Phase transfer catalysts are well established in the field of nucleophilic fluorination as the low solubility of MF in non-protic solvents (required for sufficient fluoride nucleophilicity) necessitates their use. Established phase transfer agents include metal chelators (e.g. cryptands), organic cations (e.g. [R4N] + ), Lewis acids that weakly bind fluoride (e.g. in hypercoordinated silicates) and compounds that function as multiple hydrogen bond donors to fluoride. Boranes with low FIA (relative to BF3) have been largely overlooked in this area. Even the stoichiometric use of fluoroborates derived from lower fluoride affinity boranes in nucleophilic fluorination is rare, with the very limited exceptions including the use of PinBF in the ring opening fluorination of epoxides 10 and the use of fluoroborate A (Figure , top) to fluorinate a range of organic electrophiles. 11 In the latter, formation of a B←SR2 dative bond contributes to making fluoride transfer from boron to carbon thermodynamically favourable. This factor will be absent using simpler, Lewis base free, boranes in MF phase transfer / nucleophilic fluorination cycles (Figure , bottom).