Paramagnetic hexafluoride anions of Group VI

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Abstract
Certain isotropic ESR spectra observed in γ−irradiated SF6 and in γ−irradiated solid solutions of SeF6 and TeF6 in SF6 are attributed to the hexafluoride anions of the Group VI elements. Hyperfine interaction measurements for the species 33SF6−, 77SeF6−, and 125TeF6−, observed in natural abundance, show that the central atom outer s orbital makes a very large contribution to the (totally symmetric) semioccupied orbital in these radicals. INDO MO calculations for SF6− gratifyingly predict a half−filled orbital which has the representation A1g in Oh symmetry and which is primarily composed of S 3s and F 2pσ atomic orbitals. An additional isotropic spectrum present in γ−irradiated 1% SeF6 in SF6 is believed to be that of SeF5 in which hyperfine interaction with the unique (apical) F nucleus is not detectable.