Çakır Sinem, Kavukcu Serdar Batıkan, Karabıyık Hande, Rethinam Senthil, Türkmen Hayati
Department of Chemistry, Ege University 35100 Bornova Izmir Turkey
Department of Physics, Faculty of Science and Art, Dokuz Eylül University Izmir Turkey.
RSC Adv. 2021 Nov 23;11(60):37684-37699. doi: 10.1039/d1ra07231e.
Application of N-heterocyclic carbene (NHC) palladium complexes has been successful for the modulation of C-C coupling reactions. For this purpose, a series of azolium salts (1a-f) including benzothiazolium, benzimidazolium, and imidazolium, bearing a CN-substituted benzyl moiety, and their (NHC)PdBr (2a-c) and PEPPSI-type palladium (3b-f) complexes have been systematically prepared to catalyse acylative Suzuki-Miyaura coupling reaction of acyl chlorides with arylboronic acids to form benzophenone derivatives in the presence of potassium carbonate as a base and to catalyse the traditional Suzuki-Miyaura coupling reaction of bromobenzene with arylboronic acids to form biaryls. All the synthesized compounds were fully characterized by Fourier Transform Infrared (FTIR), and H and C NMR spectroscopies. X-ray diffraction studies on single crystals of 3c, 3e and 3f prove the square planar geometry. Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), metal mapping analyses and thermal gravimetric analysis (TGA) were performed to get further insights into the mechanism of the Suzuki-Miyaura cross coupling reactions. Mechanistic studies have revealed that the stability and coordination of the complexes by the CN group are achieved by the removal of pyridine from the complex in catalytic cycles. The presence of the CN group in the (NHC)Pd complexes significantly increased the catalytic activities for both reactions.
N-杂环卡宾（NHC）钯配合物已成功应用于C-C偶联反应的调控。为此，系统地制备了一系列含氰基取代苄基部分的唑盐（1a - f），包括苯并噻唑盐、苯并咪唑盐和咪唑盐，以及它们的（NHC）PdBr（2a - c）和PEPPSI型钯（3b - f）配合物，用于在碳酸钾作为碱的存在下催化酰氯与芳基硼酸的酰基化铃木 - 宫浦偶联反应以形成二苯甲酮衍生物，并催化溴苯与芳基硼酸的传统铃木 - 宫浦偶联反应以形成联芳基。所有合成的化合物均通过傅里叶变换红外光谱（FTIR）、氢核磁共振光谱（1H NMR）和碳核磁共振光谱（13C NMR）进行了全面表征。对3c、3e和3f单晶的X射线衍射研究证实了其平面正方形几何结构。进行了扫描电子显微镜（SEM）、能量色散X射线光谱（EDS）、金属映射分析和热重分析（TGA），以进一步深入了解铃木 - 宫浦交叉偶联反应的机理。机理研究表明，在催化循环中通过从配合物中除去吡啶来实现配合物通过氰基的稳定性和配位。（NHC）Pd配合物中氰基的存在显著提高了这两种反应的催化活性。
