| Aryl halides(ArX)have rather limited applications in organic synthesis due to the inertness of their carbon-halogen bonds.Improving the low reactivity of aryl halides is an extremely challenging topic in modern synthetic chemistry.Compared with iodoarenes and bromoarenes,the C-Cl and C-F bonds in chlorinated and fluorinated arenes have higher bond energy and are less likely to be activated.The transition metal complexes play an important role in the activation and functionalization of the C-Cl bonds and C-F bonds of halogenated aromatics,and new organometallic compounds and organic compounds are also constructed while activating the inert bonds.Among them,organometallic compounds can be used in the field of homogeneous catalysis,while new organic compounds have wider application value in the fields of medicine and chemical industry due to the introduction of the aryl moiety of halogenated aromatics.Organosilicon compounds are ubiquitous in people’s daily life and industrial production.Transition metal-catalyzed hydrosilylation of alkenes is considered to be one of the most efficient methods for the synthesis of organosilicon compounds,and most of the catalysts used are metal halides supported by bidentate or pincer ligands,and metal halides supported by monodentate ligands are less reported.In mechanistic studies,transition metal hydrides are considered as key intermediates in catalytic reactions.The reduction of aldehydes and ketones is very important in organic synthesis,and transition metal-catalyzed hydrosilylation of aldehydes and ketones is an economical and efficient method to realize the reduction of aldehydes and ketones,in which metal hydrides are widely used as catalysts for hydrosilylation of aldehydes and ketones.In this paper,a series of iron,cobalt and nickel aryl chlorides and hydrides were synthesized by using electrophilic Fe(PMe3)4,Co(PMe3)4 and Ni(PMe3)4 while realizing C-X bond activation,and their reaction properties and catalytic activities were studied.The specific research content is divided into the following two parts:1.Synthesis of novel aryl metal chlorides and their catalytic effect on hydrosilylation of alkenes.A variety of novel aryl iron,cobalt and nickel chlorides were synthesized by the reaction of electrophilic Fe(PMe3)4,Co(PMe3)4 and Ni(PMe3)4 with 3-chloro-2,4,5,6-tetrafluoropyridine,chloropentafluorobenzene and 3-chloropyridine,respectively.The synthetic compounds were characterized,and the properties of the complexes were investigated,focusing on the catalytic effect of aryl cobalt chlorides on the hydrosilylation of alkenes.The results show that the tetrafluoropyridine cobalt chloride complex is the optimal catalyst for hydrosilylation of alkenes.The catalytic reaction can be carried out under mild conditions(40℃)with the addition of NaBHEt3,and the catalytic system has high conversion and good selectivity for most substrates.Aryl alkenes mainly delivered Markovnikov addition products,while aliphatic alkenes mainly afforded anti-Markovnikov addition products.In addition,the possible mechanism of catalytic reaction was proposed.As monodentate ligand chlorides,the catalytic system is simpler to synthesize than bidentate ligand and multidentate ligand chlorides.2.Catalytic activity of iron hydrides supported by fluoroimine ligands for the hydrosilylation of aldehydes and ketones.Using Fe(PMe3)4 to react with different fluoroimine ligands,the fluoroimine ligand-supported iron hydrides were synthesized while realizing the selective activation of C-F/C-H bonds.In addition,the effect of Lewis acid MgBr2 on the selective activation of C-F/C-H bond was studied,and a new type of fluorinated aryl iron bromide was synthesized.The results show that when phenylsilane was used as the hydrogen source and THF as the solvent,the iron hydrides could effectively catalyze the hydrosilylation of aldehydes and ketones.And the mechanism of the catalytic reaction was preliminarily studied. |
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