The compound under consideration contains fluorine, but according to rule for oxidation numbers, fluorine cannot attain any other oxidation number than -1, so disproportionation reaction are not possible with fluorine compounds.

Another reason is the electronic configuration of fluorine,

EC = 2s² 2p⁵

The possibility of electrons being removed from fluorine can be considered by supplying external energy, but as removing 2 or 5 electrons would require large amount of external energy which is not generally present during a chemical reaction which only proceeds using the enthalpy of the reaction. Thus instead of giving any of its electrons, F can just accept 1 e^- and complete its octate and attain stability. This process is spontaneous as shown by the high reduction potential of 2.87 V.

E° = 2.87 V

Thus the possibility of F giving electron is diminished hence it cannot undergo disproportionation reaction.