A Pentacoordinate Mn(II) Precatalyst That Exhibits Notable Aldehyde and Ketone Hydrosilylation Turnover Frequencies

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• 作者：Chandrani Ghosh ; Tufan K. Mukhopadhyay ; Marco Flores ; Thomas L. Groy ; Ryan J. Trovitch
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 2, 2015
• 年：2015
• 卷：54
• 期：21
• 页码：10398-10406
• 全文大小：575K
• ISSN：1520-510X

文摘

Heating (THF)₂MnCl₂ in the presence of the pyridine-substituted bis(imino)pyridine ligand, ^PyEtPDI, allowed preparation of the respective dihalide complex, (^PyEtPDI)MnCl₂. Reduction of this precursor using excess Na/Hg resulted in deprotonation of the chelate methyl groups to yield the bis(enamide)tris(pyridine)-supported product, (魏⁵-N,N,N,N,N-^PyEtPDEA)Mn. This complex was characterized by single-crystal X-ray diffraction and found to possess an intermediate-spin (S = ³/₂) Mn(II) center by the Evans method and electron paramagnetic resonance spectroscopy. Furthermore, (魏⁵-N,N,N,N,N-^PyEtPDEA)Mn was determined to be an effective precatalyst for the hydrosilylation of aldehydes and ketones, exhibiting turnover frequencies of up to 2475 min^鈥? when employed under solvent-free conditions. This optimization allowed for isolation of the respective alcohols and, in two cases, the partially reacted silyl ethers, PhSiH(OR)₂ [R = Cy and CH(Me)(ⁿBu)]. The aldehyde hydrosilylation activity observed for (魏⁵-N,N,N,N,N-^PyEtPDEA)Mn renders it one of the most efficient first-row transition metal catalysts for this transformation reported to date.