Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal.
Org Biomol Chem. 2019 Sep 7;17(33):7706-7714. doi: 10.1039/c9ob01442j. Epub 2019 Aug 6.
Three new copper(ii) coordination compounds formulated as Cu(Hbdea)·2HO (1), [Cu(μ-Hbdea)(aca)]·4HO (2), and [Cu(μ-Hbdea)(μ-bdca)] (3) were generated by aqueous medium self-assembly synthesis from Cu(NO), N-butyldiethanolamine (Hbdea) as a main N,O-chelating building block and different carboxylic acids [4-hydroxybenzoic (Hhba), 9-anthracenecarboxylic (Haca), or 4,4'-biphenyldicarboxylic (Hbdca) acid] as supporting carboxylate ligands. The structures of products range from discrete mono- (1) or dicopper(ii) (2) cores to a 1D coordination polymer (3), and widen a family of copper(ii) coordination compounds derived from Hbdea. The obtained compounds were applied as bioinspired homogeneous catalysts for the mild C-H functionalization of saturated hydrocarbons (cyclic and linear C-C alkanes). Two model catalytic reactions were explored, namely the oxidation of hydrocarbons with HO to a mixture of alcohols and ketones, and the carboxylation of alkanes with CO/SO to carboxylic acids. Both processes proceed under mild conditions with a high efficiency and the effects of different parameters (e.g., reaction time and presence of acid promoter, amount of catalyst and solvent composition, substrate scope and selectivity features) were studied and discussed in detail. In particular, an interesting promoting effect of water was unveiled in the oxidation of cyclohexane that is especially remarkable in the reaction catalyzed by 3, thus allowing a potential use of diluted, in situ generated solutions of hydrogen peroxide. Moreover, the obtained values of product yields (up to 41% based on alkane substrate) are very high when dealing with the C-H functionalization of saturated hydrocarbons and the mild conditions of these catalytic reactions (50-60 °C, HO/CHCN medium). This study thus contributes to an important field of alkane functionalization and provides a notable example of new Cu-based catalytic systems that can be easily generated by self-assembly from simple and low-cost chemicals.
三种新的铜（II）配合物通过水溶液自组装合成，化学式分别为Cu(Hbdea)·2HO（1）、[Cu(μ-Hbdea)(aca)]·4HO（2）和[Cu(μ-Hbdea)(μ-bdca)]（3），其中 Hbdea 是主要的 N,O-螯合构筑块，不同的羧酸（4-羟基苯甲酸（Hhba）、9-蒽羧酸（Haca）或 4,4'-联苯二甲酸（Hbdca））作为辅助羧酸配体。产物的结构从离散的单核（1）或双核（2）核心到 1D 配位聚合物（3）不等，拓宽了 Hbdea 衍生的铜（II）配合物家族。所得到的化合物被用作生物启发的均相催化剂，用于温和地对饱和烃（环状和直链 C-C 烷烃）进行 C-H 功能化。探索了两种模型催化反应，即烃类与 HO 的氧化反应生成醇和酮的混合物，以及烷烃与 CO/SO 的羧化反应生成羧酸。这两个过程都在温和条件下以高效率进行，研究并详细讨论了不同参数（例如反应时间和酸促进剂的存在、催化剂和溶剂组成的量、底物范围和选择性特征）的影响。特别是，在环己烷的氧化中发现了水的有趣促进作用，在 3 催化的反应中尤为明显，因此可以潜在地使用稀释的原位生成的过氧化氢溶液。此外，在处理饱和烃的 C-H 功能化时，产物收率（基于烷烃底物高达 41%）非常高，并且这些催化反应的条件温和（50-60°C，HO/CHCN 介质）。因此，本研究为烷烃功能化的重要领域做出了贡献，并提供了一个显著的例子，说明了可以通过简单廉价的化学品自组装生成新的基于 Cu 的催化体系。
