Lithium, sodium, potassium and calcium amine-bis(phenolate) complexes in the ring-opening polymerization of <i>rac</i>-lactide

Devaine-Pressing, Katalin; Oldenburg, Fabio; Menzel, Jan Philipp; Springer, Maximilian A.; Kozak, Christopher M.

doi:10.1039/c9dt04561a

Cited by 30 publications

(29 citation statements)

References 92 publications

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“…In the literature, there are some reports on the formation of sodium complexes [ 39 , 40 ], but, to our knowledge, only the following have been proposed as MOCVD precursors: the Na(tmhd)•phen and Na(tmhd)•bipy (Htmhd = 2,2,6,6-tetramethyl-3,5-heptanione, phen= 1,10-phenanthroline, bipy = 2,2′-bipyridyl) complexes [ 41 ]. Nevertheless, these complexes do not contain fluorine in their architecture, and furthermore their mass transport studies show thermal instability.…”

Section: Introductionmentioning

confidence: 99%

Sodium β-Diketonate Glyme Adducts as Precursors for Fluoride Phases: Synthesis, Characterization and Functional Validation

et al. 2022

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Very few sodium complexes are available as precursors for the syntheses of sodium-based nanostructured materials. Herein, the diglyme, triglyme, and tetraglyme (CH3O(CH2CH2O)nCH3, n = 2–4) adducts of sodium hexafluoroacetylacetonate were synthesized in a single-step reaction and characterized by IR spectroscopy, 1H, and 13C NMR. Single-crystal X-ray diffraction studies provide evidence of the formation of the ionic oligomeric structure [Na4(hfa)6]2−•2[Na(diglyme2]+ when the diglyme is coordinated, while a mononuclear seven-coordinated complex Na(hfa)•tetraglyme is formed with the tetraglyme. Reaction with the monoglyme (CH3OCH2CH2OCH3) does not occur, and the unadducted polymeric structure [Na(hfa)]n forms, while the triglyme gives rise to a liquid adduct, Na(hfa)•triglyme•H2O. Thermal analysis data reveal great potentialities for their applications as precursors in metalorganic chemical vapor deposition (MOCVD) and sol-gel processes. As a proof-of-concept, the Na(hfa)•tetraglyme adduct was successfully applied to both the low-pressure MOCVD and the sol-gel/spin-coating synthesis of NaF films.

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Section: Introductionmentioning

confidence: 99%

Sodium β-Diketonate Glyme Adducts as Precursors for Fluoride Phases: Synthesis, Characterization and Functional Validation

et al. 2022

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“…In this context, biologically benign metal-based catalysts are of great interest for the production of this bioassimilable material, with calcium [ 22 , 23 , 24 , 25 ], magnesium [ 26 , 27 , 28 , 29 ] and zinc [ 30 , 31 , 32 , 33 , 34 , 35 ] (see Chart 2 ), as the most representative centres, although other metals from group 13 (aluminium [ 36 ] and indium [ 37 ]), group 4 [ 38 ], as well as rare earth [ 39 ] metals, have been also successfully described, all of them supported by a wide variety of ancillary ligands. These examples constitute a much greener alternative to the toxic industrially employed tin(II) 2-ethylhexanoate, which, despite its robustness, offers poor control of polymer parameters [ 40 ].…”

Section: Introductionmentioning

confidence: 99%

Efficient Bulky Organo-Zinc Scorpionates for the Stereoselective Production of Poly(rac-lactide)s

et al. 2021

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The direct reaction of the highly sterically demanding acetamidinate-based NNN′-scorpionate protioligand Hphbptamd [Hphbptamd = N,N′-di-p-tolylbis(3,5-di-tertbutylpyrazole-1-yl)acetamidine] with one equiv. of ZnMe2 proceeds in high yield to the mononuclear alkyl zinc complex [ZnMe(κ3-phbptamd)] (1). Alternatively, the treatment of the corresponding lithium precursor [Li(phbptamd)(THF)] with ZnCl2 yielded the halide complex [ZnCl(κ3-phbptamd)] (2). The X-ray crystal structure of 1 confirmed unambiguously a mononuclear entity in these complexes, with the zinc centre arranged with a pseudotetrahedral environment and the scorpionate ligand in a κ3-coordination mode. Interestingly, the inexpensive, low-toxic and easily prepared complexes 1 and 2 resulted in highly efficient catalysts for the ring-opening polymerisation of lactides, a sustainable bio-resourced process industrially demanded. Thus, complex 1 behaved as a single-component robust initiator for the living and immortal ROP of rac-lactide under very mild conditions after a few hours, reaching a TOF value up to 5520 h−1 under bulk conditions. Preliminary kinetic studies revealed apparent zero-order dependence on monomer concentration in the absence of a cocatalyst. The PLA materials produced exhibited narrow dispersity values, good agreement between the experimental Mn values and monomer/benzyl alcohol ratios, as well as enhanced levels of heteroselectivity, reaching Ps values up to 0.74.

