Isomerization is expected to play a role in reaction selectivity in non-heme iron halogenases. We found that while chloride and bromide Fe(IV)=O intermediates have readily stabilized monodentate succinate isomers, fluoride monodentate isomers collapse back to bidentate structures, suggesting additional interactions with the greater protein environment might be necessary to enable the formation of this isomer for fluoride intermediates. Furthermore, we find that the much shorter Fe-F bonds relative to Fe-Cl/Fe-Br bonds suggest difficulty in the substrate approaching the oxo or hydroxo intermediates which could explain why C-H fluorination is challenging.