Rate constants for silylene reactions

Safarik, I.; Sandhu, V.; Lown, E. M.; Strausz, O. P.; Bell, T. N.

doi:10.1163/156856790x00210

Cited by 51 publications

(49 citation statements)

References 73 publications

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“…1,2 Although early work (pre-1985) concentrated on product identification and mechanisms, in recent years there has been a increasing number of direct, time-resolved kinetic studies of silylene reactions leading to a steadily accumulating database of absolute rate constants. [3][4][5] A significant number of these have been carried out in our own laboratories, among which are the prototype addition reactions: [6][7][8][9] Reactions 1 and 2 have pressure-dependent second-order rate constants close to the collision value (at the high-pressure limit), together with small negative activation energies, consistent with third-body assisted association mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH₂ + C₃H₆, SiH₂ + i-C₄H₈, and SiMe₂ + C₂H₄. The Effects of Methyl Substitution on Strain Energies in Siliranes

et al. 1998

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Time-resolved studies of the title reactions have been carried out over the pressure range 1−100 Torr (in SF6 bath gas) and at temperatures in the range 293−600 K, using laser flash photolysis techniques to generate and monitor the silylenes, SiH2 and SiMe2. All three reactions showed evidence of pressure dependence, consistent with third-body assisted association reactions to form silirane products. Extrapolation of the pressure-dependent rate constants gave the following Arrhenius parameters: SiH2 + C3H6, log(A/cm3 molecule-1 s-1) = −9.79 ± 0.03, Ea (kJ mol-1) = −1.9 ± 0.3; SiH2 + C4H8, log(A/cm3 molecule-1 s-1) = −9.91 ± 0.04, Ea (kJ mol-1) = −2.5 ± 0.3; SiMe2 + C4H8, log(A/cm3 molecule-1 s-1) = −12.12 ± 0.02, Ea(kJ mol-1) = −8.5 ± 0.2. These parameters are consistent with fast, nearly collision-controlled processes for SiH2 but a tighter transition state for SiMe2. Rice, Ramsperger, Kassel, Marcus theory (RRKM) modeling, based on consistent transition states for silirane decomposition, and employing a weak collisional deactivation model, gave good fits to the pressure-dependent curves for each system, provided an appropriate value of Eo (fitting parameter) was used for each reaction. The kinetic results are consistent with an electrophilically led addition mechanism, although methyl substitution in the alkene hardly affects the rate constants. The RRKMderived Eo values have been used to derive reaction enthalpies which are in reasonable agreement with values obtained by ab initio calculations at the G2 (MP2,SVP) level. The experimental ΔH° values yield strain energies of 190, 196, and 216 kJ mol-1 for 2-methyl-, 2,2-dimethyl-, and 1,1-dimethylsilirane, respectively. Compared to the strain enthalpy of 167 kJ mol-1 for silirane itself, this shows that methyl substituents in the silirane products substantially increase the strain energies. Theory supports this. Disciplines Chemistry CommentsReprinted (adapted) M. S. Gordon Department of Chemistry, Iowa State UniVersity, Ames, Iowa 50011-3111ReceiVed: April 22, 1998; In Final Form: June 16, 1998 Time-resolved studies of the title reactions have been carried out over the pressure range 1-100 Torr (in SF 6 bath gas) and at temperatures in the range 293-600 K, using laser flash photolysis techniques to generate and monitor the silylenes, SiH 2 and SiMe 2 . All three reactions showed evidence of pressure dependence, consistent with third-body assisted association reactions to form silirane products. Extrapolation of the pressuredependent rate constants gave the following Arrhenius parameters: SiH 2 + C 3 H 6 , log(A/cm 3 molecule -1 s -1 ) ) -9.79 ( 0.03, E a (kJ mol -1 ) ) -1.9 ( 0.3; SiH 2 + C 4 H 8 , log(A/cm 3 molecule -1 s -1 ) ) -9.91 ( 0.04, E a (kJ mol -1 ) ) -2.5 ( 0.3; SiMe 2 + C 4 H 8 , log(A/cm 3 molecule -1 s -1 ) ) -12.12 ( 0.02, E a (kJ mol -1 ) ) -8.5 ( 0.2. These parameters are consistent with fast, nearly collision-controlled processes for SiH 2 but a tighter transition state for SiMe 2 . Rice, Ramsperger, Kassel, Marcus theory (RRKM) m...

