Formation of mixed-ligand complexes of cadmium(II) with chloride and substituted pyridines in 1,2-dichloroethane as solvent

Abstract

The formation of mixed-ligand complexes of cadmium(II) chloride with pyridine (py) and substituted pyridines R-py [R-py = 4-methyl-(4Me-py), 3-methyl-(3Me-py), 2-methyl-(2Me-py), 2-ethyl-(2Et-py), 4-acetyl-(4MeCO-py), and 4-cyano-pyridine (4CN-py)] in 1,2-dichloroethane, given by equations (i) and (ii), has been investigated at 25.0 °C by means of solvent extraction. The successive, (NBu₄)₂CdCl₄+ R-py [graphic omitted] (NBu₄)CdCl₃(R-py)+ NBu₄Cl (i), (NBu₄)CdCl₃(R-py)+ R-py [graphic omitted] CdCl₂(R-py)₂+ NBu₄Cl (ii) formation constants, K₁ and K₂, were determined as log K₁=–0.56, –0.24, –0.34, –0.66, –1.00, –1.02, and –1.50 ±0.03, and log K₂=–3.20, –2.74, –2.98, –3.75, –4.07, –3.89 ±0.05, and <–4.5 for the py, 4Me-py, 3Me-py, 2Me-py, 2Et-py, 4MeCO-py, and 4CN-py complexes, respectively. Except for the 2Me-py and 2Et-py complexes, the values of log K₁ and log K₂ show linear correlations with the pK_a of the conjugate acid of the substituted pyridines.