Molybdenum-Catalyzed Transformation of Molecular Dinitrogen into Silylamine: Experimental and DFT Study on the Remarkable Role of Ferrocenyldiphosphine Ligands

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• 作者：Hiromasa Tanaka ; Akira Sasada ; Tomohisa Kouno ; Masahiro Yuki ; Yoshihiro Miyake ; Haruyuki Nakanishi ; Yoshiaki Nishibayashi ; Kazunari Yoshizawa
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：March 16, 2011
• 年：2011
• 卷：133
• 期：10
• 页码：3498-3506
• 全文大小：1017K
• 年卷期：v.133,no.10(March 16, 2011)
• ISSN：1520-5126

文摘

A molybdenum鈭抎initrogen complex bearing two ancillary ferrocenyldiphosphine ligands, trans-[Mo(N₂)₂(depf)₂] (depf = 1,1鈥?bis(diethylphosphino)ferrocene), catalyzes the conversion of molecular dinitrogen (N₂) into silylamine (N(SiMe₃)₃), which can be readily converted into NH₃ by acid treatment. The conversion has been achieved in the presence of Me₃SiCl and Na at room temperature with a turnover number (TON) of 226 for the N(SiMe₃)₃ generation for 200 h. This TON is significantly improved relative to those ever reported by Hidai始s group for mononuclear molybdenum complexes having monophosphine coligands [J. Am. Chem. Soc.1989, 111, 1939]. Density functional theory (DFT) calculations have been performed to figure out the mechanism of the catalytic N₂ conversion. On the basis of some pieces of experimental information, SiMe₃ radical is assumed to serve as an active species in the catalytic cycle. Calculated results also support that SiMe₃ radical is capable of working as an active species. The formation of five-coordinate intermediates, in which one of the N₂ ligands or one of the Mo鈭扨 bonds is dissociated, is essential in an early stage of the N₂ conversion. The SiMe₃ addition to a 鈥渉ydrazido(2鈭?鈥?intermediate having the NN(SiMe₃)₂ group will give a 鈥渉ydrazido(1鈭?鈥?intermediate having the (Me₃Si)NN(SiMe₃)₂ group rather than a pair of a nitrido (鈮) intermediate and N(SiMe₃)₃. The N(SiMe₃)₃ generation would not occur at the Mo center but proceed after the (Me₃Si)NN(SiMe₃)₂ group is released from the Mo center. The flexibility of the Mo鈭扨 bond between Mo and depf would play a vital role in the high catalysis of the Mo鈭扚e complex.