Carbon Linked Amidinate-Amido Complexes:Synthesis,Characterization And Application

This dissertation focuses on the designing and synthesis of multi-dentate nitrogen-centered ligands(trimethylsilyl and phenyl substituted diamine,carbon linked amidinate-amido)and corresponding transition compounds.The structures of the obtained new compounds were characterized by X-ray,elemental analysis and 1H,13C-NMR.In addition,the synthesized group 4 metal compounds were used as catalysts for the olefin polymerization reaction in the presence of cocatalysts such as methylaluminoxane(MAO).Moreover,the synthesized post transition metal compounds were determined at 298 K using Lake Shore VSM 7307 magnetometer.Five main parts are included in this dissertation:Part 1: Some study content and background related to the main study of this paper.It is divided into two parts:(1)important organometallic compounds in organic synthesis and catalysis;(2)the constrained geometry compounds(CGC)as catalyst for the oligmerization and polymerization of olefins.Part 2: A group of multi-dentate nitrogen-centered ligands(trimethylsilyl and phenyl substituted diamine,carbon linked amidinate-amido)were synthesized and characterized by X-ray,NMR and elemental analysis(Scheme 1).Part 3: A series of zirconium compounds 3a-3d were prepared by the zirconium chlorides ZrCl4 reacted with ligands L1 and L2(Schemes 2 and 3).And zirconium complex 3e and titanium complex 3f(Scheme 4)were synthesized and all metal compounds were characterized by X-ray,NMR and elemental analysis.The influences of various catalytic systems formed from 3a-3d in the presence of a cocatalyst such as methylaluminoxane(MAO)on ethylene activation were evaluated.It was found that the catalytic activities of these zirconium complexes toward ethylene polymerization were closely related to bonding patterns(?3:?1,?3 or ?1),the number of chlorine in procatalysts and the availability of the coordination site in the molecule.Zirconium trichloride complex 3b showed the highest catalytic activities because of its ?1 bonding pattern.Procatalysts 3b and 3c showed good activity toward ethylene polymerization(up to 4.86 × 105 g PE mol-1(Zr)h-1),producing polymers with high molecular weights and broad molecular distributions.All the melting points of the resultant polyethylene are within relatively narrow ranges and higher than 132 °C,which indicates the formation of high-density polyethylene(HDPE).DSC,1H-NMR and 13C-NMR studies indicated that the polyethylene produced is highly crystalline and highly linear.More importantly,the current zirconium procatalysts showed excellent thermal stability at 70 °C,suitable for meeting industrial requirement.Part 4: A series of metal compounds 4a-4e were prepared by the Group metal chlorides MCl4(M = Ti,Zr,Hf)or FeCl2 reacted with ligand L3(Scheme 5 and Scheme 6).All metal compounds were characterized by X-ray and elemental analysis.And metal complexes 4a-4d were also characterized by 1H,13C-NMR.The pro-catalysts 4a-4c were screened for ethylene polymerization and titanium compound 4a exhibited good activity toward(up to 1.784 × 105 g mol-1(Ti)h-1),producing polymers with high molecular weights,broad molecular distributions and relatively narrow ranges and higher than 132 °C,which indicates the formation of high-density polyethylene(HDPE).More importantly,the current titanium procatalyst showed excellent thermal stability at 80 °C regarding the aspect of industrial requirement.The magnetic properties of complexes 4d and 4e in the form of magnetization versus magnetic field plot showed the curves of Type-S,illustrating that complexes 4d and 4e are superparamagnetic.Part 5: A series of late transition metal compounds 5a-5d were prepared by the late transition metal chlorides MCl2(M = Fe,Co,Ni)or FeCl2 reacted with ligand L2(Schemes 7 and 8).All metal complexes were characterized by X-ray and elemental analysis.The magnetic properties of complexes 5a-5c in the form of magnetization versus magnetic field plot showed the curves of Type-S,illustrating that late transition metal complexes 5a-5c are superparamagnetic.In nickel complex 5d,an unanticipated methylene-bridged bis(distorted five-membered heterocycle)compound,as an interesting C-C coupling reaction product.It was proposed that this coupling reaction was accelerated by the addition of NiCl2.