Nitride-Bridged Triiron Complex and Its Relevance to Dinitrogen Activation

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• 作者：David M. Ermert ; Jesse B. Gordon ; Khalil A. Abboud ; Leslie J. Murray
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：October 5, 2015
• 年：2015
• 卷：54
• 期：19
• 页码：9282-9289
• 全文大小：465K
• ISSN：1520-510X

文摘

Using a simple metathesis approach, the triiron(II) tribromide complex Fe₃Br₃L (1) reacts with tetrabutylammonium azide to afford the monoazide dibromide analogue Fe₃(Br)₂(N₃)L (2) in high yield. The inclusion of azide was confirmed by IR spectroscopy with a 谓(N₃) = 2082 cm^鈥? as well as combustion analysis and X-ray crystallography. Heating 2 in the solid state results in the complete loss of the azide vibration in the IR spectra and the isolation of the olive-green mononitride complex Fe₃(Br)₂(N)L (3). Solution magnetic susceptibility measurements support that the trimetallic core within 2 is oxidized upon generation of 3 (5.07 vs 3.09 渭_B). Absorption maxima in the UV鈥搗isible鈥搉ear-IR (NIR) spectra of 2 and 3 support the azide-to-nitride conversion, and a broad NIR absorption centered at 1117 nm is similar to that previously reported for the intervalence charge-transfer band for a mixed-valent nitridodiiron cluster. The cyclic voltammograms recorded for 3 are comparable to those of 1 with no reductive waves observed between 鈭? and 鈭?.5 V (vs Fc/Fc⁺), whereas a reversible one-electron redox process is observed for Fe₃(NH₂)₃L (4). These results suggest that intercluster cooperativity is unlikely to predominate the dinitrogen reduction mechanism when 1 is treated with KC₈ under N₂.