Synthesis Of Lanthanide Diolate Complexes And Its Catalysis For The Polymerization Of ε-caprolactone

By using N-phenyldiethanolamine as the source of alkanediol, trivalent lanthanide diolate complexes and tetravalent lanthanide(cerium) diolate complex as well as sodium aminε-bis(phenolate) complex were synthesized and their catalytic behaviors for the polymerization of ε-caprolactone were investigated.(1) Reaction of LnCl3 first with three equivalent of C5H5 Na in THF, then with one equivalent of N-phenyldiethanolamine in THF-DME afforded complexes of{[CpLn( m-OCH2CH2)2NPh]4( m4-Cl)}[Na(DME)4](Ln=Sm, Yb), being characterized by infrared spectra, elemental analyses and X-ray crystallography. They are ionic pair compounds and isostructural. The cationic part is a sodium ion coordinated by four DME molecules and the anionic part is a tetranuclear cluster.(2) Polymerization of ε-caprolactone catalyzed by complexes of{[CpLn(m-OCH2CH2)2NPh]4(m4-Cl)}[Na(DME)4](Ln=Sm, Yb) were studied. The activity of Sm complex is higher than that of Yb complex. The molecular weight of polycaprolactone obtained is rather low. This polymerization is not living. The 1H NMR analysis for oligomers of ε-caprolactone shows that there are not any N-phenyldiethanolamine species in the oligomer molecules, indicating that the insertion ofε-caprolactone molecules into Ln-OR bond does not happen.(3) Reaction of ammonium ceric nitrate firstly with four equivalent of sodium tert-butoxide in THF, then with one equivalent of N-phenyldiethanolamine afforded a black solution. As the solution was layered by a THF solution of o-phenanthroline, crystals of Ce(NO3)3(phen)2 and tetravalent cerium diolate complex were simultaneously produced.The ratio of reaction materials and the reaction temperature were both very important for the sythnesis.(4) The X-ray diffraction anaylysis for the tetravalent cerium diolate complex shows that it is a novel tridecanuclear tetravalent cerium cluster, with eighteen N-phenyldiethanolamine ligands in the external and thirteen cerium atoms and eight oxygen atoms in the interior.(5) It is found that tetravalent cerium diolate complex can catalyze the polymerization of ε-caprolactone. With the increase of temperature, the catalytic activity improves. The molecular weight increases with the yield increasing, and the molecular weight distribution is rather narrow(1.11 < PDI < 1.18).(6) A sodium aminε-bis(phenolate)/o-phenanthroline complexe [LNa2(phen)2]2(DME)(L2-=Me2NCH2CH2CH2N[CH2-(3,5-But-2-C6H2-2-O)]2-) was synthesized and characterized by infrared spectra, elemental analyses and X-ray crystallography. Complex of[LNa2(phen)2]2(DME) is a dimer connected by one DME molecule. Each sodium atom of the complex is coordinated by one o-phenanthroline molecule.(7) Polymerization of ε-caprolactone catalyzed by sodium aminε-bis(phenolate)complexes was investigated. The molecular weights of polymers obtained by LNa2 and[LNa2(phen)2]2(DME) are similar. The activity of LNa2 is higher than that of[LNa2(phen)2]2(DME). The polymerization catalyzed by LNa2 accords with one order reaction kinetics for monomer concentration at 65 °C.