Kinetic and mechanism of alkene polymerization

Manfred Bochmann; Roderick D. Cannon; Fuquan Song

doi:10.1134/S0023158406020029

Kinetic and mechanism of alkene polymerization

Manfred Bochmann, Roderick D. Cannon, Fuquan Song

Research output: Contribution to journal › Article › peer-review

23 Citations (Scopus)

Abstract

Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C₆F₅)₃}₂]^- (1), [H₂N{(C₆F₅)₃}₂]^- and [M{CNB(C₆F₅)₃}₄]^2- (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe₂/1/AlBu ₃ ⁱ (SBI = rac-Me₂Si(Ind)₂) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl₂/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C₆F₅)₃}₂]^- > [H₂N{(C₆F₅)₃}₂]^- ˜ B(C₆F₅) ₄ ^- » [MeB(C₆F₅)₃]^-. The highest productivities were of the order of ca. 3.0 × 10⁸ g PP (mol Zr)^-1 h^-1 [C₃H₆]^-1, about 1.3–1.5 times higher than with B(C₆F₅) ₄ ^- as the counter anion. The titanium system CGCTiMe₂/1/AlBu ₃ ⁱ gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH₂SiMe₃)(µ-Me)B(C₆F₅)₃ and [(SBI)MCH₂SiMe ₃ ⁺ ...B(C₆F₅) ₄ ^- ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C₆F₅)₃ compound exists as a simple inner-sphere ion-pair, the B(C₆F₅) ₄ ^- compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the ?-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I _a) pathway.

Original language	English
Pages (from-to)	160-169
Number of pages	10
Journal	Kinetics and Catalysis
Volume	47
Issue number	2
DOIs	https://doi.org/10.1134/S0023158406020029
Publication status	Published - 2006

Access to Document

10.1134/S0023158406020029

Cite this

@article{84801d26f7fd448981451bb57feddc3f,

title = "Kinetic and mechanism of alkene polymerization",

abstract = "Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C6F5)3}2]- (1), [H2N{(C6F5)3}2]- and [M{CNB(C6F5)3}4]2- (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe2/1/AlBu 3 i (SBI = rac-Me2Si(Ind)2) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl2/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C6F5)3}2]- > [H2N{(C6F5)3}2]- ˜ B(C6F5) 4 - » [MeB(C6F5)3]-. The highest productivities were of the order of ca. 3.0 × 108 g PP (mol Zr)-1 h-1 [C3H6]-1, about 1.3–1.5 times higher than with B(C6F5) 4 - as the counter anion. The titanium system CGCTiMe2/1/AlBu 3 i gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH2SiMe3)(µ-Me)B(C6F5)3 and [(SBI)MCH2SiMe 3 + ...B(C6F5) 4 - ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C6F5)3 compound exists as a simple inner-sphere ion-pair, the B(C6F5) 4 - compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the ?-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I a) pathway.",

author = "Manfred Bochmann and Cannon, {Roderick D.} and Fuquan Song",

year = "2006",

doi = "10.1134/S0023158406020029",

language = "English",

volume = "47",

pages = "160--169",

journal = "Kinetics and Catalysis",

publisher = "Maik Nauka-Interperiodica Publishing",

number = "2",

}

TY - JOUR

T1 - Kinetic and mechanism of alkene polymerization

AU - Bochmann, Manfred

AU - Cannon, Roderick D.

AU - Song, Fuquan

PY - 2006

Y1 - 2006

N2 - Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C6F5)3}2]- (1), [H2N{(C6F5)3}2]- and [M{CNB(C6F5)3}4]2- (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe2/1/AlBu 3 i (SBI = rac-Me2Si(Ind)2) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl2/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C6F5)3}2]- > [H2N{(C6F5)3}2]- ˜ B(C6F5) 4 - » [MeB(C6F5)3]-. The highest productivities were of the order of ca. 3.0 × 108 g PP (mol Zr)-1 h-1 [C3H6]-1, about 1.3–1.5 times higher than with B(C6F5) 4 - as the counter anion. The titanium system CGCTiMe2/1/AlBu 3 i gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH2SiMe3)(µ-Me)B(C6F5)3 and [(SBI)MCH2SiMe 3 + ...B(C6F5) 4 - ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C6F5)3 compound exists as a simple inner-sphere ion-pair, the B(C6F5) 4 - compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the ?-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I a) pathway.

AB - Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C6F5)3}2]- (1), [H2N{(C6F5)3}2]- and [M{CNB(C6F5)3}4]2- (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe2/1/AlBu 3 i (SBI = rac-Me2Si(Ind)2) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl2/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C6F5)3}2]- > [H2N{(C6F5)3}2]- ˜ B(C6F5) 4 - » [MeB(C6F5)3]-. The highest productivities were of the order of ca. 3.0 × 108 g PP (mol Zr)-1 h-1 [C3H6]-1, about 1.3–1.5 times higher than with B(C6F5) 4 - as the counter anion. The titanium system CGCTiMe2/1/AlBu 3 i gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH2SiMe3)(µ-Me)B(C6F5)3 and [(SBI)MCH2SiMe 3 + ...B(C6F5) 4 - ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C6F5)3 compound exists as a simple inner-sphere ion-pair, the B(C6F5) 4 - compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the ?-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I a) pathway.

U2 - 10.1134/S0023158406020029

DO - 10.1134/S0023158406020029

M3 - Article

VL - 47

SP - 160

EP - 169

JO - Kinetics and Catalysis

JF - Kinetics and Catalysis

IS - 2

ER -