Time-resolved infrared observation of a long-lived transient in the photo-decarbonylation of Mn(CO)[sub 5]C(O)CH[sub 3]: Potential relevance to the CO migratory insertion mechanism
- Univ. of California, Santa Barbara, CA (United States)
Flash photolysis experiments have been carried out at ambient temperature to probe potential reaction intermediates in the carbonylation of the methylmanganese complex CH[sub 3]Mn(CO)[sub 5](M) to give the acyl product CH[sub 3]C(O)Mn(CO)[sub 5](A). Photo-decarbonylation of A gives a long-lived transient C, whose time-resolved infrared spectrum shows but modest sensitivity to the coordinating ability of the solvent such as cyclohexane, perfluoromethylcyclohexane, tetrahydrofuran, and 2,5-dimethyl-THF. Notably, C has an unexpectedly long lifetime (exceeding milliseconds) in each of the solvents investigated. Kinetics studies in cyclohexane show the competing trapping by CO to re-form A and isomerization to M occurs with the respective rate constants k[sub CO] = 3.8 x 10[sup 3] M[sup [minus]1] s[sup [minus]1] and 10 s[sup [minus]1]. The former value is 3 orders of magnitude less than expected for a solvent complex under these conditions. Thus, it is concluded that TRIR spectra and reactivity patterns of C reflect stabilization of this intermediate by [eta][sup 2]-coordination of the acyl group. 18 refs., 2 figs., 1 tab.
- DOE Contract Number:
- FG03-85ER13317
- OSTI ID:
- 5115499
- Journal Information:
- Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 12:12; ISSN 0276-7333; ISSN ORGND7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
ALKANES
CARBONYLATION
CARBONYLS
CATALYSTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
COORDINATION VALENCES
CYCLOALKANES
CYCLOHEXANE
DECOMPOSITION
HYDROCARBONS
INFRARED SPECTRA
ISOMERIZATION
KINETICS
MANGANESE COMPLEXES
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
REACTION KINETICS
SOLVENTS
SPECTRA
STABILIZATION
TRANSIENTS
TRANSITION ELEMENT COMPLEXES
VALENCE