Half-sandwich samarium (III) diketiminate bromide as a catalyst for methyl methacrylate polymerization

Fabri, Fabio; Muterle, Roberto Bineli; Oliveira, Wanda de; Schuchardt, Ulf

doi:10.1016/j.polymer.2006.04.055

Cited by 11 publications

(7 citation statements)

References 11 publications

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“…Several other research groups have also reported the use of REM complexes incorporating half-sandwich-type ligands for polymerization of polar vinyl monomers, including linked Cp-amido ligands for acrylate and acrylonitrile polymerization by Okuda, 5 linked Cp-amino ligands for MMA polymerization by Cui, 6 linked fluorenyl-amido ligands for MMA polymerization by Carpentier, 7 boron-bridged indenyl-carboranyl ligands for MMA polymerization by Xie, 8 and nonlinked Cp-β-diketiminate ligands for MMA polymerization by Shen 9 and Schuchardt. 10 However, from polymerization control and syndiospecificity points of view, none of the above systems rivals the simple Cp*-based system reported by Yasuda. 4 As petroleum resources continue to be depleted, there exists an imminent challenge of gradually replacing existing petroleumbased polymeric materials with those derived from naturally occurring, renewable resources in a technologically and economically competitive fashion.…”

Section: Introductionmentioning

confidence: 99%

“…Upon increasing the reaction temperature to 0 and 25 °C, the activity drastically increased to 100 and 200 h −1 TOF, but the syndiotacticity dropped to 80 and 74% rr , respectively. Several other research groups have also reported the use of REM complexes incorporating half-sandwich-type ligands for polymerization of polar vinyl monomers, including linked Cp-amido ligands for acrylate and acrylonitrile polymerization by Okuda, linked Cp-amino ligands for MMA polymerization by Cui, linked fluorenyl-amido ligands for MMA polymerization by Carpentier, boron-bridged indenyl-carboranyl ligands for MMA polymerization by Xie, and nonlinked Cp-β-diketiminate ligands for MMA polymerization by Shen and Schuchardt . However, from polymerization control and syndiospecificity points of view, none of the above systems rivals the simple Cp*-based system reported by Yasuda …”

Section: Introductionmentioning

confidence: 99%

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Polymerization of Naturally Renewable Methylene Butyrolactones by Half-Sandwich Indenyl Rare Earth Metal Dialkyls with Exceptional Activity

Zhang

et al. 2010

Macromolecules

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Four discrete half-sandwich dialkyl rare earth metal (REM) complexes incorporating a disilylated indenyl ligand, (1,3-(SiMe 3 ) 2 C 9 H 5 )M(CH 2 SiMe 3 ) 2 (THF) (M = Sc, Y, Dy, Lu), have been investigated for the coordination-addition polymerization of naturally renewable methylene butyrolactones, R-methylene-γ-butyrolactone (MBL) and γ-methyl-R-methylene-γ-butyrolactone (MMBL). Initial screening for the polymerization of methyl methacrylate highlighted several differences in catalytic behavior between these half-sandwich REM catalysts and well-studied sandwich REM catalysts in terms of reactivity trend, polymer tacticity, and solvent dependence. Most significantly, all four catalysts herein exhibit exceptional activity for polymerization of MMBL in DMF, achieving quantitative monomer conversion in <1 min with a 0.20 mol % catalyst loading and giving a high turnover frequency of >30 000 h -1 . Slower polymerizations occur in CH 2 Cl 2 , allowing for establishment of the activity trend within this REM series, which follows: Dy (largest ion) g Y > Lu > Sc (smallest ion). The most active and effective Dy catalyst has been examined in detail, demonstrating its ability to control the polymerization for producing PMMBL with high T g (221 °C) and with molecular weight ranging from a medium M n of 1.89 Â 10 4 Da to a high M n of 1.63 Â 10 5 Da, programmed by the [MMBL]/[Dy] ratio. Kinetic experiments have revealed a first-order dependence on [monomer] and a second-order dependence on [REM]. These kinetic results, coupled to catalyst efficiencies, NMR studies, as well as with chain-end group analysis by MALDI-TOF mass spectrometry, have yielded a chain initiation mechanism that involves both alkyl groups on each metal center and a bimolecular chain propagation that involves two metal centers in the rate-limiting C-C bond forming step. The Dy catalyst response to enolizable organo acids, externally added as chain-transfer agents, has also been examined.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polymerization of Naturally Renewable Methylene Butyrolactones by Half-Sandwich Indenyl Rare Earth Metal Dialkyls with Exceptional Activity

Zhang

et al. 2010

Macromolecules

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“…Chelating systems such as b-diketones 1,2 and their nitrogen analogues, b-iminoketones and b-diketimines (1,5diazapentadienes), [3][4][5][6][7][8][9][10][11][12][13][14][15][16] are some of the most ubiquitous ligands in chemistry. They have been utilized widely in coordination chemistry [17][18][19][20] and to prepare homogeneous catalysts [21][22][23][24] as well as for modeling active sites of metalloenzymes.…”

