1. The Synthesis And Properties Of High-valent Transition-metal Phosphonio-methyliden/yne Complexes 2. The Application Of Electron-rich Cobalt Complexes In C-H Bond Activation

The discovery of ferrocene in the 1950s is a milestone in the development of organometallic Chemistry.During these 50 years,the research of transition metal organic compounds has made great achievements.The application of these compounds in organic synthesis and catalytic fields has promoted the development of organic chemistry greatly. Currently,transition metal organic compounds have been used for hydrogenation, dehydrogenation,oxidation,reduction,isomerization,carbonylation,hydroformylation, carboxylation,polymerization reaction.The synthesis and properties of metal-carbyne complexes is always a hot topic in the research field of organometallic chemistry since the first synthesis of transition metal complexes with a formal metal-carbon triple bond reported by E.O.Fischer et al.in 1973. Since these compounds have various particular reactions in organic synthesis,especially in vitamins,peptides,synthesis of anti-cancer drugs and natural products,and as olefins, alkyne polymerization catalysts demonstrated its unique advantages and broad application prospects.Due to the difficulty synthesis of the metal-carbyne complexes and their complicated reaction,the development of metal-carbyne is not perfect until now.The functional group linked to carbyne carbon has a strong effect on the reactivity and strength of metal-carbon triple bond.The phosphorous ylide carbyne complexes as a kind of special carbyne complexes(M≡C—PR₃??M = C =PR₃ ) could be regarded as a double-metal substituted complex of phosphorous ylide and they have special chemical properties with application potential in organic synthesis and catalysis.Very few examples of high-valent transition metal phosphonio methylidyne complexes with d⁰ electron configuration are known so far.This part of dissertation mainly concerns the synthesis and properties of high-valent transition metal phosphonio methylidene/yne complexes with d⁰ electron configuration.The main contents are shown as follows:1.Formation of high-valent transiton metal tantalum ylide adduct complexesThe synthesis and chemistry of transition-metal phosphonium ylide complexes have been extensively investigated.Interet in this class of organometallic complexes arises principally because these complexes may be important intermediates in catalytic reactions and are considered potential catalysts for new processes.Additionally,however, ylide complexes are beginning to be exploited in stoichiometric organometallic chemistry as versatile substrates for further synthetic manipulation:essentially the same reason phosphonium ylides are used so extensively in organic synthesis,and ylide complexes can be as a precursor for the formation of phosphonio methylidyne complexes of trasition metal with d⁰ electron configurations.Herein we employed(Et₂N)₃P=CH₂ ylide and studied their reaction with cyclopentadienyl(Cp) tantulum(V) tetrachloride and pentamethylcyclopendienyl(Cp*) tantulum(V) tetrachloride,and finally two ylide adduct complexes trans-CpTaCl₄[H₂C-P(NEt₂)₃](4) and trans-Cp*TaCl₄[H₂C-P(NEt₂)₃] (5) and an ionic complex[H₃C-P(NEt₂)₃][Cp*TaCl₅](7) were obtained.2.The simply synthesis and property of high-valent transition titanium phosphonio methylideneA simple synthesis ofα-phosphonio(methylidene) complexes of titanium [Cp*TiCl₂(=CH-PPh₃)](8) was obtained from transylidation reactions of pentamethylcyclopentadienyl titanium trichloride Cp*TiCl₃ with 2 equiv of Ph₃P=CH₂. Because of the smaller atomic radius of titanium and the bigger steric hindrance of Cp* and PPh₃,more than two molecular of ylide,LiN(SiMe₃)₂ and NaN(SiMe₃)₂ were used to depronated another phosphonium chloride from complex 8 in order to obtain phosphonio-methylidyne or ylide-bridged metallacycle complex,but failed.These unexpected dinuclear[Cp*Ti(μ-Cl)Cl]₂(9) and trinuclear[Cp*Ti(μ-Cl)Cl]₃(10) titanium(â…¢) complexes were formed through reduction reaction of complex 8 with CO.3.The synthesis and properties of high-valent transition tantulum phosphonio methylidyneTheα-phosphonio(methylidyne) complexes of tantalum CpTa(≡C—PPh₃)(=CH-PPh₃) ₂(11) was obtained from transylidation reactions of cyclopentadienyl tantalum tetrachloride CpTaCl₄(1) with 7 equiv of Ph₃P=CH₂.In order to improve the yield and the stablity of the carbyne complexes,thiophenol group was introduced to connect to the tantalum center of compound 1.And "one pot" ylide transylidation reactions were carried out and the carbyne complexes(12-19) were also obtained. Cp*TaCl₄(CH₂=PPh₃)(6) can be got from the reaction of Cp*TaCl₄ with one equiv of Ph₃P=CH₂,and regioselective deprotoned by the different bases Ph₃P=CH₂,(Me₃Si)₂N^-and pyridine to giveα-phosphonio(methylidyne) complexes of tantalum(21) and complex(20) coordinated by two methylene groups.The properties of carbye compound 11 has also been studied.For example,the addition reaction with small molecular,the metathetical reaction with alkynes and Wittig reaction to prepare high-valent transtion-metal allenylidene complexes.The reactions with small molecular,the main products maybe further proved;the metathetical reaction was effect by the polarity and spatial property of alkynes;and the Wittig reaction were carried out to stand the intermediate(24).All of the new complexes are characterized by IR,¹H,¹³C and ³¹p NMR.Structrures of some single crystals have been confirmed by X-ray diffraction techniques.