Single site catalysts for stereoselective ring-opening polymerization of lactides

Dijkstra, Pieter J.; Du, Hongwang; Feijén, Jan

doi:10.1039/c0py00204f

Cited by 369 publications

(225 citation statements)

References 61 publications

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“…Several important families of single-site zinc catalysts have been developed that exhibit high polymerization activity and afford polymers with controlled molecular weights and microstructures. [10,11] Neutral catalytic species supported by anionic ancillary ligands of the type LZnX, where L is often a chelating phenoxy-or alkoxide-based ligand and X is an alkyl or amide group, have been predominantly employed. [12][13][14][15][16][17][18][19][20] Many recent P NMR studies highlighted marked flexibility of the phosphido pincer ligand in coordination at the metal center.…”

Section: Introductionmentioning

confidence: 99%

Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand

D’Auria

Lamberti

Mazzeo

et al. 2012

Chemistry A European J

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The preparation and characterization of new Zn(II) complexes of the type [(PPP)ZnR] in which R = Et (1) or N(SiMe(3))(2) (2) and PPP is a tridentate monoanionic phosphido ligand (PPP-H = bis(2-diphenylphosphinophenyl)phosphine) are reported. Reaction of ZnEt(2) and Zn[N(SiMe(3))(2)](2) with one equivalent of proligand PPP-H produced the corresponding tetrahedral zinc ethyl (1) and zinc amido (2) complexes in high yield. Homoleptic (PPP)(2) Zn complex 3 was obtained by reaction of the precursors with two equivalents of the proligand. Structural characterization of 1-3 was achieved by multinuclear NMR spectroscopy ((1)H, (13)C, and (31)P) and X-ray crystallography (3). Variable-temperature (1)H and (31)P NMR studies highlighted marked flexibility of the phosphido pincer ligand in coordination at the metal center. A DFT calculation on the compounds provided theoretical support for this behavior. The activities of 1 and 2 toward the ring-opening polymerization of ε-caprolactone and of L- and rac-lactide were investigated, also in combination with an alcohol as external chain-transfer agent. Polyesters with controlled molecular parameters (M(n), end groups) and low polydispersities were obtained. A DFT study on ring-opening polymerization promoted by these complexes highlighted the importance of the coordinative flexibility of the ancillary ligand to promote monomer coordination at the reactive zinc center. Preliminary investigations showed the ability of these complexes to promote copolymerization of L-lactide and ε-caprolactone to achieve random copolymers whose microstructure reproduces the composition of the monomer feed.

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Section: Introductionmentioning

confidence: 99%

Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand

D’Auria

Lamberti

Mazzeo

et al. 2012

Chemistry A European J

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“…As a result of the modern renaissance in polymer technologies, contemporary studies have been initiated to develop single-site (homogeneous) catalysts for the polymerization of heterocyclic monomers. Though many of these studies primarily involve transition metal catalysts, the polymerization of cyclic esters, especially lactide [102], a cyclic diester monomer, is frequently initiated by rare earth complexes [103,104].…”

Section: Ring-opening Polymerization Of Cyclic Estersmentioning

confidence: 99%

Rare Earth Pincer Complexes: Synthesis, Reaction Chemistry, and Catalysis

Hänninen

Zamora

Hayes

2015

The Privileged Pincer-Metal Platform: Coordination Chemistry &Amp; Applications

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The research field surrounding rare earth pincer complexes has reached a stage where a comprehensive review about the reactivity and catalytic behavior of these species is justified. In this contribution, we begin with a brief introduction on common strategies for the preparation of rare earth pincer complexes, continuing with a section devoted to the versatile reactivity observed for this class of compound. Thereafter, several types of compounds are discussed, including extremely reactive hydrides, cationic species, and intriguing scandium imido complexes. Finally, the last portion of this chapter sums up the hitherto reported catalytic studies, including discussions on ring-opening polymerization of cyclic esters, polymerization of olefins and hydroamination reactions, as well as several examples of more infrequently encountered catalytic processes.

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“…After the discovery of the stereoselective polymerization of racemic lactides by chiral binaphthyl Schiff base aluminum complex [21], a large synthetic effort has been devoted to the preparation of five-coordinate SALEN aluminum complexes and their use in the ROP of lactones and lactides. The relationship between structure of the catalytic complexes and stereoselectivity of the polymerization has been investigated and elucidated [6][7][8][9][10]22]. Recent organometallic literature has featured reports of many alkylaluminum compounds bearing bidentate N,N-, N,S-, or N,O-donor ligands [23][24][25][26][27][28][29][30].…”

Section: Dimethyl(salicilaldiminato)aluminum Complexesmentioning

confidence: 99%

“…A large variety of aluminum complexes active in the ROP of lactones and lactides have been described with different coordination environments [6][7][8][9][10]. Recent literature reviews described the use of various aluminum complexes as polymerization catalysts [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Aluminum Alkyl Complexes Bearing Salicylaldiminato Ligands: Versatile Initiators in the Ring-Opening Polymerization of Cyclic Esters

Fuoco

Pappalardo

2017

Catalysts

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Linear aliphatic polyesters are degradable thermoplastic polymers, which can be obtained by ring-opening polymerization (ROP) of cyclic esters through a coordination-insertion mechanism. Aluminum based organometallic complexes have a leading position as efficient catalysts for this polymerization process. Aluminumalkyl complexes bearing salicylaldiminato ligands, although less explored, have been shown to be efficient and versatile catalysts for the ROP of various cyclic esters. These species have the potential to function as active catalysts in the ROP because of their less coordinatively saturated nature with respect to analogous SALEN-type complexes. They have been used as efficient catalysts in the ROP of commercially available cyclic esters, such as ε-caprolactone, L-lactide, rac-lactide, and glycolide. Moreover, they resulted in efficient catalysts for the ROP of cyclic esters with large ring-size and for the ROP of functionalized lactide. Furthermore, they have been used in the co-and ter-polymerization of various cyclic esters affording well controlled polymerization and a plethora of microstructural architectures, ranging from random to block to multiblock.

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Single site catalysts for stereoselective ring-opening polymerization of lactides

Cited by 369 publications

References 61 publications

Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand

Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand

Rare Earth Pincer Complexes: Synthesis, Reaction Chemistry, and Catalysis

Aluminum Alkyl Complexes Bearing Salicylaldiminato Ligands: Versatile Initiators in the Ring-Opening Polymerization of Cyclic Esters

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