Group 4 Organometallic Complexes Supported By Pyrrolide Ligands:Synthesis,Structures And Reactivities

This thesis presents the studies on the synthesis,structures and catalytic activities of the titanium and zirconium organometallic complexes based on the pyrrolide ligands.We also investigated their application in synthesis of C-N bonds.It includes the following three parts.Firstly,the pyrrolide ligand HL1(HL1 = 2-cyano-1H-pyrrole)was synthesized.Then titanium and zirconium complexes,Ti2(L2)2(NMe2)4(1)and Zr3(L2)3(NMe2)6(2)(L2 = N,N-dimethyl-1H-2-carboximidamide,NMe2-L1),supported by this ligand were synthesized and their structures were established by single crystal X-ray diffraction.They were also characterized by 1H NMR and 13 C NMR and elemental analysis.There were tested as catalysts for the intramolecular hydroamination of aminoalkenes.Complex 2 was an efficient catalyst for primary amine substrates with great catalytic activity and selectivity.Secondary amine substrates were resistant to cyclization in presence of complex 2.It suggests that this reaction undergoes a [2+2] cycloaddition route,which is necessary to form a metal-nitrogen double bond in the process of catalysis.Secondly,reaction of complex 1 and excess isopropanol,benzil alcohol gave Ti(L2)2(OiPr)2(3),Ti2(L2)2(OBn)6(4),respectively,which underwent transformation of Ti-N bonds to Ti-O bonds.The structures of 3 and 4 were determined by single-crystal X-ray diffraction and 1H NMR.Both complexes were good initiators for the polymerization of ?-caprolactone.Moreover,we investigated the effect of different solvents on the catalytic activity.Thirdly,reaction of Ti(NMe2)4 with two equivalents of ligand HL1 afforded Ti2(L2)4(NMe2)2(5).Hydrolysis of complex 5,resulted in the formation of an addition product T1,indicating that the amination of C?N bonds can be considered as a new and rapid way to synthesize new C-N bonds.Then,ligand HL3(HL3 = 2-hydroxy-benzonitril)was tried in same method,afforded T2,which revealed that the cyano can be activated in presence of Ti(NMe2)4 at the mild reaction conditions.Finally,ligands HL4(HL4 = 1,7-bis(phthalimido)-4-(2-hydroxyl-benzyl)-1,4,7-triazaheptane)and HL5(HL5 = 1,7-bis(5-Cl-phthalimido)-4-(2-hydroxyl-benzyl)-1,4,7-triazaheptane)were synthesized.The reactions of ligands with Ti(NMe2)4 gave T{(NMe2)2-L4}(NMe2)(6)and Ti{(NMe2)2-L5}(NMe2)(7).According to the results of single crystal X-ray diffraction,C=O bonds of phthalimido were activated,and dimethylamino groups of Ti(NMe2)4 were transferred to carbon atoms.C-N bond of phthalimido was broken and the five-membered ring was opened.However,phthalimido on the other side was unchanged so that a rare asymmetrical structure was afforded.