# Acid HClF6 and HIF6

I was wondering about $$\ce{HClO4}$$ which is a very strong acid . I thought it can be made stronger by replacing $$\ce O$$ with $$\ce F$$ to make $$\ce{HClF6}$$ but didn't find its existence . I thought that it might be unstable due to repulsions between $$\ce F$$ . So than i switched to $$\ce{HIF6}$$ and there was no existence of this also as well as $$\ce{HBrF6}$$ . Is there a reason that the halogens cannot form $$\ce{HXF6}$$ acids similar to $$\ce{HSbF6}$$?

• Related (involving sfur as the centrasl atom): chemistry.stackexchange.com/questions/102290/…. You tend to lose hydrogen halide molecules from your proposed complexes. – Oscar Lanzi Oct 3 '18 at 14:50
• ClF6- , BrF6- and IF6- all exist, as does IF8- . However I doubt the parent acids will be stable, but my good chemistry books are a long way away at the moment. – Ian Bush Oct 3 '18 at 16:43
• There are a whole bunch of these ions. But the reference does not document any case where anions can be protonated to acids. – Oscar Lanzi Oct 4 '18 at 1:24
• Why can't they protonated to acids. is there any known reason – Harsh jain Oct 4 '18 at 5:05
• Nothing wrong with protonation as such. The issue could be they decompose when protonated; compare with a nitrite or a bicarbonate.. – Oscar Lanzi Oct 4 '18 at 10:00