Kinetics and mechanism of reaction of α-picolinic acid with dichloro-{2-(arylazo)- heterocycle}palladium(II) complexes

Ghosh

2005

Nucleophilic substitution of Pd(RaaiR¢)Cl 2 [RaaiR¢=1-alkyl-2-(arylazo)imidazole, p-RAC 6 H 4 AN@NAC 3 H 2 NN-1-R¢; where R= H(a)/Me(b)/Cl(c) and R¢ = Et(1)/Bz(2)] with adenine (A) in MeCN-water (1:1) at 298 K, to form [Pd(A) 2 ]Cl 2 , has been studied spectrophotometrically under pseudo-first-order conditions and the analyses support a nucleophilic association path. The reaction follows the rate law, rate = {a+k [A] 2 0 g[Pd(RaaiR¢)Cl 2 ]: first-order in Pd(RaaiR¢)Cl 2 and second-order in A. The rate increases as follows: Pd(RaaiEt)Cl 2 (1) < Pd(RaaiBz)Cl 2 (2) and Pd(MeaaiR¢)Cl 2 (b) < Pd(HaaiR¢)Cl 2 (a) < Pd(ClaaiR¢)Cl 2 (c). External addition of Cl ) (LiCl) suppresses the rate (rate µ 1/[Cl ) ]). The activation parameters, D z H 0 and D z S 0 of the reactions were calculated from the Eyring plot and support the proposed mechanism.

Section: Resultsmentioning

confidence: 83%

Interaction Between Pd(RaaiR′)Cl2 and Adenine: Reaction Dynamics and Mechanism [RaaiR′ = 1-alkyl-2-(arylazo)imidazole]

Ghosh

2005

“…It was then chromatographed following above mentioned procedure. Yield: 0.028 g, -2-(arylazo)imidazoles are N,N¢-chelating ligands having an azoimine group, )N=N)C=N), as the chelating unit [5][6][7][8][9][10][11]. In this work, six known 1-alkyl-2-(arylazo)imidazole complexes of palladium(II) were used, see Scheme 1.…”

Section: Product Isolation and Characterizationmentioning

confidence: 99%

“…They form Pd(N,N¢)Cl 2 complexes having the cis-PdCl 2 configuration [7]. We have been engaged for several years in the study of the reactions of pyridines [8], a-diimines [9], and picolinic acid [10] with Pd(N,N¢)Cl 2 . As a sequel to our earlier observations, in this work we now explore the reaction of picolinic acid (picH), a monoanionic-N, O donor, with Pd(N,N¢)Cl 2 .…”

Section: Introductionmentioning

confidence: 99%

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

Sarkar

2006

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.

“…This fact has encouraged us to study the kinetics and mechanism of reactions of heterocyclic bases with Pd(N,N¢)Cl 2 complexes. So far we have studied the kinetics and mechanism of reactions of pyridine bases [6], DNA bases [7], mono anionic-N,O donor picolinic acid [8] with Pd(N,N¢)Cl 2 . Our present programme is to study the reactions of pyridine derivatives with Pd(N,N¢)Cl 2 .…”

Section: Introductionmentioning

confidence: 99%

Kinetic and mechanistic studies of the interaction of 2-mercapto pyridine with dichloro[1-alkyl-2-(arylazo)imidazole]palladium(II) complexes

Majumdar

2006

Nucleophilic substitution of Pd(RaaiR¢)Cl 2 [(RaaiR¢ = 1-alkyl-2-(arylazo)imidazole, p-R-C 6 H 4 -N=N-C 3 H 2 NN-1-R¢; where R = H(a)/ Me(b)/ Cl(c) and R¢ = Et(1)/Bz(2)] with 2-Mercaptopyridine (2-SH-Py) in acetonitrile (MeCN) at 298 K, to form [Pd 2 (2-S-Py) 4 ], has been studied spectrophotometrically under pseudo-first-order conditions and the analyses support the nucleophilic association path. The reaction follows the rate law, Rate = {k 0 + k [2-SH-Py] 0 2 }[Pd(RaaiR¢)Cl 2 ]: first order in Pd(RaaiR¢)Cl 2 and second order in 2-SH-Py. The rate of the reaction follows the order: Pd(RaaiEt)Cl 2 (1) < Pd(RaaiBz)Cl 2 (2) and Pd(MeaaiR¢)Cl 2 (b) < Pd(HaaiR¢)Cl 2 (a) < Pd(ClaaiR¢)Cl 2 (c). External addition of Cl ) (LiCl) and HCl suppresses the rate (Rate µ 1/[Cl ) ] 0 & µ1/[HCl] 0 ). The reactions have been studied at different temperatures (293-308 K) and activation parameters (D z H o and D z S o ) of the reactions were calculated from the Eyring plot and support the proposed mechanism.