Coordination of NaBAr F 4 to 1-Al was calculated to be exergonic by DG°(298K) = -1.4 kcal mol -1 consistent with a reversible binding event. Binding was calculated to occur through a chelating k 2mode in which Na + interacts with lone-pairs on the two adjacent fluoride ligands of 1-Al. A similar coordination geometry and exergonic reaction DG°(298K) = -2.9 kcal mol -1 was calculated for reaction of NaBAr F 4 with 1-Ga (Figure ). NBO and QTAIM calculations were used to better understand the changes of electronic structure comparing 1-Ga-NaBAr F 4 to 1-Ga. Calculated Ga-F bond lengths in 1-Ga are ca. 0.03 Å shorter than in 1-Ga-NaBAr F 4. The NPA charges on the fluoride ligands become more negative when comparing 1-Ga (-0.67,-0.67) to 1-Ga-NaBAr F 4 (-0.69,-0.70), this is perhaps expected and would be consistent with the binding of Na + effecting a polarisation of the Ga-F bonds. Second-order perturbation analysis within the NBO framework reveals donor-acceptor interactions between 2p LP on F and the empty 3s orbital of Na + . QTAIM calculations return bond paths between Ga and F atoms along with F and Na atoms in 1-Ga-NaBAr F 4. Comparison of the r(bcp) values for bond critical points connecting Ga and F between 1-Ga (0.11 and 0.11 e bohr -3 ) and 1-Ga-NaBAr F 4 (0.10 and 0.11 e bohr -3 ) is consistent with similar electron-density between these atoms on coordination. r(r) and Ñ 2 r(r) values for bond critical points between Na and F atoms in 1-Ga-NaBAr F 4 support the idea that the binding interaction is primarily electrostatic (Figure ). Based on the analysis, it is possible that the increased 2 JH-F coupling constant for 6-Ga-NaBAr F 4 compared to 6-Ga might be due to a lower p-character (and hence increased s-character) for the main group fluoride bond in the Ga-F---Na interaction compared with Ga-F.