| Green chemistry is a frontier subject in current chemical research.The raw materials are more green in this new chemical process.The harmful products or by-products are eliminated in the chemical reactions.For green chemistry,the safety and selectivity of catalysts are one of the primary principles.Although liquid acid catalysts have been widely used in the past,their disadvantages such as corrosivity and pollution can not be ignored.Therefore,it is urgent to develop new solid acid catalysts.In addition,the catalytic selectivity of transition metal is very high,and it plays an significant role in the green synthesis of catalysts.In this paper,four transition metal Cadmium coordination complexes[Cd(L1)2(btp)2]n(1,CCDC:2006842),[Cd(L2)2(btp)2]n(2,CCDC:2038964),[Cd(L3)2(btp)2]n(3,CCDC:2070111),{[Cd(L1)2(btb)2]·2H2O}n(4,CCDC:2070112)were synthesized by bridge-linking different sulfonic acid ligands(HL1=p-toluene sulfonic acid,HL2=3-nitrobenzene sulfonic acid,HL3=4-nitrotoluene-2-sulphonic acid)and flexible bistriazole ligands btp and btb[btp=(1,3-bis(1H-1,2,4-triazole)propane;btb=1,4-bis(1H-1,2,4-triazole)butane]with transition metal Cadmium as the central metal ion.They were used as Lewis acid catalyst in green chemical reaction to investigate its catalytic activity.The spatial structure of them and the Biginelli reaction mechanism were studied by density functional theory(DFT).Three major contents are as follows:1.The btp and btb flexible ligands were prepared.Four crystal complexes were synthesized by hydrothermal method under the same condition at 90? for 60 h.Their structures were characterized.Complex 1belongs to Monoclinic crystal system,P2(1)/c space group.Complexes 2 and 3belong to the same Triclinic crystal system,P-1space group.Complex 4belongs to Orthorhombic crystal system and Pnna space group,each presents a chain-like or netlike spatial structure.2.The green catalytic performance of complexes 1-4 was studied using Biginelli reaction and Kabachnik-Fields reaction as probes,respectively.(1)They catalyzed Biginelli reaction under the solvent-free conditions.The optimum reaction temperature was 80?,and the ratio of n benzaldehyde:n ethyl acetoacetate:n methyl urea=1:1:1.1,dosage of catalyst is 2.5 mol%with complex1 as a catalyst for the synthesis of a series of 3,4-dihydropyrimidine.The product yield is 76.1-94.4%.(2)The catalytic property of the complexes 1 and 4 was examined in the Kabachnik-Fields under solvent-free conditions.The optimum reaction conditions are n benzaldehyde:n aniline:n diethyl phosphite=1:1:1.4,the reaction temperature=40? and catalyst dosage=5 mol%.The complex 1 still showed prior catalytic ability,and a series of?-amino phosphonates were synthesized.The product yield is 70.7-93.5%.The study showed the Cadmium complexes 1-4 as Lewis acid catalysts are in line with the concept of green environmental protection.The have advantages such as high selectivity,reusability,simple operation and easy recovery.3.The space structure,NBO charge distribution and frontier orbital distribution of ligands and complexes were calculated and analyzed by DFT.The coordination environment of crystal structure was well confirmed.The mechanism of the Biginelli reaction was verified,and the structure of four intermediates was optimized.What's more,two transition states were found.The calculation process is completed well using Gaussian 09 software package. |
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