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

Nucleophilic substitution of Pd(RaaiR′)Cl2 [RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R—C6H4— N=N—C3H2NN-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]Cl2, 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] 02[Pd(RaaiR′)Cl2]: first-order in Pd(RaaiR′)Cl2 and second-order in A. The rate increases as follows: Pd(RaaiEt)Cl2(1) < Pd(RaaiBz)Cl2(2) and Pd(MeaaiR′)Cl2(b) < Pd(HaaiR′)Cl2(a) < Pd(ClaaiR′)Cl2(c). External addition of Cl− (LiCl) suppresses the rate (rate 1/[Cl−]). The activation parameters, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \delta_\ddagger $$ \end{document}H0 and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \delta_\ddagger $$ \end{document}S0 of the reactions were calculated from the Eyring plot and support the proposed mechanism.