Initially we sought to determine if the fluoroborates derived from low fluoride affinity triorganoboranes will transfer fluoride to weaker (than Aryl + ) carbon electrophiles, as suggested by previous computational studies. For these initial studies [NMe4] + salts were used to minimise any complications associated with strong interactions between anion and cation. In contrast, significant R3B⋯F⋯M (M = group 1 metal cation) interactions are expected, particularly in weakly coordinating solvents, which could significantly modify fluorination reactivity using MF salts. To guide subsequent studies and identify other boranes with potential as phase transfer fluorination catalysts we calculated fluoride ion affinity values using a closely related method to that reported by Greb et al. These values are a useful initial indicator of utility in this context, as sufficient fluoride affinity is required for the borane to react with MF and form the fluoroborate salt, but if the FIA is too great then subsequent transfer of fluoride from the fluoroborate to an electrophile will be disfavoured. Therefore the borane with the lowest fluoride affinity value that enables phase transfer of a MF salt was our initial target as this should have the maximum fluorination scope as it will form the most nucleophilic fluoroborate (i.e. the fluoroborate with the weakest B-F bond). These calculations (Figure ) enabled us to identify commercially available or readily synthesised boranes (including two enantioenriched examples) spanning a range of fluoride affinity values for study, with the value for BF3 at this level provided for comparison. The calculations were consistent with the expected outcomes e.g. electron withdrawing groups (in 1-3) increase fluoride affinity (relative to PhBPin). While increased multiple bond character, e.g. B=NR2 double bond character being greater than B=OR double bond character, leads to CBS catalyst 4 being a weaker Lewis acid towards fluoride than PhBPin. Several boranes with very similar calculated fluoride affinity values also were identified to probe the effect different functional groups (e.g. NO2 Vs CF3 in 1 and 3) and substituent size (e.g. BEt3 Vs 5) have on reacting with MF and controlling the subsequent reactivity of the fluoroborate. This is important as in contrast to [R4N] + , the solvation of M + and F -needs to be considered along with the effect of any strong interactions between M + and the fluoride of the fluoroborate persisting in solution.