Journal of Physical Chemistry A, Vol.114, No.27, 7382-7390, 2010
Cationic Noble Gas Hydrides: A Theoretical Investigation of Dinuclear HNgFNgH(+) (Ng = He-Xe)
Theoretical calculations at the B3LYP, MP2, and CCSD(T) levels of theory disclose the conceivable existence of cationic noble gas hydrides containing two Ng atoms. These species have a general formula of HNgFNgH(+) (Ng = He-Xe), and are the cationic counterparts of the neutral HNgF. The optimized geometries, harmonic frequencies, and bonding properties point to ion-dipole complexes between a fluoride anion and two covalent H-Ng(+) cations, best formulated as (H-Ng(+))(2)F-. The HXeFXeH+ is also isoelectronic with the recently experimentally observed HXeOXeH (Khriachtchev et al. J. Am. Chem. Soc. 2008, 130, 6114-6118). The resulting HNgFNgH(+) are thermochemically stable with respect to dissociation into HNg(+) + HNgF and HNg(+) + H + Ng + F, but are largely unstable with respect to both the loss of HNg(+) (with formation of HNg(+) + Ng) and H2F+ (with formation of two Ng atoms). These decompositions pass through bent transition structures, and only the heaviest HAtFArH+, HKrFKrH+, and HXeFXeH+ are protected by energy barriers large enough (ca. 10-15 kcal mol(-1)) to support their conceivable metastability. In line with other series of noble gas compounds, the neon cation HNeFNeH+ is the least stable among the various HNgFNgH(+).