Xenon secondary bonding

The halogen pentafluorides and the [XeF5]+ cation have a square pyramidal configuration and any weak secondary bonds are found below the base of the pyramid and situated to avoid the axial, lone pair position. These contacts are much more significant for the xenon compounds than for the interhalogens, where they are so weak as to be virtually indistinguishable from normal intermolecular contacts, as seen in the structure of IF5.40... 

The IE growth with a temperature rise from 4.2 to 50 K was observed by Iwasaki and co-workers in the reactions of H- and D-atom abstraction from saturated hydrocarbon molecules in crystalline xenon matrices [95]. The temperature rise causes a growing selectivity of various CH-bond breaks under H-atom abstraction. The ratio of the accumulation rates of radicals formed under a break of primary, secondary, and tertiary CH bonds in isobutane is 1 1 1 at 4.2 K and 1 6 14 at 30 K [96-98], These data also indicate the existence of the pretunneling molecular shifts of the reagents within the nearest coordination spheres. It is assumed in ref. 82 that these shifts are quasi-reversible, and the kinetic pattern of H-atom transfer reactions has the form... 

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