Hydrogen-Bonded Homoleptic Fluoride-Diarylurea Complexes: Structure, Reactivity, and Coordinating Power.

Hydrogen bonding with fluoride is a key interaction encountered when analyzing the mode of action of 5′-fluoro-5′-deoxyadenosine synthase, the only known enzyme capable of catalyzing the formation of a C–F bond from F–. Further understanding of the effect of hydrogen bonding on the structure and reactivity of complexed fluoride is therefore important for catalysis and numerous other applications, such as anion supramolecular chemistry. Herein we disclose a detailed study examining the structure of 18 novel urea–fluoride complexes in the solid state, by X-ray and neutron diffraction, and in solution phase and explore the reactivity of these complexes as a fluoride source in SN2 chemistry. Experimental data show that the structure, coordination strength, and reactivity of the urea–fluoride complexes are tunable by modifying substituents on the urea receptor. Hammett analysis of aryl groups on the urea indicates that fluoride binding is dependent on σp and σm parameters with stronger binding being observed f...