Soluble small molecular/polymeric ligands are often used in Pd-catalyzed semi-hydrogenation of alkynes as an efficient strategy to improve the selectivity of targeted alkene products. The use of soluble ligands requires their thorough removal from the reaction products, which adds significant extra costs. In the paper, commercially available, inexpensive, metallic sulfide-based solid-phase ligands (SPL8-4 and SPL8-6) are demonstrated as simple yet high-performance insoluble ligands for a heterogeneous Pd nanocatalyst (Pd@CaCO₃) toward the semi-hydrogenation of alkynes. Based on the reactions with a range of terminal and internal alkyne substrates, the use of the solid-phase ligands has been shown to markedly enhance the selectivity of the desired alkene products by efficiently suppressing over-hydrogenation and isomerization side reactions, even during the long extension of the reactions following full substrate conversion. A proper increase in the dosage or a reduction in the average size of the solid-phase ligands enhances such effects. With their insoluble nature, the solid-phase ligands have the distinct advantage in their simple, convenient recycling and reuse while without contaminating the products. A ten-cycle reusability test with the SPL8-4/Pd@CaCO₃ catalyst system confirms its well-maintained activity and selectivity over repeated uses. A mechanistic study with x-ray photoelectron spectroscopy indicates that the solid-phase ligands have electronic interactions with Pd in the supported catalyst, contributing to inhibit the binding and further reaction of the alkene products. This is the first demonstration of solid-phase ligands for highly selective semi-hydrogenation of alkynes, which show strong promise for commercial applications.

可溶性小分子/聚合物配体通常在钯催化的炔烃半加氢反应中用作提高目标烯烃产物选择性的有效策略。使用可溶性配体需要将它们从反应产物中彻底除去，这增加了显着的额外成本。在本文中，市售的廉价的基于金属硫化物的固相配体（SPL8-4和SPL8-6）被证明是用于异质Pd纳米催化剂（Pd @ CaCO ₃）的简单而高性能的不溶性配体），用于炔烃的半氢化反应。基于与一定范围的末端和内部炔烃底物的反应，即使在长时间内，通过有效抑制过氢化和异构化副反应，固相配体的使用也可以显着提高所需烯烃产物的选择性。完全底物转化后反应的延伸。适当增加剂量或减少固相配体的平均尺寸可增强这种效果。固相配体由于具有不溶性，因此具有简单，方便的回收利用和再利用而又不污染产品的独特优势。使用SPL8-4 / Pd @ CaCO _3进行十周期可重用性测试催化剂体系证实了其在反复使用中保持良好的活性和选择性。X射线光电子能谱的机械研究表明，固相配体与负载型催化剂中的Pd具有电子相互作用，有助于抑制烯烃产物的键合和进一步反应。这是用于炔烃高度选择性半加氢的固相配体的首次展示，其在商业应用中显示出广阔的前景。