A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

Chakraborty, Debashis; Mandal, Dipa; Ramkumar, V.; Subramanian, V.; Sundar, J. Vijaya

doi:10.1016/j.polymer.2014.10.074

Cited by 31 publications

(13 citation statements)

References 132 publications

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“…There are currently a wide variety of metal complexes that have been studied as ROP catalysts, with general success in the use of Al as a metal center [13][14][15][16][17][18][19], some alkaline [20][21][22]and alkaline earth metals [23][24][25],and also some transition metals like Ti or Zr [26]. However, Zinc-based complexes are among the most outstanding, mainly because of good polymerization control via ROP, which translates into good catalytic activity, high molecular weight, low polydispersity, and even stereochemical control of synthesized PLA [27][28][29][30][31][32][33].In addition, Zn has low toxicity compared to other metals.…”

Section: Introductionmentioning

confidence: 99%

Binuclear Schiff-base zinc(II) complexes: Synthesis, crystal structures and reactivity toward ring opening polymerization of rac-lactide

et al. 2019

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Upon crystallization from DMF/diethyl ether or CH2Cl2/pyridine of tetracoordinated Zn(II) complexes containing either 4-fluorophenyl or 4-anisyl substituted O,N,O-tridentate Schiff base ligands and pyridine as auxiliary ligand, three new doubly phenoxide-bridged dimeric Zn(II) complexes were isolated and their catalytic properties for the ring opening polymerization (ROP) of rac-lactide were explored. The single-crystal XRD analysis allowed to corroborate the molecular structures of the binuclear complexes, showing that the pentacoordinated Zn(II) metal ion adopts a slightly distorted square pyramidal geometry. The basal plane Is formed by the O,N,O-donor set of the tridentate Schiff base ligand and a phenoxo bridging oxygen, while a pyridine or a DMF molecule is located at the apex of the pyramid. The binuclear complexes were employed as catalysts in the ROP of rac-lactide for polylactide (PLA) synthesis. Polymerization conditions such as reaction time, catalyst concentration and use of benzyl alcohol as cocatalyst were studied, as well as their influence on the conversion rate, average molecular weight and polydispersity of the obtained PLA. The catalyst substituted with fluorine was more reactive, but with a lower control on the molecular weight compared to the methoxy-substituted catalyst. On the other hand, the presence of pyridine as an auxiliary ligand generates an improvement in the polydispersity of PLA.

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Section: Introductionmentioning

confidence: 99%

Binuclear Schiff-base zinc(II) complexes: Synthesis, crystal structures and reactivity toward ring opening polymerization of rac-lactide

et al. 2019

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“…For instance, Kol group synthesized titanium (IV) and zirconium (IV) alkoxo complexes chelating amine‐phenolate ligands in a single‐step reaction between the pro‐ligands and metal alkoxides precursors and also these complexes were found to be active catalyts for lactide polymerizations 28 . In this context, our group also contributed well‐defined Ti, Zr, and Hf mono or dinuclear active site catalyts for these ROP reactions 29‐34 . Also from our group some of the synthesized polymers were used as drug delivery and tissue engineering applicartions 35‐39 .…”

Section: Introductionmentioning

confidence: 84%

Benzoxazole phenoxide ligand supported group IV catalysts and their application for the ring‐opening polymerization of rac‐lactide and ε‐caprolactone

Pappuru

Ramkumar

Chakraborty

2021

Polymers for Advanced Techs

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Monomeric titanium [C48H62N2O6Ti] (1) and zirconium [C48H62N2O6Zr] (2) complexes were synthesized by combining the monoanionic salicylbenzoxazole pro‐ligand 2‐(5‐X‐benzoxazol‐2‐yl)‐6‐R1‐4‐R2‐phenol, LH (R1, R2, X = tBu, tBu, H, respectively) with Ti(OiPr)4 or Zr(OiPr)4∙(iPrOH) in a 2:1 stoichiometric ratio. Controlled hydrolysis of the monomeric Ti complex with deionized water yielded a new unusual hexanuclear titanium complex [C126H144N6O21Ti6] (3). In addition, the cage formed in this complex 3 was surrounded by all‐oxygen and penta‐coordinated Ti(IV) atoms, which leads to an hexanuclear drum‐shaped Ti complex 3 with a trigonal‐bipyramidal geometry at the metal center. The catalytic activity of these complexes toward ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and rac‐lactide (rac‐LA) was studied. All these complexes showed moderate to good catalytic activity without using any co‐catalyst additives. Single‐site zirconium alkoxide 2 showed the best catalytic activity and was able to convert 400 units of ε‐CL or rac‐LA into the polymer product in high yield (≥90%) within 1 hour under solvent‐free conditions. The obtained polymers showed good control in molecular weight (Mn = 46.2–6.3 kg/mol) and molecular weight distributions (MWD's = 1.37–1.15). The polymerization of rac‐LA by 2 yielded iso‐enriched polylactide (Pm = 0.60).

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“…Complexes of hafnium have been predominantly used as Lewis acid catalysts in various organic transformations, such as the polymerization of cyclic esters, and as catalysts for the homo‐ and copolymerization of α‐olefins . Recently, Hf‐MOF compounds have been used as active catalysts for the activation of small molecules .…”

Section: Introductionmentioning

confidence: 99%

Hydroboration of Aldehydes, Ketones, and Carbodiimides Promoted by Mono(imidazolin‐2‐iminato) Hafnium Complexes

et al. 2020

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Imidazolin‐2‐iminato hafnium complexes of the type [(ImRN)Hf(CH2Ph)3] were synthesized (ImtBuN = 1,3‐di‐tert‐butylimidazolin‐2‐iminato); ImDippN = 1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐iminato. The complexes were crystallized and structurally characterized. Despite the oxophilicity of the hafnium center, both hafnium complexes were catalytically active in the hydroboration of aldehydes, ketones, and carbodiimides. Herein, we present the influence of different substrates bearing electron‐withdrawing or electron‐donating groups on the catalytic reactions. Based on stoichiometric reaction in each process, plausible mechanistic scenarios are presented.

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A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

Cited by 31 publications

References 132 publications

Binuclear Schiff-base zinc(II) complexes: Synthesis, crystal structures and reactivity toward ring opening polymerization of rac-lactide

Binuclear Schiff-base zinc(II) complexes: Synthesis, crystal structures and reactivity toward ring opening polymerization of rac-lactide

Benzoxazole phenoxide ligand supported group IV catalysts and their application for the ring‐opening polymerization of rac‐lactide and ε‐caprolactone

Hydroboration of Aldehydes, Ketones, and Carbodiimides Promoted by Mono(imidazolin‐2‐iminato) Hafnium Complexes

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