Substitution of fluorine in M[C6F5BF3] with organolithium compounds: distinctions between O- and N-nucleophiles

Borates M[C6F5BF3] (M = K, Li, Bu4N) react with organolithium compounds, RLi (R = Me, Bu, Ph), in 1,2-dimethoxyethane or diglyme to give M[4-RC6F4BF3] and M[2-RC6F4BF3]. When R is Me or Bu, the nucleophilic substitution of the fluorine atom at the para position to boron is the predominant route. When R = Ph, the ratio M[4-RC6F4BF3]/M[2-RC6F4BF3] is ca. 1:1. Substitution of the fluorine atom at the ortho position to boron is solely caused by the coordination of RLi via the lithium atom with the fluorine atoms of the BF3 group. This differs from the previously reported substitution in K[C6F5BF3] by O- and N-nucleophiles that did not produce K[2-NuC6F4BF3].