Expanding the scope of ‘Click’ derived 1,2,3-triazole ligands: New palladium and platinum complexes

Using the ‘Click Protocol’ the new ligands 1-(cyclohexyl)-4-(2-pyridyl)-1,2,3-triazole (1), 1-(2-trifluoromethyl phenyl)-4-(2-pyridyl)-1,2,3-triazole (2), 1-(4-hexyl phenyl)-4-(2-pyridyl)-1,2,3-triazole (3), 1-(2-mercaptomethyl phenyl)-4-(2-pyridyl)-1,2,3-triazole (4) and 1-(4-N,N-dimethylamino phenyl)-4-(2-pyridyl)-1,2,3-triazole (5) were prepared by reacting 2-ethynylpyridine with the corresponding azides. In the next step the ligands were reacted with suitable palladium and platinum precursors to yield the cis-dichloro-palladium complexes 1a–4a and platinum complexes 1b–4b. Investigation of the molecular structure of the free ligands 1 and 5 reveals the formation of infinite chains in the 3D structure which are governed by hydrogen bonds between the triazole units. Likewise the 3D structure of 1a shows infinite chains which are held together by multiple remarkably short C–H⋯Cl–Pd contacts. Electrochemical investigation of the free ligands by cyclic voltammetry showed irreversible reduction processes at highly negative potential. Upon metal complexation huge anodic shifts of the reduction potential were observed. To further characterize the electronic properties of all the compounds UV–Vis spectra were also analyzed.