Spectroscopic and Crystallographic Characterization of the R 3 N + -C-H⋅⋅⋅X Interaction.

As appreciation for nonclassical hydrogen bonds has progressively increased, so have efforts to characterize these interesting interactions. Whereas several kinds of C-H hydrogen bonds have been well-studied, much less is known about the R 3 N + -C-H⋅⋅⋅X variety. Herein, we present crystallographic and spectroscopic evidence for the existence of these interactions, with special relevance to Selectfluor chemistry. Of particular note is the propensity for Lewis bases to engage in nonclassical hydrogen bonding over halogen bonding with the electrophilic F atom of Selectfluor. Further, the first examples of 1 H NMR experiments detailing R 3 N + -C-H⋅⋅⋅X (X=O, N) hydrogen bonds are described.