Department of Chemistry and Center for Atomic Engineering of Advanced Materials, Anhui Province Key Laboratory of Chemistry for Inorganic/Organic Hybrid Functionalized Materials, Anhui University, Hefei, Anhui 230601, China.
Key Laboratory of Structure and Functional Regulation of Hybrid Materials (Anhui University), Ministry of Education, Hefei 230601, China.
J Am Chem Soc. 2021 Feb 3;143(4):1768-1772. doi: 10.1021/jacs.0c12498. Epub 2021 Jan 22.
The classic Fokin mechanism of the CuAAC reaction of terminal alkynes using a variety of Cu(I) catalysts is well-known to include alkyne deprotonation involving a bimetallic σ,π-alkynyl intermediate. In this study, we have designed a CNT-supported atomically precise nanocluster AuCu (noted AuCu/CNT) that heterogeneously catalyzes the CuAAC reaction of terminal alkynes σ,π. Therefore, three nanocluster-π-alkyne intermediates [AuCu(π-CH≡C-p-CHR)], R = H, Cl, and CH, have been captured and characterized by MALDI-MS. This AuCu/CNT system efficiently catalyzed the CuAAC reaction of terminal alkynes, and internal alkynes also undergo this reaction. DFT results further confirmed that HC≡CPh was activated by π-complexation with AuCu, unlike the classic dehydrogenation mechanism involving the bimetallic σ,π-alkynyl intermediate. On the other hand, a Cu/CNT catalyst was shown to catalyze the reaction of terminal alkynes following the classic deprotonation mechanism, and both Au/CNT and Cu/CNT catalysts were inactive for the AAC reaction of internal alkynes under the same conditions, which shows the specificity of AuCu involving synergy between Cu and Au in this precise nanocluster. This will offer important guidance for subsequent catalyst design.
经典的 Fokin 机制涉及双金属 σ,π-炔基中间体，包括末端炔烃的 CuAAC 反应使用各种 Cu(I)催化剂，炔烃的去质子化。在这项研究中，我们设计了一种 CNT 负载的原子精确纳米团簇 AuCu（记为 AuCu/CNT），它可以非均相催化末端炔烃的 CuAAC 反应。因此，通过 MALDI-MS 捕获并表征了三种纳米团簇-π-炔中间体[AuCu(π-CH≡C-p-CHR)]，R = H、Cl 和 CH。该 AuCu/CNT 体系高效催化末端炔烃的 CuAAC 反应，且内部炔烃也能进行此反应。DFT 结果进一步证实，HC≡CPh 被 AuCu 的π-络合激活，这与涉及双金属 σ,π-炔基中间体的经典脱氢机制不同。另一方面，Cu/CNT 催化剂可通过经典的去质子化机制催化末端炔烃的反应，而在相同条件下，Au/CNT 和 Cu/CNT 催化剂对内炔的 AAC 反应均无活性，这表明 AuCu 的特异性涉及该精确纳米团簇中 Cu 和 Au 的协同作用。这将为后续的催化剂设计提供重要指导。
