Synthesis And Reactivity Of Alkyl Groups Containing Guanidino Or Amidino Radicals

Studies on rare-earth metal alkyl complexes have always been an intensive research field. It has been proven that the variation of the ligands could lead to specific changes in catalytic activity, chemical and physical properties. As alternatives for cyclopentadienyl ligands, amidinate and guanidinate ligands attract more interests because of the ease of steric and electronic tunability. In past decades, more and more amidinate and guanidinate ligands have been developed, not only focused on the tunability of steric and electronic properties, but also paid attention to the development of dinuclear complexes. Therefore, based on the similarity between amidinate ligand and monoanionic guanidinate ligand, our works were extend to the synthesis of guanidinato-stabilized methyl complexes and the development of a series of new heterobimetallic Ln(III)/Al complexes containing monoanionic guanidinate ligands. In the meanwhile, we studied the influence factors on the degree of alkylation in the generated heterobimetallic compounds. Their catalytic behaviors on olefin polymerization have also been investigated. Besides, this dissertation will describe the synthesis of new dinuclear rare earth amidinate complexes with a rigid phenylene linker, and studies on their reactivities toward organic small molecules and olefin polymerization. In summary, we have synthesized nineteen new compounds including seventeen rare earth metal complexes, among which eleven complexes were characterized by X-ray structural analysis. The main achievements are as follows:1. The reactions of monoanionic guanidinate rare-earth metal bis(aminobenzyl) complexes with AlMe3were intensively investigated. A series of heterobimetallic Ln(III)/Al complexes containing monoanionic guanidinate ligands were synthesized by the reaction of complexes2-2a and2-2b with AlMe3. The addition of one equivalents of AlMe3to a solution of [(PhCH2)2NC(NR)2]Lu(o-CH2C6H4NMe2)2(R=2,6-iPr2-C6H3)(2-2b) in toluene resulted in complex [(PhCH2)2NC(NR)2]Lu(o-CH2C6H4NMe2)(Me)(THF)(R=2,6-iPr2-C6H3)(2-3), while two equivalents of AlMe3was added into a solution of [(PhCH2)2NC(NR)2]Ln(o-CH2C6H4NMe2)2(R=2,6-iPr2-C6H3, Ln=Y(2-2a), Lu(2-2b)) in toluene, bismethyl complexes [(PhCH2)2NC(NR)2]Ln(Me)2(THF)(R=2,6-iPr2-C6H3, Ln=Y(2-4a), Lu(2-4b)) were obtained in good yields. Interestingly, when three equivalents of AlMe3were used to react with complexes2-2a and2-2b, colorless heterobimetallic mono(tetramethylaluminate) complexes [(PhCH2)2NC(NR)2]Ln(AlMe4)(Me)(R=2,6-iPr2-C6H3, Ln=Y(2-5a), Lu(2-5b)) were obtained in moderate yields. However, out of our expectation, complex2-5a could turn into complex [(PhCH2)2NC(NR)2]2Y2(μ2-Me)(AlMe3)2(μ4-CH)(R=2,6-’Pr2-C6H3)(2-6) via multiple C-H bonds activation. When four equivalents of AlMe3were used to react with complexes2-2a and2-2b respectively, colorless heterobimetallic bis(tetramethylaluminate) complexes [(PhCH2)2NC(NR)2]Ln(AlMe4)2(R=2,6-’Pr2-C6H3, Ln=Y(2-7a), Lu(2-7b)) were obtained in good yields. In the meanwhile, we found that2-2show high catalytic activity in the polymerization of8-Caprolactone and rac-lactide.2. A series of dinuclear rare earth metal complexes bearing a rigid phenylene linked amidinate ligands1,4-C6H4[C(NR)2Ln(o-CH2C6H4NMe2)2]2(R=2,6-iPr2-C6H3, Ln=Y(3-2a), Lu(3-2b), Sc(3-2c)) were synthesized. The insertion reaction took place between complexes3-2a,3-2b and PhNCO, PhNCS smoothly, resulting in the corresponding amidinate dinuclear rare-earth metal complexes1,4-C6H4-[C(NR)2Ln(THF){(Ph)NC(o-CH2C6H4NMe2)O}2]2(R=2,6-iPr2-C6H3, Ln=Y(3-3a), Lu(3-3b)) and1,4-C6H4[C(NR)2Ln(THF){(Ph)NC(o-CH2C6H4NMe2)S}2]2(R=2,6-iPr2-C6H3, Ln=Y(3-4a), Lu(3-4b)). These results give us routes to synthesize multidentate ligands containing O, N, S atoms and their related complexes.3. It is interesting that the complexes3-2a,3-2b,3-2c not only exhibit extremely high catalytic activity in the polymerization of ε-Caprolactone at room or lower temperature, but also show good catalytic activity for polymerizing Lactide at elevated temperature. The detailed experimental conditions such as polymerization solvent, polymerization temperature, the radii of the metal centers have been investigated. The results indicate that this type of dinuclear complexes can promote the Caprolactone polymerization in livingness fashion, cooperative effect between two metal centers was also observed.