Synthesis And Characterization Of Bis-β-diketiminato Rare-Earth-Metals Complexes And Their Catalytic Activity

Based on the β-diketiminato ligands, a series of bis-β-diketiminatorare-earth-metals monoborohydrides, bis-β-diketiminato lanthanide mono-phenoxides（alkoxides） and bis-β-diketiminato europium （II） complexes were synthesized in thisthesis. All of them were characterized by X-ray single crystal diffraction. Furthermore,catalytic behavior of some of these complexes for the polymerization of caprolactone,lactide and methyl methacrylate were studied. The main contents were listed below.1. The mono-borohydrides (L_Ph^2,6-ipr2)₂LnBH₄（Ln=Yb（1）, Y（2））(L^2,6-ipr2Ph:[（2,6-Pr2C6H3）NC（Me）CHC（Me）N（C6H5）]–) were obtained from L_Ph^2,6-ipr2LnCl andNaBH₄, whereas L^2-Me2LnBH₄（Ln=Yb（3）, Y（4））(L^2-Me:[N（2-MeC₆H₄）C（Me）]₂CH^–) were obtained from in situ prepared L₂^2-MeLnCl （Ln=Yb, Y） and NaBH₄. All of them were characterized by standardanalytical/spectroscopic techniques and their solid-state structures were establishedby an X-ray structure determination. Each central metal is ligated by one BH4-group and two β-diketiminato ligands and the coordination polyhedron around5-coordinated metal can be described as a distorted trigonal bipyramid.2. The mono-phenoxides L₂^2-MeLn-OAr1（Ln=Nd（5）, Eu（6）, Y（7）） andL₂^2-MeYb-OAr²（THF）（8） were obtained from in situ prepared L^2-Me₂LnCl andNaOAr （Ar1=2,6-^tBu₂-4-Me-C₆H₂, Ar²=4-^tBu-C₆H₄） in a1:0.95molar ratio atthe room temperature. All of them were characterized by standardanalytical/spectroscopic techniques and their solid-state structures were establishedby an X-ray structure determination. Each central metal of complexes5-7is ligatedby one aryloxy group and two β-diketiminato ligands and the coordinationpolyhedron around5-coordinated metal can be described as a distorted trigonal bipyramid, whereas the central metal of complex8by one aryloxy group, one THFmolecular and two β-diketiminato ligands and the coordination polyhedron around6-coordinated metal can be described as an octahedron.3. The mono-alkoxides L₂^2-MeLn-OtBu（THF）_x(（Ln=Nd（9） x=1, Yb（10） x=0） weresynthesized from in situ prepared L₂^2-MeLnCl and KOtBu in a1:0.95molar ratio atthe room temperature, whereas L₂^2-MeYb-OiPr （11） were obtained from in situprepared L₂^2-MeLnCl and NaOiPr under the same condition. All of them werecharacterized by standard analytical/spectroscopic techniques and their solid-statestructures were established by an X-ray structure determination.4. The influence of steric effect on synthesis of mono-phenoxides/alkoxidesrare-earth-metals complexes bearing bis-β-diketiminato ligands was studied. Themetathesis reaction of in situ prepared L₂^HYbCl with NaOAr1in a1:0.95molarratio at the room temperature afforded LH3Yb. The metathesis reaction of in situprepared L2,6-Me22YCl with NaOAr1in a1:0.95molar ratio at the room temperatureafforded L₂^{2,6-Me2Y-（OAr1）}（12）. The metathesis reaction of in situ prepared L₂^{2,6-Me22YbCl with NaOiPr in a1:1molar ratio at the room temperature afforded L2,6-Me}Yb（Cl）-OiPr（THF）（13）. All of them were characterized by an X-ray structuredetermination. These results indicated that mono-phenoxides/alkoxidesrare-earth-metals complexes bearing bis-β-diketiminato ligands can not be obtainedunless the steric size of β-diketiminato ligands is appropriate.5. The metathesis reaction of anhydrous EuCl3with sodium salt of bulkyβ-diketiminato NaL (L=[N（2,4,6-Me₃C₆H₂）C（Me）]₂CH–, L^2,4,6-Me3;[N（2,6-iPr2C₆H₃）C（Me）]₂CH–, L^2,6-ipr2and [（2,6-iPr2C₆H₃）NC（Me）CHC（Me）N-（C6H5）]–, L^2,6-ipr2Ph) in THF at60oC afforded the corresponding EuIIcomplexes:Eu^II(L₂^2,4,6-Me3)（THF）（14）, Eu^II(L^2,6-ipr2)₂（16） and Eu^II(L^2,6-ipr2Ph)₂（18） with theformations of dimers （L2,4,6-Me3）2（15） and （L2,6-ipr2）₂（17） for the former tworeactions and proligand L^2,6-ipr2PhH （19） for the latter one. Complexes14,16and18were characterized by standard analytical/spectroscopic techniques and thesolid-state structures of compounds14-19were confirmed by an X-ray crystalstructure analysis. 6. The catalytic behaviors of complexes1-4were explored. It is clear that all of themwere very efficient initiators for both polymerizations of ε-CL and L-LA. Notably,the initiator3gives good control of molecular weight of poly（ε-CL） and relativelynarrow polydispersity in toluene whthin a short period of time. The3/iPrOH systemproved able to quantitatively convert10000equivalents of lactide with200equivalents of chain-transfer agent per metal initiator, and the obtained PLAsshowed monomodal, very narrow distributions with an excellent correlationbetween the experimental and calculated Mnvalues. Complex1also affordedpoly（methylmethacrylate） efficiently at0oC and poly（MMA） tacticity wasimproved to about80%mm.7. The catalytic behaviors of mono-phenoxides5-8and mono-alkoxides9-10in thepolymerizations of ε-CL and L-LA were preliminary studied. It is found thatcomplexes5,7,9and10were very efficient initiators under mild condition andgave control of the molecular weight. Random copolymerization of ε-caprolactonewith lactide using complex7was preliminary explored.