Allylic Amination of Pd(II)-Allyl Complexes via High-Valent Pd Intermediates
Allylic Amination of Pd(II)-Allyl Complexes via High-Valent Pd Intermediates
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DOI：
10.1021/acs.organomet.2c00215
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发表时间：
2022-07-12
期刊：
影响因子：
2.8
通讯作者：
Mirica，Liviu M.
中科院分区：
文献类型：
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作者：
Wang，Yung-Ching;Rath，Nigam P.;Mirica，Liviu M.
最近有人提出有机金属高价 Pd(烯丙基)配合物作为催化烯丙基官能化反应的中间体。虽然已经分离和表征了一些 PdIV(η1-烯丙基) 配合物，但迄今为止尚未检测或分离出 PdIII(η3-烯丙基) 或 PdIII(η1-烯丙基) 配合物。本文报道了由四齿吡啶芬配体 N,N'-二叔丁基-2,11-二氮杂[3.3](2,6)吡啶芬 (tBuN4) 支持的一系列 PdII(η3-烯丙基)配合物的合成、表征和反应性 和N,N'-二叔甲基-2,11-二氮杂[3.3](2,6)吡啶并芬(MeN4)。这些 PdII(η3-烯丙基) 配合物表现出可接近的氧化电位，氧化后生成 PdIII(烯丙基) 配合物，并通过电子顺磁共振 (EPR) 光谱进行表征。有趣的是，[(MeN4)PdIII(η3-烯丙基)]2+配合物在低温下会重排为[(MeN4)PdIII(η1-烯丙基)]2+物质。此外，[(MeN4)PdII(η3-烯丙基)]+配合物与N-氟苯磺酰亚胺(NFSI)反应时，在室温下15分钟内发生快速烯丙基胺化，并且C-N键形成步骤被认为发生在Pd(IV)氧化态，可能通过PdIV(η1-烯丙基)中间体。
Organometallic high-valent Pd(allyl) complexes have been recently proposed to act as intermediates in catalytic allylic functionalization reactions. While a few PdIV(η1-allyl) complexes have been isolated and characterized, PdIII(η3-allyl) or PdIII(η1-allyl) complexes have not been detected or isolated to date. Reported herein is the synthesis, characterization, and reactivity of a series of PdII(η3-allyl) complexes supported by the tetradentate pyridinophane ligandsN,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane (tBuN4) andN,N′-di-tert-methyl-2,11-diaza[3.3](2,6)pyridinophane (MeN4). These PdII(η3-allyl) complexes exhibit accessible oxidation potentials and upon oxidation generate PdIII(allyl) complexes that were characterized by electron paramagnetic resonance (EPR) spectroscopy. Interestingly, the [(MeN4)PdIII(η3-allyl)]2+complex undergoes a rearrangement to the [(MeN4)PdIII(η1-allyl)]2+species at low temperatures. Moreover, fast allylic amination occurred within 15 min at room temperature upon the reaction of [(MeN4)PdII(η3-allyl)]+complexes with N-fluorobenzenesulfonimide (NFSI), and the C–N bond formation step is proposed to occur at the Pd(IV) oxidation state, likely via a PdIV(η1-allyl) intermediate.