Decomposition mechanisms of trimethylgallium

Abstract The thermal decomposition of trimethylgallium (TMGa) has been studied in a variety of carrier gases, using a time-of-flight mass spectrometer to analyze the products and obtain kinetic information. N 2 and He give almost identical pyrolysis curves. Addition of toluene in He shifts the decomposition to higher temperatures; thus methyl radical attack on the parent TMGa is important in the inert carriers. H 2 and D 2 accelerate the reaction compared to N 2 . Addition of a small amount of CH 3 radicals from trimethylindium pyrolysis lowers the pyrolysis temperature significantly, indicating a chain reaction. The products of a D 2 /toluene mixture show that the active species are the H or D atoms rather than CH 3 radicals. These data show that the major reactions involved in TMGa decomposition in N 2 or He are (CH 3 ) 3 Ga → CH 3 + (CH 3 ) 2 Ga and CH 3 + (CH 3 ) 3 Ga → CH 4 + CH 2 Ga(CH 3 ) 2 . In H 2 a chain reaction takes place: CH 3 + H 2 → CH 4 + H and H + (CH 3 ) 3 Ga → CH 4 + CH 3 + CH 3 Ga. Numerical modeling was used to test these proposals. By this means it was determined that in addition to the reactions above, a key reaction is decomposition of CH 2 Ga(CH 3 ) 2 to give CH 2 GaCH 3 + CH 3 . As with other main group organometallics, the entire decomposition mechanism is complex.

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