Time-resolved gas-phase kinetic study of the reaction of germylene with propene over the temperature range 293–415 K: the thermal stabilities of germiranes

Absolute rate constants have been obtained for the title reaction over the pressure range 1–100 Torr (in SF6 bath gas) and the temperature range 293–415 K, by means of laser flash photolysis to generate and monitor germylene, GeH2. The reaction showed the characteristic pressure dependence of a third-body assisted association reaction. The high pressure rate constants, obtained by extrapolation, gave the Arrhenius equation: The parameters correspond to a fast reaction occurring at ca. 59% of the collision rate at room temperature. Collision efficiencies for GeH2 π-additions are not much less than those of SiH2. RRKM (Rice, Ramsperger, Kassel, Marcus) modelling, based on a variational transition state consistent with the kinetics, gave a good fit to the data, with the value of Eo=105 kJ mol−1 corresponding to ΔH°=122±12 kJ mol−1 for 2-methylgermirane decomposition. This result in conjunction with other work shows that C-methyl substitution lowers the thermal stability of germirane, and that germiranes are ca. 50–60 kJ mol−1 less stable to decomposition than their silirane counterparts.