Aluminium complexes bearing functionalized trisamido ligands and their reactivity in the polymerization of ε-caprolactone and rac-lactide

Thibault, Marie‐Hélène; Fontaine, Frédéric‐Georges

doi:10.1039/c0dt00005a

Cited by 43 publications

(16 citation statements)

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“…A similar trend was also observed by Thibault and Fontaine. 40 Kinetic studies of ε-caprolactone polymerization e The M n value was calculated according to M n = 0.56M n GPC , where M n GPC was determined by GPC (chloroform), and is relative to polystyrene standards. first-order dependence of reaction rate on monomer concentration.…”

Section: Ring-opening Polymerization Of ε-Caprolactonementioning

confidence: 99%

Ring-opening polymerization of ε-caprolactone by lithium piperazinyl-aminephenolate complexes: synthesis, characterization and kinetic studies

et al. 2012

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A series of lithium complexes were prepared from 2(N-piperazinyl-N′-methyl)-2-methylene-4-R′-6-Rphenols ([ONN] RR′ ) and characterized through elemental analysis, 1 H and 13 C{ 1 H} NMR spectroscopy, and X-ray crystallography. Treatment of the ligands with n-butyllithium afforded {Li [ONN] RR′ } 3 [R = Me, R′ = t Bu, (1); R = R′ = t Bu (2); R = R′ = t Am, (3), t Am = C(CH 3 ) 2 CH 2 CH 3 ], with trimetallic structures in the solid-state as shown by single-crystal X-ray diffraction. The reactivity of these complexes in the ring-opening polymerization of ε-caprolactone (ε-CL), as well as the influences of monomer concentration, monomer/Li molar ratio, polymerization temperature and time, was studied. Rates of polymerization were first order with respect to both monomer and lithium concentrations, and activation energies for the reactions were determined. MALDI-TOF MS analysis revealed that transesterification had occurred during the polymerization.

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Section: Ring-opening Polymerization Of ε-Caprolactonementioning

confidence: 99%

Ring-opening polymerization of ε-caprolactone by lithium piperazinyl-aminephenolate complexes: synthesis, characterization and kinetic studies

et al. 2012

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“…Mu and coworker reported that, in the absence of alcohol, dinuclear aluminum dimethyl complexes supported by aldimine‐anilido ligands were inactive toward the polymerization of cyclic esters. Thibault and Fontaine found that, without the addition of alcohol, the ROP of ε ‐CL catalyzed by aluminum methyl complexes with phosphine/thiol‐amido ligands was badly controlled and no clear initiation mechanism could be drawn. The aluminum complexes reported in this work are rare examples that could initiate the ROP of cyclic esters with living features in addition to our previous report …”

Section: Resultsmentioning

confidence: 99%

Well‐controlled ring‐opening polymerization of cyclic esters catalyzed by aluminum amido complexes: Kinetics and mechanism

Liu

2014

J. Polym. Sci. Part A: Polym. Chem.

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A series of aluminum dimethyl complexes 1–6 bearing N‐[2‐(pyrrolidinyl)benzyl]anilido ligands were synthesized and well characterized. The molecular structure of complex 1 determined by an X‐ray diffraction study indicates the bidentate chelating mode of the pyrrolidinyl‐anilido ligand. In the absence of a coinitiator, these complexes exhibited excellent control toward the polymerizations of ε‐caprolactone and rac‐lactide, affording polyesters with quite narrow molecular weight distributions (Mw/Mn = 1.04–1.26). The end group analysis of ε−CL oligomer via 1H NMR and ESI‐TOF MS methods gave strong support to the hypothesis that the polymerization catalyzed by these aluminum complexes proceeds via a coordination‐insertion mechanism involving a unique AlN (amido) bond initiation. Via 1H NMR scale oligomerization studies, it is suggested that the insertion of the first lactide monomer into AlN bond of the complex is much easier than the insertion of lactide monomer into the newly formed AlO (lactate) bond and might also be easier than the insertion of the first ε−CL monomer into AlN bond. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3096–3106

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“…A key step to obtain well defined materials with beneficial mechanical properties is rigid control of the polymer chain microstructure. Although there are reports on highly active and very selective dinuclear organoaluminium catalysts for ring opening polymerisations (ROP) of cyclic esters, structural studies and analyses concerning potential cooperative effects remain relativly scarce 56–58. On the other hand, in the last twenty years numerous examples of β ‐diketiminato aluminium complexes have been published, [1,43,44,47–54] including a homoleptic tris‐ β ‐ diketiminato aluminium complex,55 an aluminium(I) complex52 and a complex containing an Al–O–Al moiety, claimed to be the smallest MAO model conceivable 54.…”

