Synthesis and characterization of new N-Heterocyclic-BF3 adducts and their reactivity vs water

Species derived from N-Heterocycles with BF3 Lewis acids generate adducts that are redox active. Here we report the synthesis and characterization of 5 N-Heterocycle-BF3 adducts: Py-(BF3)2, Q-(BF3)2, Ph-(BF3)2, TMQ-(BF3), and Dipy-(BF3)2. The new adducts were structurally characterized by 1H, 11B, and 19F NMR. As an example, the Q-BF3 adduct is stable in an inert environment but in the presence of oxygen or water, its voltammetric profile decays, suggesting chemical decomposition of the adduct. Furthermore, this decomposition is accompanied by the generation of BF4-. The crystalline structure of the reaction product of TMQ-(BF3) with traces of water was obtained, showing that the BF3 generates BF4- counterion. Based on our observations, we proposed a plausible reaction mechanism for the generation of BF4-.