Synthesis and Structural Aspects of Hg (II) and Pb (II) Complexes with N, N-bis(2-methylbenzimidazolyl)-p-toluidine

Solid complexes of Hg (II) and Pb (II) with N, N-bis(2methylbenzimidazolyl)-p-toluidine (C₂₃H₂₁N₅), a neutral tridentate tripodal (NNN) ligand, have been synthesized and characterized.The ligand coordinates through three tertiary nitrogen atoms to form diacido complexes of the general formula MLX₂ (M = Hg (II) or Pb (II); X = Cl⁻, Br⁻, CH₃COO⁻, or NCS⁻).Molar conductance measurements of freshly prepared DMF solutions (10-12 Ω⁻¹ cm² mol⁻¹) indicate non-electrolytic behaviour, confirming coordination of the anions.Infrared spectral studies reveal monodentate coordination of acetate and thiocyanate ions.The ν(C≡N) stretching frequencies of thiocyanate at 2105 cm⁻¹ (Pb) and 2117 cm⁻¹ (Hg), along with ν(C-S) bands near 715-708 cm⁻¹, confirm S-bonded NCS coordination.The ν(C=N) band of the free ligand at 1632 cm⁻¹ shifts to lower frequencies (1610-1595 cm⁻¹) upon complexation, indicating coordination through benzimidazole nitrogen atoms.Based on stoichiometry, spectroscopic data, and the d¹⁰ electronic configuration of Hg (II) and Pb(II), a five-coordinate trigonal bipyramidal geometry is proposed for all complexes.