 (2)
C1	0.63589 (7)	0.08280 (19)	0.22390 (13)	0.0192 (3)
C2	0.56606 (7)	0.21774 (18)	0.22550 (12)	0.0153 (3)
C3	0.5	0.0899 (2)	0.25	0.0150 (3)
C4	0.64796 (10)	0.5018 (2)	0.34926 (19)	0.0311 (3)
H3	0.4785 (8)	0.008 (2)	0.1636 (14)	0.016 (3)*
H4A	0.6446 (9)	0.598 (3)	0.4222 (18)	0.032 (4)*
H4B	0.6369 (10)	0.559 (3)	0.251 (2)	0.043 (5)*
H4C	0.7027 (13)	0.450 (3)	0.383 (2)	0.056 (6)*
H2	0.4960 (10)	0.351 (3)	0.0706 (18)	0.036 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0227 (4)	0.0299 (4)	0.0202 (4)	0.0092 (3)	0.0038 (3)	0.0038 (3)
F2	0.0285 (4)	0.0259 (4)	0.0241 (4)	0.0068 (3)	0.0083 (3)	−0.0070 (3)
F3	0.0198 (4)	0.0341 (5)	0.0382 (5)	0.0039 (3)	0.0179 (3)	0.0044 (3)
O1	0.0171 (4)	0.0168 (4)	0.0207 (4)	−0.0048 (3)	0.0085 (3)	−0.0045 (3)
O2	0.0164 (5)	0.0238 (5)	0.0187 (4)	0.0031 (4)	0.0076 (3)	0.0064 (3)
C1	0.0181 (6)	0.0226 (6)	0.0171 (6)	0.0024 (5)	0.0062 (5)	−0.0007 (4)
C2	0.0159 (6)	0.0162 (5)	0.0143 (6)	0.0011 (4)	0.0057 (4)	0.0001 (4)
C3	0.0149 (8)	0.0148 (8)	0.0152 (8)	0	0.0049 (6)	0
C4	0.0336 (8)	0.0291 (8)	0.0342 (8)	−0.0165 (6)	0.0159 (7)	−0.0074 (6)

Geometric parameters (Å, º)

F1—C1	1.3354 (15)	C1—C2	1.5438 (17)
F2—C1	1.3399 (16)	C2—C3	1.5352 (15)
F3—C1	1.3402 (15)	C3—C2^i	1.5352 (15)
O1—C2	1.4107 (15)	C3—H3	0.945 (13)
O1—C4	1.4405 (17)	C4—H4A	0.954 (17)
O2—C2	1.3968 (15)	C4—H4B	0.950 (17)
O2—H2	0.835 (17)	C4—H4C	0.98 (2)
C2—O1—C4	118.10 (10)	O1—C2—C1	109.72 (9)
C2—O2—H2	104.9 (11)	C3—C2—C1	109.55 (11)
F1—C1—F2	107.32 (11)	C2—C3—C2^i	112.00 (14)
F1—C1—F3	107.38 (10)	C2—C3—H3	108.1 (8)
F2—C1—F3	107.00 (10)	C2^i—C3—H3	109.8 (8)
F1—C1—C2	111.41 (10)	O1—C4—H4A	105.3 (10)
F2—C1—C2	111.35 (10)	O1—C4—H4B	111.8 (11)
F3—C1—C2	112.12 (11)	H4A—C4—H4B	112.1 (14)
O2—C2—O1	113.56 (11)	O1—C4—H4C	111.7 (12)
O2—C2—C3	113.38 (9)	H4A—C4—H4C	107.4 (15)
O1—C2—C3	106.02 (9)	H4B—C4—H4C	108.4 (15)
O2—C2—C1	104.60 (9)
C4—O1—C2—O2	−48.50 (14)	F3—C1—C2—O1	−71.61 (13)
C4—O1—C2—C3	−173.64 (11)	F1—C1—C2—C3	−67.23 (11)
C4—O1—C2—C1	68.14 (14)	F2—C1—C2—C3	52.54 (12)
F1—C1—C2—O2	170.92 (9)	F3—C1—C2—C3	172.38 (8)
F2—C1—C2—O2	−69.30 (12)	O2—C2—C3—C2^i	−71.42 (8)
F3—C1—C2—O2	50.54 (12)	O1—C2—C3—C2^i	53.84 (6)
F1—C1—C2—O1	48.77 (13)	C1—C2—C3—C2^i	172.17 (10)
F2—C1—C2—O1	168.55 (9)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1^i	0.835 (17)	1.935 (17)	2.6648 (14)	145.4 (16)
O2—H2···O2^ii	0.835 (17)	2.640 (17)	3.073 (2)	113.7 (14)
C4—H4A···F3^iii	0.954 (17)	2.741 (17)	3.644 (2)	158.4 (13)
C3—H3···F2^iv	0.945 (13)	2.663 (13)	3.4022 (17)	135.5 (10)
C4—H4A···F1^v	0.954 (17)	2.853 (17)	3.383 (3)	116.1 (11)

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