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Gas‐Phase Kinetics of Chlorosilylene Reactions II. ClSiH + C 2 H 4 : Absolute Rate Measurements and Quantum Chemical and RRKM Calculations for the Prototype π Addition Reaction
Author(s) -
Becerra Rosa,
Boganov Sergey E.,
Egorov Mikhail P.,
Krylova Irina V.,
Nefedov Oleg M.,
Promyslov Vladimir M.,
Walsh Robin
Publication year - 2010
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200900490
Subject(s) - chemistry , kinetics , chemical kinetics , gas phase , reaction rate constant , chemical reaction , chemical reaction kinetics , computational chemistry , reaction mechanism , rrkm theory , thermodynamics , physics , catalysis , organic chemistry , quantum mechanics
Time‐resolved studies of chlorosilylene, ClSiH, generated by the 193 nm laser flash photolysis of 1‐chloro‐1‐silacyclopent‐3‐ene, are carried out to obtain rate constants for its bimolecular reaction with ethene, C 2 H 4 , in the gas‐phase. The reaction is studied over the pressure range 0.13–13.3 kPa (with added SF 6 ) at five temperatures in the range 296–562 K. The second order rate constants, obtained by extrapolation to the high pressure limits at each temperature, fitted the Arrhenius equation: log( k ∞ /cm 3 molecule −1 s −1 )=(−10.55±0.10) + (3.86±0.70) kJ mol −1 / RT ln10. The Arrhenius parameters correspond to a loose transition state and the rate constant at room temperature is 43 % of that for SiH 2 + C 2 H 4 , showing that the deactivating effect of Cl‐for‐H substitution in the silylene is not large. Quantum chemical calculations of the potential energy surface for this reaction at the G3MP2//B3LYP level show that, as well as 1‐chlorosilirane, ethylchlorosilylene is a viable product. The calculations reveal how the added effect of the Cl atom on the divalent state stabilisation of ClSiH influences the course of this reaction. RRKM calculations of the reaction pressure dependence suggest that ethylchlorosilylene should be the main product. The results are compared and contrasted with those of SiH 2 and SiCl 2 with C 2 H 4 .