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首页> 外文期刊>Bulletin of the Chemical Society of Japan >Kinetics and Mechanisms of the Axial Ligand Substitution Reaction of the Head-to-head 2-Pyridonato-bridged cis-Diammineplatinum(III) Inuclear Complex
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Kinetics and Mechanisms of the Axial Ligand Substitution Reaction of the Head-to-head 2-Pyridonato-bridged cis-Diammineplatinum(III) Inuclear Complex

机译:头对头2-吡啶酮桥联的顺式-二氨合铂(III)核络合物的轴向配体取代反应的动力学和机理。

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摘要

The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex ([(H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(H_2O)]~(4+)] with halide ions X~- (X~-= Cl~- and Br~-) to give monohalogeno and dihalogeno complexes were studied kinetically:[(H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(H_2O)]~(4+) +X~- reversible [(H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(X)]~(3+) +H_2O[(H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(H_2O)]~(3+)+X~- reversible [(X)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(X)]~(2+)+H_2O.The acid dissociation constant (K_(h1) of the axial aqua ligand in the HH dimer and the formation constants (K_1~x and K_2~x) of the monohalogeno and dihalogeno complexes were determined spectrophotometrically ot be - log(K_(h1/M) =1.71(+-) 0.04; log(K_1~(Cl)/M~(-1)) = 5.93(+-)0.02, log(K_2~(Cl)/M~(-1))= 3.71 (+-) 0.00 for the reaction with Cl~-, and log(K_1~(Br)/M~(-1))= 6.20(+-) 0.05, log(K_2~(Br)/M~(-1))=4.55 (+-)0.01 for the reaction with Br~-.The two latinum atoms are nonequivalent in the HH dimer,in which the first deprotonatio occurs selectively to the water molecule on the Pt(N_4) atom and the first nucleophilic substitution with X~- occurs preferentially to the Pt(N_2O_2) atom,where the atoms in parentheses are the corrdinating atoms.The fist water substitution with X~- proceeds via two similar substitution paths,whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule,providing a coordinatively unsaturated complex.These reaction paths are reasonably explained by the relative strength o the trans effect of the water,hydroxide,and halide ions in the monohalogeno complexes.
机译:头对头(HH)2-吡啶酮桥联的顺-二氨铂(III)双核配合物([[H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)的以下连续轴向配体取代反应)_2(H_2O)]〜(4+)]与卤离子X〜-(X〜-= Cl〜-和Br〜-)动力学研究了单卤代和二卤代配合物:[[H_2O)Pt(NH_3)_2 (#mu#-C_5H_4NO)_2Pt(NH_3)_2(H_2O)]〜(4+)+ X〜-可逆[[H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(X) ]〜(3+)+ H_2O [(H_2O)Pt(NH_3)_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(H_2O)]〜(3 +)+ X〜-可逆[[X)Pt(NH_3) )_2(#mu#-C_5H_4NO)_2Pt(NH_3)_2(X)]〜(2 +)+ H_2O.HH二聚体中轴向水基配体的酸解离常数(K_(h1)和形成常数(K_1)分光光度法测定一卤代和二卤代配合物的〜x和K_2〜x)-log(K_(h1 / M)= 1.71(+-)0.04; log(K_1〜(Cl)/ M〜(-1)) = 5.93(+-)0.02,log(K_2〜(Cl)/ M〜(-1))= 3.71(+-)0.00用于与Cl〜-反应,log(K_1〜(Br)/ M〜( -1))= 6.20(+-)0.05,log(K_2〜(Br)/ M〜(-1))= 4.55( +-)0.01与Br〜-反应。在HH二聚体中两个拉丁原子是不等价的,其中第一个去质子化选择性地发生在Pt(N_4)原子上的水分子上,并且第一个被X〜-亲核取代优先出现在Pt(N_2O_2)原子上,其中括号中的原子是相关原子。用X〜-进行的第一个水取代通过两个相似的取代路径进行,而第二个取代通过两个不同的路径进行:一个是简单取代另一途径是通过水分子的解离,提供了一个配位不饱和的配合物。这些反应路径可以通过单卤代配合物中水,氢氧根和卤化物离子的反作用的相对强度来合理解释。

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