To gain further insight into this unique reactivity, the mechanism of defluorination of HFC-134a was studied using computational techniques (DFT). Binding of DMAP to 1 was assumed to be fast and reversible under the reaction conditions, reinforced by observed fluxionality in 1 H NMR spectroscopic data for 1•DMAP suggesting that the DMAP can move rapidly between Mg centres. The reaction is initiated by nucleophilic attack of 1•DMAP at the sp 3 C-F bond of -CH2F group of HFC-134a, via TS-1 (∆G ‡ 298K = 19.5 kcal mol -1 ), to form Int-1. This reactivity mode for 1•DMAP has been established previously in the defluorination of poly(tetrafluoroethene) (PTFE). The mechanism proposed based on DFT calculations is perhaps intuitive. The fluorophilicity of 1 likely results in selective sp C-F bond activation over sp C-H bond activation, while the trends in bonds strengths would favour reaction at the isolated sp 3 C-F bond. Alternative mechanisms were calculated and found to lead to transition states that were less energetically accessible than TS-1.