Time-resolved gas-phase kinetic study of the germylene addition reaction, GeH2 + CH3CCCH3

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, CH3C[triple bond, length as m-dash]CCH3. 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(kinfinity/cm3 molecule(-1) s(-1)=(-10.46+/-0.06)+(5.16+/-0.47) kJ mol(-1)/RT ln 10. Calculations 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 CH3C[triple bond, length as m-dash]CCH3 are compared and contrasted.