Aluminum Complexes of Fluorinated Dialkoxy-Diimino Salen-like Ligands: Syntheses, Structures, and Use in Ring-Opening Polymerization of Cyclic Esters

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• 作者：Miloud Bouyahyi ; Ekaterina Grunova ; Nicolas Marquet ; Evgueni Kirillov ; Christophe M. Thomas ; Thierry Roisnel ; Jean-Franç ; ois Carpentier
• 刊名：Organometallics
• 出版年：2008
• 出版时间：November 24, 2008
• 年：2008
• 卷：27
• 期：22
• 页码：5815-5825
• 全文大小：309K
• 年卷期：v.27,no.22(November 24, 2008)
• ISSN：1520-6041

文摘

The coordination chemistry of new fluorinated dialkoxy-diimino ligands onto Al(III) centers has been studied. Diimino-diols (CF₃)₂C(OH)CR¹₂C(R²)N−R³−NC(R²)CR¹₂C(OH)(CF₃)₂ ({ON^EtNO}H₂, R¹ = H, R² = Me, R³ = C₂H₄; {ON^CyNO}H₂, R¹ = H, R² = Me, R³ = trans-1,2-cyclohexyl; {^MeON^EtNO}H₂, R¹ = Me, R² = iPr, R³ = C₂H₄) react selectively with AlMe₃, AlMe₂Cl, and Al(OiPr)₃ to give the corresponding complexes {ON^EtNO}AlX (X = Me, 1; Cl, 2; OiPr, 3), {ON^CyNO}AlX (X = Me, 5; Cl, 6; OiPr, 7), and {^MeON^EtNO}AlX (X = Me, 8; Cl, 9) with concomitant alkane or alcohol elimination, respectively. Single-crystal X-ray diffraction studies revealed that complexes 2, 5, 7, 8, and 9 are mononuclear in the solid state with distorted trigonal-bipyramidal to square-pyramidal geometries. Complexes 1−9 were also characterized in CD₂Cl₂ solution by ¹H, ¹³C, and ¹⁹F NMR spectroscopy. Only one symmetric isomer was observed for complexes 1−7, but mixtures of two isomers (one symmetric, one dissymmetric on the NMR time scale) were observed for complexes 8 and 9. The Al-OiPr complexes 3 and 7 are effective initiators for the ring-opening polymerization of ε-caprolactone and racemic lactide, giving polymers with high molecular weights (M_n up to 37 500 g mol⁻¹) and relatively narrow polydispersities (M_w/M_n = 1.08−1.91). The PLAs produced, both under slurry or melt conditions, with either achiral complex 3 or chiral complex 7, have a highly isotactic-enriched stereoblock microstructure (P_meso = 0.87).