Crystal Structure Elucidation of Geminal and Vicinal Bis(Trifluoromethanesulfonate) Ester

What is it about?

The article reports the crystal structures of methylene and ethylene bis(trifluoromethanesulfonate) esters, which are highly reactive alkylene synthons used in potent electrophilic reactions. The structures were determined using single-crystal X-ray diffraction, and the dominant interactions present in both compounds were found to be non-classical C—H⋯O hydrogen bonds and intermolecular C—F⋯F—C interactions between trifluoromethyl groups. The bond distances of both esters were almost identical, while the mean bond length of the adjacent S-O bond was elongated in 2. The structures were refined using the SHELXT and SHELXL programs, and molecular electrostatic potential calculations were performed using the ORCA quantum chemistry package.

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Why is it important?

This research is important for several reasons. Firstly, it provides the crystal structures of two geminal and vicinal bis(trifluoromethanesulfonate) esters, which are highly reactive alkylene synthons used in electrophilic substitution reactions. These structures can be useful in the development of new organic synthesis methods and the synthesis of novel compounds. Secondly, this research provides insight into the self-sorting of these bis(trifluoromethanesulfonate) esters in polar and non-polar domains within the crystal structure, which can help in the design of new materials with specific properties. Finally, this research demonstrates the use of single-crystal X-ray diffraction (SC-XRD) in the characterization of organic compounds, which can be useful in the determination of the structures of other organic compounds. Key Takeaways: 1. The crystal structures of methylene bis(trifluoromethanesulfonate) (1) and ethylene bis(trifluoromethanesulfonate) (2) have been determined using single-crystal X-ray diffraction (SC-XRD). 2. Both compounds are air- and moisture-sensitive oils and were crystallized at 277 K to afford two-component non-merohedrally twinned crystals. 3. The dominant interactions present in both compounds are non-classical C—H⋯O hydrogen bonds and intermolecular C—F⋯F—C interactions between trifluoromethyl groups. 4. Molecular electrostatic potential (MEP) calculations by DFT-D3 helped to quantify the polarity between O⋯H and F⋯F contacts to rationalize the self-sorting of both bis(trifluoromethanesulfonate) esters in polar (non-fluorous) and non-polar (fluorous) domains within the crystal structure.