Kinetics and mechanism of the germane decomposition

The homogeneous gas-phase thermal decomposition kinetics of germane have been measured in a single-pulse shock tube between 950 and 1060 K at pressures around 4000 torr. The initial decomposition is GeH4 GeH2 + H2 in its pressure-dependent regime, with log k = 13.83 ± 0.78 – 50,750 ± 3570 cal/2.303RT. RRKM calculations suggest that the high-pressure Arrhenius parameters are log k GeH4(M ∞) = 15.5 – 54,300 cal/2.303RT. Extrapolations to static system pyrolysis conditions (T ∼ 600 K, P ∼ 200 torr) give homogeneous reaction rates which are much slower than those observed, hence the static system pyrolysis of germane must be predominantly heterogeneous. Shock-initiated pyrolysis reaction stoichiometry is 2 mol H2 per mole GeH4, suggesting that the subsequent decomposition of germylene is essentially quantitative. Investigations of the hydrogen product yields for pyrolysis of GeD4 in oCH3 further indicate that the germylene decomposition reaction is mainly GeH2 H2 + Ge, but that a small amount of reaction to H atoms may also occur.