Cationic noble gas hydrides-2: A theoretical investigation on HNgHNgH+ (Ng = Ar, Kr, Xe)
✍ Scribed by Stefano Borocci; Maria Giordani; Felice Grandinetti
- Publisher
- Elsevier
- Year
- 2011
- Tongue
- English
- Weight
- 681 KB
- Volume
- 964
- Category
- Article
- ISSN
- 2210-271X
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✦ Synopsis
The linear, centrosymmetric HNgHNgH + (Ng = Ar, Kr, Xe) were characterized as true energy minima at the MP2, CCSD(T), and B3LYP levels of theory. The optimized geometries, atomic charges, AIM bond topologies, and harmonic frequencies point to ion-dipole complexes between a hydride anion and two covalent NgH + cations, best formulated as (H-Ng + ) 2 H À . The xenon cation HXeHXeH + resulted thermochemically stable with respect to dissociation into XeHXe + and 2H, and protected by a barrier of ca. 17-22 kcal mol À1 with respect to the largely exothermic extrusion of a Xe atom so to form XeH + and H 2 . On the other hand, both HArHArH + and HKrHKrH + , even though kinetically stable by ca. 5-15 and 12-19 kcal mol À1 with respect to dissociation into NgH + , Ng, and H 2 , are however largely unstable with respect to the loss of two H atoms and formation of NgHNg + . Therefore, they are predicted to be unstable even at the lowest temperatures. The HNgHNgH + cations (Ng = Ar, Kr, Xe) are also considerably less stable than the isomeric clusters (Ng) 2 -H þ 3 , recently proposed as intermediates in the sequestration of noble gases by H þ 3 in protoplanetary objects. In any case, our calculations invite the theoretical investigation of the stability of these clusters with respect to dissociation into the low-energy fragments NgHNg + and H 2 .