Synthesis,Structures And Properties Of Pyrrolyl Mono/Bimetal Compounds

As one of the most abundant C1 resources on the planet,carbon dioxide has the advantages of being safe,non-toxic,non-flammable,inexpensive,readily available,abundant in reserves,and renewable.The method for effectively converting and preparing carbon dioxide into high value-added chemicals has received widespread attention in the academic community.Various types of catalysts have been developed to achieve the chemical fixation of carbon dioxide.Because of its non-toxicity and rich earth content,aluminum metal has attracted widespread attention from chemists.In recent years,some mono-or bi-metal aluminum complexes using salen,salophen,etc.as ligands have been reported as catalysts to catalyze the formation of cyclic carbonates from CO2 and epoxides.However,during the reaction,there are problems that the catalyst loading is high,the reaction time is relatively long,and the catalytic activity is easily restricted by the environment.Due to its metal-metal synergy,organic aluminum lithium bimetal compounds can effectively improve the performance of single metal components compared to single metal reagents,and can show better reactivity under mild reaction conditions.1.After extensive literature research and preliminary work by the research group,the research purpose of this paper is to synthesize a series of organoaluminum lithium bimetallic compounds through pyrrole ligands with butyl lithium reagent and alkyl aluminum.X-ray single crystal diffraction characterizes the structural information of the complex.They were used as catalyst to catalyze CO2 and epoxide to form cyclic carbonate.The specific research work is as follows:pyrrole ligand C4H3NH(2-CH2NH(Bu)undergoes an alkali metallation reaction with nBuLi,after adding aluminum alkyl reaction,four organolithium aluminate compounds are obtained:{C4H3N(AlMe3)[2-CH2NH(tBu)Li(TMEDA)]}·C7Hg(2a),{C4H3N(AlMe2)[2-CH2N(tB u)Li(TMEDA)]}(2b),{C4H3N(AlEt3)[2-CH2NH(tBu)Li(TMEDA)]}(2c),{[C4H3N(AlE t3)(2-CH2NHLitBu)][C4H3NLi(2-CH2NHtBu)]} 2(2d)The single crystal structure of compounds 2a-2d will be obtained and characterized by nuclear magnetic analysis.The compounds 2a-2d were used to catalyze the reaction of carbon dioxide and epoxide to synthesize cyclic carbonates Experiments showed that the complex 2d was used in combination with tetrabutylammonium iodide(TBAI),and showed better performance than other organo-aluminum lithium bimetal compound.The reaction was performed at 50?and 1 atm CO2 pressure.Different cyclic carbonates obtained with a yield of 62-99%2.During the study of pyrrolyl aluminum-lithium compounds,we also synthesized[C4H3N(2-CH=N'Bu)K(THF)](3a)and[C4H3N(2-CH2NHtBu)K](3b)Two potassium metal compounds were characterized by nuclear magnetic resonance and X-ray single crystal diffraction analysis.The structure of complex 3a exists in the form of a one-dimensional zigzag coordination polymer in the solid state.And complex 3b is a two-dimensional supramolecular network.The synthesized 3a and 3b are used to catalyze the cyclization trimerization reaction of isocyanate.When the catalyst 3a is loaded at 0.25 mol%and THF is the solvent,it can have a higher catalytic activity,and the yield can reach more than 99%.