Controlled Photocatalytic Hydrocarbon Oxidation by Uranyl Complexes
Controlled Photocatalytic Hydrocarbon Oxidation by Uranyl Complexes
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DOI：
10.1002/cctc.201900037
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发表时间：
2019-08-21
期刊：
影响因子：
4.5
通讯作者：
Austin, Jonathan
中科院分区：
文献类型：
--
作者：
Arnold, Polly L.;Purkis, Jamie M.;Austin, Jonathan
可控的光催化C-H键活化是现代合成化学家工具箱中的关键反应。虽然已知铀（VI）离子[（UO 2）-O-VI]（2+）（铀的环境主导形式）具有光活性，但大多数文献研究了其发光性质，忽略了其用于光催化C-H键断裂的潜在合成效用。本文合成了一种空气稳定、烃溶性的铀酰邻菲咯啉配合物[（UO_2）-O-VI（NO_3）（2）（Ph（2）phen）]，U-Ph_2 phen，并证明了它在可见光照射下能催化从多种有机底物中夺取氢原子。我们发现，市售的母体配合物，硝酸铀酰（[（UO 2）-O-VI（NO 3）（2）（OH 2）（2）]中心点4 H（2）O; U-NO 3），也是胜任的，但从电子光谱，我们归因于更高的速率和选择性的U-Ph 2 phen配体介导的电子效应。酮相对于其它氧化产物（醇等）选择性地形成，并且含有苄基C-H位置的底物的催化氧化对于U-Ph 2 phen特别改善。我们还首次在模型木质素化合物中显示了铀酰介导的光催化C-C键断裂。
Controlled, photocatalytic C-H bond activations are key reactions in the toolkits of the modern synthetic chemist. While it is known that the uranyl(VI) ion, [(UO2)-O-VI](2+), the environmentally dominant form of uranium, is photoactive, most literature examines its luminescent properties, neglecting its potential synthetic utility for photocatalytic C-H bond cleavage. Here, we synthesise and fully characterise an air-stable and hydrocarbon-soluble uranyl phenanthroline complex, [(UO2)-O-VI(NO3)(2)(Ph(2)phen)], U-Ph2phen, and demonstrate that it can catalytically abstract hydrogen atoms from a variety of organic substrates under visible light irradiation. We show that the commercially available parent complex, uranyl nitrate ([(UO2)-O-VI(NO3)(2)(OH2)(2)]center dot 4H(2)O; U-NO3), is also competent, but from electronic spectroscopy we attribute the higher rates and selectivity of U-Ph2phen to ligand-mediated electronic effects. Ketones are selectively formed over other oxygenated products (alcohols, etc.), and the catalytic oxidation of substrates containing a benzylic C-H position is particularly improved for U-Ph2phen. We also show uranyl-mediated photocatalytic C-C bond cleavage in a model lignin compound for the first time.