What is the structure of Cl₂O₆?
Dichlorine hexoxide has different structures depending upon whether it is in the gas or solid phase. In the gas phase, the molecule adopts structure (a) (reference 1, reference 2).  It is a relatively unstable molecule having a half-life measured in minutes.



In the solid phase it exists as the dark-red ionic material as shown in (b) and is often referred to as chloryl perchlorate.  Both forms are very strong oxidizing agents and react explosively with organic compunds.