Observation of a Short-Lived Triplet Precursor in CpCo(CO)-Catalyzed Alkyne Cyclotrimerization

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• 作者：Justin P. Lomont ; Son C. Nguyen ; Matthew C. Zoerb ; Adam D. Hill ; Jacob P. Schlegel ; Charles B. Harris
• 刊名：Organometallics
• 出版年：2012
• 出版时间：May 14, 2012
• 年：2012
• 卷：31
• 期：9
• 页码：3582-3587
• 全文大小：296K
• 年卷期：v.31,no.9(May 14, 2012)
• ISSN：1520-6041

文摘

The picosecond dynamics of CpCo(CO), a catalytic intermediate in the cyclotrimerization of alkynes, have been studied using time-resolved infrared spectroscopy and density functional theory calculations. In neat 1-hexyne or 1-hexene solution, the first intermediate to form is a triplet 畏²-coordinated species, which then converts to a singlet 畏² species in ca. 30鈥?0 ps. The 畏² triplet is the only solvent-coordinated species observed at early times, suggesting that this is the dominant mechanistic pathway for coordination of alkynes and alkenes to the CpCo(CO) catalyst. These new results complement the recent discovery that CpCo(CO) can coordinate to certain solvent molecules in both singlet and triplet spin states and further support previous studies implicating triplet intermediates in cobalt-catalyzed cyclotrimerization and cyclo-oligomerization reaction mechanisms.