STRUCTURAL PRINCIPLES OF THE COORDINATION-NUMBER 8 - WF8(2-), REF8(2-), AND XEF8(2-)

WF6, ReFn (n = 6 and 7), and XeF6 combined with NOF to give (NO+)(2) W F82-, (NO+)(2)ReF82-, and (NO+)(2) XeF82-, respectively. Also NO2F rea cted with ReF6 to form (NO2+)(2)ReF82-. Cs2XeF8 .4BrF5 crystallized fr om a solution of Cs2XeF8 in BrF5. These five compounds were subjected to X-ray structure determinations. The structure of [NO(NOF)(2)](IF8-) -I-+ was used as a standard for comparison. All anions exhibit square- antiprismatic geometry, independent of their electronic configurations . Bond lengths in ReF82- and XeF82- are larger than in WF82- and IF8-, owing to the presence of nonbonding electrons. Deviations from the id eal structure in XeF82- are attributed to cation-anion interactions.