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  Sequential Photosubstitution of Carbon Monoxide by (E)-Cyclooctene in Hexacarbonyltungsten:  Structural Aspects, Multistep Photokinetics, and Quantum Yields

Grevels, F.-W., Jacke, J., Klotzbücher, W. E., Mark, F., Skibbe, V., Schaffner, K., et al. (1999). Sequential Photosubstitution of Carbon Monoxide by (E)-Cyclooctene in Hexacarbonyltungsten:  Structural Aspects, Multistep Photokinetics, and Quantum Yields. Organometallics, 18(17), 3278-3293. doi:10.1021/om990300t.

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Grevels, Friedrich-Wilhelm1, Author
Jacke, Jürgen1, Author
Klotzbücher, Werner E.1, Author
Mark, Franz1, Author
Skibbe, Volker1, Author
Schaffner, Kurt1, Author
Angermund, Klaus2, Author           
Krüger, Carl3, Author           
Lehmann, Christian W.4, Author           
Özkar, Saim5, Author
Affiliations:
1Max-Planck-Institut für Strahlenchemie, Postfach 10 13 65, D-45413 Mülheim an der Ruhr, Germany , ou_persistent22              
2Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445590              
3Service Department Krüger (XRAY), Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445624              
4Service Department Lehmann (EMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445625              
5Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey, ou_persistent22              

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 Abstract: The photochemical conversion of W(CO)6 (1) into a trans-W(CO)42-olefin)2 complex has been investigated using (E)-cyclooctene (eco) as a model olefin possessing extraordinary coordination properties. trans-W(CO)42-eco)2 (4) is generated as an equimolar mixture of two diastereoisomers (4a, S symmetry; 4b, D2 symmetry) which can be separated by fractional crystallization. The entire reaction sequence involves the intermediate formation of W(CO)2-eco) (2) and cis-W(CO)2-eco)2 (3:  two diastereoisomers, 3a and 3b, with apparent C and C symmetry, respectively). Complexes 2 and 3, although difficult to isolate from the photochemical reaction mixture, are conveniently accessible via alternative thermal ligand exchange routes. The molecular structures of 2 and 4a in the crystal were determined by X-ray diffraction techniques. The olefin double bonds, with trans-orthogonal arrangement in 4a, are eclipsed to a OC−W−CO axis in either case. The course of the conversion of 1 into the olefin-substituted products was monitored by quantitative IR spectroscopy. Photokinetic equations developed for this study describe the concentrations of all four components as implicit functions of the amount of light absorbed by the system, of the quantum yields of the individual photoprocesses, and of the UV−vis absorbance coefficients of the compounds involved. Based on these functional relationships, the individual quantum yields at λexc = 365 nm (Φ12 = 0.73, Φ23 = 0.34, Φ24 = 0.16, Φ34 = 0.15) were evaluated from a series of experimental data sets by an iterative procedure which involves variation of the quantum yield input data until the best fit of the computed to the measured concentrations is achieved. Low-temperature matrix isolation techniques were employed to characterize the W(CO)2-eco) fragment (5) as a key intermediate in the photolysis of W(CO)52-eco) (2).

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Language(s): eng - English
 Dates: 1999-04-231999-07-241999-08-01
 Publication Status: Published in print
 Pages: 16
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/om990300t
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Title: Organometallics
  Other : Organometallics
Source Genre: Journal
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Publ. Info: Washington, D.C. : American Chemical Society
Pages: - Volume / Issue: 18 (17) Sequence Number: - Start / End Page: 3278 - 3293 Identifier: ISSN: 0276-7333
CoNE: https://pure.mpg.de/cone/journals/resource/954925505259