Kinetic study on the ligand exchange reactions between bis(alkylxanthato)palladium(II)and bis(N,N-dialkyldithiocarbamato)palladium(II)by high-performance liquid chromatography

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 ina temperature range of 20—50°C by means of high-performance liquid chromatography.It was foundthat both the forward and reverse reactions are of second order.All of the equilibrium constants Kdetermined are 10.3±1.0,much greater than the value(K=4)calculated statistically which indicatesthat the ternary complexes are more stable than the binary complexes.The experimental resultsrevealed that the reaction rate decreases with the increase in the size of R and R~1 groups and the latterare more remarkable,consistent with the deduction of steric effect.The activation parameters ofthe 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.

Kinetic study on the ligand exchange reactions between bis(alkylxanthato)palladium(II) and bis(N,N-dialkyldithiocarbamato)palladium(II) by high-performance liquid chromatography

The rate constants and equilibrium constants of ligand exchange reactions between bis (alkylxanthato)palladium(II), Pd (S₂COR)₂ (R =Am, n-Hex, Bz), and bis(N, N-dialkyldithiocarbamato) palladium(II), Pd(S₂CNR₂)₂ (R =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 R¹ 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 temperatures β =390±8 K and β =346 ± 15 K have been observed respectively. A plausible mechanism involving an eight-membered ring intermediate has been proposed on the basis of experimental results.