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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Synthesis of mixed Ar,Ar'-BIAN ligands(Ar,Ar'-BIAN = bis(aryl)acenaphthenequinonediimine).Measurement of the coordination strength of hemilabile ligands with respect to their symmetric counterparts
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Synthesis of mixed Ar,Ar'-BIAN ligands(Ar,Ar'-BIAN = bis(aryl)acenaphthenequinonediimine).Measurement of the coordination strength of hemilabile ligands with respect to their symmetric counterparts

机译：混合的Ar，Ar'-BIAN配体的合成（Ar，Ar'-BIAN =双（芳基）ac萘醌二胺）。半不稳定配体相对于对称配体的配位强度的测量

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The synthesis of Ar,Ar'-BIAN ligands(Ar,Ar'-BIAN = bis(aryl)acenaphthenequinonediimine)having different aryl groups bound to the two nitrogen atoms is reported for the first time.The ligands were obtained by two different strategies:(I)by a transimination reaction starting from a symmetric Ar,Ar-BIAN ligand having aryl groups bearing strongly electron-withdrawing substituents or(II)by a two-step-one-pot sequence.The ligands synthesized have been chosen so that the electronic difference between the two aryl groups is very large,but the steric difference is variable and,in one case,the ligand is almost sterically symmetric.The coordination strength of the new ligands towards three palladium complexes has been measured by a competition experiment following a protocol previously described by us.The coordination strength of the mixed ligands is the mean of those of the corresponding symmetric counterparts.The X-ray crystal structure of a palladium n-allyl complex of the electronically asymmetric-sterically symmetric ligand(3,5-(CF_3)_2C_6H_3),(3,5-Me_2C_6H_3)-BIAN has been solved,together with those of the two symmetric analogues to allow a comparison.Despite the fact that the dodecafluorinated ligand has a AT_(eq)value about three orders of magnitude lower than the non-fluorinated counterpart,no notable difference is observed in the N-Pd and Pd-C_(allyl)distances in the three complexes.Calculations at the density functional level confirm that Pd-BIAN distances are not strictly correlated to the coordination energies,which are in qualitative agreement with the spectroscopic evidence.The bond length is thus not a good indication of the bond strength in these cases.
机译：首次报道了在两个氮原子上键合不同芳基的Ar，Ar'-BIAN配体（Ar，Ar'-BIAN =双（芳基）ac萘醌二亚胺）的合成，这些配体是通过两种不同的策略获得的： （I）通过具有芳基的带有强吸电子取代基的对称Ar，Ar-BIAN配体开始的氨基转移反应，或（II）通过两步一锅法序列进行合成反应。两个芳基之间的电子差异很大，但空间差异是可变的，在一种情况下，配体几乎是空间对称的。新的配体对三种钯配合物的配位强度是通过竞争实验测定的。我们先前描述的方案。混合配体的配位强度是相应对称配位体的配位强度的平均值。电子不对称钯n-烯丙基配合物的X射线晶体结构立体对称的配体（3,5-（CF_3）_2C_6H_3），（3,5-Me_2C_6H_3）-BIAN已与两个对称类似物的配体一起被解析，可以进行比较。尽管十二氟化配体具有AT_（eq）值比非氟化物低约三个数量级，三种配合物的N-Pd和Pd-C_（烯丙基）距离均未观察到明显差异。在密度泛函水平上的计算证实Pd-BIAN距离与配位能并不严格相关，这与光谱证据在质量上是一致的。因此，键长不能很好地表明这些情况下的键合强度。

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