Selective metal–ligand interactions have been used to prepare supramolecular bidentate ligands by mixing monodentate ligands with a suitable template. For these assemblies pyridine phosphorus ligands and a zinc(II) porphyrin dimer were used. In the rhodium-catalysed hydroformylation of 1-octene and styrene improved selectivities have been obtained for some of the assembled bidentate ligand systems. In the palladium catalysed asymmetric allylic alkylation similar effects were observed; the enantioselectivity increased by using a bisporphyrin template. The preparation of supramolecular catalyst systems was also explored using tin–oxygen interactions. Dihydroxotin(IV) porphyrin and carboxylic phosphorus ligands assemble into supramolecular ligands and the phosphorus donor atom coordinates to transition metals. The stronger oxygen–tin bond, compared to pyridine–zinc does not result in a better performance of the catalyst.
选择性
金属–
配体相互作用已被用于通过混合单齿
配体和合适模板来制备超分子双齿
配体。在这些组合中,使用了
吡啶膦配体和
锌(II)
卟啉二聚体。在
铑催化的1-
辛烯和
苯乙烯氢甲酰化反应中,一些组合的双齿
配体系统获得了更好的选择性。在
钯催化的不对称烯丙基烷基化反应中,也观察到了类似的效果;使用双
卟啉模板增加了对映选择性。还探索了利用
锡–氧相互作用制备超分子催化剂系统的方法。二羟
锡(IV)
卟啉和
羧酸膦配体组装成超分子
配体,膦供体原子与过渡
金属配位。与
吡啶–
锌相比,更强的氧–
锡键并未导致催化剂性能的提升。