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

Abstract

Nucleophilic substitution of Pd (RaaiR^/)Cl₂ [(RaaiR^/= l-alkyl-2 -(arylazo) imid azole, <i>p</i>-R-C₆H₄-N=N-C₃H₂NN-1-R^/: where R = H(<b>a</b>)/Me(<b>b</b>)/Cl(<b>c</b>) and R^/ = Et(<b>1</b> )/Bz(<b>2</b>)] with 2-aminopyrimidine (2-NH₂- Pym) in MeCN at 303 K, to form [Pd₂(2-NH₂- Pym)₂ Cl₄], has been studied spectrophotometrically under pseudo-first-order conditions. The results obtained support a nucleophilic association path . The reaction follows the rate law, Rate = {<i>k₀ </i>+ <i>k </i>[2-NH₂-Pym]₀} Pd (RaaiR^/)Cl₂ ], first order each in Pd (RaaiR^/)Cl₂ and 2-NH₂-Pym. The rate increases as follows: Pd (RaaiEt)Cl₂< Pd (RaaiBz)Cl₂ and Pd (MeaaiR^/)Cl₂ < Pd (HaaiR^/)Cl₂ < Pd (ClaaiR^/)Cl₂ . External addition of Cl^- (LiCl) suppresses the rate inversely. The reactions have been studied at different temperatures (298-3 13 K) and activation parameters.Δ^#<i>H</i>^o and Δ^#<i>S</i>^o of the reactions have been calculated from the Eyring plot. The data support the proposed mechanism.