Bis(imino)phenoxide complexes of zirconium possess spectacular reactivity towards the solvent-free polymerization of cyclic ester monomers and lactides. Polymerization of lactide is living and the resulting product has exceptionally high number average molecular weights (Mn). Polymerization of β-butyrolactone gives syndiotactic poly(3-hydroxybutyrate) with good M n and molecular weight distribution (MWD). © The Royal Society of Chemistry 2010.

Debashis Chakraborty

Department Of Chemistry

Tanmoy Kumar Saha

Bijja Rajashekhar

Venkatachalam Ramkumar

BUTYROLACTONES

CYCLIC ESTERS

Lactides

NUMBER AVERAGE MOLECULAR WEIGHT

POLY(3-HYDROXYBUTYRATE)

POLYMERIZATION OF LACTIDE

Solvent free

Structural characterization

SYNDIOTACTICS

Esterification

Esters

LIVING POLYMERIZATION

Molecular weight distribution

Polymers

Synthesis (chemical)

Zirconium

Zirconium compounds

Ring opening polymerization

BIS(IMINO)PHENOXIDE

DILACTIDE

dioxane derivative

ester

imine

organometallic compound

phenol derivative

chemical structure

chemistry

Polymerization

synthesis

X ray crystallography

Crystallography, X-Ray

Dioxanes

Imines

Models, Molecular

Molecular Structure

Organometallic Compounds

Phenols

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IIT Madras

Dalton Transactions

The synthesis of homoleptic salalen ligand supported group 4 complexes and their applications in the ring-opening polymerization (ROP) of ε-caprolactone (ɛ-CL) and lactide (LA) are described. All these complexes of type M(L)2 (LH = (E)-N-(2-(3,5-dibromo-2-hydroxybenzylideneamino)phenyl)-4-methylbenzenesulfonamide: M = Ti (1), M = Zr (4), M = Hf (7); LH = (E)-N-(2-(2-hydroxybenzylideneamino)phenyl)-4-methylbenzenesulfonamide: M = Ti (2), M = Zr (5), M = Hf (8); LH = (E)-N-(2-(3,5-di-t-butyl-2-hydroxybenzylideneamino)phenyl)-4-methylbenzenesulfonamide: M = Ti (3), M = Zr (6), M = Hf (9)) are characterized by various spectroscopic techniques. The single crystal X-ray diffraction analysis confirmed that the metal centres in complexes 6 and 8 adopt distorted dodecahedral geometry. The self-assembly of the complexes in solid state through the molecular interactions demonstrated that the supramolecular network forms molecular channels which act as a host lattice for the assembly of toluene solvent molecules. Complexes (1–9) are effective catalysts for the ROP of ɛ-CL and LA and produced high molecular weight (Mn) polycaprolactone (PCL) and poly (lactic acid) (PLA) respectively with narrow molecular weight distributions (MWDs) in the range of 1.17–1.28. PLA produced from the polymerization of rac-LA is atactic. However, better control over the polymerization process was achieved in the presence of toluene as solvent at 80 °C. All these polymerizations follow first-order kinetics with respect to monomer concentration. MALDI-TOF and NMR spectral analysis suggested that the polymerization proceeds through the coordination-insertion mechanism. © 2018

Journal of Organometallic Chemistry

Group 4 metal complexes containing the salalen ligands: Synthesis, structural characterization and studies on the ROP of cyclic esters

Ring-opening polymerization (ROP) of maleic anhydride (MA) or L-Lactide (L-LA) with tert-butyl glycidyl ether (tBGE) were carried out in the presence of Ti and Zr complexes of benzoxazole substituted 8-hydroxyquinoline ligands (1a-3a and 1b-3b), delivering nearly alternative P(tBGE-co-MA) and block-like P(tBGE)-b-PLLA co-polymers with high molecular weight (Mn) and narrow to broad molecular weight distributions (Mw/Mn). The molecular structures of the Ti and Zr complexes (1a and 3b) were confirmed by single-crystal X-ray diffraction analysis. The Zr complex 3b exhibited superior reactivity and produced copolymers within one hour at 80 °C in dry toluene (Mn,GPC = 14–40 Kg mol-1 and Mw/Mn = 1.19–1.55). In case of P(tBGE-co-MA) copolymer synthesis, the polymer arm with tBGE fraction was building faster (82–100 unit%) compared to MA (52–99 unit%). In contrast, incorporation of L-LA was higher (82–99 unit%) compared to tBGE insertion (20–60 unit%) in P(tBGE)-b-PLLA copolymer synthesis. © 2017 Elsevier Ltd

Polymer

Ring-opening copolymerization of maleic anhydride or L-Lactide with tert-butyl glycidyl ether by using efficient Ti and Zr benzoxazole-substituted 8-Hydroxyquinolinate catalysts

