Generation of the organo-rare gas dications HCCRg(2+) (Rg = Ar and Kr) in the reaction of acetylene dications with rare gases

Using doubly ionized acetylene as a superelectrophilic reagent, the new rare-gas compounds HCCAr++ and HCCKr++ have been prepared for the first time in hyperthermal collisions of mass-selected C2H2++ with neutral rare gases (Rg). However, electron transfer from the rare gas to the acetylene dication as well as proton transfer from C2H2++ to the rare gas efficiently compete with formation of HCCRg++. The computational investigations show that the formation of HCCRg++ from acetylene dication is endothermic with Rg = He, Ne, Ar and Kr and only weakly exothermic with Xe. These energetic factors, as well as the pronounced competition with the other reactive channels help to explain why HCCRg++ is only observed with Rg = Ar and Kr.