19-Electron Intermediates and Cage-Effects in the Photochemical Disproportionation of [CpW(CO)] with Lewis Bases.
The role of 19-electron intermediates in the photochemical disproportionation of [CpW(CO)] (Cp = CH) with Lewis bases (PR R = OMe, Bu, Ph) is investigated on the ultrafast time scale using femtosecond VIS-pump, IR-probe spectroscopy. Formation of a 19-electron (19e) species CpW(CO) ∙ by coordination...
| Publicado en: | Journal of the American Chemical Society Vol. 127; no. 36; pp. 12555 - 12566 |
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| Autores principales: | , , , |
| Formato: | Artículo |
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American Chemical Society
9/14/2005
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=18276065&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 18276065 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 9/14/2005 vid: 127 iid: 36 pid: 997 pub: American Chemical Society artinfo: ui: 18276065 10.1021/ja052221g ppf: 12555 ppct: 11 formats: tig: atl: 19-Electron Intermediates and Cage-Effects in the Photochemical Disproportionation of [CpW(CO)] with Lewis Bases. aug: au: Cahoon, James F. Kling, Matthias F. Schmatz, Stefan Harris, Charles B. affil: Department of Chemistry, University of California, Berkeley, California 94720. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720. Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany. su: Photochemistry Hydrogen-ion concentration Spectrum analysis Density functionals Particles (Nuclear physics) Radicals sug: subj: Photochemistry Hydrogen-ion concentration Spectrum analysis Density functionals Particles (Nuclear physics) Radicals ab: The role of 19-electron intermediates in the photochemical disproportionation of [CpW(CO)] (Cp = CH) with Lewis bases (PR R = OMe, Bu, Ph) is investigated on the ultrafast time scale using femtosecond VIS-pump, IR-probe spectroscopy. Formation of a 19-electron (19e) species CpW(CO) ∙ by coordination of PR with photogenerated 17-electron (17e) radicals CpW(CO) ∙ is directly observed, and equilibrium is established between the 17e radicals and the 19e intermediates favoring 19e intermediates in the order: Bu> OMe» Ph. Steric effects dominate the 17e/19e equilibrium when the cone-angle of the Lewis base exceeds a certain limiting value (between 132° and 145°), but below this value electronic properties of the Lewis base control the 17e/19e dynamics. Disproportionation occurs in less than 200 picoseconds by electron transfer between a solvent caged 17e radical and 19e, highly reducing species. The rate and extent of ultrafast disproportionation depends on both the identity and concentration of the Lewis base. In low concentrations of PR3 (typically 1-2 M or less) or with Lewis bases whose equilibrium heavily favors 17e radicals (e.g., PPh), disproportionation is rate-limited by breakdown of the solvent cage. Density functional theory calculations on vibrational frequencies and charge distributions of the various complexes support the experimental results. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2005 holdings: @attributes: islocal: N |
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