Polymerization of ε-caprolactone using bulky alkoxo-titanium complexes and structural analysis of [Ti(OBorneoxo)2Cl2(thf)2]

Pérez, Yolanda; Hierro, Isabel del; Sierra, Isabel; Gómez‐Sal, Pilar; Fajardo, Mariano; Otero, Antonío

doi:10.1016/j.jorganchem.2006.03.019

Cited by 15 publications

(7 citation statements)

References 35 publications

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“…Based on the obtained results, we suggest that the ring‐opening polymerization of ε‐caprolactone initiated by titanocanes and spirobititanocanes, similarly to other titanium alkoxides,12, 15, 16, 18 proceeds through a “coordination‐insertion” mechanism. In the case of titanocanes, the first step of reaction is the coordination of ε‐caprolactone to the pentacoordinated titanium atom having one vacant site.…”

Section: Discussionmentioning

confidence: 68%

“…On the other hand, structurally well‐defined non‐metallocene Ti‐based catalysts were successfully applied for the living polymerization of olefins 14. Besides, some titanium complexes having bulky alkoxo,15 bis(aryloxo)16, 17 or amine(bisphenolate)18, 19 ligands as well as half‐metallocenes (CpTiCl 3 )20 showed distinctively high activity in the polymerization of ε‐caprolactone or lactide. Poly(ε‐caprolactone) with molecular weight as high as 60,000 g mol −1 and narrow molecular weight distribution ( M w / M n ≤ 1.3) can be typically prepared by living ROP of ε‐caprolactone using aforementioned catalytic complexes 16.…”

Section: Introductionmentioning

confidence: 99%

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Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

Piskun

Vasilenko

Kostjuk

et al. 2010

J. Polym. Sci. A Polym. Chem.

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The titanium complexes with one (1a, 1b, 1c) and two (2a, 2b) dialkanolamine ligands were used as initiators in the ring-opening polymerization (ROP) of e-caprolactone. Titanocanes 1a and 1b initiated living ROP of e-caprolactone affording polymers whose number-average molecular weights (M n ) increased in direct proportion to monomer conversion (M n 30,000 g mol À1 ) in agreement with calculated values, and were inversely proportional to initiator concentration, while the molecular weight distribution stayed narrow throughout the polymerization (M w /M n 1.2 up to 80% monomer conversion). 1 H-NMR and MALDI-TOF-MS studies of the obtained poly(e-caprolactone)s revealed the presence of an isopropoxy group originated from the initiator at the polymer termini, indicating that the polymerization takes place exclusively at the Ti-O i Pr bond of the catalyst. The higher molecular weight polymers (M n 70,000 g mol À1 ) with reasonable MWD (M w /M n 1.6) were synthesized by living ROP of e-caprolactone using spirobititanocanes (2a, 2b) and titanocane 1c as initiators. The latter catalysts, according MALDI-TOF-MS data, afford poly(e-caprolactone)s with almost equal content of a,x-dihydroxyl-and ahydroxyl-x(carboxylic acid)-terminated chains arising due to monomer insertion into ''Ti-O'' bond of dialkanolamine ligand and from initiation via traces of water, respectively.

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Section: Discussionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

Piskun

Vasilenko

Kostjuk

et al. 2010

J. Polym. Sci. A Polym. Chem.

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“…Titanium complexes play a pivotal role in the polymerization of lactones. [25][26][27][28][29][30][31][32] Among the titanium alkoxides applied for the ROP of lactones, simple compounds like titanium tetramethoxide, titanium tetraisopropoxide, and titanium tetratertbutoxide so far played a subordinate role as catalysts due to their rather moderate activity. 16 However, the polymerization of ε-CL and dilactide catalyzed by Ti(OiPr) 4 was successfully accomplished.…”

mentioning

confidence: 99%

Synthesis of dihydroxy telechelic oligomers of β‐butyrolactone catalyzed by titanium(IV)‐alkoxides and their use as macrodiols in polyurethane chemistry

Altmann

Machat

Wolf

et al. 2021

Journal of Polymer Science

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We report on a solvent-free approach for the synthesis of low molecular weight, α,ω-dihydroxy telechelic poly(β-butyrolactone). In the presence of Ti(IV) alkoxides, mixtures of β-butyrolactone and diols, like di-or triethylene glycol, were reacted in ratios between 4:1 and 10:1. The oligomerization proceeds at elevated temperatures (80-100 C). Different alkoxide substituents (R = Me, iPr, tBu) of the Ti(IV)(OR) 4 catalyst were investigated. The resulting oligomers were characterized by nuclear magnetic resonance (NMR), infra-red (IR), gel-permeation chromatography (GPC), titration, and matrix-assisted laser desorption-time-of-flight mass spectrometry (MALDI-ToF-MS) analysis. Aside from low molecular weight products, special effort was devoted to achieve high O-acyl cleavage selectivity and to circumvent the formation of unsaturated end-groups in order to form exclusively dihydroxy-telechelic oligomers. Optimized results in terms of selectivity and reaction rates were achieved at 100 C using catalyst loadings of 0.2 mol% with respect to the monomer. The molecular weights determined by GPC were in good accordance with the ratio of monomer to diol used, confirming successful oligomer formation. Polyurethanes prepared from crude macrodiols without any additional catalyst feature molecular weights up to 50,000 g/mol. The reported work serves as concept to utilize β-lactones for tailored polyol synthesis; the resulting products are suitable for polyurethane chemistry.

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“…1, 15 However, the alkoxo group is not only an ancillary ligand, but also plays an important role in the activation of cyclic esters such as caprolactone and lactide. [16][17][18][19][20][21][22][23] Our interest in studying functionalized cyclopentadienyl compounds with SiClMe 2 moieties, 24-32 moved our research group to synthesize bimetallic cyclopentadienyl disiloxane derivatives with Si-O-Si bridges for Nb, 25 presented two stereogenic Si atoms although formation of the Si-O-Si bridge required the reaction to be regioselective and only one diastereoisomer of C 2 symmetry was obtained. Whereas these types of dinuclear complexes have two potentially active metal centres for olefin polymerization, reactions of the titanium complexes [(TiBz 2 ) 2 (m-{h 5 2 (m-O)})] with Lewis acids formed benzyl bridges between the Ti atoms, which react further in halogenated solvents providing halogen bridges.…”

Section: Introductionmentioning

confidence: 99%

Dinuclear dialkoxo-bridged cyclopentadienylsiloxo titanium complexes

et al. 2009

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Polymerization of ε-caprolactone using bulky alkoxo-titanium complexes and structural analysis of [Ti(OBorneoxo)2Cl2(thf)2]

Cited by 15 publications

References 35 publications

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

Synthesis of dihydroxy telechelic oligomers of β‐butyrolactone catalyzed by titanium(IV)‐alkoxides and their use as macrodiols in polyurethane chemistry

Dinuclear dialkoxo-bridged cyclopentadienylsiloxo titanium complexes

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