Synthesis And Characterization Of Zirconium Complexes Supported By Amine Bridged Bis(Phenolato) Ligands And Their Catalytic Behavior Toward Hydroamination And Alkylation

This dissertation focuses on design, synthesis and characterization of a series of new zirconium complexes bearing amine-bridged bis（phenolato） ligands, and their application in hydroamination and alkylation reactions. All of these complexes were characterized by elemental analysis, IR, 1H and 13 C NMR spectroscopy, as well as X-ray single crystal diffraction for selected complexes. The influence of ligands on the synthesis, stability and reactivity of the zirconium bis（phenolate） complexes were elucidated. Furthermore, the catalytic behaviors of these complexes for hydroamination and alkylation reactions were studied.The amine bridged bis（phenol）s used in this thesis are :The main findings are listed below.1. Reactions of MX₄（M = Ti, Zr; X = NMe₂, CH₂Ph） with bis（phenol）s L¹H₂-L⁴H₂, bearing different amine bridges and different substituents gave neutral group 4 metal complexes L¹Zr（NMe2）₂（1）, L¹Ti（NMe2）₂（2）, L¹Zr（CH₂Ph）₂（3）, L²Zr（CH₂Ph）₂（4）, L3Zr（CH₂Ph）₂（5） and L⁴Zr（CH₂Ph）₂（6）. The catalytic behavior of complexes 1–6 for the intermolecular hydroamination reaction was studied. In general, hexacoordinate zirconium complexes 1–6 stabilized by either [ONNO]- or [ONOO]-type amine-bridged bis（phenolato） ligands were found to be efficient catalysts for the reaction of alkynes and amines in the presence of [Ph3C][B（C6F5）₄]（TB）. Excellent yields（up to >99%） and 100% regioselectivity for a broad range of terminal alkynes and anilines were observed within a reaction time of 1 h.2. Zirconium complexes L₅Zr（CH₂Ph）₂（7）,L⁶₂Zr（8）,L7Zr（CH₂Ph）₂（9） bearing [ONO]- type ligands were synthesized and characterized. The catalytic behaviors of complexes 7–9 for the hydroamination reaction were studied. In general, pentacoordinate dibenzyl zirconium complexes 7 and 9 stabilized by [ONO]- type amine-bridged bis（phenolato） ligands were found to be efficient catalysts for the reactions of alkynes and primary amines, which are in contrast to inactive hexacoordinate zirconium complexes 1–6.3. Cationic species derived from pentacoordinate dibenzyl zirconium complexes 7 and 9 showed high efficiency in catalyzing the hydroamination reactions of alkynes and secondary amines. Excellent yields（up to 93%） and 100% regioselectivity for a broad range of alkynes and aromatic secondary amines were observed within a reaction time of 4 h, which are the first examples of group 4 metal based catalysts capable of catalyzing intermolecular hydroamination of N-aryl/alkyl amines.4. Zirconium complexes L₈Zr（CH₂Ph）₂（10）,L⁹₂Zr（11） and L¹⁰Zr（CH₂Ph）₂（12） were synthesized, and catalytic activities in the alkylation reaction of pyridine derivatives were studied and compared with complexes 3 and 7. In general, pentacoordinate zirconium complexes 7, 10 and 12 stabilized by [ONO]- type amine-bridged bis（phenolato） ligands were found to be efficient catalysts for reaction of alkenes and o-C（sp2）–H of pyridine derivatives in the presence of [Ph3C][B（C6F5）₄]（TB）. Differ from the work reported using other cationic zirconium complexes, injection of H₂ into the reaction mixture was no longer necessary. Reactions of aliphatic alkenes with pyridine derivatives afforded selectively branched alkylation products, while those of aromatic alkenes afforded mianly the linear alkylation products.5. The catalytic behavior of complexes 3, 7 and 10 – 12 for the benzylic C（sp3）–H alkylation reactions of alkyl pyridines were studied. In general, zirconium complexes 7, 10 and 12 stabilized by [ONO]- type amine-bridged bis（phenolato） ligands were found to be efficient catalysts for reaction of alkenes and benzylic C（sp3）–H of α-alkyl pyridines in the presence of [Ph3C][B（C6F5）₄]（TB）. Branched alkylation products were obtained from the reactions of aliphatic alkenes with α-alkyl pyridines. Branched products formed as the majority when catalyzed by stronger Lewis acidic complexes bearing N-aryl-bridged bis（phenolato） ligands, while linear alkylation products were isolated when catalyzed by weaker Lewis acidic complexes bearing N-alkyl amine-bridged bis（phenolato） ligands. The substituents on the ligands framework also influence the regio-selectivity of reactions.