Catalytic Activity of a Titanium(IV)/Iron(II) Heterometallic Alkoxide in the Ring-Opening Polymerization of ε-Caprolactone and<i>rac</i>-Lactide

Giese, Siddhartha O. K.; Egevardt, Cristiano; Rüdiger, André Luis; Sá, Eduardo L. de; Silva, Thiago Alessandre; Zawadzki, Sônia Faria; Soares, Jaı́sa F.; Nunes, Giovana G.

doi:10.5935/0103-5053.20150214

Cited by 4 publications

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“…Hitherto, catalytic ROP of cyclic esters, such as LAs and lactones, has been explored by the use of organocatalysts, − as well as discrete metal precursors of chiral ligands, such as complexes of tin, , aluminum, − zinc, , magnesium, , iron, , titanium, , indium, yttrium, rare-earth metals, , and organo-initiators . Generally, only a limited number of isoselective achiral catalysts are well-known in the literature (Figure ), and most isoselective ROPs are based on expensive chiral catalysts.…”

Section: Introductionmentioning

confidence: 99%

Ring Opening Polymerization and Copolymerization of Cyclic Esters Catalyzed by Group 2 Metal Complexes Supported by Functionalized P–N Ligands

Harinath

Bhattacharjee

Sarkar³

et al. 2018

Inorg. Chem.

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We report the preparation of alkali and alkaline earth (Ae) metal complexes supported by 2-picolylamino-diphenylphosphane chalcogenide [(PhP(=E)NHCH(CHN)] [E = S (1-H); Se (2-H)] ligands. The treatment of the protic ligand, 1-H or 2-H, with alkali metal hexamethyldisilazides at room temperature afforded the corresponding alkali metal salts [M(THF)(PhP(=E)NCH(CHN)] [M = Li, E = S (3a), Se (3b)] and [{M(THF) (PhP(=E)NCH(CHN)}] [M = Na, E = S (4a), Se (4b); M = K, E = Se (5b)] in good yield. The homoleptic Ae metal complexes [κ-(PhP(=Se)NCH(CHN)Mg(THF)] (6b) and [κ-{(PhP(=Se)NCH(CHN)}M(THF) ] (M = Ca (7b), Sr (8b), Ba (9b)] were synthesized by the one-pot reaction of 2-H with [KN(SiMe)] and MI in a 2:2:1 molar ratio at room temperature. The molecular structures of the protic-ligands 1-H and 2-H, as well as complexes 3a,b-5a,b and 6b-9b were established using single-crystal X-ray analysis. The Ae metal complexes 6b-9b were tested for ring-opening polymerization (ROP) of racemic lactide ( rac-LA) and copolymerization of rac-LA and ε-caprolactone (ε-CL) at room temperature. In the ROP of rac-LA, the calcium complex 7b exhibited high isoselectivity, with P = 0.89, whereas both the barium and strontium complexes showed lower isoselectivity with P = 0.78-0.62. In the copolymerization of rac-LA and ε-CL, both barium and strontium complexes proved to be efficient precatalysts for the formation of the block copolymer rac-LA-CL, but the reactivity of 9b was found to be better than that of 8b. All the polymers were fully characterized using differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography analyses. Kinetic studies on the ROP reaction of LA confirmed that the rate of polymerization followed the order Ba ≫ Sr ≈ Ca.

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Section: Introductionmentioning

confidence: 99%

Ring Opening Polymerization and Copolymerization of Cyclic Esters Catalyzed by Group 2 Metal Complexes Supported by Functionalized P–N Ligands

Harinath

Bhattacharjee

Sarkar³

et al. 2018

Inorg. Chem.

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“…However, the ESR measurements undoubtedly showed it is not phenylsilver (Figure S14). Rather, it was speculated that the oxidation state of Ag in PMP–I–Ag 1 is 0, because (1) it is paramagnetic, (2) it disappeared upon exposure to O 2 without regeneration of SAAg, and (3) it was maintained upon interaction with reducing reagents like alcohol and ascorbic acid (Tables S1 and S2). The loading of SAAg reached the minimum at t ≈ 2 h and subsequently increased, showing that SAAg could be regenerated from the system.…”

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confidence: 99%

Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation

Cui

Zhang

et al. 2019

ACS Catal.

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The dehalogenation–arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h–1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.

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“…Mid- to late d n -transition metal complexes, on the other hand, have been sparingly studied. Very few studies investigated the performance of Cr, Mn, − or Co systems. ,, Next to iron, ,− copper complexes received the highest attention. − We have reported that copper diiminopyrrolide complex 1 polymerizes rac -lactide with an isoselectivity of P m = 0.7 at room temperature (Scheme ). Isoselective stereocontrol was unprecedented for copper complexes.…”

Section: Introductionmentioning

confidence: 99%

Catalytic-Site-Mediated Chain-End Control in the Polymerization of rac-Lactide with Copper Iminopyrrolide Complexes

et al. 2018

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Reaction of copper(II) methoxide with N-R-2-iminopyrroles (LH) and pyridylmethanol (R′OH) provided the dinuclear complexes {LCu(μ-OR′)} 2 (R = naphtyl, CHPh 2 , 2,6-xylyl, 2,6-diisopropylphenyl (diip), or p-bromobenzyl). All complexes crystallized as dinuclear compounds with a square-pyramidal coordination geometry around copper and either imine or pyridine (for R = diip) in the apical position. The naphthyl-substituted complex was inactive in rac-lactide polymerization at room temperature in benzene. All other complexes showed good activity with apparent rate constants of k obs = 0.16(1)−1.89(8) h −1 at 2 mM catalyst concentration. All complexes showed a preference for slight isotactic monomer enchainment with P m = 0.60−0.68. Stereoerror analysis indicate that the chain-end determines stereocontrol. A dependance of stereocontrol on the steric bulk of the ligand, on the initial monomer concentration and on the symmetry of the catalytic site support that the chiral information on the chain-end is mediated via the catalytic site (catalytic-site-mediated chain-end control).

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Catalytic Activity of a Titanium(IV)/Iron(II) Heterometallic Alkoxide in the Ring-Opening Polymerization of ε-Caprolactone andrac-Lactide

Cited by 4 publications

References 0 publications

Ring Opening Polymerization and Copolymerization of Cyclic Esters Catalyzed by Group 2 Metal Complexes Supported by Functionalized P–N Ligands

Ring Opening Polymerization and Copolymerization of Cyclic Esters Catalyzed by Group 2 Metal Complexes Supported by Functionalized P–N Ligands

Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation

Catalytic-Site-Mediated Chain-End Control in the Polymerization of rac-Lactide with Copper Iminopyrrolide Complexes

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