Ⅰ Activation Of C-H Bond In PC(sp~3)P-type Pincer Ligands By Electron-rich Iron, Cobalt And Nickel ComplexesⅡ Synthesis Of Novel Bis(2-iminopyrrolyl)Iron Complexes

The reaction of C-H bonds in hydrocarbons with transition metal complexes to form products containing metal-carbon bonds, namely "C-H activation", has been a topic of active study for decades because of the long-term goal of conducting selective synthesis with functionalized reactants or functionalized portions of more complex molecules. Due to the strength of C(sp3)-H bonds and the weakly coordinating nature of aliphatic moieties, the activation of unreactive C(sp3)-H bonds was much more difficult than C(sp)-H and C(sp2)-H bonds. Studies in this area are becoming more and more popular in these days.Pincer-type ligands belong to a family of tridentate ligands where the central anionic or neutral donor site is flanked by two neighboring donor groups. Their η3-mer coordination to transition metals gives rise to the formation of bicyclic structures that are often translated into robust materials featuring exceptional thermodynamic stability. This placed these fascinating compounds in a domain of very intensive research activity and eventually made them very popular in many branches of catalysis, basic organometallic and coordination chemistry. PC(sp3)P-type pincer complexes of nickel and platinum group metals have been synthesized through C(sp3)-H activation facilitated by pre-coordination of two phosphorus atoms. The strongly σ-donating anionic C(sp3) increases electron density at the metal center, which in combination with a high flexibility of the aliphatic scaffolds and the presence of labile hydrogens in a-and β-positions, induce bond activation/formation via dynamic interplay between carbometalated and a-or β-H eliminated species. These properties have made PC(sp3)P-type pincer complexes particularly useful in the activation of chemical inert bonds and small molecules, as well as in catalyzed reactions.However, research in this field has been mainly focused on Pd, Ru, Rh, Ir and Pt chemistry. The use of Fe, Co and Ni complexes are relatively underrepresented, although they have potentially lower cost and environmental impact.Despite2-iminopyrrolyl ligands having been used for a long time, interest in them has increased only more recently when employed as building blocks of a-olefin polymerization metal catalysts. So far,2-iminopyrrolyl metal complexes have covered most transition metals and main-group metals. However,2-iminopyrrolyl iron(II) complexes are extremely scarce because of their instability. So a new synthetic strategy need to be built for easy access to these interesting and robust complexes. Main contents of this dissertation are shown as follows:τ. Activation of C-H bonds in PC(sp3)P-type pincer lgands by electron-rich iron, cobalt and nickel comlexes.By facile N-P bond formation,7new PC(sp3)P-type pincer ligands base on dipyrrolemethane backbones (L1-L7) were synthesized and characterized.The reactions of L1with Fe(PMe3)4, Co(PMe3)4, Co(Me)(PMe3)4, Ni(PMe3)4and Ni(Me)2(PMe3)4were explored. Two pincer-type complexes [PCHP]Fe(H)(PMe3)2(1) and [PCHP]Co(PMe3)2(3) were synthesized in the reaction of L1with Fe(PMe3)4and Co(Me)(PMe3)4. L1reacted with Co(PMe3)4and Ni(PMe3)4to afford Co(0) and Ni(0) complexes [PCH2P]Co(PMe3)2(2) and [PCH2P]Ni(PMe3)2(4).The reaction of L2-L7with Co(Me)(PMe3)4were studied. L2reacted with Co(Me)(PMe3)4to give a similar pincer complex7, L3-L5gave rare examples of cobaltacyclopropane complexes (8-10) through cyclometallation followed by β-H elimination reaction. L6gave a C(sp2)-H activation product11.New complexes were characterized by IR and NMR spectrum. Some single crystals were analyzed by X-ray diffraction techniques.2. Synthesis of novel bis(2-iminopyrroly) iron complexesA simple method for access to bis(2-iminopyrrolyl) iron complexes were discribed. The reactions of Fe(PMe3)4with six different2-iminopyrroles afforded novel bis(2-iminopyrrolyl) iron complexes (12-17).New complexes were characterized by IR and NMR spectrum. Some single crystals were analyzed by X-ray diffraction techniques.