Aullón Gabriel, Bernhardt Paul V, Bozoglian Fernando, Font-Bardía Mercè, Macpherson Brendan P, Martínez Manuel, Rodríguez Carlos, Solans Xavier
Departament de Química Inorgànica, Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain.
Inorg Chem. 2006 Oct 16;45(21):8551-62. doi: 10.1021/ic060720s.
We have investigated the isomeric distribution and rearrangement of complexes of the type [CoXLn]2+,3+ (where X = Cl-, OH-, H2O, and Ln represents a pentadentate 13-, 14-, and 15-membered tetra-aza or diaza-dithia (N4 or N2S2) macrocycle bearing a pendant primary amine). The preparative procedures for chloro complexes produced almost exclusively kinetically preferred cis isomers (where the pendant primary amine is cis to the chloro ligand) that can be separated by careful cation-exchange chromatography. For L13 and L14 the so-called cis-V isomer is isolated as the kinetic product, and for L15 the cis-VI form (an N-based diastereomer) is the preferred, while for the L14(S) complex both cis-V and trans-I forms are obtained. All these complexes rearrange to form stable trans isomers in which the pendent primary amine is trans to the monodentate aqua or hydroxo ligand, depending on pH and the workup procedure. In total 11 different complexes have been studied. From these, two different trans isomers of [CoClL14(S)]2+ have been characterized crystallographically for the first time in addition to a new structure of cis-V-[CoClL14(S)]2+; all were isolated as their chloride perchlorate salts. Two additional isomers have been identified and characterized by NMR as reaction intermediates. The remaining seven forms correspond to the complexes already known, produced in preparative procedures. The kinetic, thermal, and baric activation parameters for all the isomerization reactions have been determined and involve large activation enthalpies and positive volumes of activation. Activation entropies indicate a very important degree of hydrogen bonding in the reactivity of the complexes, confirmed by density functional theory studies on the stability of the different isomeric forms. The isomerization processes are not simple and even some unstable intermediates have been detected and characterized as part of the above-mentioned 11 forms of the complexes. A common reaction mechanism for the isomerization reactions has been proposed for all the complexes derived from the observed kinetic and solution behavior.
我们研究了[CoXLn]2 +、3 +型配合物（其中X = Cl -、OH -、H2O，Ln代表带有伯胺侧基的五齿13元、14元和15元四氮或二氮二硫（N4或N2S2）大环）的异构体分布和重排。氯配合物的制备程序几乎只产生动力学上优先的顺式异构体（其中伯胺侧基与氯配体呈顺式），可通过仔细的阳离子交换色谱法分离。对于L13和L14，所谓的顺式 - V异构体作为动力学产物被分离出来，对于L15，顺式 - VI形式（一种基于N的非对映异构体）是优选的，而对于L14(S)配合物，顺式 - V和反式 - I形式都能得到。所有这些配合物都会重排形成稳定的反式异构体，其中伯胺侧基与单齿水或羟基配体呈反式，这取决于pH值和后处理程序。总共研究了11种不同的配合物。从中，除了顺式 - V - [CoClL14(S)]2 +的新结构外，首次通过晶体学表征了[CoClL14(S)]2 +的两种不同反式异构体；所有这些都是以它们的高氯酸氯盐形式分离出来的。另外两种异构体已通过NMR鉴定并表征为反应中间体。其余七种形式对应于制备程序中产生的已知配合物。已经确定了所有异构化反应的动力学、热学和压力活化参数，这些参数涉及较大的活化焓和正的活化体积。活化熵表明配合物反应中氢键的程度非常重要，这通过对不同异构体形式稳定性的密度泛函理论研究得到证实。异构化过程并不简单，甚至还检测到了一些不稳定中间体，并将其表征为上述11种配合物形式的一部分。根据观察到的动力学和溶液行为，为所有这些配合物提出了一个共同的异构化反应机理。
