Electronic Structure Determination of Pyridine N-Heterocyclic Carbene Iron Dinitrogen Complexes and Neutral Ligand Derivatives

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• 作者：Jonathan M. Darmon ; Renyuan Pony Yu ; Scott P. Semproni ; Zo毛 R. Turner ; S. Chantal E. Stieber ; Serena DeBeer ; Paul J. Chirik
• 刊名：Organometallics
• 出版年：2014
• 出版时间：October 13, 2014
• 年：2014
• 卷：33
• 期：19
• 页码：5423-5433
• 全文大小：572K
• ISSN：1520-6041

文摘

The electronic structures of pyridine N-heterocyclic dicarbene (^iPrCNC) iron complexes have been studied by a combination of spectroscopic and computational methods. The goal of these studies was to determine if this chelate engages in radical chemistry in reduced base metal compounds. The iron dinitrogen example (^iPrCNC)Fe(N₂)₂ and the related pyridine derivative (^iPrCNC)Fe(DMAP)(N₂) were studied by NMR, M枚ssbauer, and X-ray absorption spectroscopy and are best described as redox non-innocent compounds with the ^iPrCNC chelate functioning as a classical 蟺 acceptor and the iron being viewed as a hybrid between low-spin Fe(0) and Fe(II) oxidation states. This electronic description has been supported by spectroscopic data and DFT calculations. Addition of N,N-diallyl-tert-butylamine to (^iPrCNC)Fe(N₂)₂ yielded the corresponding iron diene complex. Elucidation of the electronic structure again revealed the CNC chelate acting as a 蟺 acceptor with no evidence for ligand-centered radicals. This ground state is in contrast with the case for the analogous bis(imino)pyridine iron complexes and may account for the lack of catalytic [2蟺 + 2蟺] cycloaddition reactivity.