Interaction Modes between SF4 and Ketones; Study of Intermediates in Deoxofluorination Reactions.

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Interactions between ketones and SF4 are studied for the simplest ketone, acetone, and the bulky polycyclic 2-adamantanone. Acetone forms the 1:2 adduct SF4·[O=C(CH-3)2]2, as well as the dimeric 1:1 adducts [SF4·O=C(CH-3)2]2 as identified by low-temperature Raman spectroscopy and, for the latter, X-ray crystallography. In both adducts, SF4 acts as a double chalcogen-bond donor to two keto groups. In contrast 2-adamantanone does not form an isolable solid adduct with SF4; in the presence of HF, however, it forms SF4·O=C10H14O·HF, which comprises chains with weak S---O and S---FH chalcogen bonds in the crystal structure. Sulfur tetrafluoride in this compound is readily lost at -85 °C, leading to the isolation of C10H14O·HF at low temperature. Density functional theory (DFT) calculations aid in vibrational assignments and serve to describe the interactions of the keto group with SF4 and HF, as well as interactions between SF4 with HF. It is found that separate and combined CO---HF and CO---SF4 chalcogen bonds do not polarize the C=O group to any significant degree.