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.

The title compound, C 7 H 10 F 6 O 4 , 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-HÁ Á ÁO and an array of C-HÁ Á ÁF hydrogenbonding 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.
Financial assistance from the Advanced Metals Initiative (AMI) and the Department of Science and Technology (DST) of South Africa, the New Metals Development Network (NMDN), the South African Nuclear Energy Corporation Limited (Necsa) and the University of the Free State is gratefully acknowledged.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2464).

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).

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.

Refinement
All H atoms were located from differencee Fourier maps and refined isotropically.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.