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Dynamic environment at the Zr6 oxo cluster surface is key for the catalytic formation of amide bonds
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2022-10-28 , DOI: 10.1039/d2cy01706g Yujie Zhang 1 , Ismail Y. Kokculer 1, 2 , Francisco de Azambuja 1 , Tatjana N. Parac-Vogt 1
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2022-10-28 , DOI: 10.1039/d2cy01706g Yujie Zhang 1 , Ismail Y. Kokculer 1, 2 , Francisco de Azambuja 1 , Tatjana N. Parac-Vogt 1
Affiliation
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Zirconium compounds are an attractive alternative to costly, low abundant metals for the development of inexpensive, readily available, and robust catalysts. The air and moisture stable Zr oxo clusters such as the Zr6O8 species, are of particular interest as they are key building blocks of several Zr-based metal–organic framework (Zr-MOF) catalysts. However, broader use of these cluster-based materials as catalysts is still hampered by the modest understanding of their fundamental reactivity. To bridge this gap, we report on the activity of a soluble Zr6O8 cluster, [Zr6(OH)4O4(OMc)12] (OMc = methacrylate) (Zr6), as a discrete molecular catalyst for the atom-economic formation of amide bonds. This reaction demands two completely different substrates interacting with the Zr6 catalyst, a key step rarely addressed in MOF catalyzed reactions. Remarkably, Zr6 catalyzes the formation of amide bonds directly from non-activated carboxylic acid and amine substrates in ethanol, without requiring anhydrous conditions or water scavenging to achieve good yields. As shown by a series of kinetic, and mechanistic experiments, this promising reactivity arises from a dynamic environment at the cluster surface, where the essential coordination of both substrates requires an excess of amine to enhance the reaction output. Strikingly, Zr6 catalyst tolerates a range of substrates, including (hetero)aromatic, aliphatic, and α-branched acids, even though their nature directly impacts the reaction efficiency. Further, insights for the future design of catalysts based on Zr oxo cluster are discussed through a detailed comparison of Zr6 reactivity with a related Zr12 cluster, and Zr-MOF catalysts. Considering the advantages of zirconium, and the relevance of discrete Zr oxo clusters as building blocks of several MOF materials of varied utility, the molecular level understanding disclosed here contributes at large to the development of novel catalytic entities, and sustainable approaches to synthetic chemistry.
中文翻译：
Zr6 氧簇表面的动态环境是催化形成酰胺键的关键
锆化合物是昂贵、丰度低的金属的有吸引力的替代品，可用于开发廉价、易得且坚固的催化剂。对空气和水分稳定的 Zr 氧代团簇（例如 Zr 6 O 8物种）特别令人感兴趣，因为它们是多种 Zr 基金属有机骨架 (Zr-MOF) 催化剂的关键组成部分。然而，由于对其基本反应性的了解不足，仍然阻碍了这些基于团簇的材料作为催化剂的更广泛使用。为了弥合这一差距，我们报告了可溶性 Zr 6 O 8簇 [Zr 6 (OH) 4 O 4 (OMc) 12 ] (OMc = 甲基丙烯酸酯) ( Zr6 ), 作为原子经济形成酰胺键的离散分子催化剂。该反应需要两种完全不同的底物与Zr 6催化剂相互作用，这是 MOF 催化反应中很少涉及的关键步骤。值得注意的是，Zr 6直接催化乙醇中未活化的羧酸和胺底物形成酰胺键，无需无水条件或水清除即可获得良好的产率。正如一系列动力学和机械实验所示，这种有前途的反应性源于团簇表面的动态环境，其中两种底物的基本协调需要过量的胺来提高反应输出。引人注目的是，Zr 6催化剂耐受一系列底物，包括（杂）芳族、脂肪族和 α- 支链酸，即使它们的性质直接影响反应效率。此外，通过详细比较Zr 6与相关Zr 12簇和 Zr-MOF 催化剂的反应性，讨论了基于 Zr oxo 簇的催化剂未来设计的见解。考虑到锆的优势，以及离散的 Zr 氧代簇作为多种用途的多种 MOF 材料的构建块的相关性，此处公开的分子水平理解在很大程度上有助于新型催化实体的发展和合成化学的可持续方法。
更新日期：2022-10-28
中文翻译：
Zr6 氧簇表面的动态环境是催化形成酰胺键的关键
锆化合物是昂贵、丰度低的金属的有吸引力的替代品，可用于开发廉价、易得且坚固的催化剂。对空气和水分稳定的 Zr 氧代团簇（例如 Zr 6 O 8物种）特别令人感兴趣，因为它们是多种 Zr 基金属有机骨架 (Zr-MOF) 催化剂的关键组成部分。然而，由于对其基本反应性的了解不足，仍然阻碍了这些基于团簇的材料作为催化剂的更广泛使用。为了弥合这一差距，我们报告了可溶性 Zr 6 O 8簇 [Zr 6 (OH) 4 O 4 (OMc) 12 ] (OMc = 甲基丙烯酸酯) ( Zr6 ), 作为原子经济形成酰胺键的离散分子催化剂。该反应需要两种完全不同的底物与Zr 6催化剂相互作用，这是 MOF 催化反应中很少涉及的关键步骤。值得注意的是，Zr 6直接催化乙醇中未活化的羧酸和胺底物形成酰胺键，无需无水条件或水清除即可获得良好的产率。正如一系列动力学和机械实验所示，这种有前途的反应性源于团簇表面的动态环境，其中两种底物的基本协调需要过量的胺来提高反应输出。引人注目的是，Zr 6催化剂耐受一系列底物，包括（杂）芳族、脂肪族和 α- 支链酸，即使它们的性质直接影响反应效率。此外，通过详细比较Zr 6与相关Zr 12簇和 Zr-MOF 催化剂的反应性，讨论了基于 Zr oxo 簇的催化剂未来设计的见解。考虑到锆的优势，以及离散的 Zr 氧代簇作为多种用途的多种 MOF 材料的构建块的相关性，此处公开的分子水平理解在很大程度上有助于新型催化实体的发展和合成化学的可持续方法。
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