Syntheses And Structures Of Functionalized Alkoxo-Lanthanides And Their Catalytic Activities For The Ring-opening Polymerization Of ε-Caprolactone

Five complexes of lanthanides with nitrogen functionalized alkoxide ligand [(MeC5H4)2Ln(n-OCH2CH2NMe2)]2 (Ln = Sm 1, Y 2, Nd 3) , [Ln(OCH2CH2NMe2)6OH]2Na8 (Ln=Yb 4, Nd 5) and one complex of erbium containing OCH2CF3 ligand Er6(O)(OCH2CF3)18Na2(THF)12 6 were synthesized and characterized. Their catalytic activities for the ring-opening polymerization of s-caprolactone were also investigated for the first time.1. Reactions of (MeC5H4)3Ln (Ln = Sm, Y, Nd ) with HOCH2CH2NMe2 in 1:1 mole ratio in THF give the complexes [(MeC5H4)2Ln(-OCH2CH2NMe2 )]2 (Ln = Sm 1, Y 2, Nd 3). They were characterized by elemental analysis and IR. The molecular structure of complex [(MeC5H4)2Y(-OCH2CH2NMe2 )]2 was also determined by the X-ray diffraction. The results indicate that it is a dimmer formed by two unsymmetric oxygen bridges, which has a tricyclic skeleton with the additional two Y-N bonds via intramolecular coordination of -OCH2CH2NMe2 to metal Y.2. Reaction of anhydrous LnCl3 with NaOCH2CH2NMe2 in 1 :3 molar ratio in THF solution gave the corresponding functionalized alkoxo-lanthanide [Ln(OCH2CH2NMe2)6OH]2Na8 (Ln=Yb 4, Nd 5). The ytterbium complex was characterized by elemental analysis, ER and the X-ray analysis. The results indicate that the complex is a cluster consisted by two Yb ions, eight Na ions, twelve -OCH2CH2NMe2 and two "OH. Yb and Na connected together via the -OH group or O from -OCH2CH2NMe2, respectively. Each Yb was six-coordinated by four -OCH2CH2NMe2 and two -OH groups. The molecule has a centrosymmetric structure. To our best knowledge, this is the first cluster containing so many atoms in the molecule.3. Reaction of anhydrous ErCl3 with NaOCH2CF3 in 1:3 molar ratio in THF solution gave the alkoxo-lanthanide Er6(O)(OCH2CF3)18Na2(THF)12 6, which was characterized by elemental analysis, IR and X-ray analysis. These results indicate thatthe complex is a discrete ion-pair cluster formed from the [Er6(O)(OCH2CF3)18]2"anion and two Na+ cations. The [EreCOXOCHiCFs)18]2- has a 6-oxygen anion in the central position ,which connects six erbium atoms. Each erbium was coordinated to five -OCH2CF3 groups and 6-O2" to form the coordination number of six, and two sodium cations are coordinated by six THF, respectively.4. The investigations were made on the catalytic activities of all these synthesized complexes in the ring-opening polymerization of e-caprolactone. AH these complexes show high activities for the ring opening polymerization of caprolactone. It is surprised that the cluster [Yb(OCH2CH2NMe2)6OH]2Na8 4 exhibit very high catalytic activities. For example, PCL (Mn=4.06xl03, Mw/Mn=1.52) initiated by complex 4 at [CL]/[initiator] = 1500 was obtained with a conversion of 96% in toluene at 18 . The central metal has effect on the catalytic activities. The active order of the central metal in the complexes [(MeC5H4)2Ln(-OCH2CH2NMe2)]2 (Ln = Sm 1, Y 2, Nd3)isY>Sm>Nd.5. The polymerization mechanism initiated by [Yb(OCH2CH2NMei2)6OH]2Na8 4 was studied. A low molecular weight PCL sample was prepared, and the end group of the oligomer was determined by 'H-NMR analysis to be -OCHkCHaNMe2. The results indicated the polymerisation proceed by the coordination-insertion mechanism.6. YbCl3 reacted with CnHisLi 7, which was synthesized by the reaction of Phenyl lithium and 6,6-dimethylfulvene in diethyl ether, in THF inl :2 mole ratio to give the complex (CuH15)2YbCl 8. The complexes 7, 8 were characterized by IR spectra, MS and elemental analyses.