The University of Southampton
University of Southampton Institutional Repository

Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with nitric oxide

Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with nitric oxide
Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with nitric oxide
Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with NO. 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 299-592 K. The second-order rate constants at 10 Torr fitted the Arrhenius equation log(k/cm3 molecule-1 s-1) = (-11.66 ± 0.01) + (6.20 ± 0.10 kJ mol-1)/RT ln 10 The rate constants showed a variation with pressure of a factor of ca. 2 over the available range, almost independent of temperature. The data could not be fitted by RRKM calculations to a simple third body assisted association reaction alone. However, a mechanistic model with an additional (pressure independent) side channel gave a reasonable fit to the data. Ab initio calculations at the G3 level supported a mechanism in which the initial adduct, bent H2SiNO, can ring close to form cyclo-H2SiNO, which is partially collisionally stabilized. In addition, bent H2SiNO can undergo a low barrier isomerization reaction leading, via a sequence of steps, ultimately to dissociation products of which the lowest energy pair are NH2 + SiO. The rate controlling barrier for this latter pathway is only 16 kJ mol-1 below the energy of SiH2 + NO. This is consistent with the kinetic findings. A particular outcome of this work is that, despite the pressure dependence and the effects of the secondary barrier (in the side reaction), the initial encounter of SiH2 with NO occurs at the collision rate. Thus, silylene can be as reactive with odd electron molecules as with many even electron species. Some comparisons are drawn with the reactions of CH2 + NO and SiCl2 + NO.
absolute rate constants, potential-energy surface, germylene addition-reaction, temperature-dependence, ab-initio, prototype, molecules, silane, disilane, sih2
1089-5639
1071-1080
Becerra, Rosa
766758a2-9c71-4cab-9523-2874dfd5f84a
Bowes, Sarah-Jane
5085ec12-423d-4945-801c-2a30695d5d21
Ogden, J. Steven
5a99fd42-75e7-4f7b-a347-ac2b1717b8b3
Cannady, J. Pat
1b7d2bf5-1694-4d9f-8bc5-aab0783e9f76
Almond, Matthew J.
992a3a7b-3cbe-4818-828f-e0e6b876207f
Walsh, Robin
aacc9be2-5b7b-401b-9305-bb6cca0822a0
Becerra, Rosa
766758a2-9c71-4cab-9523-2874dfd5f84a
Bowes, Sarah-Jane
5085ec12-423d-4945-801c-2a30695d5d21
Ogden, J. Steven
5a99fd42-75e7-4f7b-a347-ac2b1717b8b3
Cannady, J. Pat
1b7d2bf5-1694-4d9f-8bc5-aab0783e9f76
Almond, Matthew J.
992a3a7b-3cbe-4818-828f-e0e6b876207f
Walsh, Robin
aacc9be2-5b7b-401b-9305-bb6cca0822a0

Becerra, Rosa, Bowes, Sarah-Jane, Ogden, J. Steven, Cannady, J. Pat, Almond, Matthew J. and Walsh, Robin (2005) Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with nitric oxide. Journal of Physical Chemistry A, 109 (6), 1071-1080. (doi:10.1021/jp045600p).

Record type: Article

Abstract

Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with NO. 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 299-592 K. The second-order rate constants at 10 Torr fitted the Arrhenius equation log(k/cm3 molecule-1 s-1) = (-11.66 ± 0.01) + (6.20 ± 0.10 kJ mol-1)/RT ln 10 The rate constants showed a variation with pressure of a factor of ca. 2 over the available range, almost independent of temperature. The data could not be fitted by RRKM calculations to a simple third body assisted association reaction alone. However, a mechanistic model with an additional (pressure independent) side channel gave a reasonable fit to the data. Ab initio calculations at the G3 level supported a mechanism in which the initial adduct, bent H2SiNO, can ring close to form cyclo-H2SiNO, which is partially collisionally stabilized. In addition, bent H2SiNO can undergo a low barrier isomerization reaction leading, via a sequence of steps, ultimately to dissociation products of which the lowest energy pair are NH2 + SiO. The rate controlling barrier for this latter pathway is only 16 kJ mol-1 below the energy of SiH2 + NO. This is consistent with the kinetic findings. A particular outcome of this work is that, despite the pressure dependence and the effects of the secondary barrier (in the side reaction), the initial encounter of SiH2 with NO occurs at the collision rate. Thus, silylene can be as reactive with odd electron molecules as with many even electron species. Some comparisons are drawn with the reactions of CH2 + NO and SiCl2 + NO.

Full text not available from this repository.

More information

Published date: 17 February 2005
Keywords: absolute rate constants, potential-energy surface, germylene addition-reaction, temperature-dependence, ab-initio, prototype, molecules, silane, disilane, sih2

Identifiers

Local EPrints ID: 20716
URI: https://eprints.soton.ac.uk/id/eprint/20716
ISSN: 1089-5639
PURE UUID: 1a1f3152-2539-4389-af49-c11b661e4833

Catalogue record

Date deposited: 01 Mar 2006
Last modified: 17 Jul 2017 16:28

Export record

Altmetrics

Contributors

Author: Rosa Becerra
Author: Sarah-Jane Bowes
Author: J. Steven Ogden
Author: J. Pat Cannady
Author: Matthew J. Almond
Author: Robin Walsh

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×