Silicon-Carbon Bond Formation Kinetics: Study of the Reactions of CH3 with SiH3, Si(CH3)3, and SiCl3

Article abstract of DOI:10.1021/j100139a023

The kinetics of three Si-C bond-forming association reactions were investigated at the high-pressure limit: SiH3 + CH3 (1), Si(CH3)3 + CH3 (2), and SiCl3 + CH3 (3).Rate constants were measured using a heatable tubular reactor coupled to a photoionization mass spectrometer.The two radical reactants were produced simultaneously (CH3 always in great excess) using pulsed 193-nm photolysis of suitable precursors diluted in helium, and the radical decays were monitored in time-resolved experiments.The radical decay profiles were fitted to appropriate expressions to obtain the desired rate constants.Reaction 1 was studied between 301 and 526 K yielding the following Arrhenius expression for the association reaction: k₁ = (5.6 +/- 2.4) * 10^-11 exp((3.0 +/- 1.6) kJ mol^-1 / RT). (All rate constants are in the units cm³ molecule^-1 s^-1.) Reaction 2 was investigated between 306 and 526 K yielding the expression k₂ = (5.2 +/- 2.2) * 10^-11 exp((2.4 +/- 1.4) kJ mol^-1 / RT).Reaction 3 was studied at one temperature, 303 K, where k₃ = (1.1 +/- 0.4) * 10^-10.Treating these association reactions as cross-combination reactions, the measured rate constants were found to be predicted with reasonable accuracy using the geometric mean rule and the rate constants of the related self-association reactions of the reactant radicals.The mechanisms of these reactions are discussed.