Metal-ligand cooperation in C-H and H2 activation by an electron-rich PNPIr(I) system:: Facile ligand dearomatization-aromatization as key steps
Metal-ligand cooperation in C-H and H2 activation by an electron-rich PNPIr(I) system:: Facile ligand dearomatization-aromatization as key steps
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DOI：
10.1021/ja066411i
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发表时间：
2006-12-06
影响因子：
15
通讯作者：
Milstein, David
中科院分区：
文献类型：
--
作者：
Ben-Ari, Eyal;Leitus, Gregory;Milstein, David
报道了一些不寻常的反应，其中芳香族PNP配体（PNP = 2,6-二-（二叔丁基磷甲基）吡啶）通过配体的易芳化/去芳化过程与金属协同作用，激活h2和苯。一种新的，去芳香化的富电子（PNP*）Ir(I)配合物2（PNP* =去质子化的PNP）激活苯形成芳香（PNP）Ir(I)Ph4，在与CO处理后，发生令人惊讶的氧化过程，形成（PNP*）Ir(III)(H)CO6，质子从配体“臂”迁移到金属，伴随着脱芳香。4经过氢的立体选择性活化，只形成反式二氢化物，而不是预期的顺式二氢化物络合物。我们的证据，包括d标记，表明Ir(I)−Ph配合物可能转化为脱芳化的Ir(III)(Ph)(H)（在低温下独立制备），这可能是进行h2活化的实际中间体。
Unusual reactions are reported, in which the aromatic PNP ligand (PNP = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine) acts in concert with the metal in the activation of H2and benzene, via facile aromatization/dearomatization processes of the ligand. A new, dearomatized electron-rich (PNP*)Ir(I) complex2(PNP* = deprotonated PNP) activates benzene to form the aromatic (PNP)Ir(I)Ph4, which upon treatment with CO undergoes a surprising oxidation process to form (PNP*)Ir(III)(H)CO6, involving proton migration from the ligand “arm” to the metal, with concomitant dearomatization.4undergoes stereoselective activation of H2to exclusively form thetrans-dihydride7, rather than the expectedcis-dihydride complex. Our evidence, including D-labeling, suggests the possibility that the Ir(I)−Ph complex is transformed to the dearomatized Ir(III)(Ph)(H) (independently prepared at low temperature), which may be the actual intermediate undergoing H2activation.