The Synthesis And Catalysis Research Of Non-Cp Rare Earth Metal Complexes

The denifition of the rare earth is that the fourteen elements of the upper row on the inner-transition metals on the periodic table that follow the element lanthanum. Some reference sources include lanthanum in this series others do not. For all of these elements the filling orbital is 4f. This series is a sub-series of the transition metals.Rare Earth has been widely used in electronic, petrochemical, metallurgy, machinery, energy, light industry, environmental protection, agriculture, and other fields. Application of Rare Earth to produce fluorescent materials, rare earth metal hydride battery materials, electric light materials, permanent magnet materials, hydrogen storage materials, catalytic materials, precision ceramic materials,laser materials, superconducting materials, magnetostrictive material, magnetic refrigeration materials, magneto-optical storage materials, optical fiber materials.Rare Earth has become the new generation catalysts for olefins polymerization after the Ziegler-Natta catalyst.Chromium-based catalysts played a significant role in coordination polymerization of olefins. The chromium catalytic systems have been largely ignored in the development of the homogeneous methylalumoxane (MAO)-activated systems that have attracted so much attention in the past decade. It is attributed to the difficulty of studying the chemistry of Cr (III) as a result of its paramagnetic nature. Recently, some of the most significant advances in rare earth metal catalyst systems have been made using precatalysts that bear an additional neutral donor, either bridged or unbridged to the Cp unit. Jolly et al. reported that half-sandwich type chromium complexes showed good activity for the polymerization of ethylene to give the polyethylene with narrow molecular weight distributions and high molecular weight. Ender et al. described cyclopentadienylchromium(III) complexes functionalized by quinoline or N, N-dimethylaniline for the polymerization of ethylene. These results revealed that nitrogen donor ligand-substituted cyclopentadienylchromium compounds could effectively catalyze the polymerizations of the olefins. However, the reports concerning oxygen donor ligand-substituted cyclopentadienyl chromium compounds are scarce.In this dissertation, a series of rare earth metal alkyl complexes based on multi -dentate N, P, O-heteroatoms containing ligands have been synthesized via alkyl el -imination. The molecular structures of the complexes are characterized by IR, NM -R spectrum and X-ray diffraction analysis. The activities of these complexes as ca -talysts for ring-opening polymerization (ROP) of lactide have been investigated. Conclusions are summarized as follows:1) three non-Cp ligand containing N\P heteroatoms have successfully been synthesized,and the reaction possibility of these ligands with rare earth metal tri(alkyl)complexes were investigated.A new rare earth metal bis(alkyl)complex has been obtained via protonolysis reaction between rare earth metal tris(alkyl)s and the corresponding ligand. To our initial disappointment, that arylimino-substituted bis(amino)cyclodiphosphazanes chelate lutetium as amino(imino)ph-osphoranates and not as diamides. Ligand HL4 is apparently predisposed to side-on coordination,due to theπ-delocalization in N-P-N moiety on chelation.2) The polymerization of lactide was carried out with the new rare-earth-metal bis(alkyl) complex 3 The effects of polymerization conditions on catalytic activity was investigated, such as the ratio of monomer to catalyst and the polymerization solvents etc. the complete conversion of the monomer into polylactide (PLA) were achieved within 1 h at 20℃. The molecular weight of the resultant PLA was close to the theoretic value with narrow molecular weight distribution.However, when the polymerization was carried out in CH2Cl2,the complete conversion of the monomer into polylactide was difficult in a long run.3)Treatment of HL5 with 1 equiv. of Ln(CH2SiMe3)3(THF)2 indeed afforded mono-alkyl bis-ligand complexes (L5)2Ln(CH2SiMe3) (4: Ln=Y,5: Ln = Lu)without alkyl migration and the formation of homoleptic counterpart. X-ray diffraction analysis revealed Complexes 4 and 5 were isostructural mono-alkyls of solvent-free stabilized by two b-ketoiminato ligands in P,N,O-tridentatemodes.4) The polymerization of the Latice were carried out with the complexes. catalytic activity of the complexes for the ring-opening polymerization(ROP) of L-lactide (L-LA) under mild conditions were higher active in toluene and THF. Complete conversions of the monomer into polylactide (PLA) were achieved within 1 h at 20℃The molecular weight of the resultant PLA was close to the theoretic value with narrow molecular weight distribution.