摘要
用ｐＨ－电位法测定了钴（Ⅱ）、镍（Ⅱ）的以α，α’－联吡啶或１，１０－邻菲咯啉为第一配体，以草酸、丙二酸、丁二酸、戊二酸为第二配体的１６组三元配合物在２５℃，离子强度为０．１０（ＫＮＯ＿３）条件下的稳定常数。由此所得的△ｌｏｇＫ和ｌｏｇＸ值表明，随第二配体螯合环的增大，配合物的稳定性逐渐下降。以草酸的配合物（五元环）为最稳定。
The stability constants of ternary complexes MAB and binary complexes MA,MB,MA_2,MB_2,and protonation constants of ligands A,B, have been respecctively determined at temperature 25℃with ionic strength I=0.1(KNO_3)by usingpH-potentiometric titration technique,where M=Co(Ⅱ)or Ni(Ⅱ);A=2,2’-bipyridyl or 1,10-phenanthroline;B=oxalate,malonate,succinate and glutarate.The loga-rithm of stability constants,the logarithm of equilibrium constants △lgKof reaction and the logarithm of equilibrium constants lgX ofreaction have been calculated,where andThe experimental results show that the 16 groupsternary complexes containing oxalate,malonate,succinate and glutarate as one ofthe ligands have an enhanced stability,because their △lgK and lgX arehigher than the corresponding statistically expected values. It is suggested that ma-in reason of the enhanced stahility is back donation of the π electron from the me-tal ion to the ligand.After analysed the experimental data(△lgK:+0. 09～-0.61,lg lgX:3.52～1.08),we come to the conclusion that the variation order of △lgK or lgX is oxalate(five menber ring)>malonate(six menber ring)>succinate(seven menber ring)>glutarate(eight menber ring),which is consistent with the size of chelate ring of dicarboxylate ligands.It is shown that there is no obvious relation between stabilty constants of ternary complexes and the basic strength of dicarboxylic acids.
出处
《辽宁大学学报（自然科学版）》
CAS
1994年第3期67-70,共4页
Journal of Liaoning University：Natural Sciences Edition
关键词
螯合环
二羧酸
镍
三元络合物
Cobalt
Nickel
Ternary complexes
Dicarboxylic acid:
stability Chelate ring.
