Catalysts for Regio- and Stereoselective C(sp3)-H Deuteration of Tricyclohexylphosphine with Benzene-d6 Generated via Dehydrochlorination of Chlorido(dihydrido)iridium Complexes Containing a Xanthene-Based Bis(silyl) Chelate Ligand
Catalysts for Regio- and Stereoselective C(sp3)-H Deuteration of Tricyclohexylphosphine with Benzene-d6 Generated via Dehydrochlorination of Chlorido(dihydrido)iridium Complexes Containing a Xanthene-Based Bis(silyl) Chelate Ligand
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DOI：
10.1021/acs.organomet.1c00359
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发表时间：
2021-09-06
期刊：
影响因子：
2.8
通讯作者：
Tobita, Hiromi
中科院分区：
文献类型：
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作者：
Komuro, Takashi;Asagami, Junpei;Tobita, Hiromi
在（Me₃Al）₂·DABCO存在下，使用铱催化剂前体Ir(κSi - 2,Si - xantsil)(H)₂(PCy₃)Cl（1）（xantsil = (9,9 - 二甲基呫吨 - 4,5 - 二基)双(二甲基硅基)，DABCO = 1,4 - 二氮杂二环[2.2.2]辛烷），在60℃下用过量的苯 - d₆实现了三环己基膦（PCy₃）的催化C(sp³) - H氘代反应。在该反应中，PCy₃的3,5 - 赤道位和4 - 轴向C - H被选择性地氘代，主要生成P(Cy - d₃)₃。为了深入了解反应机理，合成了带有不对称且体积更大的具有SiMe₂和Si(p - Tol)₂配位部分的双(硅基) - 呫吨螯合配体的铱配合物，即Ir(κSi - 2,Si - xantSi(Me)si(p - Tol))(H)₂(L)Cl（L = 吡啶(2 - py)或PCy₃(2 - PCy)），并在化学计量和催化条件下研究了使用它们的类似反应。2 - py与（Me₃Al₂）·DABCO在60℃下的化学计量反应导致脱氯化氢，生成双核配合物[Ir(μ - κSi - 1:η⁶,κSi - 1 - xantSi(Me)Si(p - Tol))(H)]₂（3）。另一方面，2 - PCy在60℃的苯中的类似反应生成热不稳定的Ir(xantSi(Me)Si(p - Tol))(H)(PCy₃)（4）。当该反应在苯 - d₆中进行时，由于4中的Ir - H和PCy₃的一些C(sp³) - H通过与苯 - d₆的H/D交换而发生氘代，形成了部分氘代的类似物Ir(xantSi(Me)Si(p - Tol))(D)(PCy₃ - dn)（4 - D）。此外，2 - PCy显示出与1相似的催化活性。基于这些结果，表明4和4 - D作为使用2 - PCy对PCy₃进行催化氘代的活性物种起作用。
The catalytic C(sp(3))-H deuteration of tricyclohexylphosphine (PCy3) with excess benzene-d(6) at 60 degrees C was achieved using the iridium catalyst precursor Ir(kappa Si-2,Si-xantsil)(H)(2)(PCy3)Cl (1), in the presence of (Me3Al)(2)center dot DABCO (xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsily1), DABCO = 1,4-diazabicyclo[2.2.2]octane). In this reaction, the 3,5-equatorial and 4-axial C-Hs of PCy3 were selectively deuterated, chiefly affording P(Cy-d(3))(3). To gain insight into the reaction mechanism, iridium complexes bearing an asymmetric and bulkier bis(silyl)-xanthene chelate ligand with SiMe2 and Si(p-Tol)(2) coordinating moieties, namely, Ir(kappa Si-2,Si-xantSi(Me)si(p-Tol))(H)(2) (L)Cl (L = pyridine (2-py) or PCy3 (2-PCy)), were synthesized, and similar reactions using them were examined under stoichiometric and catalytic conditions. The stoichiometric reaction of 2-py with (Me3Al2)center dot DABCO at 60 degrees C resulted in dehydrochlorination to give the dinuclear complex [Ir(mu-kappa Si-1:eta(6),kappa Si-1-xantSi(Me)Si(p-Tol))(H)](2) (3). On the other hand, the analogous reaction of 2-PCy in benzene at 60 degrees C afforded the thermally unstable Ir(xantSi(Me)Si(p-Tol))(H)(PCy3) (4). When this reaction was performed in benzene-d(6), the partially deuterated analogue Ir(xantSi(Me)Si(p-Tol))(D)(PCy3-dn) (4-D) was formed due to the deuteration of Ir-H and some C(sp(3))-Hs of PCy3 of 4 via H/D exchange with benzene-d(6). Moreover, 2-PCy showed catalytic activity similar to that of 1. On the basis of these results, it is suggested that 4 and 4-D functioned as active species for the catalytic deuteration of PCy3 using 2-PCy.