| Novel twenty lanthanide-alkali alkoxide clusters were first synthesized in reproducible high yield and well characterized, including X-ray structure determination for 17 clusters. The catalytic behaviors of these clusters were tested. The anionic and cationic aryloxide lanthanide complexes were synthesized and characterized, and their catalytic behavior for the polymerization ofε-CL and TMC was examined and compared with that for the corresponding neutral ones.1. Reaction of sodium aryloxide NaOAr (ArO = 2,6-di-tert-butyl-phenoxide) with LnCl3 in 4:1 molar ratio gave the anionic complexes [Ln(OAr)4][Na(DME)3] (Ln = Nd(1), Sm(2), Gd(3))。All these complexes were characterized by elemental analysis, IR spectroscopy and 1H NMR spectroscopy. Single crystal X-ray analyses for 1 established that it has a discrete ion-pairs structure consisted of an anion [Nd(OAr)4] and a cation [Na(DME)3]. The center metal Nd coordinates four phenolate ligands forming a distorted tetrahedral geometry. Anionic complexes 1-3 can really be used as single-component initiators for the ring-opening polymerization ofε-CL and TMC, and their activities are higher than those of the corresponding neutral ones. The higher activity shown by anionic complex may be attributed to the cooperation of Ln and Na metals. The present polymerization ofε-CL initiated by anionic complex possesses"living"character.2. Reaction of sodium alkoxide NaOCH2CH2NMe2 with LnCl3 in 6:1 molar ratio in the presence of one equiv of NaOH gave the novel clusters Ln2Na8 (OCH2CH2NMe2)12(OH)2 (Ln = Nd (4), Pr (5), Sm (6), Yb (7), Y (8), Ho (9)). All these complexes were characterized by elemental analysis, IR spectroscopy and 1H NMR spectroscopy. Single crystal X-ray analyses for 4, 6, 7 and 9 established that all the clusters have the same structure. Each complex contains two lanthanide metals, eight sodium metals, twelve OCH2CH2NMe3 groups and two OH groups. All the metals are connected by twoμ6–OH groups. 3. Reaction of potassium alkoxide KOCH2CH2NMe2 with LnCl3 in 13:2 molar ratio in the presence of three equiv of KOH gave the clusters Ln4K20(OCH2CH2NMe2)26(OH)6 (Ln = Nd (10), Pr (11), Sm (12), Yb (13))。All these complexes were characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy and X-ray diffraction. Single crystal X-ray analysis for them established that all the clusters have the same structure. Each complex contains four lanthanide metals, twenty potassium metals, twenty-six OCH2CH2NMe3 groups and six OH groups and each lanthanide atom is six-coordinated in a distorted octahedron.4. Reaction of potassium alkoxide KOCH2CH2NMe2 with LnCl3 in 9:1 molar ratio gave the mixed-alkali metal cluster Yb2Na6K10(OCH2CH2NMe2)18(OH)4·2C7H8 (14) in the presence of three equiv of NaOH, while Yb2Na8K8(OCH2CH2NMe2)18(OH)4·0.5C7H8 (15) and Sm2Na4K12(OCH2CH2NMe2)18(OH)4·2C7H8 (16) in the presence of two or four equiv of NaOH respectively. The three clusters were characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy and X-ray diffraction. Cluster 14 contains two lanthanide metals, ten potassium metals, six sodium metals, eighteen OCH2CH2NMe3 groups in addition to four OH groups. Cluster 15 contains two lanthanide metals, eight potassium metals, eight sodium metals, eighteen OCH2CH2NMe3 groups in addition to four OH groups. Cluster 16 consists of two lanthanide metals, twelve potassium metals, four sodium metals, eighteen OCH2CH2NMe3 groups and four OH groups.5. Reaction of sodium alkoxide NaOCH2CF3 with LnCl3 in 7:1 molar ratio gave clusters Ln2Na8(OCH2CF3)14(THF)6 (Ln = Y (17), Yb (18), Sm (19))。All these clusters were characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy and X-ray diffraction. X-ray structure analyses revealed that these clusters are centrosymmetric and the overall structure in each case is composed of two cubanes and a double open cubane, with one face of an Ln1Na2O4 open cubane cluster capped by an additional LnO2 layer. The double open cubane locates as a core capped by two cubanes in opposite side via two lanthanide atoms.6. Reaction of sodium alkoxide NaOtBu with LnCl3 in 10:1 molar ratio in the presence of one equiv of NaOH gave LnNa8(OtBu)10(OH) (Ln = Nd (20), Yb (21))。