Palladium(II) complexes of N-(pyridin-2-yl)-1,2-azol-3-carboxamide derived NNN-pincer ligands: Synthesis, unusual complexation and high-turnover catalysis in water

• Published in: Polyhedron 2024-12, Vol.264, p.117249, Article 117249
• Main Authors: Bumagin, Nikolay A., Kolesnik, Irina A., Potkin, Vladimir I., Dikusar, Evgeniy A., Lyakhov, Alexander S., Ivashkevich, Ludmila S., Zhou, Hongwei, Li, Wenliang
• Format: Article
• Language: English
• Subjects: 2-Amino(alkyl)pyridines; Catalysis; Green chemistry; Isothiazole; Isoxazole; NNN-pincer ligands; Pd(II) complexes
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2024.117249

Six new palladium(II) complexes derived from previously undescribed N-(pyridin-2-yl)-1,2-azol-3-carboxamides were synthesized and characterized. Complexation of ligands proceeded unusually by deprotonation of the amide group and elimination of HCl affording the palladium(II) pincer complexes [(k3-NNN)PdCl]n (n = 1, 2), which was proven by single crystal X-ray diffraction. The structure of the complexes depended on the length of the linker between the azole and pyridine fragments. The complexes were shown to be high-turnover catalysts for Suzuki reaction in Green Chemistry conditions. [Display omitted] Synthesis, characterization, and catalytic activity of palladium(II) complexes containing tridentate N-(pyridin-2-yl)-1,2-azol-3-carboxamide ligands with various length amide linkers [CONH(CH2)n, n = 0,1,2] is reported. Complexation of previously undescribed mixed pyridin-azol-carboxamide ligands with PdCl2 occurs unusually by deprotonation of the amide group and elimination of HCl affording the palladium(II) pincer complexes [(k3-NNN)PdCl]n (n = 1, 2), which was proven by single crystal X-ray diffraction. The first time synthesized complexes are high-turnover catalysts, as was shown during the evaluation in Suzuki reaction between aryl halides and arylboronic acids: substituted biaryls, including practically significant, were obtained with up to quantitative yields under Green Chemistry conditions.