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The addition reaction between silylene and ethyne: further isotope studies, pressure dependence studies, and quantum chemical calculations

Becerra, R., Cannady, J.P., Dormer, G. and Walsh, R. (2008) The addition reaction between silylene and ethyne: further isotope studies, pressure dependence studies, and quantum chemical calculations. Journal of Physical Chemistry A, 112 (37). pp. 8665-8677. ISSN 1089-5639

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To link to this item DOI: 10.1021/jp803391g

Abstract/Summary

Time-resolved kinetic studies of the reaction of dideutero-silylene, SiD2, generated by laser flash photolysis of phenylsilane-d(3), have been carried out to obtain rate constants for its bimolecular reaction with C2H2. The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF6 bath gas, at five temperatures in the range 297-600 K. The second-order rate constants obtained by extrapolation to the high-pressure limits at each temperature fitted the Arrhenius equation log(k(infinity)/cm(3) molecule(-1) s(-1)) = (-10.05 +/- 0.05) + (3.43 +/- 0.36 kJ mol(-1))/RT ln 10. The rate constants were used to obtain a comprehensive set of isotope effects by comparison with earlier obtained rate constants for the reactions of SiH2 with C2H2 and C2D2. Additionally, pressure-dependent rate constants for the reaction of SiH2 with C2H2 in the presence of He (1-100 Tort) were obtained at 300, 399, and 613 K. Quantum chemical (ab initio) calculations of the SiC2H4 reaction system at the G3 level support the initial formation of silirene, which rapidly isomerizes to ethynylsilane as the major pathway. Reversible formation of vinylsilylene is also an important process. The calculations also indicate the involvement of several other intermediates, not previously suggested in the mechanism. RRKM calculations are in semiquantitative agreement with the pressure dependences and isotope effects suggested by the ab initio calculations, but residual discrepancies suggest the possible involvement of the minor reaction channel, SiH2 + C2H2 - SWPO + C2H4. The results are compared and contrasted with previous studies of this reaction system.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:11006
Uncontrolled Keywords:MATRIX-SPECTROSCOPIC IDENTIFICATION, POTENTIAL-ENERGY SURFACE, ABSOLUTE RATE CONSTANTS, GAS-PHASE, MECHANISTIC COMPLEXITIES, TEMPERATURE-DEPENDENCE, AB-INITIO, GERMYLENE, PROTOTYPE, GENERATION

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