Sterically encumbered (perfluoroaryl) borane and aluminate cocatalysts for tuning cation - Anion ion pair structure and reactivity in metallocene polymerization processes. A synthetic, structural, and polymerization study

You Xian Chen, Matthew V. Metz, Liting Li, Charlotte L. Stern, Tobin J Marks

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298 Citations (Scopus)

Abstract

The synthesis and dialkyl abstraction chemistry as well as the unusual cocatalytic characteristics in metallocene-mediated polymerization of two distinctive borane and aluminate cocatalysts tris(2,2',2'nonafluorobiphenyl)borane (PBB) and triphenyl carbenium tris(2,2',2-nonafluorobiphenyl)fluoroaluminate, (Ph3C+PBA-) are reported. Reaction of PBB with Cp'2ThMe2 (Cp' = η5-C5Me5), CGCZrMe2 (CGC = Me2Si(η5-Me4C5)((l)BuN)), and Cp'MMe3 (M = Zr, Hf) cleanly affords base-free cationic complexes Cp'2ThMe+MePBB- (1), CGCZrMe+MePBB- (5), and Cp'MMe2+MePBB- (M = Zr, 7; Hf, 8). In case of CGCTiMe2 and dimethyl zirconocenes, μ-methyl dinuclear cationic complexes [(CGCTiMe)2(μ- Me)]+MePBB(6) and [(L2ZrMe)2(μ-Me)]+MePBB- (L = η5-C5H5 (Cp), 2; η- 1,2-Me2C5H3 (Cp'), 3; Cp', 4; L2 = Me2Si(Ind)2, Ind = η5-C9H6, 9; L2 = Me2C(Flu)(Cp), Flu = η5-C13H8, 10) are formed. A similar reaction with Ph3C+PBA- results in the corresponding complexes CGCZrCH3+PBA- (M = Zr, 19; Ti, 20) and L2ZrCH3+PBA- (L = Cp, 15b; Cp, 16; η5-1,3- (SiMe2)2C5H3, 17; Cp', 18; L2 = Me2Si(Ind)2, 21; L2 = Me2C(Flu)(Cp), 22). Two dinuclear complexes 3 and 13 ([Me2C(Flu)(Cp)Zr(C6F5)]2(μ- F)+MeB(C6F5)3-) derived from borane PBB and B(C6F5)3, respectively, and three other PBAbased monomeric complexes 14 (Ph3C+PBA-), 19, and 21 have been characterized by X-ray diffraction, and these determinations allow detailed analysis of the ion pairing in the solid state. In combination with solution dynamic NMR, all data indicate MePBB--cation interactions to be considerably weaker than those involving MeB(C6F5)3-, while the strongly ion-paired chiral PBA- converts previously enantiomeric cations into pairs of diastereomers. As revealed by dynamic 1H NMR studies, ion pair reorganization/symmetrization in 5 is significantly more rapid than in the MeB(C6F5)3- analogue, suggesting much looser ion pairing in 5. On the other hand, PBA- racemization is a rapid process (e.g., ΔG≠(58 °C) = 16.9(2) kcal/mol for 16), while cation-PBA- ion pairs have higher barriers for ion pair symmetrization than in analogous fluoroaryl borates. Dinuclear complexes 2 and 3 initiate efficient polymerization of methyl methacrylate (MMA) to produce syndiotactic poly(methyl methacrylate) (PMMA), while 9 produces highly isotactic PMMA, and stericalty more accessible complexes 6 and 10 exhibit no activity. For olefin polymerization and copolymerization, PBB-derived cationic complexes, both monomeric and dinuclear, generally exhibit higher catalytic activity and comonomer incorporation levels than the MeB(C6F5)3- analogues, with CGC catalysts exhibiting the greatest activity contrasts. On the other hand, PBA-derived complexes exhibit a remarkable sensitivity of olefin polymerization characteristics and ion pairing to ancillary ligand bulk, with activity differences of up to 106-fold observed. In regard to stereospecific polymerization, PBA-derived chiral complex 21 produces highly isotactic polypropylene while B(C6F5)A-derived analogue produces isotactic polypropylene with lower isotacticity under similar conditions. Microstructure analyses of poly(ethylene-co-1-hexene) samples indicate that PBB enhances comonomer incorporation randomness.

