以氮、氧为配位原子的某些铅(Ⅱ)混合配体化合物的稳定性研究(Ⅲ)

Studies of the Stabilities of some Lead(Ⅱ)Mixed Ligand Complexes Containing Oxygen and Nitrogen as the Coordination Atom(Ⅲ)

用pH-电位滴定法测定了铅(Ⅱ)的以2,2′-联吡啶(bipy)或1,10-邻二氮菲(phen)为第一配体,以邻苯二甲酸根(pht^(2-))为第二配体的混合配体化合物在15°、25°、35°和45℃时在水溶液中的稳定性。应用温度系数法求出了混合配合物形成反应的热力学函数变化△H,△S和△G。在此基础上讨论了上述混合配合物具有高稳定性的根源。

In this paper,the stability constants of mixed ligand complexes,Pb(bipy) (pht)and Pb(phen)(pht),where pht=phthlate,bipy=2,2′-bipyridyl,and phen =phenanthroline,have been determined at 15,25,35,and 45℃ respectively,with ionic strength I=0.10 by using pH-potentiometric titration technique.It has been found that the stabilities of these mixed ligand complexes are obviously higher than the expecting values based on the statistical consideration.Thermodynamical fun- ctions of the formation reactions of these mixed ligand complexes have also been obtained by a temperature coefficient method and common thermodynamical relations. The reasors resporsibl e for the high stability of the above mentioned mixed ligand complexes has been discussed in terms of the thermodynamical function values. It has been suggested that the cooperation effect of d electron back-donation between central metal ion and ligands is the principal reason for the high stability.