Experimental studies of the kinetics of association reactions between neutral molecules and carbene cations

Laboratory measurements are reported for the reactions of C3H+, C5H+, C2N+, and C4N+ with several neutral molecules chosen to allow a response to the carbene character of these cations, viz. CO, H2, HCN, CH3CN, HC3N, and C2H2. The measurements were performed with the selected-ion flow tube (SIFT) technique at 296 * 2 K in helium buffer gas at a total pressure of a few tenths of a Torr. Adduct formation was the predominant but not exclusive feature of the observed chemistry. High rates of association were observed for the addition of one molecule, with further additions being much slower. This behavior was interpreted to be consistent with the formation of strongly bound adduct ions which would be expected if the cations have carbene character. Structures of the observed adduct ions are proposed on the basis of their formation by u bond insertion or coordination of unbonded electron pairs which may occur as a result of the carbene character in the cations. The possible role of these adduct ions in the synthesis of interesting and novel neutral molecules is briefly indicated.