Time-resolved gas-phase kinetic study of the germylene addition reaction, GeH2 + CH3CCCH3

Abstract

Time-resolved kinetic studies of the reaction of germylene, GeH₂, generated by laser flash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene, have been carried out to obtain rate constants for its bimolecular reaction with 2-butyne, CH₃CCCH₃. The reaction was studied in the gas phase over the pressure range 1–100 Torr in SF₆ bath gas, at five temperatures in the range 300–556 K. The second order rate constants obtained by extrapolation to the high pressure limits at each temperature, fitted the Arrhenius equation:log(k^∞/cm³ molecule⁻¹ s⁻¹) = (−10.46 ± 0.06) + (5.16 ± 0.47) kJ mol⁻¹/ RT ln 10Calculations of the energy surface of the GeC₄H₈ reaction system were carried out employing the additivity principle, by combining previous quantum chemical calculations of related reaction systems. These support formation of 1,2-dimethylvinylgermylene (rather than 2,3-dimethylgermirene) as the end product. RRKM calculations of the pressure dependence of the reaction are in reasonable agreement with this finding. The reactions of GeH₂ with C₂H₂ and with CH₃CCCH₃ are compared and contrasted.