Original languageEnglish
Pages (from-to)6287-6305
Number of pages19
JournalJournal of the American Chemical Society
Volume120
Issue number25
DOIs
Publication statusPublished - Jul 1 1998

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Boranes
Polymerization
Anions
Cations
Negative ions
Tuning
Positive ions
Ions
Polypropylenes
Alkenes
Polymethyl Methacrylate
Polymethyl methacrylates
Olefins
Nuclear magnetic resonance
Borates
Methacrylates
metallocene
X-Ray Diffraction
Copolymerization
Catalyst activity

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{b7e5775d145f4c9183f856c871722d5e,
title = "Sterically encumbered (perfluoroaryl) borane and aluminate cocatalysts for tuning cation - Anion ion pair structure and reactivity in metallocene polymerization processes. A synthetic, structural, and polymerization study",
abstract = "The synthesis and dialkyl abstraction chemistry as well as the unusual cocatalytic characteristics in metallocene-mediated polymerization of two distinctive borane and aluminate cocatalysts tris(2,2',2'nonafluorobiphenyl)borane (PBB) and triphenyl carbenium tris(2,2',2-nonafluorobiphenyl)fluoroaluminate, (Ph3C+PBA-) are reported. Reaction of PBB with Cp'2ThMe2 (Cp' = η5-C5Me5), CGCZrMe2 (CGC = Me2Si(η5-Me4C5)((l)BuN)), and Cp'MMe3 (M = Zr, Hf) cleanly affords base-free cationic complexes Cp'2ThMe+MePBB- (1), CGCZrMe+MePBB- (5), and Cp'MMe2+MePBB- (M = Zr, 7; Hf, 8). In case of CGCTiMe2 and dimethyl zirconocenes, μ-methyl dinuclear cationic complexes [(CGCTiMe)2(μ- Me)]+MePBB(6) and [(L2ZrMe)2(μ-Me)]+MePBB- (L = η5-C5H5 (Cp), 2; η- 1,2-Me2C5H3 (Cp'), 3; Cp', 4; L2 = Me2Si(Ind)2, Ind = η5-C9H6, 9; L2 = Me2C(Flu)(Cp), Flu = η5-C13H8, 10) are formed. A similar reaction with Ph3C+PBA- results in the corresponding complexes CGCZrCH3+PBA- (M = Zr, 19; Ti, 20) and L2ZrCH3+PBA- (L = Cp, 15b; Cp, 16; η5-1,3- (SiMe2)2C5H3, 17; Cp', 18; L2 = Me2Si(Ind)2, 21; L2 = Me2C(Flu)(Cp), 22). Two dinuclear complexes 3 and 13 ([Me2C(Flu)(Cp)Zr(C6F5)]2(μ- F)+MeB(C6F5)3-) derived from borane PBB and B(C6F5)3, respectively, and three other PBAbased monomeric complexes 14 (Ph3C+PBA-), 19, and 21 have been characterized by X-ray diffraction, and these determinations allow detailed analysis of the ion pairing in the solid state. In combination with solution dynamic NMR, all data indicate MePBB--cation interactions to be considerably weaker than those involving MeB(C6F5)3-, while the strongly ion-paired chiral PBA- converts previously enantiomeric cations into pairs of diastereomers. As revealed by dynamic 1H NMR studies, ion pair reorganization/symmetrization in 5 is significantly more rapid than in the MeB(C6F5)3- analogue, suggesting much looser ion pairing in 5. On the other hand, PBA- racemization is a rapid process (e.g., ΔG≠(58 °C) = 16.9(2) kcal/mol for 16), while cation-PBA- ion pairs have higher barriers for ion pair symmetrization than in analogous fluoroaryl borates. Dinuclear complexes 2 and 3 initiate efficient polymerization of methyl methacrylate (MMA) to produce syndiotactic poly(methyl methacrylate) (PMMA), while 9 produces highly isotactic PMMA, and stericalty more accessible complexes 6 and 10 exhibit no activity. For olefin polymerization and copolymerization, PBB-derived cationic complexes, both monomeric and dinuclear, generally exhibit higher catalytic activity and comonomer incorporation levels than the MeB(C6F5)3- analogues, with CGC catalysts exhibiting the greatest activity contrasts. On the other hand, PBA-derived complexes exhibit a remarkable sensitivity of olefin polymerization characteristics and ion pairing to ancillary ligand bulk, with activity differences of up to 106-fold observed. In regard to stereospecific polymerization, PBA-derived chiral complex 21 produces highly isotactic polypropylene while B(C6F5)A-derived analogue produces isotactic polypropylene with lower isotacticity under similar conditions. Microstructure analyses of poly(ethylene-co-1-hexene) samples indicate that PBB enhances comonomer incorporation randomness.",
author = "Chen, {You Xian} and Metz, {Matthew V.} and Liting Li and Stern, {Charlotte L.} and Marks, {Tobin J}",
year = "1998",
month = "7",
day = "1",
doi = "10.1021/ja973769t",
language = "English",
volume = "120",
pages = "6287--6305",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "25",

