Synthesis Of Aluminum Complexes Stablized By Schiff-base Ligands And Their Performance In The Synthesis Of Cyclic Carbonates

In this paper,using bridged schiff-base ligands(salen type ligands)as starting materials,a series of complexes were synthesized and characterized by elemental analysis,FT-IR,NMR and X-ray single crystal diffraction.What's more,the catalytic behavior of the aluminum complexes for the cycloaddition of epoxide and carbon dioxide was also studied.The main results are summarized as follows:1.The reaction of salen ligand[(3,5-tBu2-2-(OH)C6H2)CH=N-C6H4OCH2]2(L1H2)with AlMe3 in the molar ratio of 1:1 led to the formation of the momometallic aluminum complex L1AlMe(1)and the methyl migration complex L1 Al(2)[L1'=(2-0-3,5-tBu2C6H2)CH=NC6H4OCH2CH2OC6H4NCH(Me)(2'-O-3',5','Bu2C6H2)].A large number of 2 were obtained by increasing the temperature to 110 ? and extending the reaction time.2.The reactions of salen ligands L1H2,[(3,5-(CMe2Ph)2-2-(OH)C6H2)CH=N-C6H4OCH2]2(L2H2)and[((3-'Bu-5-Me)-2-(OH)C6H2)CH=N-C6H4OCH2]2(L3H2)with AlEt3 in the molar ratio of 1:1 led to the formation of the hydrogen migration compounds L1"Al(3)[L1" =(2-O-3,5-'Bu2C6H2)CH=NC6H4OCH2CH2OC6H4NCH2(2'-O-3',5'-'Bu2C6H2),L2'Al(4)[L2'=(2-O-3,5-(CMe2Ph)2C6H2)CH=NC6H4OCH2CH2OC6H4NCH2(2'-0-3',5'-(CMe2Ph)2C6H2)and L3'Al(5)[L3'=(2-0-3-'Bu-5-MeC6H2)CH=NC6H4OCH2CH2OC6H4NCH(Me)(2'-0-3'-'Bu-5'-MeC6H2)].3.The reaction of salen ligand[(3,5-Cl2-2-(OH)C6H2)CH=N-C6H4OCH2]2(L5H2)with Al(?)in the molar ratio of 1:1 led to the formation of the dimetallic aluminum complex L43Al2(7)and no migrated product was obtained.4.Treating the non-bridged schiff-base ligands 3,5-'Bu2-2-(OH)C6H2CH=N-2-OCH3C6H4(L6H2)and 3,5-'Bu2-2-(OH)C6H2CH=N-2-CH3C6H4(L7H2)with AlMe3 in the molar ratio of 1:1,the monometallic aluminum complexes L6AlMe2(8)and L7AlMe2(9)were obtained.Treating ligand L6H2 with AlEt3 in the molar ratio of 1:1,the monometallic aluminum complex L1(AlEt2)2(10)was obtained.The alkylation reactions proceeded completely and no migrated products were obtained.5.Treating salen ligands L1H2 and L2H2 with AlMe3 in the molar ratio of 1:2,the bimetallic aluminum complexes L1(AlMe2)2(11)and L2(AlMe2)2(12)were obtained.Treating ligand L1H2 with AlEt3 in the molar ratio of 1:2,the bimetallic aluminum complex L1(AlEt2)2(13)was obtained.The alkylation reactions proceeded completely and no migrated products were obtained.6.The catalytic property of the complexes in the presence of quaternary ammonium salt for cyclic carbonate synthesis by the coupling reaction of 1,2-Epoxyhexane with carbon dioxide was studied.Through the optimization of reaction conditions,the optimum reaction conditions are 0.3 mol%of 3 and 0.9 mol%of NBu4Br,100 ?,atmospheric pressure.Furthermore,the cycloaddition of a series of monosubstituted terminal epoxides and carbon dioxide were commendably generated the corresponding cyclic carbonates in good to excellent yields(75 to 97%).The substituents included halogen,aryl,alkenyl,ether,ester groups and so on.Simultaneously,with the conditions of 1 mol%of 3 and 3 mol%of NBu4Br,100 ?,atmospheric pressure,the cycloaddition of a series of disubstituted epoxides(such as cyclopentene oxide,3,4-epoxy tetrahydrofuran and cyclohexane oxide)and carbon dioxide were commendably generated the corresponding cyclic carbonates in good to excellent yields(66 to 86%).7.The reaction of L1Na2 with LnCl3,and then reaction with NaOAr(ArOH =2,6-Bu'2-4-MeC6H2OH)afforded the corresponding salen rare-earth metal aryloxides L1LnOAr[Ln = Sc(16);Nd(17)].