SYNTHESIS AND STRUCTURE OF METAL-COMPLEXES OF TRIAZA MACROCYCLES WITH 3 PENDANT PYRIDYLMETHYL ARMS
SYNTHESIS AND STRUCTURE OF METAL-COMPLEXES OF TRIAZA MACROCYCLES WITH 3 PENDANT PYRIDYLMETHYL ARMS
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DOI：
10.1021/ic00236a031
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发表时间：
1986-07-30
影响因子：
4.6
通讯作者：
XIE, CL
中科院分区：
文献类型：
--
作者：
CHRISTIANSEN, L;HENDRICKSON, DN;XIE, CL
确定螯合物分子内重排反应的分子机制是一个长期存在的问题。所提出的三螯合物和多齿配合物构型外消旋化的机制包括以下内容：(a)围绕真正的三重分子轴的贝拉尔或三角扭曲； 3 (b) 围绕假想三重分子轴的 Ray-Dutt 或菱形扭曲；图4(c)具有悬空配体的五配位过渡态的键断裂。 5 根据低自旋三螯合 Fe (II) 配合物的动力学研究结果，得出结论：溶液中外消旋化的主要路径是分子内过程，并提出了扭曲机制。 6 如果中心离子是八面体、低自旋 d6 系统，则表明外消旋化与自旋态异构化是同步的。 9 具有三重态多重性和三棱柱几何形状的中间体被证明在能量上是有利的。在最近的一篇论文中，这些想法得到了观察结果的支持，即接近自旋交叉点的低自旋配合物表现出异常快速的外消旋动力学。 10 因此，在 [Fe (tpmbn)] 2" 1"(tpmbn=
Determination of the molecular mechanisms for intramolecular rearrangement reactions of chelate complexes is a long-standing problem. The proposed mechanisms for configurational race-mization in tris chelate and multidentate complexes include the following:(a) the Bailar or trigonal twist about the real threefold molecular axis; 3 (b) the Ray-Dutt or rhombic twist about the imaginary threefold molecular axis; 4 (c) bond rupture with five-coordinated transition states havingdangling ligands. 5 From the results of kinetic studies on low-spin, tris chelate Fe (II) complexes, it has been concluded that the major path for racemization in solution is an intramolecular process and twist mechanisms have been proposed. 6 In the case where the central ion is an octahedral, low-spin d6 system, it has been suggested that the racemization is synchronous with a spin-state isomerization. 9 An intermediate with triplet multiplicity and trigonal-prismatic geometry is shown to be energetically favorable. In a very recent paper these ideas are supported by the observation that low-spin complexes that are close to the spin-crossoverpoint exhibit un-usually rapid racemization kinetics. 10 Thus, in the case of [Fe (tpmbn)] 2" 1"(tpmbn=