}

TY - JOUR

T1 - Sterically encumbered (perfluoroaryl) borane and aluminate cocatalysts for tuning cation - Anion ion pair structure and reactivity in metallocene polymerization processes. A synthetic, structural, and polymerization study

AU - Chen, You Xian

AU - Metz, Matthew V.

AU - Li, Liting

AU - Stern, Charlotte L.

AU - Marks, Tobin J

PY - 1998/7/1

Y1 - 1998/7/1

N2 - The synthesis and dialkyl abstraction chemistry as well as the unusual cocatalytic characteristics in metallocene-mediated polymerization of two distinctive borane and aluminate cocatalysts tris(2,2',2'nonafluorobiphenyl)borane (PBB) and triphenyl carbenium tris(2,2',2-nonafluorobiphenyl)fluoroaluminate, (Ph3C+PBA-) are reported. Reaction of PBB with Cp'2ThMe2 (Cp' = η5-C5Me5), CGCZrMe2 (CGC = Me2Si(η5-Me4C5)((l)BuN)), and Cp'MMe3 (M = Zr, Hf) cleanly affords base-free cationic complexes Cp'2ThMe+MePBB- (1), CGCZrMe+MePBB- (5), and Cp'MMe2+MePBB- (M = Zr, 7; Hf, 8). In case of CGCTiMe2 and dimethyl zirconocenes, μ-methyl dinuclear cationic complexes [(CGCTiMe)2(μ- Me)]+MePBB(6) and [(L2ZrMe)2(μ-Me)]+MePBB- (L = η5-C5H5 (Cp), 2; η- 1,2-Me2C5H3 (Cp'), 3; Cp', 4; L2 = Me2Si(Ind)2, Ind = η5-C9H6, 9; L2 = Me2C(Flu)(Cp), Flu = η5-C13H8, 10) are formed. A similar reaction with Ph3C+PBA- results in the corresponding complexes CGCZrCH3+PBA- (M = Zr, 19; Ti, 20) and L2ZrCH3+PBA- (L = Cp, 15b; Cp, 16; η5-1,3- (SiMe2)2C5H3, 17; Cp', 18; L2 = Me2Si(Ind)2, 21; L2 = Me2C(Flu)(Cp), 22). Two dinuclear complexes 3 and 13 ([Me2C(Flu)(Cp)Zr(C6F5)]2(μ- F)+MeB(C6F5)3-) derived from borane PBB and B(C6F5)3, respectively, and three other PBAbased monomeric complexes 14 (Ph3C+PBA-), 19, and 21 have been characterized by X-ray diffraction, and these determinations allow detailed analysis of the ion pairing in the solid state. In combination with solution dynamic NMR, all data indicate MePBB--cation interactions to be considerably weaker than those involving MeB(C6F5)3-, while the strongly ion-paired chiral PBA- converts previously enantiomeric cations into pairs of diastereomers. As revealed by dynamic 1H NMR studies, ion pair reorganization/symmetrization in 5 is significantly more rapid than in the MeB(C6F5)3- analogue, suggesting much looser ion pairing in 5. On the other hand, PBA- racemization is a rapid process (e.g., ΔG≠(58 °C) = 16.9(2) kcal/mol for 16), while cation-PBA- ion pairs have higher barriers for ion pair symmetrization than in analogous fluoroaryl borates. Dinuclear complexes 2 and 3 initiate efficient polymerization of methyl methacrylate (MMA) to produce syndiotactic poly(methyl methacrylate) (PMMA), while 9 produces highly isotactic PMMA, and stericalty more accessible complexes 6 and 10 exhibit no activity. For olefin polymerization and copolymerization, PBB-derived cationic complexes, both monomeric and dinuclear, generally exhibit higher catalytic activity and comonomer incorporation levels than the MeB(C6F5)3- analogues, with CGC catalysts exhibiting the greatest activity contrasts. On the other hand, PBA-derived complexes exhibit a remarkable sensitivity of olefin polymerization characteristics and ion pairing to ancillary ligand bulk, with activity differences of up to 106-fold observed. In regard to stereospecific polymerization, PBA-derived chiral complex 21 produces highly isotactic polypropylene while B(C6F5)A-derived analogue produces isotactic polypropylene with lower isotacticity under similar conditions. Microstructure analyses of poly(ethylene-co-1-hexene) samples indicate that PBB enhances comonomer incorporation randomness.

