As described in Clark's book, ClF3 was discovered first (before WWII actually). But sometime later someone managed to synthesize ClF5 as well, which had slightl

As described in Clark's book, ClF3 was discovered first (before WWII actually). But sometime later someone managed to synthesize ClF5 as well, which had slightly better performance as a rocket fuel oxidizer. Although it retained all the other fun properties of ClF3.