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Mechanism of Coordination-site Exchange Reaction of the Cobalt(III) Complexes Containing Multidentate Ligands

多齿钴(III)配合物的配位交换反应机理

基本信息

批准号：
02640481
负责人：
KAWAGUCHI Hiroshi
金额：
$ 1.41万
依托单位：
Kochi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

The isomers of the [Co(edda)(en)]^+, [Co(edda)(gly)], [Co(edda)(beta-ala)], and [Co(eddp)(en)]^+ complexes were prepared and optically resolved. The stereochemistry of these complexes was studied on the basis of absorption, CD, ^1H-NMR and ^<13>C-NMR data and partially on the basis of X-ray analysis. Two beta isomers, beta(e-1) and beta(e-2), of [Co(eddp)(en)]^+ were comformational diastereomers arising from a difference of the chirality around one of the asymmetric N atoms in a coordinated eddp ligand.Coordination-site exchange (isomerization and racemization) reactions of the complexes described above were studied in a basic aqueous solution. In the [Co(edda)(en)]<@D1+@>D1 system, LAMBDA(R)-beta isomer isomerized to LAMBDA(S,S)-alpha isomer with an optical purity (o.p.) of ca. 45%. In the reactions of three isomers of [Co(edda)(gly)], LAMBDA(R)-beta-fac(O) isomerized to LAMBDA(R)-betamer(O) (o.p.:ca.100%) and LAMBDA(S,S)-alpha-mer(O) (o.p.:ca. 33%), LAMBDA(R)-beta-mer(O) to LAMBDA(R) … More -beta-fac(O) (o.p.:ca.65%) and LAMBDA(S,S)-alpha-mer(O) (o.p.: ca.40%), and LAMBDA(S,S)-alpha-mer(O) to LAMBDA(R)-beta-fac(O) (o.p.:ca.50%) and LAMBDA(R)-beta-mer(O) (o.p.:ca.65%). The isomerization behavior of the [Co(edda)(beta-ala)] system was similar to that of the [Co(edda)(gly)] system except for the low stereoselectivity of the beta-fac(O) * beta-mer(O) change. In the [Co(eddp)(en)]<@D1+@>D1 system, the beta(e-1) (] SY.tautm.[) beta(E-2) change was an inversion reaction at the asymmetric sec-N atom in the in-plane beta-alaninate ring of the coordinated eddp, and the rate was slow. The alpha (] SY.tautm.[) beta(e-1,or2) change (coordination-site exchange reaction) was stereoselective: LAMBDA(R,R)-alpha * LAMBDA(S,S)-beta(e-1) (o.p.:ca.40%), LAMBDA(R,R)-alpha * LAMBDA(S,R)-beta(e-2) (o.p.:ca.45%). These results were explained on the basis of a Co-O bond rupture mechanism: the coordination-site exchange between the sec-N and O atoms of the edda or eddp ligand occurred predominantly; consequently, the asymmetry at the sec-N center was inverted. Less

制备了[Co(edda)(en)]^+、[Co(edda)(gly)]、[Co(edda)(β -ala)]和[Co(eddp)(en)]^+的异构体，并进行了光学分辨。根据吸收、CD、^1H-NMR和^<13>C-NMR数据以及部分x射线分析对这些配合物的立体化学进行了研究。[Co(eddp)(en)]^+的两个β异构体β (e-1)和β (e-2)是由配位eddp配体中一个不对称N原子周围的手性差异引起的构象非对映体。研究了上述配合物在碱性水溶液中的配位交换（异构化和外消旋化）反应。在[Co(edda)(en)]<@D1+@>D1体系中，λ (R)- β异构体异构为λ (S，S)- α异构体，光学纯度（o.p）约为45%。在[Co(edda)(gly)]的三个异构体反应中，λ (R)- β -面(O)异构化为λ (R)- β -氨基(O) （o.p:ca.100%）和λ (S，S)- α -氨基(O) （o.p:ca.100%）。33%),λ(R) -beta-mer (O)λ(R ) ... -beta-fac (O) (o.p: ca.65%)和λ(S, S) -alpha-mer (O) (o.p: ca.40%)和λ(S, S) -alpha-mer (O)λ(R) -beta-fac (O) (o.p: ca.50%)和λ(R) -beta-mer (O) (o.p: ca.65%)。[Co(edda)(β -ala)]体系的异构化行为与[Co(edda)(gly)]体系相似，只是β -面(O) * β -mer(O)变化的立体选择性较低。在[Co(eddp)(en)]<@D1+@>D1体系中，β (e-1) (] SY.tautm。[) β (E-2)变化发生在配位eddp的面内β -丙氨酸环的不对称sec-N原子上，反应速率较慢。[au:] [au:][) β （e-1，或2）变化（配位-位点交换反应）具有立体选择性：λ (R，R)- α * λ (S，S)- β (e-1) (o.p.:ca。40%),λ(R, R) - t1 *λ(S, R)β(飞行)(o.p: ca.45%)。这些结果是基于Co-O键断裂机制来解释的：edda或eddp配体的sec-N和O原子之间的配位位交换主要发生；因此，sec-N中心的不对称性被逆转。少