A series of homoleptic iminophenoxide and bis(imino)phenoxide supported Zr and Hf complexes 1–10 has been synthesized and characterized by NMR, mass spectrometry and elemental analysis. Structural analysis of the selected complexes by single crystal X-ray diffraction method revealed that the complexes are monomeric in their solid state with distorted dodecahedral geometries. These complexes are found to be potential single-site catalysts for ring-opening polymerization (ROP) of lactide (LA) and ϵ-caprolactone (ϵ-CL) and afforded controlled molecular weight (Mn) polyesters with narrow molecular weight distributions (MWDs) of 1.12-1.28. Kinetic studies revealed that the polymerization rate have shown to be first order dependency on lactide. The low molecular weight oligomer analysis imparted that the polymerization proceeds through the coordination-insertion mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ChemistrySelect

Homoleptic Zr and Hf Complexes of Imino/Bis(imino)phenoxide Scaffolds: Synthesis, Structural Characterization and Their Catalytic Activity in the ROP of Cyclic Esters

A series of lithium, sodium and potassium salts containing various iminophenoxide ligand scaffolds have been successfully synthesized in high yields and purity. These complexes were completely characterized with different spectroscopic techniques and single crystal X-ray diffraction studies on a few of them. These compounds were found to be active towards the solvent free ring opening polymerization (ROP) of L-lactide (L-LA) and rac-lactide (rac-LA), yielding polymers with high number average molecular weight (Mn) and controlled molecular weight distribution (MWDs). Poly(lactic acid) (PLA) derived from the ROP of lactides using the Na complexes showed a close proximity between the observed Mn and theoretical molecular weight (Mntheo). In addition, the MWDs were found to be narrow. These complexes were also found to be active for the ROP of lactides in the presence of benzyl alcohol as a co-initiator. The kinetics and mechanistic studies associated with these polymerizations have been performed and reported. © 2014 Elsevier Ltd. All rights reserved.

European Polymer Journal

Group 1 salts of the imino(phenoxide) scaffold: Synthesis, structural characterization and studies as catalysts towards the bulk ring opening polymerization of lactides

A series of gallium and indium complexes containing a bis(imino)phenolate ligand framework were synthesized and completely characterized with different spectroscopic techniques. The molecular structures of a few complexes were determined using single crystal X-ray diffraction studies. These compounds were found to be extremely active towards the bulk ring opening polymerization (ROP) of lactides yielding polymers with high number average molecular weight (M<inf>n</inf>) and controlled molecular weight distributions (MWDs). The neutral complexes 1-8 produce isotactic enriched poly(lactic acid) (PLA) from rac-lactide (rac-LA) under melt conditions, whereas the ionic complex 9 produces atactic PLA. The polymerizations are controlled, as evidenced by the narrow molecular distribution (MWDs) of the isolated polymers in addition to the linear nature of number average molecular weight (M<inf>n</inf>) versus conversion plots with variations in monomer to catalyst ratios. The kinetic and mechanistic studies associated with these polymerizations have been performed. © The Royal Society of Chemistry 2015.

Gallium and indium complexes containing the bis(imino)phenoxide ligand: Synthesis, structural characterization and polymerization studies

A variety of aryloxy compounds and benzyloxy derivatives of TiIV were synthesized from. Ti(iP:rO)4 using the alcoholysis route, These compounds were characterized using various analytical methods and single-crystal X-ray diffraction, MuItinuclear NMR studies prove high degree of fluxional behavior of these compounds in solution. They adopt a dimeric structure in the solid state as seen from. X-ray diffraction studies on a few of them., These compounds are powerful catalysts for the ring-opening polymerization of e-caprolactone (CL) and δ-valerolactone (VL) resulting in high polymers with good number average molecular weights (Mn), Signifi-cant control can be achieved by performing such polymerizations in the presence of benzyl alcohol (BnOH). This is reflected by higher Mn and much narrower molecular weight: distributions (MWDs) of the resulting polymers. Kinetic studies reveal that the rates of such polymerizations are much higher in the presence of BnOH, 1H NMR and MALDI-TOF studies of low molecular weight oligomers suggest: that these polymerizations proceed by the activated monomer mechanism in the presence of BnOH, © 2009 Wiley-VCH Verlag GmbH &amp; Co, KGaA.

European Journal of Inorganic Chemistry

New aryloxy and benzyloxy derivatives of titanium as catalysts for bulk ring-opening polymerization of ε-caprolactone and δ-valerolactone

Inorganic Chemistry

Sulfonamide-Supported Group 4 Catalysts for the Ring-Opening Polymerization of ε-Caprolactone andrac-Lactide

Zinc(II) Homogeneous and Heterogeneous Species and Their Application for the Ring-Opening Polymerisation ofrac-Lactide

Complexes of Mg, Ca and Zn as homogeneous catalysts for lactide polymerization

Chemical Communications

New facets of an old ligand: titanium and zirconium complexes of phenylenediamine bis(phenolate) in lactide polymerisation catalysis

Bis(imino)phenoxide complexes of zirconium: Synthesis, structural characterization and solvent-free ring-opening polymerization of cyclic esters and lactides

Journal	Dalton Transactions
ISSN	14779226
Open Access	No