Teflic acid

Teflic acid is a chemical compound with the formula HOTeF5. This strong acid is related to orthotelluric acid, Te(OH)6. Teflic acid has a slightly distorted octahedral molecular geometry.

Preparation
Teflic acid was accidentally discovered by Engelbrecht and Sladky. Their synthesis did not yield the anticipated telluryl fluoride TeO2F2, but a mixture of volatile telluric compounds, containing HOTeF5:
 * BaTeO4 + 10 FSO2OH → HOTeF5 (25%)

Teflic acid can also be prepared from fluorosulfonic acid and barium tellurate:
 * 5 FSO2OH + Ba(2+)[TeO2(OH)4](2−) → HOTeF5 + 4 H2SO4 + BaSO4

It is also the first hydrolysis product of tellurium hexafluoride:
 * TeF6 + H2O → HOTeF5 + HF

Teflates


The conjugate base of teflic acid is called the teflate anion, F5TeO- (not to be confused with triflate). Many teflates are known, one example being B(OTeF5)3, that can be pyrolysed to give acid anhydride O(TeF5)2.
 * 2 B(OTeF5)3 → 2 B(OTeF5)2F + O(TeF5)2

The teflate anion is known to resist oxidation. This property has allowed the preparation several highly unusual species such as the hexateflates M(OTeF5)6- (in which M = As, Sb, Bi). Xenon forms the cation Xe(OTeF5)+.