High coordination chemically bound compounds of noble gases with hydrocarbons:: Ng(CCH)4 and Ng(CCH)6, (Ng=Xe or Kr)

Ab initio calculations predict the existence of the compounds Ng(- C CH)(4) and Ng(- C CH)(6), where Ng=Xe or Kr. Presently known organic noble gas compounds have a coordination number of two at most. The Ng(- C CH)(4) molecules have D-4h symmetry, and Ng(- C CH)(6) molecules have O-h symmetry. The bonding in all these compounds is partly ionic and partly covalent, with significant contributions from both types of bonding. The relatively high vibrational frequencies and the substantial Ng-(C CH) binding energy in these species indicate that these compounds should be fairly stable, at least in cryogenic conditions. These compounds could be a very interesting addition to the range of known organic noble gas compounds. Suggestions are made on possible approaches to their preparation. (c) 2006 American Institute of Physics.