Palladium(II) complexes featuring bidentate pyridine–triazole ligands: Synthesis, structures, and catalytic activities for Suzuki–Miyaura coupling reactions

• X-ray data of 2-azidopyridine reveals the fused ring pyridine–tetrazole structure.
• Three new palladium(II) complexes were isolated and fully characterized.
• All Pd(II) complexes are active catalysts for Suzuki–Miyaura coupling reactions.
• Mercury poisoning tests suggest different catalytic nature of these Pd complexes.

Preparation of the Pd(II) complexes containing 2-(4-R-1,2,3-triazol-1-yl)pyridine [R = C6H5 (1), NC5H4 (2), n-C6H13 (3)] were described. Crystal structures of 1 and 2 revealed a square planar geometry with bidentate ligand coordination to Pd using different N donor of the triazole ring. Catalytic studies indicated that 1–3 exhibited moderate to high activity for Suzuki–Miyaura coupling between aryl bromides and phenylboronic acid under mild and aerobic conditions.

The crystal structures of 1 and 2 have shown that the Pd(II) center preferentially binds to the proximal triazole nitrogen atom, giving a shorter Pd–Ntrz bond distance and stronger triazole coordination. However, the Pd(II) complex with the medial triazole nitrogen donor 1 exhibited higher catalytic activities toward Suzuki–Miyaura coupling reactions.Figure optionsDownload as PowerPoint slide