Ben-Ari Eyal, Leitus Gregory, Shimon Linda J W, Milstein David
Department of Organic Chemistry and Unit of Chemical Research Support, Weizmann Institute of Science, Rehovot, 76100 Israel.
J Am Chem Soc. 2006 Dec 6;128(48):15390-1. doi: 10.1021/ja066411i.
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 H2 and benzene, via facile aromatization/dearomatization processes of the ligand. A new, dearomatized electron-rich (PNP*)Ir(I) complex 2 (PNP* = deprotonated PNP) activates benzene to form the aromatic (PNP)Ir(I)Ph 4, which upon treatment with CO undergoes a surprising oxidation process to form (PNP*)Ir(III)(H)CO 6, involving proton migration from the ligand "arm" to the metal, with concomitant dearomatization. 4 undergoes stereoselective activation of H2 to exclusively form the trans-dihydride 7, rather than the expected cis-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 H2 activation.
有报道称存在异常反应，其中芳香族PNP配体（PNP = 2,6 - 双 -（二叔丁基膦甲基）吡啶）通过配体的简便芳构化/去芳构化过程，与金属协同作用激活氢气和苯。一种新的、去芳构化的富电子（PNP*）Ir（I）配合物2（PNP* = 去质子化的PNP）激活苯形成芳香族（PNP）Ir（I）Ph 4，用CO处理时，它会经历一个惊人的氧化过程形成（PNP*）Ir（III）（H）CO 6，这涉及质子从配体“臂”迁移到金属上，并伴随去芳构化。4对氢气进行立体选择性激活，仅生成反式二氢化物7，而不是预期的顺式二氢化物配合物。我们包括氘标记在内的证据表明，Ir（I）-Ph配合物有可能转化为去芳构化的Ir（III）（Ph）（H）（在低温下独立制备），它可能是实际经历氢气激活的中间体。
