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首页> 外文期刊>Chemistry: A European journal >Structures and interligand interaction pattern of phosphoramidite Pd complexes by NMR spectroscopy: Modulations in extended interaction surfaces as stereoselection mode of a privileged class of ligands
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Structures and interligand interaction pattern of phosphoramidite Pd complexes by NMR spectroscopy: Modulations in extended interaction surfaces as stereoselection mode of a privileged class of ligands

机译：NMR光谱分析亚磷酰胺Pd配合物的结构和配位体相互作用模式：扩展相互作用表面中的调制作为特权级配体的立体选择模式

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During the last decade, phosphoramidites have been established as a so-called privileged class of ligands in various transition metal catalyses. However, the interactions responsible for their favorable properties have hitherto remained elusive. To address this issue, the formation trends, structural features, and interligand interaction patterns of several trans- and cis-[PdLL′Cl_2] complexes have been investigated by NMR spectroscopy. The energetic contribution of their interligand interactions has been measured experimentally using the supramolecular balance for transition-metal complexes. The resulting energetics combined with an analysis of the electrostatic potential surfaces reveal that in phosphoramidites not only the aryl groups but the complete (CH)CH_3Ph moieties of the amine side chains form extended quasi-planar CH-π and π-π interaction surfaces. Application of the supramolecular balance has shown that modulations in these extended interaction surfaces cause energetic differences that are relevant to enantioselective catalysis. In addition, the energetics of these interligand interactions are quite independent of the actual structures of the complexes. This is shown by similar formation and aggregation trends of complexes with the same ligand but different structures. The extended quasi-planar electrostatic interaction surface of the (CH)CH_3Ph moiety explains the known pattern of successful ligand modulation and the substrate specificity of phosphoramidites. Thus, we propose modulations in these extended CH-π and π-π interaction areas as a refined stereoselection mode for these ligands. Based on the example of phosphoramidites, this study reveals three general features potentially applicable to various ligands in asymmetric catalysis. First, specific combinations of alkyl and aryl moieties can be used to create extended anisotropic interaction areas. Second, modulations in these interaction surfaces cause energetic differences that are relevant to catalytic applications. Third, bulky substituents with matching complementary interaction surfaces should not only be considered in terms of steric hindrance but also in terms of attractive and repulsive interactions, a feature that may often be underestimated in asymmetric catalysis.
机译：在过去的十年中，亚磷酰胺已被确立为各种过渡金属催化剂中所谓的特权级配体。然而，迄今为止，对其有利性质负责的相互作用仍然难以捉摸。为了解决这个问题，已经通过NMR光谱研究了几种反式和顺式[PdLL'Cl_2]配合物的形成趋势，结构特征和配体相互作用模式。它们的配体相互作用的能量贡献已经使用过渡金属络合物的超分子平衡进行了实验测量。所得的能量学与对静电势表面的分析相结合表明，在亚磷酰胺中，不仅芳基基团，而且胺侧链的完整（CH）CH_3Ph部分都形成了扩展的准平面CH-π和π-π相互作用表面。超分子平衡的应用表明，在这些扩展的相互作用表面中的调节引起与对映选择性催化有关的能量差异。另外，这些配位体相互作用的能量学完全不依赖于配合物的实际结构。具有相同配体但结构不同的复合物的相似形成和聚集趋势表明了这一点。 （CH）CH_3Ph部分的扩展的准平面静电相互作用表面解释了成功进行配体调节的已知模式以及亚磷酰胺的底物特异性。因此，我们建议在这些扩展的CH-π和π-π相互作用区域中进行调制，作为这些配体的精细立体选择模式。基于亚磷酰胺的实例，本研究揭示了三个潜在的潜在特征，这些特征可能适用于不对称催化中的各种配体。首先，烷基和芳基部分的特定组合可以用于产生扩展的各向异性相互作用区域。其次，这些相互作用表面中的调节导致与催化应用有关的能量差异。第三，具有互补互补相互作用表面的大取代基不仅应考虑空间位阻，而且还应考虑吸引和排斥相互作用，这在不对称催化中常常被低估。

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