Palladium-catalyzed cross-coupling reactions owing to their high specificity and superb chemoselectivity represent a powerful tool for the rapid construction of C–C and C–X bonds across various areas of chemical research, including pharmaceutical development, polymer and agrochemical industries, bioactive natural products, and advanced functional materials, rendering them indispensable for modern synthetic chemists. The major driving force for the advances in this critical field is the design of increasingly more reactive and more selective ligands and precatalysts that aim not only to address challenging cross-coupling processes but also to achieve optimal reactivity, selectivity, and functional group compatibility under mild, user-friendly, operationally simple, and broadly applicable conditions. In this context, Pd(II)–N-heterocyclic carbene complexes (NHC = N-heterocyclic carbene) have garnered prevalent attention among practitioners of organic synthesis due to their unique electronic and steric characteristics that are unmatched among other ligands. In particular, the superior σ-donating ability of NHC ligands in conjunction with conformational flexibility as well as the ease of steric and electronic modification and high stability to air and moisture enable highly effective fundamental elementary steps in catalytic cycles and facile formation of well-defined complexes.

中文翻译：

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[Pd（NHC）（μ-Cl）Cl]2：用于交叉偶联反应的高反应性空气和水分稳定、定义明确的 Pd（II）-N-杂环卡宾 （NHC） 配合物


钯催化的交叉偶联反应由于其高特异性和出色的化学选择性，是化学研究各个领域快速构建 C-C 和 C-X 键的有力工具，包括药物开发、聚合物和农用化学工业、生物活性天然产物和先进的功能材料，使其成为现代合成化学家不可或缺的。这一关键领域进步的主要驱动力是设计越来越反应性和选择性更强的配体和预催化剂，其目的不仅是为了解决具有挑战性的交叉偶联过程，而且是为了在温和、用户友好、操作简单和广泛适用的条件下实现最佳反应性、选择性和官能团兼容性。在这种情况下，Pd（II）-N-杂环卡宾配合物 （NHC = N-杂环卡宾） 因其独特的电子和空间特性而引起了有机合成从业者的普遍关注，这是其他配体无法比拟的。特别是，NHC 配体卓越的σ供体能力与构象灵活性以及空间和电子修饰的易用性以及对空气和水分的高稳定性相结合，能够在催化循环中实现高效的基本基本步骤，并轻松形成明确的复合物。