三齿钳状配体对仲氢诱导极化的影响,ChemPhysChem

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三齿钳状配体对仲氢诱导极化的影响
ChemPhysChem ( IF 2.3 ) Pub Date : 2021-05-27 , DOI: 10.1002/cphc.202100178
Safiyah R Muhammad ₁ , Joseph W Nugent ₁ , Rianna B Greer ₁ , Brian C Lee ₁ , Jumanah Mahmoud ₁ , Steven B Ramirez ₁ , Boyd M Goodson ₂ , Alison R Fout ₁

Affiliation

配体在铑和铱催化的对位氢诱导极化 (PHIP) 和 SABRE（可逆交换信号放大）化学中的作用已在基准系统 [Rh(diene)(diphos)] ⁺和 [Ir( NHC)(sub) ₃ (H) ₂ ] ⁺，并显示对观察到的超极化程度有很大影响。在这里，我们检查了侧翼部分在富电子单阴离子双（卡宾）芳基钳状配体^{Ar 中的作用}钴催化的 PHIP 和 PHIP-IE（通过插入和消除的 PHIP）化学上的 CCC（Ar=Dipp，2,6-二异丙基或 Mes，2,4,6-三甲基苯基）我们之前报道过。将异丙基苯交换为二异丙基苯基以生成 ( ^Dipp CCC)Co(N ₂ ) 催化剂，这导致更快的氢化和高达 390 倍的¹ H 信号增强，大于 ( ^Mes CCC)Co-py (py=吡啶)催化剂。此外，还报道了 ( ^Dipp CCC)Rh(N ₂ ) 复合物的合成，并将其应用于丙烯酸乙酯与对位氢的氢化，以产生¹ H 和¹³ C 核。最后，提出了两种 ( ^Mes CCC) Ir 配合物的生成，并将其应用于 SABRE 和 PHIP-IE 化学，以仅产生部分氢化产物 (PHIP) 的小¹ H 信号增强，而没有 SABRE 超极化。

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Effects of a Tridentate Pincer Ligand on Parahydrogen Induced Polarization

The role of ligands in rhodium- and iridium-catalyzed Parahydrogen Induced Polarization (PHIP) and SABRE (signal amplification by reversible exchange) chemistry has been studied in the benchmark systems, [Rh(diene)(diphos)]⁺ and [Ir(NHC)(sub)₃(H)₂]⁺, and shown to have a great impact on the degree of hyperpolarization observed. Here, we examine the role of the flanking moieties in the electron-rich monoanionic bis(carbene) aryl pincer ligand, ^ArCCC (Ar=Dipp, 2,6-diisopropyl or Mes, 2,4,6-trimethylphenyl) on the cobalt-catalyzed PHIP and PHIP-IE (PHIP via Insertion and Elimination) chemistry that we have previously reported. The mesityl groups were exchanged for diisopropylphenyl groups to generate the (^DippCCC)Co(N₂) catalyst, which resulted in faster hydrogenation and up to 390-fold ¹H signal enhancements, larger than that of the (^MesCCC)Co-py (py=pyridine) catalyst. Additionally, the synthesis of the (^DippCCC)Rh(N₂) complex is reported and applied towards the hydrogenation of ethyl acrylate with parahydrogen to generate modest signal enhancements of both ¹H and ¹³C nuclei. Lastly, the generation of two (^MesCCC)Ir complexes is presented and applied towards SABRE and PHIP-IE chemistry to only yield small ¹H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization.

更新日期：2021-07-19

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