The pyrolysis of trimethyl gallium has been studied in a toluene carrier flow system from 686" K to 983' K using total pressures from 6.1 mm to 31.1 mm. The progress of the reaction was followed by measuring the amount of methane, ethane, and ethylene formed. The rate constants decline rapidly if the toluene-to-alkyl ratio is decreased below 45. Part of this decrease has been shown to result from the loss of methyl radicals as ethylbenzene, propane, propylene, and xylenes. In an unseasoned vessel, the decomposition is markedly dependent on surface conditions. In the unpacked conditioned vessel, the reaction is 94% homogeneous in the first bond region and 97% homogeneous in the second bond region.The decomposition occurs in two steps:

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The pyrolysis of trimethylindium has bcen studied ill a toluene carrier flow sysie!n from 550' I< to '781' I< using total pressures from 6.0 to 33.5 mln. The progress of the reaction was follo\\~ed by ~lleasuri~lg thc ainount of methane, ethane, ethylene, propane, and ethylbenzene formed and in a number of cases by direct i~idium analysis. Thc cleconiposition occurs in three stcps:At all temperatures reaction [2] follows rapidly after reaction [I]. Reaction [3] occurs a t a measurable rate only a t tenlperat~~res sufficiently high that reactions [I] and [2] arc coillplctcd in a very sn~all fraction of the contact time. At lowcr temperatures the InCI-13 produccd deposits in the reaction zone as a white hIn1 of (InCH3),,.Both k1 and k3 declinc rapidly if the toluene-to-alkyl ratio is clecreascd below 150. In ail ~~nseasonecl vessel, the decomposition is mar1;edly dependent on surface conclitions. In the unpacbed conditioned vessel thc reaction is a t least 8'3% honlogeneous in the lirst bo~ltl regioil and 07% l~oinogeneous in the third bond region. Both k, and k J depcnd on the total pressure in the systein, the depencle~lce of hl being vcry slight. . ISTRODUCTIONNo previous lcinetic studies of the thermal decomposition of trimethylindiuin have been reported.A study of the reaction of triisobutylindium with 1-decene a t 150° C for 100 hours (1) yielded tridecylindiunl and 83y0 isobutylene. The tridecylindium brolte down further t o yield only 64y0 free indiuin inetal plus 1/2 CI-I2=CI-I-C81-117 and 3/2 CH,-CHs-C8I-I17. The reinailling indiuin was assumed to be in sonle polyineric form.A lcinetic study of the therinal deconlposition of trimethylgalliuu~ has been reported (2). T h e rate constants obtained were extreinely sensitive to the nature of the surface in the reaction zone. After a series of runs, the reaction zone became conditioned and reproducible results were obtained. T h e experilnental results showed D l = 59.5 lccal/mole and D 2 = 35.4 ltcal/mole. From a lcnowledge of the total bond energies, D3 = 77.5 kcal/mole was calculated.The thermal decomposition of trimethylindium is expected to be similar to that of triinethylgalliuln and the other neighboring methyl metallic alltyls that have been studied (3,4,5). The mean metal-carbon bond dissociation energy in trimethylindium has not been reported.

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