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].