Intermediates relevant to the carbonylation of manganese alkyl complexes interrogated by time resolved infrared and optical spectroscopy
- Univ. of California, Santa Barbara, CA (United States)
Intermediates relevant to the carbonylation of metal alkyl complexes have been generated by laser flash photolysis of the manganese acyl complexes RC(O)Mn(CO){sub 5} (R = CH{sub 3}, CD{sub 3}, CH{sub 2}CH{sub 3}, CH{sub 2}F, CF{sub 3}). This results in immediate CO photodissociation to give intermediate acyl complexes which were observed by time resolved infrared (TRIR) and time resolved optical (TRO) spectroscopy. In the presence of added ligands, such intermediates are trapped to form stable cis-substituted octahedral complexes in competition with alkyl migration from the acyl group to give the alkyl pentacarbonyl complexes RMn(CO){sub 5}. The spectra and reactivity of the intermediate (I) derived from CH{sub 3}C(O)Mn(CO){sub 5} (A) indicate that this exists as the chelated acyl complex ({eta}{sup 2}-CH{sub 3}CO)Mn(CO){sub 4} in weakly coordinating solvents such as cyclohexane but as the solvento species cis-CH{sub 3}C(O)Mn(CO){sub 4}(THF) in tetrahydrofuran. Comparisons with thermal reaction kinetics support the assertion that the intermediates generated photochemically are indeed relevant to understanding the mechanism for CH{sub 3}Mn(CO){sub 5} carbonylation. The CF{sub 3} and CH{sub 2}F analogs of I are much more reactive than I in cyclohexane solution, and this has been interpreted in terms of the {eta}{sup 2}-acyl configuration being destabilized by these electron-withdrawing groups. 33 refs., 10 figs., 4 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG03-85ER13317; FG05-91ER79039
- OSTI ID:
- 102862
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 32 Vol. 117; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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