Kinetics and Mechanism of the Reactions of Picolinic Acid with Dichloro-{1-alkyl-2-(arylazo)imidazole}palladium(II) Complexes

Abstract

The reaction between Pd(N,N¢)Cl 2 [N,N¢ " 1-alkyl-2-(arylazo)imidazole (N,N¢) and picolinic acid (picH) have been studied spectrophotometrically at k=463 nm in MeCN at 298 K. The product is [Pd(pic) 2 ] which has been verified by the synthesis of the pure compound from Na 2 [PdCl 4 ] and picH. The kinetics of the nucleophilic substitution reaction have been studied under pseudo-first-order conditions. The reaction proceeds in a two-step-consecutive manner (A fi B fi C); each step follows first order kinetics with respect to each complex and picH where the rate equations are: Rate 1={k¢ 0 +k¢ 2 [picH] 0 } Â [Pd(N,N¢)Cl 2 ] and Rate 2={k¢¢ 0 +k¢¢ 2 [picH] 0 }[Pd(N,O)(monodentate N,N¢)Cl 2 ] such that the first step second order rate constant (k¢ 2 ) is greater than the second step second order rate constant (k¢¢ 2 ). External addition of Cl ) (as LiCl) suppresses the rate. Increase in p-acidity of the N,N¢ ligand, increases the rate. The reaction has been studied at different temperatures and the activation parameters (D à H°and D à S°) were calculated from the Eyring plot.

Kinetic and mechanistic studies on the Pd–Cl cleavage of dichloro‐ [1‐alkyl‐2‐(naphthylazo)imidazole]palladium(II) complexes by 2,2′‐bipyridine

“…A bidentate neutral N,N′‐chelating ligand is very useful for the preparation of Pd(II) complexes with cis ‐MCl 2 pattern, which is a model system to allow for exploration of the mechanism of the antitumor activity of cis platin. The kinetics and mechanism of the substitution reactions involving Pd(II) complexes of 1‐alkyl‐2‐(phenylazo)imidazoles ( i ) with adenine 17, cytosine 18, 2‐mercapto‐pyridine 19, 2‐amino‐pyrimidine 20, picolinic acid 21, and 8‐hydroxy quinoline 22 was reported. We are intending to incorporate higher steric crowding around the target metal center by using different ligands with azoimine‐chelating mode (–NNCN–), which will open a new avenue for exploring the mechanistic aspects of the nucleophilic interaction with the metal center under different local environments.…”

Interaction of adenine with dichloro-[1-alkyl-2-(naphthylazo)-imidazole]palladium(II) complexes: kinetic and mechanistic studies

“…The reaction of DNA bases with Pd(II) complexes of the chelating N,N 0 -donor systems having cis-MCl 2 configuration constitutes a model system that allows exploration of the mechanism of the antitumor activity of the complexes. The kinetics and mechanism of the substitution reactions involving Pd(II) complexes of dichloro-[1-alkyl-2-(a-/b-naphthylazo)]imidazoles (ii) with cytosine [24], 2-amino-pyrimidine [25], picolinic acid [26] and 8-hydroxy quinoline [27] have been reported. This information has encouraged us to study the kinetics and mechanism of reaction of adenine with dichloro-[1-alkyl-2-(a-/b-naphthylazo)imidazole] palladium(II)] or Pd(a/bNaiR)Cl 2 complexes.…”

Mechanism of interaction of DNA bases with dichloro‐[1‐alkyl‐2‐(naphthylazo)imidazole]palladium(II) complexes: A cytosine case

“…An alternative approach is to carry out reactions with structurally analogous Pd(II) complexes and extend this information to Pt(II) chemistry. The kinetics and mechanism of the nucleophilic substitution reactions involving Pd(II) complexes of 1‐alkyl‐2‐(phenylazo)imidazoles ( i ) with adenine 18, cytosine 19, 2‐mercapto‐pyridine 20, 2‐amino‐pyrimidine 21,22, picolinic acid 23,24, and 8‐hydroxy quinoline 25,26 were reported. We intend to incorporate higher steric crowding around the target metal center by using different ligands with azoimine chelating mode (NNCN), which will open an avenue to investigate the mechanism of the nucleophilic interaction with the metal center under different local environments.…”