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    Laser Photochemistry and Transient Raman Spectroscopy of Silyl-Substituted Fischer-Type Carbene Complexes


    Rooney, A. Denise and McGarvey, John J. and Gordon, Keith C. and McNicholl, Ruth-Anne and Schubert, Ulrich and Hepp, Wolfgang (1993) Laser Photochemistry and Transient Raman Spectroscopy of Silyl-Substituted Fischer-Type Carbene Complexes. Organometallics, 12 (4). pp. 1277-1282. ISSN 0276-7333

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    Abstract

    Pulsed laser irradiation of the silyl-substituted carbene complexes (CO)5W=C(XR)SiPh3 (XR = NC4H8 (1); = OEt (2)) in various solvents has been investigated using transient absorbance and time-resolved resonance Raman scattering as monitoring techniques. Irradiation of (1) in noncoordinating or weakly-coordinating solvents at 355 nm within the ligand field absorption band results in the rapid formation, within the laser pulse duration, of a permanent photoproduct. Saturation of the irradiated solution with CO results in regeneration of the starting complex 1. IR and Raman spectral data suggest that the photoproduct is the internally stabilized 16- electron species (CO)4W=C(NC,iH8)SiPh3. The observations are discussed in relation to the previously reported formation of the same 16-electron species by thermolysis of 1. When the irradiation is carried out in CH3CN as solvent, UV-visible evidence suggests formation of the photosubstituted species (CO)4(CH3CN) W=C(NC4Hg)SiPh3. No photoactivity, either transient or permanent, is seen in any solvent when the irradiation is carried out at 416 nm, a wavelength which falls within the MLCT absorption region of 1. When the ethoxy-substituted carbene complex 2 is irradiated in either the LF or MLCT absorption regions a transient species forms rapidly, within the laser pulse duration, and decays on a time scale of several μß, with a lifetime dependent on solvent polarity but independent of CO concentration in solution. Time-resolved resonance Raman studies in which the sample is photolyzed at 355 nm and probed by means of a delayed pulse at 406 nm show the formation and decay of a transient consistent with the flash photolysis results. The data are interpreted in terms of photoinduced anti-syn isomerization of 2 about the Ccarbene~0 bond.

    Item Type: Article
    Additional Information: Cite as: Organometallics 1993, 12, 4, 1277–1282
    Keywords: Laser; Photochemistry; Transient; Raman; Spectroscopy; Silyl-Substituted; Fischer-Type; Carbene; Complexes;
    Academic Unit: Faculty of Science and Engineering > Chemistry
    Item ID: 14526
    Identification Number: https://doi.org/10.1021/om00028a050
    Depositing User: Dr. Denise Rooney
    Date Deposited: 09 Jun 2021 15:24
    Journal or Publication Title: Organometallics
    Publisher: American Chemical Society
    Refereed: Yes
    URI:

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