Synthesis And Properties Of Titanocene(?)?-diketone Complexes

Titanium(?)complexes have attracted great attention of researchers because of their wide applications in single-electron transfer radical catalyzed reactions.The structure of the complex is one of the most important steps in determining its catalytic reactivity.The design,synthesis and basic properties of new titanocene(?)complexes can not only enrich the theoretical system of titanocene coordination chemistry,but also have important significance for understanding the relevant catalytic performance and further rationally designing single-electron transfer catalysts.Therefore,this thesis is devoted to the synthesis of a series of relatively stable new titanocene(?)complexes.Through structure characterization,property characterization and theoretical calculation,the structure-effect relationship of the novel titanocene(?)complexes is explored,which will be helpful for understanding free radical catalytic reactions of such type of complexes.The main research contents of this thesis are as follows:1)Bidentate ligands,?-diketones,are selected to synthesize ?-diketone titanocene(?)complex.The synthetic reactions are:Cp2Ti(?)Cl was firstly obtained by reduction of Cp2TiCl2 in naphthalene/sodium system and then sodium salts of?-diketones were synthesized through reaction sodium hydride with the ?-diketones and finally the desired products were given by the reaction of Cp2Ti(?)Cl and sodium salts of ?-diketones.Nine new ?-diketone titanocene(?)complexes were successfully obtained.In addition,two novel ?-diketone dichloropentamethylmonolocene titanium(?)complexes were obtained by reaction of Cp*TiCl3 and sodium salts of ?-diketones.This novel method has good substrate applicability,high product purity,cost-effectiveness and large-scale synthesis.2)Single crystal X-ray diffraction,electron paramagnetic spectroscopy(EPR)and fluorescence spectroscopy were used to systematically characterize the complex of?-diketone titaniumLocene(?).The single crystal structure analyses show that hydrogen bonding interaction(including aromatic hydrogen bonding)is common in the 11 new complexes.The coordination configurations of the ?-diketone titanocene(?)complexes and the ?-diketone dichloropentamethylmonotitanium(IV)complexes are of tetrahedron and pentahedron,respectively.The ?-? aromatic accumulation exists only in the molecules of benzoylacetonatodichloropentamethylmonotitanium(IV)complex.EPR analysis confirmed the existence of the titanocene(?)species.The substituents of the diketone ligands and the coordination solvent molecules exert effects on the g values and the crystal field splitting energy and the effects alter regularly.Freezing low-temperature EPR spectra indicate that each of the Ti(?)complexes is of an orthorhombic symmetric coordination environment.The single electrons distribute around the dz2 orbits most probably.3)DFT calculation results were used to study the structural stability of the complexes and to explore the relationship between the dihedral angles of O…O axis folding and the structural stability.The structure-effect between the structure and properties of the complexes were explored by conducting ground-state front-line orbitals,vertical excitation properties and ultraviolet-visible spectroscopy(UV-Vis)calculations,fluorescence spectrum calculations,spin density calculations,and charge transfer percentage calculations.