Section: Introductionmentioning

confidence: 99%

Silver(i) and copper(i) complexes supported by fully fluorinated 1,3,5-triazapentadienyl ligands

et al. 2011

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Synthesis of the perfluorinated 1,3,5-triazapentadiene [N{(CF(3))C(C(6)F(5))N}(2)]H and the use of its conjugate base as a supporting ligand for the isolation of silver(i) and copper(i) complexes are reported. Some of the related chemistry involving [N{(C(3)F(7))C(C(6)F(5))N}(2)](-) (that has bulkier -C(3)F(7) groups on the 1,3,5-triazapentadienyl ligand backbone) is also presented. X-ray crystallographic data show a wide variety of structures ranging from intermolecular, hydrogen-bonded chain structure for [N{(CF(3))C(C(6)F(5))N}(2)]H with a twisted W-shaped N(3)C(2) core, monomeric [N{(CF(3))C(C(6)F(5))N}(2)]Ag(CN(t)Bu)(2) and [N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(CN(t)Bu)(2) where the κ(1)-bonded triazapentadienyl ligand bonding to the metal fragment via the central nitrogen atom, monomeric [N{(CF(3))C(C(6)F(5))N}(2)]Ag(PPh(3))(2) and [N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(PPh(3))(2) that feature κ(1)-bonded triazapentadienyl ligand bonding to the metal fragment via one of the terminal nitrogen atoms, to that of the monomeric [N{(CF(3))C(C(6)F(5))N}(2)]Cu(CN(t)Bu)(2) containing a κ(2)-bonded triazapentadienyl ligand and a U-shaped NCNCN ligand backbone. The isocyanide adducts show relatively high ν(CN) values in the IR spectra.

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“…So far, the hydride is still coordinated to the boron atom (B-H distance of 1. 33 A and C-H distance of 1.41 A). The activation barrier is found to be kinetically accessible (18.9 kcal mol À1 for 2 and 16.5 kcal mol À1 for 1).…”

Section: Resultsmentioning

confidence: 95%

“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] On the other hand, isotactic-enriched PMMA prepared from related group 3 metals are much less common. [31][32][33][34] Regarding rare earth borohydride derivatives, mono-, bis-or tris-borohydridodiamide-diamine, guanidinate, amino-or alkylsubstituted cyclopentadienyl, and alkoxide complexes have been recently reported to polymerize MMA. [35][36][37][38][39][40] Molar mass values typically ranged from 7500 up to 100 000 g mol À1 (as high as 615 000 g mol À1 ) whereas molar mass distributions were quite large (1.2 < M w / M n < 2.9), and even multi-modal in several instances.…”

Section: Introductionmentioning

confidence: 99%

Bis(phosphinimino)methanide borohydride complexes of the rare-earth elements as initiators for the polymerization of methyl methacrylate: combined experimental and computational investigations

Guillaume¹,

Brignou²,

Susperrégui³

et al. 2011

Polym. Chem.

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International audienceRare earth borohydride complexes are known as efficient initiators for the polymerization of both apolar and polar monomers. Significant contribution of the phosphiniminomethanide ligand on the reactivity of group 3 derivatives was previously established in the polymerization of ε-caprolactone. Investigations of the capability of bis(phosphinimino)methanide rare earth metal bisborohydrides, [{CH(PPh2NSiMe3)2}La(BH4)2(THF)] (1) and [{CH(PPh2NSiMe3)2}Ln(BH4)2] (Ln = Y (2), Lu (3)) to polymerize methyl methacrylate (MMA) both experimentally and computationally, are reported here. All three metallic compounds allowed the preparation of PMMA at room temperature. However, the overall performances of 1-3 remain quite poor based on experimental observations. DFT investigations on the insertion of the first two MMA molecules revealed that the incoming of the first MMA molecule was the most important step regardless of the nature of the metal center. The nucleophilic attack of MMA leads to the formation of a first adduct B followed by the unprecedented trapping of the liberated BH3 group by the nitrogen of the phosphiniminomethanide ligand to afford the active enolate species C. The unique significant role played by the phosphiniminomethanide ligand has thus been clearly unveiled and evidenced computationally. This whole first insertion of the MMA process is both kinetically and thermodynamically favorable. Trapping of the BH3 by the ancillary ligand appeared to make the second MMA insertion more energetically favorable than the first one, especially for lanthanum. The ketoenolate thus formed, Prod., is thermodynamically and kinetically favorable. In the case of yttrium, steric considerations, in addition to energetically comparable first and second MMA insertions , support the experimentally observed difficulty to polymerize MMA. DFT calculations closely corroborate experimental findings

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Half-sandwich samarium (III) diketiminate bromide as a catalyst for methyl methacrylate polymerization

Cited by 11 publications

References 11 publications

Polymerization of Naturally Renewable Methylene Butyrolactones by Half-Sandwich Indenyl Rare Earth Metal Dialkyls with Exceptional Activity

Polymerization of Naturally Renewable Methylene Butyrolactones by Half-Sandwich Indenyl Rare Earth Metal Dialkyls with Exceptional Activity

Silver(i) and copper(i) complexes supported by fully fluorinated 1,3,5-triazapentadienyl ligands

Bis(phosphinimino)methanide borohydride complexes of the rare-earth elements as initiators for the polymerization of methyl methacrylate: combined experimental and computational investigations

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