Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation
Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation
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DOI：
10.1038/nchem.1392
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发表时间：
2012-08-01
期刊：
影响因子：
21.8
通讯作者：
McKay, David
中科院分区：
文献类型：
--
作者：
Arnold, Polly L.;Mansell, Stephen M.;McKay, David
过渡金属-芳烃配合物，如双（苯）铬Cr（eta（6）-C6 H6）（2）在历史上对d-轨道成键理论很重要，在有机合成，催化和有机自旋电子学中具有现代重要性。然而，在f-区化学的研究中，芳烃总是被用作溶剂而不是配体。在这里，我们表明，简单的铀配合物UX 3（X =芳氧基，酰胺）自发地不相称，转移电子和X-配体，使所得的UX 2结合和还原芳烃，形成反夹心分子[X2 U（mu-eta（6）：eta（6）-arene）UX 2]和UX 4副产物。计算和动力学研究表明，“合作的小分子活化”机制，涉及自发芳烃还原作为X-配体被转移。这些温和的反应条件允许引入官能化芳烃如芳基硅烷。大体积的UX 3对试剂如硼烷也是惰性的，这些试剂将与传统的苛刻反应条件反应，从而允许开发新的原位芳烃C-H键官能化方法，将C-H键转化为C-B键。
Transition-metal-arene complexes such as bis(benzene)chromium Cr(eta(6)-C6H6)(2) are historically important to d-orbital bonding theory and have modern importance in organic synthesis, catalysis and organic spintronics. In investigations of f-block chemistry, however, arenes are invariably used as solvents rather than ligands. Here, we show that simple uranium complexes UX3 (X = aryloxide, amide) spontaneously disproportionate, transferring an electron and X-ligand, allowing the resulting UX2 to bind and reduce arenes, forming inverse sandwich molecules [X2U(mu-eta(6):eta(6)-arene)UX2] and a UX4 by-product. Calculations and kinetic studies suggest a 'cooperative small-molecule activation' mechanism involving spontaneous arene reduction as an X-ligand is transferred. These mild reaction conditions allow functionalized arenes such as arylsilanes to be incorporated. The bulky UX3 are also inert to reagents such as boranes that would react with the traditional harsh reaction conditions, allowing the development of a new in situ arene C-H bond functionalization methodology converting C-H to C-B bonds.