Cluster 21 was characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy and X-ray diffraction. X-ray structure analyses of 21 revealed that the ytterbium atom is six-coordinated with five oxygen atoms of the OtBu ligands and one oxygen atom of OH in a distorted octahedron.7. Reaction of sodium alkoxide NaOiPr with YbCl3 in 12:1 molar ratio gave Yb4O4(OiPr)16Na12 (22)。Cluster 22 was characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy and X-ray diffraction.8. Clusters Ln2Na8 (OCH2CH2NMe2)12(OH)2 (Ln = Nd (4), Pr (5), Sm (6), Yb (7), Y (8), Ho (9)), Ln4K20(OCH2CH2NMe2)26(OH)6 (Ln = Nd (10), Pr (11), Sm (12), Yb (13)), Yb2Na6K10(OCH2CH2NMe2)18(OH)4·2C7H8 (14), Yb2Na8K8(OCH2CH2NMe2)18(OH)4·0.5C7H8 (15) and Sm2Na4K12(OCH2CH2NMe2)18(OH)4·2C7H8 (16) show extremely high activity for the ring-opening polymerization ofε-CL and TMC. It is noteworthy that the polymerization system was still active even after complete consumption of the substrate. The polymerization mechanism was also investigated with cluster 4 by analyzing the terminal group of the oligomer.9. Clusters Ln2Na8 (OCH2CH2NMe2)12(OH)2 (Ln = Nd (4), Pr (5), Sm (6), Yb (7), Y (8), Ho (9)) were found to be active single-component catalyst for the polymerization of methyl methacrylate to give isotactic-rich and high molecular weight polymers. The isotectic content increases with decreasing reaction temperature. To our best knowledge this is the first example for polymerization of methyl methacrylate catalyzed by lanthanide alkoxide complex alone. In order to understand further the polymerization mechanism the stoichiometric reaction of Yb2(OCH2CH2NMe2)12(OH)2Na8 (7) with MMA in 1:2 molar ratio was conducted and the intermediate Yb2Na6(OCH2CH2NMe2)10[OOCC(CH3)CH2]2 (23), which can also catalyze the polymerization of MMA, was isolated and fully characterized including X-ray crystal structure.10. Clusters Ln2Na8 (OCH2CH2NMe2)12(OH)2 (Ln = Nd (4), Pr (5), Sm (6), Yb (7), Y (8), Ho (9)), Yb2Na6K10(OCH2CH2NMe2)18(OH)4·2C7H8 (14) and Sm2Na4K12(OCH2CH2NMe2)18(OH)4·2C7H8 (16) were found to be active single-component catalysts for the polymerization of N-PMI under mild conditions. Their activities are much higher than those found for the catalyst systems published previously。The polymerization mechanism was postulated based on the 1H NMR and 13C NMR of the polymers.11. The clusters Ln2Na8(OCH2CH2NMe2)12(OH)2 (Ln = Nd (4), Pr (5), Sm (6), Yb (7), Y (8), Ho (9)) were found to be efficient catalysts for Tischenko reaction, and their activity is comparable to La[N(SiMe3)2]3。12. It was found that Ln2Na8(OCH2CF3)14(THF)6 (Ln = Y (17), Yb (18), Sm (19)) and YbNa8(OtBu)10(OH) (21) show high activity for the ring-opening polymerization ofε-CL and TMC.13. Cationic samarium complex [(Ar′O)2Sm(DME)2][BPh4] (OAr′= 2,6-di-tert-butyl-4-metyl-phenoxide) (24) was synthesized conveniently by the oxidation reaction of the corresponding divalent complex (Ar′O)2Sm(THF)3 with AgBPh4. While the same reaction of (ArO)2Sm(THF)3 with AgBPh4 afforded no definite complex but a small amount of by-product [(ArO)2Sm(μ-OH)(THF)]2?2THF (ArO = 2,6-di-tert-butyl-phenoxide) (25). The two complexes were characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy and single crystal X-ray. The cationic complex 24 can be used as single-component initiator for the ring-opening polymerization ofε-CL and TMC with high activity. Its activity is much higher than that of the corresponding neutral trivalent complex (ArO)3Sm(THF)2. The higher catalytic activity observed for cationic complex in comparison with the neutral complex may be attributed to the enhanced electrophilicity of the Sm metal bearing a formal positive charge, which makes both the coordination ofε-CL and the cleavage of acyl-oxygen bond more favorable.14. Reaction of Yb[N(SiMe3)2]3 with cinchonine in 1:3 mole ratio in THF gives the complex Yb2(cinchonine)6 (26). Complex 26 was characterized by elemental analysis, IR spectroscopy, 1H NMR spectroscopy, and X-ray diffraction. X-ray structure analyses revealed 26 being dimmer in which two six-coordinated ytterbium atoms are connected by threeμ-O atoms.
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