Synthesis And Characterization Of Bis(β-diketiminato) Rare-Earth-Metal Amides And Lanthanide(Ⅱ) Complexes And Their Catalytic Activity

Based on the β-diketiminato ligands, a series of bis(β-diketiminato)rare-earth-metal amides and bis(β-diketiminato) lanthanide(II) complexes weresynthesized in this thesis. Furthermore, catalytic behavior of some of these complexesfor the polymerization of caprolactone/lactide，guanidine-forming reaction betweenamine and carbodiimine and the guanylation mechanism were studied. The maincontents were listed below.1. Reaction of anhydrous LnCl3with NaL2-Me(L2-Me=[N(2-MeC6H4)C(Me)]2CH–)in1:2molar ratio afforded bis(β-diketiminato) lanthanide chlorides:(L2-Me)2LnCl (Ln=Sm (1), Nd (2)). Complexes1and2were characterized by elemental analysis, IR andX-ray diffraction. Single crystal structure analysis showed that these complexes aredimeric without any solvent coordination.2. The mono-amides (L2-Me)2LnN(SiMe3)2(Ln=Sm (3)，Nd (4)) were obtainedfrom (L2-Me)2LnCl(Ln=Sm (1), Nd (2)) and NaN(SiMe3)2. The mono-amides(L2-Me)2LnN(SiMe3)2(Ln=Yb (5)，Y(6), Pr (7)) were obtained from in situ prepared(L2-Me)2LnCl and NaN(SiMe3)2in a1:1molar ratio at the room temperature. All ofthem were characterized by elemental analysis, IR spectroscopy, and complex6wascharacterized by NMR spectroscopy. The state structures of these complexes werestudied by X-ray diffraction. Each central metal of complexes3-7is ligated by twoβ-diketiminato ligands and one amido group and the coordination polyhedron around5-coordinated metal can be described as a distorted trigonal bipyramid. 3. Complexes3-7are efficient precatalysts for catalytic addition of amines tocarbodiimides, and complex3show the highest activity for the addition of variousamines to carbodiimides at60oC under solvent free condition. The catalytic additionreaction with3showed a good scope of substrates.4. In order to gain information about the real active species and the reactionpathways, the reaction of3-5with PhNH2in a1:1molar ratio was firstly carried out inTHF at60oC. After stirring for24h, the amides exchange products(L2-Me)2LnNHPh(THF)(Ln=Sm (8)，Nd (9), Yb (10))were successfully obtained. Thenthe reaction of8and9with CyNCNCy at a molar ratio of1:1were carried out at60oC,respectively. The reactions took place smoothly, and the monoguanidinate complexessupported by two β-diketiminato ligands,(L2-Me)2Ln[(C6H5NH)C(NCy)-NCy](Ln=Sm(11)，Nd (12)) were isolated in medium yield. Complexes8-12were characterized byelemental analysis, IR spectroscopy, and complexes8-10and12were characterized byX-ray diffraction. In order to prove the process speculated of the catalytic reaction, westudied reaction activity of the complexes11and12for catalytic addition of amine tocarbodiimide into guanidine, finding that both complexes can efficiently catalyze thereaction, which proved that complexes11and12were intermediates of(L2-Me)2LnN(SiMe3)2for catalytic addition of amine to carbodiimide into guanidine.5. The mono-amides (L2,6-ipr2Ph)2LnNH(2,6-iPr2C6H3)(Ln=Y (13), Yb (14))(L2,6-ipr2Ph=[(2,6-iPr2C6H3)NC(Me)CHC(Me)N(C6H5)]–) were obtained from(L2,6-ipr2Ph)2LnCl and NaNH(2,6-iPr2C6H3), whereas (L2,6-ipr2Ph)2LnNH(2,6-iPr2C6H3)(Ln=Sm (15), Nd (16)) were obtained from in situ prepared (L2,6-ipr2Ph)2LnCl andNaNH(2,6-iPr2C6H3). The mono-amides(L2-Me)2LnNH(2,6-iPr2C6H3)(Ln=Y (17), Yb(18)) were obtained from in situ prepared (L2-Me)2LnCl and NaNH(2,6-iPr2C6H3) in a1:1molar ratio at the room temperature. Complexes16-18were characterized byelemental analysis, IR spectroscopy, and complex17was characterized by NMRspectroscopy. The state structures of these complexes were studied by X-ray diffraction.Each central metal of complexes16-18is ligated by two β-diketiminato ligands and oneamido group and the coordination polyhedron around5-coordinated metal can be described as a distorted trigonal bipyramid.6. The catalytic behavior of complexes13-18were explored. Complexes13-18were found to be very active single-site initiators for the controlled ring-openingpolymerization of ε-caprolactone and L-lactide. Remarkably, the binary15/benzylalcohol (BnOH) system exhibited a striking “immortal” nature and proved able toquantitatively convert5000equiv of L-LA with up to100equiv of BnOH per metalinitiator. All the resulting PLAs showed monomodal, narrow distributions (Mw/Mn=1.061.08), with the molar mass (Mn) decreasing proportionally with an increasingamount of BnOH. The binary16/BnOH system also exhibited an “immortal” nature inthe polymerization of ε-CL in toluene.7. Anhydrous LnCl3reacted with2equiv. of NaL in THF, followed by treatmentwith Na/K alloy in THF, giving various divalent lanthanide complexes supported by twoβ-diketiminato ligands,(L2,6-Me2)2Eu(THF)(19),(L2,6-Me2=[N(2,6-Me2C6H3)C(Me)]2CH);(L2,4,6-Me3)2Eu(THF)(20),(L2,4,6-Me3=[N(2,4,6-Me3C6H2)C(Me)]2CH);(L2,6-ipr2)2Eu·CH3C6H5(21),(L2,6-ipr2=[N(2,6-iPr2C6H3)C(Me)]2CH);(L2,6-ipr2Ph)2Eu (22),(L2,6-ipr2)2Sm·CH3C6H5(23),(L2,6-ipr2)2Yb (24);(L2-Me)2Yb(THF)(25). Complexes19-25are efficient precatalysts forcatalytic addition of amines to carbodiimides, and complex22show the highest activityfor the addition of various amines to carbodiimides at60oC under solvent freecondition.8. In order to gain information about the real active species and the reactionpathways, the reaction of19and22with PhNH2and CyNCNCy in a1:1:1molar ratiowas firstly carried out in THF at60oC. After stirring for24h, the monoguanidinatecomplexes L2,6-Me2Eu[(C6H5NH)C(NCy)-NCy](DME)(26) andL2,6-ipr2PhEu[(C6H5NH)C(NCy)-NCy](THF)2(27) were successfully obtained. Then thereaction of25with CyNCNCy at a molar ratio of1:1were carried out at60oC. Andthe amidinate complex supported by two β-diketiminato ligands,L2-MeYb[(C3H6OCH)C(NCy)-NCy](28) were isolated in medium yield. The reaction of 25with PhNH2and CyNCNCy in a1:1:1molar ratio was carried out in THF at60oC,respectively. After stirring for5days, the bis-guanidinate complexL2-MeYb[(C6H5NH)C(NCy)-NCy]2(29) was successfully obtained. Complexes26-29were characterized by elemental analysis, IR spectroscopy, and X-ray diffraction. Inorder to prove the process of the catalytic reaction, we studied reaction activity of thecomplexes19,22,25and26-29for catalytic addition of amine to carbodiimide intoguanidine, finding that all the complexes can efficiently catalyze the reaction, whichproved that complexes26-27and29were intermediates of (L)2Ln(II) for catalyticaddition of amine to carbodiimide into guanidine.