The crystal structure of O2+RuF6- and the nature of O2RhF6

The 146 degrees K X-ray structure of an O2+RuF6- single crystal {cubic: a = 9.9125(15) Angstrom, V = 974.0( 4) Angstrom(3) Z = 8, space group Ia3} obt ained from a liquid anhydrous HF (aHF) solution has proved the previously c onjectured three-fold disorder of the O-2(+) species and gives interatomic distances O-O = 1.125(17) and RuF = 1.851(2) Angstrom. Interaction of RhF6 with O-2 in aHF at less than or equal to 20 degrees C, gives a red-brown cu bic solid having a similar X-ray powder pattern (XRDP) to that of O2+RuF6- but, contrary to expectation for O-2 +RhF6-, it has a larger cell, with a = 10.17( 1) Angstrom, V = 1052(3) Angstrom(3), Z = 8. NO+RhF6- is rhombohedr al with a = 5.046(5) Angstrom, alpha = 97.8( 5) degrees, V = 124.6( 4) Angs trom(3) and isostructural with NO+AuF6-, and O2+AuF6-, the latter having sm aller formula unit volume than the former. This suggests that the charge tr ansfer in O2RhF6 is less complete than in O2+RuF6-. and that the electron a ffinity of RhF6 may be less than that of RuF6.