AB - The synthesis and dialkyl abstraction chemistry as well as the unusual cocatalytic characteristics in metallocene-mediated polymerization of two distinctive borane and aluminate cocatalysts tris(2,2',2'nonafluorobiphenyl)borane (PBB) and triphenyl carbenium tris(2,2',2-nonafluorobiphenyl)fluoroaluminate, (Ph3C+PBA-) are reported. Reaction of PBB with Cp'2ThMe2 (Cp' = η5-C5Me5), CGCZrMe2 (CGC = Me2Si(η5-Me4C5)((l)BuN)), and Cp'MMe3 (M = Zr, Hf) cleanly affords base-free cationic complexes Cp'2ThMe+MePBB- (1), CGCZrMe+MePBB- (5), and Cp'MMe2+MePBB- (M = Zr, 7; Hf, 8). In case of CGCTiMe2 and dimethyl zirconocenes, μ-methyl dinuclear cationic complexes [(CGCTiMe)2(μ- Me)]+MePBB(6) and [(L2ZrMe)2(μ-Me)]+MePBB- (L = η5-C5H5 (Cp), 2; η- 1,2-Me2C5H3 (Cp'), 3; Cp', 4; L2 = Me2Si(Ind)2, Ind = η5-C9H6, 9; L2 = Me2C(Flu)(Cp), Flu = η5-C13H8, 10) are formed. A similar reaction with Ph3C+PBA- results in the corresponding complexes CGCZrCH3+PBA- (M = Zr, 19; Ti, 20) and L2ZrCH3+PBA- (L = Cp, 15b; Cp, 16; η5-1,3- (SiMe2)2C5H3, 17; Cp', 18; L2 = Me2Si(Ind)2, 21; L2 = Me2C(Flu)(Cp), 22). Two dinuclear complexes 3 and 13 ([Me2C(Flu)(Cp)Zr(C6F5)]2(μ- F)+MeB(C6F5)3-) derived from borane PBB and B(C6F5)3, respectively, and three other PBAbased monomeric complexes 14 (Ph3C+PBA-), 19, and 21 have been characterized by X-ray diffraction, and these determinations allow detailed analysis of the ion pairing in the solid state. In combination with solution dynamic NMR, all data indicate MePBB--cation interactions to be considerably weaker than those involving MeB(C6F5)3-, while the strongly ion-paired chiral PBA- converts previously enantiomeric cations into pairs of diastereomers. As revealed by dynamic 1H NMR studies, ion pair reorganization/symmetrization in 5 is significantly more rapid than in the MeB(C6F5)3- analogue, suggesting much looser ion pairing in 5. On the other hand, PBA- racemization is a rapid process (e.g., ΔG≠(58 °C) = 16.9(2) kcal/mol for 16), while cation-PBA- ion pairs have higher barriers for ion pair symmetrization than in analogous fluoroaryl borates. Dinuclear complexes 2 and 3 initiate efficient polymerization of methyl methacrylate (MMA) to produce syndiotactic poly(methyl methacrylate) (PMMA), while 9 produces highly isotactic PMMA, and stericalty more accessible complexes 6 and 10 exhibit no activity. For olefin polymerization and copolymerization, PBB-derived cationic complexes, both monomeric and dinuclear, generally exhibit higher catalytic activity and comonomer incorporation levels than the MeB(C6F5)3- analogues, with CGC catalysts exhibiting the greatest activity contrasts. On the other hand, PBA-derived complexes exhibit a remarkable sensitivity of olefin polymerization characteristics and ion pairing to ancillary ligand bulk, with activity differences of up to 106-fold observed. In regard to stereospecific polymerization, PBA-derived chiral complex 21 produces highly isotactic polypropylene while B(C6F5)A-derived analogue produces isotactic polypropylene with lower isotacticity under similar conditions. Microstructure analyses of poly(ethylene-co-1-hexene) samples indicate that PBB enhances comonomer incorporation randomness.

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U2 - 10.1021/ja973769t

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VL - 120

SP - 6287

EP - 6305

JO - Journal of the American Chemical Society

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SN - 0002-7863

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