A stoichiometric reaction between 1-Al and NaBAr F 4 in fluorobenzene is consistent with an interaction between the two pre-catalyst components (Scheme 2). Hence at 298 K, a 50 mM solution of 1:1 mixture of 1-Al and NaBAr F 4 displayed a defined and sharp F NMR resonance at d = -180.2 ppm. For comparison, 1-Al alone demonstrates a resonance at d = -174.5 ppm at the same concentration. Varying the ratio of NaBAr F 4 : 1-Al from 0.5:1 to 2:1 suggests that the binding event is 1:1 as the maximum Dd » 6ppm is observed at this ratio with only small changes in chemical shift occurring at higher ratios. The reaction between 1-Al and NaBAr F 4 was investigated at nine different temperatures across a 233 -313 K temperature range, with consistent results supporting 1:1 binding at all temperatures (Figure ). No attempts were made to quantify this data as it is likely that the equilibria at play are complicated by the potential for the solvent, fluorobenzene, to act as a competitive ligand for Na + . A similar reaction between a 1:1 mixture of Transition metal fluoride complexes are known to be effective hydrogen bond (and halogen bond donors), examples of coordination of metal fluorides to s-block cations are however, less common. DFT calculations were undertaken to understand the nature of the binding event.