A Chiral Macrocyclic Tetra-N-Heterocyclic Carbene Yields an "All Carbene" Iron Alkylidene Complex.,Chemistry - A European Journal

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A Chiral Macrocyclic Tetra-N-Heterocyclic Carbene Yields an "All Carbene" Iron Alkylidene Complex.
Chemistry - A European Journal ( IF 3.9 ) Pub Date : 2020-01-22 , DOI: 10.1002/chem.201905360
Joseph F DeJesus ₁ , David M Jenkins ₁

Affiliation

The first chiral macrocyclic tetra-N-heterocyclic carbene (NHC) ligand has been synthesized. The macrocycle, prepared in high yield and large scale, was ligated onto palladium and iron to give divalent C2 -symmetric square planar complexes. Multinuclear NMR and single crystal X-ray diffraction demonstrated that there are two distinct NHCs on each ligand, due to the bridging chiral cyclohexane. Oxidation of the iron(II) complex with trimethylamine N-oxide yielded a bridging oxo complex. Diazodiphenylmethane reacted with the iron(II) complex at room temperature to give a paramagnetic diazoalkane complex; the same reaction yielded the "all carbene" complex at elevated temperature. Electrochemical measurements support the assignment of the "all carbene" complex being an alkylidene. Notably, the diazoalkane complex can be directly transformed into the alkylidene complex, which had not been previously demonstrated on iron. Finally, a test catalytic reaction with a diazoalkane on the iron(II) complex does not yield the expected cyclopropane, but actually the azine compound.

中文翻译：

手性大环四-N-杂环卡宾产生“全卡宾”铁亚烷基络合物。

合成了第一个手性大环四-N-杂环卡宾（NHC）配体。以高产率和大规模制备的大环化合物连接到钯和铁上，得到二价 C2 对称方形平面配合物。多核核磁共振和单晶 X 射线衍射表明，由于桥接手性环己烷，每个配体上有两个不同的 NHC。铁(II)配合物与三甲胺N-氧化物的氧化产生了桥接氧配合物。重氮二苯甲烷与铁(II)配合物在室温下反应得到顺磁性重氮烷配合物；同样的反应在高温下产生“全卡宾”络合物。电化学测量支持“全卡宾”络合物是亚烷基的认定。值得注意的是，重氮烷配合物可以直接转化为亚烷基配合物，此前尚未在铁上得到证实。最后，与重氮烷在铁(II)络合物上进行的测试催化反应并没有产生预期的环丙烷，而是实际上产生了吖嗪化合物。

更新日期：2020-01-23

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