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本文应用高效液相色谱法研究了钯(II)-N,N-二烷基二硫代氨基甲酸螯合物间的配体交换反应动力学及其平衡性质.发现配体交换反应的正逆反应皆为二级,反应速率在不同溶剂中按以下顺序递减,n-BuOH>CH_3CO_2C_2H_5>CS_2>CCl_4>CH_2Cl_2.当螯合物上取代基为同系列烷基时,交换反应速率几乎不变,当不是同系列基而且体积相差较大时,由于位阻效应反应速率明显下降.交换反应的活化熵为负.平衡常数随交换配体上取代基在体积和结构上差异的加大而增大,同时也随溶剂本性有明显变化,但偏离统计计算值K=4并不太远(K_(实验)=1.9～9.8).根据以上实验事实并结合螯合物电子结构和立体构型提出,交换反应按S_N2机理进行,并给出了反应过程模型.
In this paper, the kinetics and equilibrium properties of the ligand-exchange reaction of palladium (II) -N, N-dialkyldithiocarbamate chelates with high performance liquid chromatography were investigated. The results showed that the forward and reverse reaction The reaction rates decrease in different solvents in the order of n-BuOH> CH_3CO_2C_2H_5> CS_2> CCl_4> CH_2Cl_2. When the substituents on the chelate are the same series of alkyl groups, the exchange reaction rate is almost unchanged. The results show that the rate of activation is negative due to the steric effect and the activation entropy of the exchange reaction is negative.It is found that the equilibrium constant increases with the increase of the volume and the structure of substituents on the exchange ligands, But also with the nature of the solvent there are significant changes, but deviate from the calculated value of K = 4 is not too far (K_ (experiment) = 1.9 ~ 9.8) .According to the above experimental facts combined with the chelate electronic structure and three-dimensional configuration proposed exchange The reaction was carried out according to S_N2 mechanism and the reaction process model was given.