 The most common rhenium chlorides are ReCl6 , ReCl5 , ReCl4 , and ReCl3 . The structures of these compounds often feature extensive Re @-@ Re bonding , which is characteristic of this metal in oxidation states lower than VII . Salts of [ Re2Cl8 ] 2 − feature a quadruple metal @-@ metal bond . Although the highest rhenium chloride features Re ( VI ) , fluorine gives the d0 Re ( VII ) derivative rhenium heptafluoride . Bromides and iodides of rhenium are also well known . 
