Application Of Electron-rich Cobalt And Iron Complexes In C-X(X=H, F) Bond Activation

Cobalt and Iron belong toⅧfamily of transition metals. Because of their fine coordination activity and relatively low price, they have been widely used in organic synthesis, industrial catalysis, etc. Trivalent phosphine as a strong ligand can form stable complexes with transition metals, and can be widely found in organometallic compouds. Organocobalt and Organoiron compounds supported by trimethylphosphine have high reaction activity and selectivity.1. Reaction of the complexes containing [S-Fe-H] fragment supported by trimethylphosphine with alkynesA [M-H] moiety in hydrido compounds of transition metals can react with alkenes or alkynes giving rise toσ-alkyl orσ-alkenyl metal compounds.Metallothionein complex is a common regulator in biological electron transfer, metallothionein complexes exist in the basic catalyst and biological processes. Therefore, the study of this domain has been a hotspot in the fields of coordination chemistry for recent years.Reactions of thiophenolato hydrido iron(Ⅱ) complexes with alkynes afforded bisalkynyl iron(Ⅱ) complexes (7,9,10). The novel complexes were isolated and characterized.2. Application of CoMe(PMe3)4 with caffeinePurine derivatives are an important class of pharmaceutical intermediates. Addition of 8-position substituent is of particular interest with reference to their bioavailability such as antivirus, anticancer and lowering blood pressure.The novel cobalt(Ⅰ) complex 11 was prepared by reaction of caffeine with CoMe(PMe3)4. Reactions of the cobalt(Ⅰ) complex 11 with bromobenzene, 2-bromopyridine, bromopentafluorobenzene and 4,4'-diiodobiphenyl afforded complex 12 and 17. At the same time, the expected C-C coupling products 14,15 and 16 were obtained. It was a stoichiometric reaction, however, it may be a synthetically useful route for the generation of 8-position substituent.3. Reation of Co(PMe3)4 with perfluoroareneThe study of C-F bond activation has important significance and value. Mastery of the activation of C-F bond will help us to study the new fluorinated organic synthesis, and to solve the increasingly serious problem of environmental pollution. Our group has successfully achieved C-F bond activation using cobalt complexes supported by trimethylphosphine with octafluorotoluene and octafluoronaphthalene.In this study, based on a detailed study of the reaction of Co(PMe3)4 with octaflurotoluene, the reaction mechanism involving the synergistic effect between trimethyl phosphate and Co(PMe3)4 was proposed, for the first time.Reactions of Co(PMe3)4 with hexafluorobenzene, pentafluoropyridine and decafluorobiphenyl in mild conditions afforded C-F activated products(24,26,27,29). During the reaction of Co(PMe3)4 with pentafluoropyridine, a novel dinitrogen complex of cobalt with the dinitrogen molecule bonded in a "sideways" fashion to Cobalt atom, which will show favorable development prospects in the fixation of N2When we treated the Co(I) 22 with bromopentafluorobenzene, the expected C-C coupling products wasn't isolated. However, the Co(Ⅲ) complex 33 was unexpectedly obtained during the addition of hydrochloric acid into the reaction.Reaction of fluorinated arene with Co(PMe3)4 under 1 bar of CO prepared new dicarbonyl compounds(35,36,37,38).4. Reation of Fe(PMe3)4 with perfluoroareneReactions of Fe(PMe3)4 with a series of perfluoroarene in mild conditions afforded C-F activated products (39,42,43,46), which are similar with the products of Co(PMe3)4 with perfluoroarene.Reactions of Fe(PMe3)4 with pentafluoropyridine afforded hydrido iron(Ⅱ) complex 43. A mechanism for the formation of 44 is proposed.During the reaction of Fe(PMe3)4 with octafluoronaphthalene, theπcoordinated intermediates (47) was isolated.5. Reation of Co(PMe3)4 and Co(PMe3)4Me with perfulorobenzaldiminesReaction of Cobalt complexes supported by trimethylphosphine with perfulorobenzaldimines instead of orthofulorobenzaldimines entirely afforded C-F activated products. It proved that the electrophilic capacity of aromatic ring carbon atom enhances with the increase of fluorine atoms. Reaction of Co(PMe3)4 with perfulorobenzaldimines gave rise to the new complexes(60,63,66). Specially, the complex 63 is the product of bicyclometalation reaction at the same central atom by the activation of C-H bond and C-F bond. Reactions of [CoMe(PMe3)4] with perfulorobenzaldimines proceed by oxidative addition of the C-F bond to give rise to the ortho-metalated diorgano cobalt (Ⅲ) fluorides 67 and 68.6. C-C Coupling reaction of octafluorotoluene with Grignard reagent Functionalization of C-F bond is the target of chemists. Literature reports on this kind of reaction are mainly concentrated on Palladium and Nickel compleses as catalysts. The catalysts have the advantage of mild reaction conditions, high yield, wide applicability, they also have the following several shortcomings:(1) the price of Palladium is expensive; (2)Palladium and Nickel complexes are toxic; (3) Catalytic reaction often requires expensive and highly toxic phosphorus ligands. In 1971, Kochi reported the cross-coupling reaction between Grignard reagents and alkenyl halides or aromatic halides in the.presence of catalyst of low-cost and low toxicity of iron. Take this opportunity to a class of new catalysts in the chemical stage of history.The C-C coupling reactions of octafluorotoluene with Grignard reagent were primarily studied using FeCl2 and PMe3 as the catalysts, respectively. Self-coupling products were mainly obtained with FeCl2 as the catalyst, while the cross-coupling products were prepared with PMe3 as the catalyst. A possible reaction mechanism was proposed. The catalytic reaction is only a preliminary exploration. The reaction conditions may be optimized by adjusting the reaction time, solvent, catalyst amount, and additives.All of the new complexes are characterized by IR,1H NMR,13C NMR and 31P NMR. Structures of some compounds have been confirmed by X-ray diffraction techniques.