Their Chiral Synthesis Of Symmetric N₂O₂ Ligands And Zr(Ⅳ) Complexes

The research on the chiral metal compexes have been developed rapidely in the recently 20 years, which have all obtained the great success in both the basic research and the development chiraltechnology. The chiral metal complexes are mainly used on the chiral catalytic reaction as catalyzer. In recent years,some high activity chiral catalysts brought more and more people's attention. Previous studies in our group have showed that the tert-butyl substituted unsymmetrical N₂O₂ ligand affords a chiral dinuclear zirconium complex when it is reacted with ZrCl₄. In order to make further investigations on this promising subject, we have designed and synthesized six new unsymmetrical N₂O₂ ligands as well as the corresponding zirconium complexes. All the ligands and complexes have been characterized with ¹H-NMR, MS and EA.X-Ray single crystal diffraction reveals that zirconium complex containing the tert-butyl substituted N₂O₂ ligand is an oxo- and hydroxyl-bridged dinuclear structure, which is possibly formed by partial hydrolysis of chlorides at one of the zirconium centers. A tetranuclear zirconium complex has been obtained and chacaterized, which is formed by complete hydrolysis of the chlorides at the zirconium centers. The dinuclear zirconium complex crystallizes in a chiral space group as conglomerates.By changing the crystallization on conditions, such as method, solvent and temperature of the dinuclear zirconium complex, we have optimized the way for crystal growth and successfully prepared single crystals with proper sizes for further studies. Circlur dichroism analysis has been made on the chiral dinuclear zirconium complexes to find the relationship between the spatial configurations and the circlur dichroism signals of the two enantiomer complexes. In this chiral dinuclear zirconium complex there are three active chlorides atoms, which makes it a promising catalyst in some catalytic asymmetric reactions such as the carbometalation reaction, etc. This kind of compounds can be expected to find applications in the asymmetrical syntheses if the conglomerates could be resolved. Therefore, resolution methods and the possible applications of these chiral dinuclear Zirconium complexes in catalytic asymmetric reactions are worth further studying. Synthesis of chiral organometallic compounds from achiral materials, and their potential use in asymmetric organic reactions are of significance and will provide useful information for the research on the origin of the chirality.