Selective Hydrogenation of Azobenzene to Hydrazobenzene via Proton-Coupled Electron Transfer from a Polyoxotungstate Cluster,JACS Au

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Selective Hydrogenation of Azobenzene to Hydrazobenzene via Proton-Coupled Electron Transfer from a Polyoxotungstate Cluster
JACS Au ( IF 8.5 ) Pub Date : 2024-03-21 , DOI: 10.1021/jacsau.4c00127
Zhou Lu ₁ , Shannon E Cooney ₁ , James R McKone ₂ , Ellen M Matson ₁

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In this report, we describe proton-coupled electron transfer (PCET) reactivity at the surface of the Keggin-type polyoxotungstate cluster [ⁿBu₄N]₃[PW^VI₁₂O₄₀] (PW₁₂) in acetonitrile. Bond dissociation free energies (BDFEs) of the O–H groups generated upon reduction of PW₁₂ in the presence of acid are determined through the construction of a potential–pK_a diagram. The surface O–H bonds are found to be weak (BDFE(O–H)_avg < 48 kcal mol^–1), comparable to the BDFE of H₂. This is consistent with the observed formation of H₂ upon addition of a suitably strong organic acid, H₂NPh₂⁺ (pK_a MeCN = 5.98), to the reduced form of the cluster. The one-electron reduced form of PW₁₂ is isolated and used in conjunction with acid to realize the stoichiometric semihydrogenation of azobenzene via PCET from the surface of the reduced cluster.

中文翻译：

通过多钨酸簇的质子耦合电子转移将偶氮苯选择性加氢为肼苯

在本报告中，我们描述了乙腈中 Keggin 型多钨酸簇 [ ⁿ Bu ₄ N] ₃ [PW ^VI ₁₂ O ₄₀ ] ( PW ₁₂ ) 表面的质子耦合电子转移 (PCET) 反应性。在酸存在下还原PW ₁₂时产生的 O-H 基团的键解离自由能 (BDFE) 通过构建势-p K _a图来确定。发现表面 O-H 键很弱（BDFE(O-H) _avg < 48 kcal mol ^–1 ），与 H ₂的 BDFE 相当。这与在将适当强的有机酸H ₂ NPh ₂ ⁺ (p K _{a MeCN} = 5.98)添加到簇的还原形式时观察到的H ₂形成一致。分离出PW ₁₂的单电子还原形式，并与酸结合使用，通过还原团簇表面的 PCET 实现偶氮苯的化学计量半氢化。

更新日期：2024-03-21

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