Section: Resultsmentioning

confidence: 99%

Organoelement Complexes of a Dinucleating Double β‐Diiminato Ligand – Precedent Cases from Groups 1, 2, and 13

Falkenhagen

Haack

Limberg

et al. 2011

Zeitschrift anorg allge chemie

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Main group chemistry of dinucleating ligands based on a xanthene backbone and two parallel diiminato binding sites (Xanthdim) has been investigated. To complement studies concerning the coordination modes adopted by Xanthdim in combination with alkali metal ions a di-rubidium complex with toluene co-ligands has been prepared. Its structural parameters lie in between those previously observed AlMe 2 ) 2 (5) were isolated and fully characterised.They were found to be dynamic in solution and Al-CH 3 ···F-aryl interactions were detected in case of 5. The solid-state structures and NMR spectroscopic properties of all compounds were determined and analysed. ARTICLEScheme 3. Synthesis of 1(tol) 2 (R = 2,3-dimethylphenyl).of lithium, potassium, caesium, magnesium and calcium complexes (whereas the second valences of magnesium and calcium were saturated by amido and diiminato ligands, respectively). [31] The research described here expands these investigations to organometallic chemistry of the elements rubidium and magnesium. Moreover, for the first time a group 13 element, namely aluminium, has been included, as the Xanthdim ligand matrix may also be expected to support the cooperation of two aluminium atoms in polymerisation catalysis. Results and Discussion Group 1 Organometallics: Coordination of Rubidium Ions with Toluene Co-LigandsAddition of RbOtBu·0.81tBuOH to a solution of [ Me 2 C 6 H 3 Xanthdim]H 2 in thf caused a rapid colour change from yellow to orange indicating a spontaneous deprotonation of the ligand precursor. Subsequent addition of excessive hexane to a concentrated solution of the product in toluene led to the precipitation of [ Me 2 C 6 H 3 Xanthdim](Rb(tol)) 2 (1(tol) 2, Scheme 3). It is noteworthy that the toluene molecules coordinated to the rubidium ions can be removed completely in vacuo, resulting in [ Me 2 C 6 H 3 Xanthdim](Rb) 2 (1), which could be isolated in 81 % yield. Complex 1 is readily soluble in benzene, toluene, thf and dichloromethane; stability in dichloromethane is clearly limited, though, due to the not unexpected reactivity of 1 against halogenated solvents. However, NMR spectroscopic characterisation of a [D 2 ]dichloromethane solution was offhandedly possible, and the 1 H NMR spectrum showed characteristics that confirmed the quantitative formation of [ Me 2 C 6 H 3 Xanthdim] 2and thus a complete conversion of [ Me 2 C 6 H 3 Xanthdim]H 2 to 1: a singlet resonance at δ = 7.84 ppm for the diiminato protons instead of a doublet (as observed in case of [ Me 2 C 6 H 3 Xanthdim]H 2 ), and the absence of the signal at around 12 ppm corresponding to the acidic NH protons of the ligand precursor.Crystals of 1(tol) 2 ·2(tol) suitable for single-crystal X-ray diffraction analysis could be obtained by slow evaporation of the solvent from a concentrated solution of 1 in toluene at room temp. The molecular structure is shown in Figure 1. As recently reported for dinuclear potassium as well as caesium complexes of the [ Me 2 C 6 H 3 Xanthdim] 2ligand, [31] also in 1(tol) 2 · 2(tol) the β-di...

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Aluminium complexes bearing functionalized trisamido ligands and their reactivity in the polymerization of ε-caprolactone and rac-lactide

Cited by 43 publications

References 63 publications

Ring-opening polymerization of ε-caprolactone by lithium piperazinyl-aminephenolate complexes: synthesis, characterization and kinetic studies

Ring-opening polymerization of ε-caprolactone by lithium piperazinyl-aminephenolate complexes: synthesis, characterization and kinetic studies

Well‐controlled ring‐opening polymerization of cyclic esters catalyzed by aluminum amido complexes: Kinetics and mechanism

Organoelement Complexes of a Dinucleating Double β‐Diiminato Ligand – Precedent Cases from Groups 1, 2, and 13

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