SYNTHESIS OF 3-(2-PYRIDYL)-N-METHYL-1,2,4-TRIAZOLES AND THEIR COORDINATION COMPOUNDS WITH PD(II)

UDC 546.98+547.792+543.429.23

Abstract

Alkylation of 3-(2-pyridyl)-1,2,4-triazole with iodomethane leads to formation of 3-(2-pyridyl)-N¹-methyl-1,2,4-triazole (L¹) and 3-(2-pyridyl)-N²-1,2,4-triazole (L²), which were used for synthesis of palladium(II) complexes PdL¹Cl₂ and PdL²Cl₂. The composition and structure of obtained compounds were proposed on the basis of IR and ¹H NMR spectroscopy data and elemental analysis.

IR spectra of synthesized ligands have a lot in common, due to their structure similarity. In the IR spectrum of ligands L¹ and L² we observe intense CH band of triazole fragment in the 3000 cm^-1, bands of valence and deformation vibrations of CH of pyridine ring in the 1200-1600 cm^-1. As a result of coordination all signals in the IR spectra are shifted.

Complexes PdL¹Cl₂ and PdL²Cl₂ have mononuclear structure. PdL¹Cl₂ partially dissociate in solution of DMSO, it is detected by means of ¹H NMR spectra in which we observe signals of ligands protons. It is could be due to structural features of formed coordination compound.

¹H NMR spectra of obtained ligands is bit similar, this is due to their structure. Signals of pyridine ring protons 3-(2-pyridyl)-N¹-methyl-1,2,4-trazol shifted to 0.11-0.12 ppm in a weak field in compare with 3-(2-pyridyl)-N²-methyl-1,2,4-triazol. Signals of protons in the 5th position L¹ are shifted in a strong field compared to L². N¹-CH₃ signals are shifted to weaker field than N²-CH₃, it can be explained by the influence of negative magnetic anisotropy of pyridine ring.

Coordination of all ligands occurs through the nitrogen atom of pyridine ring and N⁴-triazole. In this case all L¹ and L² signals of pyridine  protons suffer shift to a weak field (L¹: Δδ = 0,28 ... 0,36; L²: Δδ = 0,27 ... 0,38). Triazole proton is shifted to 0.36 ppm for Pd(L¹)Cl₂ and 0.63 for Pd(L²)Cl₂ in compare with uncoordinated ligands.