Heterometallic CoIII4FeIII2 Schiff Base Complex: Structure, Electron Paramagnetic Resonance, and Alkane Oxidation Catalytic Activity

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• 作者：Dmytro S. Nesterov ; Eduard N. Chygorin ; Volodymyr N. Kokozay ; Volodymyr V. Bon ; Roman Bo膷a ; Yuriy N. Kozlov ; Lidia S. Shul鈥檖ina ; Julia Jezierska ; Andrew Ozarowski ; Armando J. L. Pombeiro ; Georgiy B. Shul鈥檖in
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：August 20, 2012
• 年：2012
• 卷：51
• 期：16
• 页码：9110-9122
• 全文大小：625K
• 年卷期：v.51,no.16(August 20, 2012)
• ISSN：1520-510X

文摘

The heterometallic complex [Co₄Fe₂OSae₈]路4DMF路H₂O (1) was synthesized by one-pot reaction of cobalt powder with iron chloride in a dimethylformamide solution of salicylidene-2-ethanolamine (H₂Sae) and characterized by single crystal X-ray diffraction analysis, magnetic measurements, high frequency electron paramagnetic resonance (HF-EPR), and M枚ssbauer spectroscopies. The exchange coupling in the Fe(III)鈥揊e(III) pair is of antiferromagnetic behavior with J/hc = 鈭?90 cm^鈥?. The HF-EPR spectra reveal an unusual pattern with a hardly detectable triplet signal of the Fe(III) dimer. The magnitude of D (ca. 13.9 cm^鈥?) was found to be much larger than in related dimers. The catalytic investigations disclosed an outstanding activity of 1 toward oxidation of cycloalkanes with hydrogen peroxide, under mild conditions. The most efficient system showed a turnover number (TON) of 3.57 脳 10³ with the concomitant overall yield of 26% for cyclohexane, and 2.28 脳 10³/46%, respectively, for cyclooctane. A remarkable turnover frequency (TOF) of 1.12 脳 10⁴ h^鈥? (the highest initial rate W₀ = 3.5 脳 10^鈥? M s^鈥?) was achieved in oxidation of cyclohexane. Kinetic experiments and selectivity parameters led to the conclusion that hydroxyl radicals are active (attacking C鈥揌 bonds) species. Kinetic and electrospray ionization mass spectrometry (ESI-MS) data allowed us to assume that the trinuclear heterometallic particle [Co₂Fe(Sae)₄]⁺, originated from 1 in solution, could be responsible for efficient generation of hydroxyl radicals from hydrogen peroxide.