Oxidation of ethane to ethanol by N2O in a metal–organic framework with coordinatively unsaturated iron(II) sites
作者:Dianne J. Xiao、Eric D. Bloch、Jarad A. Mason、Wendy L. Queen、Matthew R. Hudson、Nora Planas、Joshua Borycz、Allison L. Dzubak、Pragya Verma、Kyuho Lee、Francesca Bonino、Valentina Crocellà、Junko Yano、Silvia Bordiga、Donald G. Truhlar、Laura Gagliardi、Craig M. Brown、Jeffrey R. Long
DOI:10.1038/nchem.1956
日期:2014.7
Enzymatic haem and non-haem high-valent ironâoxo species are known to activate strong CâH bonds, yet duplicating this reactivity in a synthetic system remains a formidable challenge. Although instability of the terminal ironâoxo moiety is perhaps the foremost obstacle, steric and electronic factors also limit the activity of previously reported mononuclear iron(IV)âoxo compounds. In particular, although nature's non-haem iron(IV)âoxo compounds possess high-spin S = 2 ground states, this electronic configuration has proved difficult to achieve in a molecular species. These challenges may be mitigated within metalâorganic frameworks that feature site-isolated iron centres in a constrained, weak-field ligand environment. Here, we show that the metalâorganic framework Fe2(dobdc) (dobdc4â = 2,5-dioxido-1,4-benzenedicarboxylate) and its magnesium-diluted analogue, Fe0.1Mg1.9(dobdc), are able to activate the CâH bonds of ethane and convert it into ethanol and acetaldehyde using nitrous oxide as the terminal oxidant. Electronic structure calculations indicate that the active oxidant is likely to be a high-spin S = 2 iron(IV)âoxo species. Selective functionalization of light hydrocarbons is a challenging but desirable transformation. Now a family of Fe(II)-based metalâorganic frameworks has been shown to convert ethane into ethanol and acetaldehyde using N2O. Electronic structure calculations indicate that the active Fe oxidant in the MOF is a high-spin S = 2 iron(II)âoxo species.
众所周知,酶血红素和非血红素高价氧化铁能激活强CH键,然而在合成系统中复制这种反应性仍然是一项艰巨的挑战。虽然末端氧化铁分子的不稳定性可能是最大的障碍,但立体和电子因素也限制了之前报道的单核氧化铁(IV)化合物的活性。特别是,虽然自然界中的非haem铁(IV)âoxo化合物具有高自旋SÂ =Â 2基态,但这种电子构型在分子物种中很难实现。这些挑战可以在金属有机框架中得到缓解,该框架的特点是在受限的弱场配体环境中具有位点隔离的铁中心。在这里,我们展示了金属有机框架 Fe2(dobdc)(dobdc4=2,5-二氧代-1,4-苯二甲酸酯)及其镁稀释类似物 Fe0.1Mg1.9(dobdc)能够激活乙烷的 CH 键,并以氧化亚氮为末端氧化剂将其转化为乙醇和乙醛。电子结构计算表明,活性氧化剂可能是高自旋 SÂ =Â 2 铁(IV)âoxo 物种。轻烃的选择性官能化是一项具有挑战性的理想转化。现在,一个以铁(II)为基础的金属有机框架家族已经证明可以利用氧化亚氮将乙烷转化为乙醇和乙醛。电子结构计算表明,MOF 中的活性铁氧化剂是一种高自旋 SÂ =Â 2 铁(II)âoxo 物种。