Synthesis Of Iron, Cobalt, Nickel Pincer Complexes And Their Applications In Catalytic Carbon-Carbon Cross-Coupling Reaction

The direct functionalization of hydrocarbons to various useful chemicals via transition-metal-mediated selective C-H bond activation has now become a major topic of research. Until recently, the majority of the catalytic processes reported were applicable to only sp2 C-H bonds. Owing to the strength of sp3 C-H bonds and the weakly coordinating nature of aliphatic moieties, the activation of unreactive sp3 C-H bonds was much more difficult. Transition metal complexes with pincer ligands have attracted a substantial amount of interest. However, research activity in this field has also mainly focused on sp2-carbon (rigid phenyl ring backbone) rather than sp3-carbon-based (aliphatic backbone) compounds. Pd, Ru, Rh and Ir-based catalysts have attracted much more attention in C-H activation and catalysis. Fe, Co and Ni complexes are relatively underrepresented, although they have potentially lower cost and environmental impact.Main contents of this dissertation are shown as below:1. The application of Fe, Co and Ni complexes in the activation of C-H bonds, especially sp3 C-H bonds. C(sp2/sp3)-cyclometalated complexes were obtained under mild conditions, and sp3 C-H bond was selectively methylated in iron complex. In our investigation, the pre-coordination of two donor atoms from the substrate can facilitate the interaction between C-H bonds and metal center and results in an easier and highly selective C-H bond cleavage. Oxidative addition and proton abstraction mechanism play the same important role. New complexes are characterized by IR and NMR. Structrures of some single crystals have been confirmed by X-ray diffraction techniques.2. Under the investigation of the first part, we reasoned that the PCP-Ni complex might be able to promote the coupling of alkyl halides with nucleophiles. This protocol proves productive and unactivated alkyl halides could be coupled with phenylethynyl-and trimethylsilyethynyllithium reagents at room temperature efficiently. In comparison with the traditional ways in preparing the corresponding substituted alkynes, which were carried out in liquid ammonia, this simple system shows much advantage.