The rate constants and equilibrium constants of ligand exchange reactions between his (alkylxanthato)palladium(Ⅱ),Pd(S_2COR)_2(R=Am,n-Hex,Bz),and bis(N,N-dialkyldithiocarbamato) palladium(Ⅱ),Pd(S_2CNR_2)_2(K=Et,n-Pr...The rate constants and equilibrium constants of ligand exchange reactions between his (alkylxanthato)palladium(Ⅱ),Pd(S_2COR)_2(R=Am,n-Hex,Bz),and bis(N,N-dialkyldithiocarbamato) palladium(Ⅱ),Pd(S_2CNR_2)_2(K=Et,n-Pr,n-Bu),in chloroform solution have been determined in a temperature range of 20—50°C by means of high-performance liquid chromatography.It was found that both the forward and reverse reactions are of second order.All of the equilibrium constants K determined are 10.3±1.0,much greater than the value(K=4)calculated statistically which indicates that the ternary complexes are more stable than the binary complexes.The experimental results revealed that the reaction rate decreases with the increase in the size of R and R^1 groups and the latter are more remarkable,consistent with the deduction of steric effect.The activation parameters of the reactions have been calculated.In reaction series(11)and(12)(in the text)the isokinetic tempera- tures B=390±8K and β=346±15 K have been observed respectively.A plausiblemechanism in- volving an eight-membered ring intermediate has been proposed on the basis of experimental results.展开更多
基金Project supported by the National Natural Science Foundation of China.
文摘The rate constants and equilibrium constants of ligand exchange reactions between his (alkylxanthato)palladium(Ⅱ),Pd(S_2COR)_2(R=Am,n-Hex,Bz),and bis(N,N-dialkyldithiocarbamato) palladium(Ⅱ),Pd(S_2CNR_2)_2(K=Et,n-Pr,n-Bu),in chloroform solution have been determined in a temperature range of 20—50°C by means of high-performance liquid chromatography.It was found that both the forward and reverse reactions are of second order.All of the equilibrium constants K determined are 10.3±1.0,much greater than the value(K=4)calculated statistically which indicates that the ternary complexes are more stable than the binary complexes.The experimental results revealed that the reaction rate decreases with the increase in the size of R and R^1 groups and the latter are more remarkable,consistent with the deduction of steric effect.The activation parameters of the reactions have been calculated.In reaction series(11)and(12)(in the text)the isokinetic tempera- tures B=390±8K and β=346±15 K have been observed respectively.A plausiblemechanism in- volving an eight-membered ring intermediate has been proposed on the basis of experimental results.