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“…The bulk of our synthetic studies have focused on the L 8 H 8 system given its cost versus L 6 H 6 or deBuL 8 H 8 . We note that lithiated species as catalysts for the ROP of cyclic esters have been reviewed, , while catalytic ROP systems based lithium-containing rings, cages, and ladders have been reported. − …”

Section: Introductionmentioning

confidence: 99%

Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters

et al. 2021

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A variety of lithiated calix[n]arenes, for which n = 6 or 8, have been isolated, structurally characterized, and evaluated as catalysts for the ring-opening polymerization (ROP) of the cyclic esters ε-caprolactone (ε-CL), δ-valerolactone (δ-VL), and rac-lactide (r-LA). In particular, interaction of p-tert-butylcalix[6]areneH6 (L6H6) with LiOtBu in THF led to the isolation of [Li14(L6H)2(CO3)2(THF)6(OH2)6]·14THF (1·14THF), the core of which has a chain of five Li2O2 diamonds. Similar use of p-tert-butylcalix[8]areneH8 (L8H8) afforded [Li10(L8)(OH)2(THF)8]·7THF (2·7THF), where the core is composed of a six-rung Li–O ladder. Use of debutylated calix[8]areneH8 (deBuL8H8) led to an elongated dimer [Li18(deBuL8)2(OtBu)2(THF)14]·4THF (3·4THF) in which the calix[8]arenes possess a wavelike conformation forming bridges to link three separate Li x O y clusters (where x and y = 6, ignoring the THF donor oxygens). Interaction of L8H8 with LiOH·H2O afforded [Li4(L8H4)(OH2)4(THF)6]·5.5THF (4·5.5THF), where intramolecular H-bond interactions involving Li, O, and H construct a cage in the core of the structure with six- and eight-membered rings. Lastly, addition of Me3Al to the solution generated from L8H8 and LiOtBu led to the isolation of [(AlMe2)2Li20(L8H2)2(OH2)4(O2–)4(OH)2(NCMe)12]·10MeCN (5·10MeCN) in which Li, O, Al, and N centers build a polyhedral core. These complexes have been screened for their potential to act as precatalysts in the ring-opening polymerization (ROP) of ε-CL, δ-VL, and r-LA. For the ROP of ε-CL, δ-VL, and r-LA, systems 1–4 exhibited moderate activity at 130 °C over 8 h. In the case of ROP using the mixed-metal (Li/Al) system 5, better conversions and high molecular weight polymers were achieved. In the case of the ROP of ω-pentadecalactone (ω-PDL), the systems proved to be inactive under the conditions employed herein.

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Lithium, sodium, potassium and calcium amine-bis(phenolate) complexes in the ring-opening polymerization of rac-lactide

Abstract: Li, Na, K and Ca complexes capable of rac-lactide polymerization in both the melt and in solution were synthesized. MALDI-TOF MS showed mainly cyclic PLA was obtained even in the presence of an alcohol co-initiator.

Cited by 30 publications

References 92 publications

Sodium β-Diketonate Glyme Adducts as Precursors for Fluoride Phases: Synthesis, Characterization and Functional Validation

Sodium β-Diketonate Glyme Adducts as Precursors for Fluoride Phases: Synthesis, Characterization and Functional Validation

Efficient Bulky Organo-Zinc Scorpionates for the Stereoselective Production of Poly(rac-lactide)s

Lithiated Calix[n]arenes (n = 6 or 8): Synthesis, Structures, and Use in the Ring-Opening Polymerization of Cyclic Esters

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