Structural Principles of the Coordination Number Eight: WF 2− 8 , ReF 2− 8 , and XeF 2− 8

WF 6 , ReF n ( n = 6 and 7), and XeF 6 combined with NOF to give (NO + 2 ) WF   2− 8 , (NO + ) 2 ReF   2− 8 , and (NO + ) 2 XeF 2– 8 , respectively. Also NO 2 F reacted with ReF 6 to form (No 2 + )ReF 2– 8 . Cs 2 XeF 8 ·4BrF 5 crystallized from a solution of Cs 2 XeF 8 in BrF 5 . These five compounds were subjected to X‐ray structure determinations. The structure of [NO(NOF) 2 ] + IF – 8 was used as a standard for comparison. All anions exhibit square‐antiprismatic geometry, independent of their electronic configurations. Bond lenghts in ReF 2– 8 and XeF 2– 8 are larger than in WF 2– 8 and IF – 8 , owing to the presence of nonbonding electrons. Deviations from the ideal structure in XeF 2– 8 are attributed to cation‐anion interactions.