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Section: Introductionmentioning

confidence: 99%

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH₂ + C₃H₆, SiH₂ + i-C₄H₈, and SiMe₂ + C₂H₄. The Effects of Methyl Substitution on Strain Energies in Siliranes

et al. 1998

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“…The volatile and solid products can thus be rationalized in terms of Scheme 2, showing that chemical vapour deposition of the solid films involves reactions of silylene and species produced by buta-1,3-diene photolysis. Rate constants for silylene additions to buta-1,3-diene and insertion into the SiÐH bond are somewhat higher 5,7 than those for addition of silylene to ethyne and ethene. High concentrations of SCP and buta-1,3-diene and low concentrations of C 1 ±C 4 hydrocarbons therefore make reactions between silylene and buta-1,3-diene or SCP (resulting in the respective formation of the initial SCP and of the observed 1-silyl-1-silacyclopent-3-ene) more important than reactions between silylene and C 1 ±C 4 hydrocarbons (ethyne, ethene, 1,2-butadiene, 1-buten-3-yne).…”

mentioning

confidence: 87%

UV laser photolysis of silacyclopent‐3‐ene: effect of admixtures on nature of chemically vapour‐deposited organosilicon films

Urbanová

Pola

2002

Applied Organom Chemis

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Examination of ArF laser‐induced gas‐phase photolysis of silacyclopent‐3‐ene, occuring as extrusion of silylene, in the presence of admixtures reveals that photolysis is not interfered with in the presence of N2, CO and CO2, but it is in the presence of O2, 2‐C4F8, CH3OH, CD3OH, CF3CH2OH and CH3CO2H. Formation of volatile products and solid deposited films incorporating fluorine or oxygen atoms is interpreted in terms of reactions of silylene with the admixtures. Copyright © 2002 John Wiley & Sons, Ltd.

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“…Kinetic measurements on the gas-phase reactions of the halosilylenes SiF 2 , SiHCl, SiCl 2 and SiBr 2 have been reviewed by Strausz and coworkers 327 . Donation of lone-pair electrons from halogen substituents to the divalent silicon atom would be expected to decrease reactivity, and indeed SiF 2 does not react at an appreciable rate with H 2 even at 1400 K, nor with molecular oxygen whose rates of reaction with SiCl 2 and SiBr 2 could be measured.…”

Section: Kinetics Of Silylene Reactionsmentioning

confidence: 99%

“…A number of rate constants for individual silylene reactions and the references to their original reports can be found in the major reviews cited here 322,323,327 . One must echo Becerra and Walsh 323 in stating that there remains much to be done in silylene kinetic studies.…”

Section: Kinetics Of Silylene Reactionsmentioning

confidence: 99%

Silylenes

Gaspar¹,

West²

2009

Patai's Chemistry of Functional Groups

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Introduction Generation of Silylenes Reactions of Silylenes Theoretical Calculations Spectroscopic Characterization of Silylenes Kinetics of Silylene Reactions Silylene–Transition Metal Complexes Special Topics Speculations on the Future of Silylene Chemistry

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Rate constants for silylene reactions

Cited by 51 publications

References 73 publications

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH₂ + C₃H₆, SiH₂ + i-C₄H₈, and SiMe₂ + C₂H₄. The Effects of Methyl Substitution on Strain Energies in Siliranes

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH₂ + C₃H₆, SiH₂ + i-C₄H₈, and SiMe₂ + C₂H₄. The Effects of Methyl Substitution on Strain Energies in Siliranes

UV laser photolysis of silacyclopent‐3‐ene: effect of admixtures on nature of chemically vapour‐deposited organosilicon films

Silylenes

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Rate constants for silylene reactions

Cited by 51 publications

References 73 publications

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH2 + C3H6, SiH2 + i-C4H8, and SiMe2 + C2H4. The Effects of Methyl Substitution on Strain Energies in Siliranes

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH2 + C3H6, SiH2 + i-C4H8, and SiMe2 + C2H4. The Effects of Methyl Substitution on Strain Energies in Siliranes

UV laser photolysis of silacyclopent‐3‐ene: effect of admixtures on nature of chemically vapour‐deposited organosilicon films

Silylenes

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Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH₂ + C₃H₆, SiH₂ + i-C₄H₈, and SiMe₂ + C₂H₄. The Effects of Methyl Substitution on Strain Energies in Siliranes

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH₂ + C₃H₆, SiH₂ + i-C₄H₈, and SiMe₂ + C₂H₄. The Effects of Methyl Substitution on Strain Energies in Siliranes