DECOMPOSITION STUDIES OF TRIISOPROPYLANTIMONY AND TRIALLYLANTIMONY

The pyrolysis of triisopropylantimony ((C3H7)3Sb) and triallylantimony ((C3H5)3Sb) has been investigated mass-spectrometrically in He and D2 using a SiO2 flow tube reactor at atmospheric pressure. Both temperature and time dependencies of percent decomposition were studied and the reaction products were analyzed. The overall decomposition processes for both compounds were found to be homogeneous and first order. (C3H7)3Sb pyrolyzes at 250-350-degrees-C with no effect of the ambient gas. However, C3H6, C3H8, and C6H14 (2,3-dimethylbutane) were produced in He whereas C3H7D appeared in D2. The pyrolysis is believed to begin via bond cleavage to generate the free C3H7 radicals that, in turn, recombine and disproportionate. Isopropyl radicals react slowly with D2, producing the C3H7D detected. For (C3H5)3Sb, the pyrolysis takes place at 100-160-degrees-C. The only major product is C6H10 (1,5-hexadiene). Both the pyrolysis rate and products were independent of the ambient. Two possible mechanisms, homolysis and reductive coupling, are discussed. Assuming that homolysis is the rate-limiting step for the pyrolysis of both (C3H7)3Sb and (C3H5)3Sb, bond strengths of 30.8 and 21.6 kcal/mole for C3H7-Sb and C3H5-Sb were determined from the experimental data. When either (C3H7)3Sb or (C3H5)3Sb was mixed with trimethylindium, a nonvolatile, liquid material, probably an adduct, was formed.