Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106, United States.
Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States.
J Am Chem Soc. 2018 Jan 10;140(1):394-400. doi: 10.1021/jacs.7b10960. Epub 2017 Dec 27.
The development of atomically precise nanoclusters (APNCs) protected by organometallic ligands, such as acetylides and hydrides, is an emerging area of nanoscience. In principle, these organometallic APNCs should not require harsh pretreatment for activation toward catalysis, such as calcination, which can lead to sintering. Herein, we report the synthesis of the mixed-valent organometallic copper APNC, [Cu(CCPh)(OAc))] (1), via reduction of Cu(OAc) with PhSiH in the presence of phenylacetylene. This cluster is a rare example of a two-electron copper superatom, and the first to feature a tetrahedral [Cu] core, which is a unique "kernel" for a Cu-only superatom. Complex 1 can be readily immobilized on dry, partially dehydroxylated silica, a process that cleanly results in release of 1 equiv of phenylacetylene per Cu cluster. Cu K-edge EXAFS confirms that the immobilized cluster 2 is structurally similar to 1. In addition, both 1 and 2 are effective catalysts for [3+2] cycloaddition reactions between alkynes and azides (i.e., "Click" reactions) at room temperature. Significantly, neither cluster requires any pretreatment for activation toward catalysis. Moreover, EXAFS analysis of 2 after catalysis demonstrates that the cluster undergoes no major structural or nuclearity changes during the reaction, consistent with our observation that supported cluster 2 is more stable than unsupported cluster 1 under "Click" reaction conditions.
由有机金属配体（如炔烃和氢化物）保护的原子精确纳米团簇（APNCs）的发展是纳米科学的一个新兴领域。原则上，这些有机金属 APNCs 不应该需要苛刻的预处理来进行催化激活，例如煅烧，这可能导致烧结。在此，我们报告了通过在苯乙炔存在下用 PhSiH 将 Cu(OAc)还原合成混合价态有机金属铜 APNC [Cu(CCPh)(OAc))] (1)。该簇是二电子铜超原子的罕见实例，也是第一个具有四面体形 [Cu]核心的实例，这是铜-only 超原子的独特“核心”。复合物 1 可以很容易地固定在干燥的部分脱羟化的二氧化硅上，该过程可以干净地释放每个铜簇 1 当量的苯乙炔。Cu K 边 EXAFS 证实固定化的簇 2 在结构上与 1 相似。此外，1 和 2 都是室温下炔烃和叠氮化物（即“点击”反应）之间 [3+2]环加成反应的有效催化剂。重要的是，两个簇都不需要任何预处理来进行催化激活。此外，催化后对 2 的 EXAFS 分析表明，在反应过程中簇没有发生主要的结构或核变化，这与我们观察到的负载化的 2 在“点击”反应条件下比未负载化的 1 更稳定的情况一致。
