Synthesis, characterization, and crystal structure determination of palladacycles of para-substituted 2-thiobenzylazobenzenes

Abstract

Bichelated neutral palladacycles (1–3), [Pd(L)Cl], were synthesized from reaction of the new potential tridentate (C,N,S) ligands, 2-thiobenzylazobenzene (L₁), 4′-methyl-2-thiobenzylazobenzene (L₂), and 4′-chloro-2-thiobenzylazobenzene (L₃) with sodium tetrachloropalladate(II), Na₂[PdCl₄], in ethanol. The compounds were characterized by elemental analysis, FT-IR, ¹H NMR, UV–visible, and thermogravimetric analysis. The crystal structures of L₂ and 1–3 were determined by single-crystal X-ray diffraction. In 1–3, the geometry around palladium remains almost square planar, coordinated to carbon, nitrogen, and sulfur of the ligand forming a bichelated cyclopalladate complex. The C–H…Cl type intermolecular hydrogen bonds, weak π…π, C–H…π, and van der Waals interactions are believed to be the stabilizing forces for the crystal packing of these palladacycles.

Graphical Abstract

Keywords:

• Palladacycles
• 2-Thiobenzylazobenzene
• CNS-donor ligand
• Thermogravimetric analysis
• Crystal structure

Acknowledgements

Authors thank the Council of Scientific and Industrial Research (CSIR), New Delhi for the award of Senior Research Fellowship (T.B.) and Director of NIT, Silchar for financial assistance (M.K.). Authors also thank SAIF, IIT Bombay; IASST, Guwahati and Tezpur University, Tezpur for spectral and TGA analysis.