Pd–Cl cleavage of dichloro-[1-alkyl-2-(naphthylazo)imidazole]palladium(II) complexes by picolinic acid: Kinetic and mechanistic studies

Picolinic acid (picH) reacts with [Pd(α-/β-NaiR)Cl2] [α-/β-NaiR = 1-alkyl-2-(naphthyl-α-/β-azo)imidazole] in acetonitrile (MeCN) medium to give [Pd(α-/β-NaiR)(pic)](ClO4). The products are characterized by spectroscopic techniques (FT-IR, UV–Vis, NMR). The reaction kinetics show first order dependence of rate on each of the concentration of Pd(II) complex and picH. Addition of LiCl to the reaction decreases the rate of reaction and has proved the cleavage of Pd–Cl bond at the rate-determining step. Thermodynamic parameters (Δ‡H° and Δ‡S°) are determined from variable temperature kinetic studies. The magnitude of the second order rate constant, k2 increases as in the order: Pd(NaiEt)Cl2 < Pd(NaiMe)Cl2 <  Pd(NaiBz)Cl2 as well as Pd(β-NaiR)Cl2 <  Pd(α-NaiR)Cl2.

Graphical abstractThis work describes kinetics and mechanism of the reaction between picolinic acid (picH) and [Pd(α-/β-NaiR)Cl2] [α-/β-NaiR = 1-alkyl-2-(naphthyl-α/β-azo)imidazole] in acetonitrile (MeCN) medium. The product is characterized as [Pd(α/β-NaiR)(pic)](ClO4) by different spectroscopic routes. It is established that the cleavage of Pd–Cl bond is the rate-determining step. Thermodynamic parameters (Δ‡H° and Δ‡S°) are determined from variable temperature kinetic studies.Figure optionsDownload full-size imageDownload as PowerPoint slide