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Article: Intrinsic reaction coordinate analysis of the activation of CH4 by molybdenum atoms: A density functional theory study of the crossing seams of the potential energy surfaces

TitleIntrinsic reaction coordinate analysis of the activation of CH4 by molybdenum atoms: A density functional theory study of the crossing seams of the potential energy surfaces
Authors
Issue Date2008
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/organometallics
Citation
Organometallics, 2008, v. 27 n. 2, p. 181-188 How to Cite?
AbstractDensity functional theory (DFT) calculations were performed to investigate the quintet, triplet, and singlet potential energy surfaces associated with the C-H activation of methane by laser-ablated molybdenum (Mo) atoms recently observed experimentally by Andrews and co-workers. The present computational study aims to better understand the nature of the reaction mechanisms for C-H activation by Mo atoms. The processes for activation of methane by the excited Mo atoms appear to produce CH 3-MoH, CH 2=MoH 2, and CH≡MoH 3 complexes. The crossing seams between the potential energy surfaces and possible spin inversion processes for the direct conversion of methane to a high oxidation state transition metal complex that contains a carbon-metal double or triple bond are examined using the intrinsic reaction coordinate (IRC) approach. The minimum energy reaction pathway is found to involve spin inversion three times in different reaction steps. In total, three spin states (quintet, triplet, and singlet) are involved in going from the entrance channel to the exit channel: 5Mo + CH 4 → CH 3 - MoH ( 51) → CH 2=MoH 2 ( 32) → CH≡MoH 3 ( 13). The first crossing seam exists prior to TS 1-2, a three-centered transition state for the H-transfer of complex 1 to form a double carbon-metal bond complex 2. This crossing seam is a key aspect in the reaction pathway because the molecular system should change its spin multiplicity from the quintet state to the triplet state near this crossing region, which leads to a significant decrease in the barrier height of TS 1-2 from 51.0 to 33.8 kcal mol -1 at the B3LYP level of theory. The second crossing seam between the quintet potential energy surface (PES) and the singlet PES is found not to play a significant role because the triplet potential energy surface lies significantly below the quintet and singlet potential energy surfaces. Accordingly, the molecular system would preferentially move on the triplet potential energy surfaces before encountering the second seam. The crossing seam between the triplet exit channel and the singlet exit channel can take place, in which complex 13 containing a triple carbon-metal bond is formed via an H-transfer process. This crossing seam will again lead to a spin inversion from the triplet to the singlet state, and this leads to a large decrease in the height of the reaction barrier from 40.8 to 17.2 kcal mol -1. © 2008 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/168275
ISSN
2015 Impact Factor: 4.186
2015 SCImago Journal Rankings: 2.043
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorGuo, Zen_US
dc.contributor.authorKe, Zen_US
dc.contributor.authorPhillips, DLen_US
dc.contributor.authorZhao, Cen_US
dc.date.accessioned2012-10-08T03:16:56Z-
dc.date.available2012-10-08T03:16:56Z-
dc.date.issued2008en_US
dc.identifier.citationOrganometallics, 2008, v. 27 n. 2, p. 181-188en_US
dc.identifier.issn0276-7333en_US
dc.identifier.urihttp://hdl.handle.net/10722/168275-
dc.description.abstractDensity functional theory (DFT) calculations were performed to investigate the quintet, triplet, and singlet potential energy surfaces associated with the C-H activation of methane by laser-ablated molybdenum (Mo) atoms recently observed experimentally by Andrews and co-workers. The present computational study aims to better understand the nature of the reaction mechanisms for C-H activation by Mo atoms. The processes for activation of methane by the excited Mo atoms appear to produce CH 3-MoH, CH 2=MoH 2, and CH≡MoH 3 complexes. The crossing seams between the potential energy surfaces and possible spin inversion processes for the direct conversion of methane to a high oxidation state transition metal complex that contains a carbon-metal double or triple bond are examined using the intrinsic reaction coordinate (IRC) approach. The minimum energy reaction pathway is found to involve spin inversion three times in different reaction steps. In total, three spin states (quintet, triplet, and singlet) are involved in going from the entrance channel to the exit channel: 5Mo + CH 4 → CH 3 - MoH ( 51) → CH 2=MoH 2 ( 32) → CH≡MoH 3 ( 13). The first crossing seam exists prior to TS 1-2, a three-centered transition state for the H-transfer of complex 1 to form a double carbon-metal bond complex 2. This crossing seam is a key aspect in the reaction pathway because the molecular system should change its spin multiplicity from the quintet state to the triplet state near this crossing region, which leads to a significant decrease in the barrier height of TS 1-2 from 51.0 to 33.8 kcal mol -1 at the B3LYP level of theory. The second crossing seam between the quintet potential energy surface (PES) and the singlet PES is found not to play a significant role because the triplet potential energy surface lies significantly below the quintet and singlet potential energy surfaces. Accordingly, the molecular system would preferentially move on the triplet potential energy surfaces before encountering the second seam. The crossing seam between the triplet exit channel and the singlet exit channel can take place, in which complex 13 containing a triple carbon-metal bond is formed via an H-transfer process. This crossing seam will again lead to a spin inversion from the triplet to the singlet state, and this leads to a large decrease in the height of the reaction barrier from 40.8 to 17.2 kcal mol -1. © 2008 American Chemical Society.en_US
dc.languageengen_US
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/organometallicsen_US
dc.relation.ispartofOrganometallicsen_US
dc.titleIntrinsic reaction coordinate analysis of the activation of CH4 by molybdenum atoms: A density functional theory study of the crossing seams of the potential energy surfacesen_US
dc.typeArticleen_US
dc.identifier.emailPhillips, DL:phillips@hku.hken_US
dc.identifier.authorityPhillips, DL=rp00770en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1021/om7007452en_US
dc.identifier.scopuseid_2-s2.0-39049105259en_US
dc.identifier.hkuros151582-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-39049105259&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume27en_US
dc.identifier.issue2en_US
dc.identifier.spage181en_US
dc.identifier.epage188en_US
dc.identifier.isiWOS:000252554700008-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridGuo, Z=36554069300en_US
dc.identifier.scopusauthoridKe, Z=14048262500en_US
dc.identifier.scopusauthoridPhillips, DL=7404519365en_US
dc.identifier.scopusauthoridZhao, C=7403563836en_US

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