Kinetics of dichlorosilylene trapping by methane and mechanism and kinetics of the methyldichlorosilane decomposition

Abstract

Data relative to methane trapping of SiCl 2 and a rate constant for the SiCl 2 into C9 H bond insertion process of at 921 K are reported. Results on thedecomposition of the trapping product, methyldichlorosilane, are also reported. This decomposition follows first-order kinetics with a rate constant of at 905 K Ϫ3 Ϫ1k ϭ 1.5 Ϯ 0.2 ϫ 10 s and produces methane, trichlorosilane, methyltrichlorosilane, and tetrachlorosilane. It is argued that the decomposition involves silylene intermediates, is nonchain, and is initiated primarily by the molecular methane elimination process MeSiHCl 2 91 : Free CH ϩ SiCl .4 2 radicals and Si9 C bond fission may also contribute to the decomposition but are not dominant. The kinetics of MeSiHCl 2 decomposition are shown to be consistent with the kinetics of the reverse SiCl 2 /CH 4 trapping reaction and with the overall reaction thermochemistry. Reaction modeling gives product yields, reactant conversions, and rates in reasonable agreement with the data.

Synthesis, Structure, and α-Elimination Chemistry of Hafnocene Triarylstannyl Complexes

“…α-Elimination processes related to those described here have also been described for main group compounds in which the reacting main group center is closed shell. Such α-elimination decomposition pathways have been extensively studied for oligo- and polysilanes . These studies suggest that polysilanes R 3 Si(SiR 2 ) n R undergo α-elimination as a major decomposition pathway, to give R 3 Si(SiR 2 ) n - 1 R and R 2 Si.…”

Theoretical Study of the Pyrolysis of Methyltrichlorosilane in the Gas Phase. 3. Reaction Rate Constant Calculations

“…Ring, O’Neal, and Walker measured the rate constant data for the reaction SiCl 2 + CH 4 → CH 3 SiHCl 2 to be (2.23 ± 0.415) × 10 −20 cm 3 molecule −1 s −1 at 921 K and 1133−12932 Pa …”

“…Ring, O'Neal, and Walker measured the rate constant data for the reaction SiCl 2 + CH 4 f CH 3 SiHCl 2 to be (2.23 ( 0.415) × 10 -20 cm 3 molecule -1 s -1 at 921 K and 1133-12932 Pa. 14 Kerr, Slater, and Young determined that the rate constant expression for the reaction CH 3 + CH 3 SiCl 3 f CH 4 + CH 2 SiCl 3 is [1.26 × 10 -11 , 0, 48.14 ( 1.45] at 378-478 K. 15 They also determined the rate constant data for SiHCl 3 + CH 3 f SiCl 3 + CH 4 to be [4.37 × 10 -11 , 0, 35.50 ( 0.36] at 303-393 K and 1867-8399 Pa. 15 Kerr, Stephens, and Young later proposed a different expression, [1.12 × 10 -13 , 0, 17.96 ( 0.36], for the same SiHCl 3 + CH 3 f SiCl 3 + CH 4 reaction, using experimental data collected at 333-443 K and 2666-4133 Pa. 16 The above three experiments were carried out in an azomethane bath gas.…”

Identifying the mechanism of formation of chlorinated silane polymer by‐products during chemical vapor infiltration of SiC from CH3SiCl3/H2

“…Although this countermeasure is effective, the reaction mechanism at these temperatures has not been definitively characterized. With respect to elementary reactions involving SiCl 2 , there have been many reports regarding molecules containing one or two SiCl 2 units, 11–17 but only two reports of molecules with more than two SiCl 2 units 18,19 . Mosecatteli et al.…”

“…9 It is known that by-product accumulation in the reactor exhaust is suppressed when the exhaust line is maintained at 500-950 • C. 10 Although this countermeasure is effective, the reaction mechanism at these temperatures has not been definitively characterized. With respect to elementary reactions involving SiCl 2 , there have been many reports regarding molecules containing one or two SiCl 2 units, [11][12][13][14][15][16][17] but only two reports of molecules with more than two SiCl 2 units. 18,19 Mosecatteli et al evaluated the reaction rate constants of SiCl 2 forming cyclic-(SiCl 2 ) 4 via quantum chemical calculation using the B3LYP method with several basis functions: the amount of chlorinated silane polymers was negligibly small at 800 • C. 18 Neumeyer et al 19 studied the reaction mechanism for the formation of chlorinated silane polymers with up to eight SiCl 2 units using quantum chemical calculations with the RI-M06-L/6-311++G(2d,2p)//RI-M06-L/6-31+G(dp) method.…”