PNNL

Abstract

The crystal structures of a-KrF2 and salts containing the KrF+ and Kr2F3+ cations have been investigated for the first time using low temperature single crystal X-ray diffraction. The terminal Kr-F bond lengths of KrF+ and Kr2F3+ are very similar, exhibiting no crystallographically significant variation in the structures investigated (range, 1.765(3) to 1.774(6) ? and 1.780(7) to 1.805(5) ?, respectively). The Kr--F bridge bond lengths are significantly longer, with values ranging from 2.089(6) to 2.140(3) ? in the KrF+ salts and from 2.027(5) to 2.065(4) ? in the Kr2F3+ salts. The Kr-F bond lengths of KrF2 in [Kr2F3][SbF6]$KrF2 and [Kr2F3]2[SbF6]2$KrF2 range from 1.868(4) to 1.888(4) ? and are in close agreement with that observed in a-KrF2 (1.894(5) ?). The synthesis and Raman spectrum of the new salt, [Kr2F3][PF6]$nKrF2, are also reported. Theoretical calculations at the Hartree-Fock and local density functional theory levels were used to predict the gas phase geometries, charges, Mayer bond orders and Mayer valencies of KrF+, KrF2, Kr2F3+, and the ion pairs, [KrF][MF6] (M = P, As, Sb, Bi), and to assign their experimental vibrational frequencies.