Autocatalytic Behavior of Trimethylindium during Thermal Decomposition

Pyrolysis of trimethylindium (TMIn) in a hot-wall flow-tube reactor has been investigated at temperatures between 573 and 723 K using a modulated molecular-beam mass-sampling technique and detailed numerical modeling. The TMIn was exposed to various mixtures of carrier gases: He, H 2, D 2, and C 2 H 4, in an effort to elucidate the behavior exhibited by this compound in different chemical environments. The decomposition of TMIn is a heterogeneous, autocatalytic process with an induction period that is carrier-gas dependent and lasts on the order of minutes. After activation of the tube wall, the thermolysis exhibits a steady-state behavior that is surface mediated. This result is contrary to prior literature reports, which state that decomposition occurs in the gas phase via successive loss of the CH 3 ligands. This finding also suggests that the bond dissociation energy for the (CH 3 ) 2 In−CH 3 bond derived from flow-tube investigations is erroneous and should be reevaluated.