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.