Synthesis Of New Cis-9,10-Dihydrophenanthrenediamide Ligands And Titanium Complexes Through Sequential C-C Bond-forming Reactions

Carbon-carbon bond-forming reactions have been one of the most active research areas in organic and organometallic chemistry. In particular, transition metal mediated carbon-carbon bond-forming reactions have been extensively studied for constructing the basic carbon backbone of small organic molecules and extended polymeric structures. Mechanistic studies for the transition metals mediated C-C bond-forming reactions indicate that the stoichiometric and catalytic C-C bond-forming reactions mediated by mid-and late-transition metals can take place through several pathways, such as reductive elimination, oxidative coupling, migratory insertion,σ-bond orπ-bond metathesis, while the reactions mediated by group 4 metals go mainly through the migratory insertion pathway, which operates without requiring redox changes at the metal center such as the cases happen in the Ziegler-Natta polymerization reactions. The group 4 metals also mediate C-C bond-forming reactions through the reductive elimination process. However, most commonly observed C-C bond-forming reductive elimination reactions involving group 4 metal complexes are the coupling reactions of alkyl, acyl, and 1-alkenyl groups. For the aryl-aryl bond-forming reductive elimination reactions mediated by group 4 metals, only very few examples have been reported so far although the analogous process on group 10 metals is well documented. On the other hand, the oxidative coupling of unsaturated organic compounds on low valent group 4 metals is an efficient pathway for the construction of carbon-carbon bond. In the oxidative coupling reactions, the low valent group 4 metals, such as Ti (II) or Zr (II) reagents, are usually generated by treatment of Ti (IV) or Zr (IV) complexes with Grignard or organolithium reagents, followed by a reductive elimination process. In principle, both the reductive elimination and oxidative coupling processes can be used to construct carbon-carbon bond. However, there is no example of forming two C-C bonds in one molecule utilizing the sequential reductive elimination and oxidative coupling reactions. Recently, in the attempt to synthesize a type of new titanium complexes, [ortho-C6H4(CH=NR)]2TiCl2, as potential olefin polymerization catalysts, some new titanium complexes with a cis-9,10-dihydrophenanthrene diamide ligand were obtained in high yields. These new titanium complexes are obviously produced through the sequential C-C bond-forming reductive elimination and oxidative coupling reactions from the original formed complexes [ortho-C6H4(CH=NR)]2TiCl2. To the best of our knowledge, this is the first example of utilizing such a sequential C-C bond-forming process to synthesize complexes of this type.In chapter two, six new titanium (IV) complexes with cis-9,10-dihydrophen anthrenediamide ligands, have been synthesized from the reactions of TiCl4 with 2 or 3 equiv of corresponding ortho-C6H4(CH=NR)Li by sequential intra-molecular C-C bond-forming reductive elimination and oxidative coupling reactions. Attempts to isolate the intermediates, [ortho-C6H4(CH=NR)]2 TiCl2 were unsuccessful. By following the reaction of TiCl4 with 2 equiv lithium salt of la at-50℃with 1H NMR spectroscopy, useful information for understanding the reaction mechanism was obtained.In chapter three, three symmetric and two asymmetric titanium (IV) complexes with cis-9,10-dihydrophenanthrenediamide ligands, have been synthesized from the reactions of TiCl2(O'Pr)2 with 2 equiv of same or different corresponding ortho-C6H4(CH=NR)Li by sequential intra-molecular C-C bond-forming reductive elimination and oxidative coupling reactions. Two new titanium (IV) complexes with ortho-metalated arylimine and symmetric cis-9,10-dihydrophenanthrenediamide ligands [cis-9,10-PhenH2(NR1)2] NR2)] TiO'Pr [R1= 2,6-iPr2C6H3, R2=2,6-Et2C6H3; R1=2,6-iPr2C6H3, 2,6-Me2C6H3], were also isolated from the synthetic systems for TiCl2(O'Pr)2 with 2 equiv of different corresponding ortho-C6H4(CH=NR)Li.In chapter four, five new cis-9,10-dihydrophenanthrenediamide compounds and seven other interesting compounds have been synthesized and isolated from the reactions of TiCl2(O'Pr)2 with 2 equiv of same or different corresponding ortho-C6H4(CH=NR)Li by sequential intra-molecular C-C bond-forming reductive elimination and oxidative coupling reactions. All different molecular structures of these compounds were determined by X-ray crystallography, 1H and 13C NMR spectroscopy. The special NMR spectroscopy of cis-9,10-dihydrophenanthrenedi amide derivatives due to the slow conformational change and its substituent group effect have been researched by variable-temperature NMR spectroscopy.In chapter five, three diffenent structures of Al complexes with cis-9,10-dihy drophenanthrenediamide ligands have been synthesized by AlMe3 with three cis-9,10-dihydrophenanthrenediamide ligands due to the different steric hinderance of different substituent group and characterized by elemental analysis, NMR spectra, and single crystal X-ray diffraction.