CaltechAUTHORS
  A Caltech Library Service

Model Ziegler-Natta α-Olefin Polymerization Catalysts Derived from [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}(PMe_3)Sc(µ_2-H)]_2 and [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}Sc(µ_2-CH_2CH_2CH_3)]_2. Synthesis, Structures, and Kinetic and Equilibrium Investigations of the Catalytically Active Species in Solution

Shapiro, Pamela J. and Cotter, W. Donald and Schaefer, William P. and Labinger, Jay A. and Bercaw, John E. (1994) Model Ziegler-Natta α-Olefin Polymerization Catalysts Derived from [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}(PMe_3)Sc(µ_2-H)]_2 and [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}Sc(µ_2-CH_2CH_2CH_3)]_2. Synthesis, Structures, and Kinetic and Equilibrium Investigations of the Catalytically Active Species in Solution. Journal of the American Chemical Society, 116 (11). pp. 4623-4640. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20180530-134833370

[img] PDF - Supplemental Material
See Usage Policy.

6Mb
[img] PDF - Supplemental Material
See Usage Policy.

1236Kb

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20180530-134833370

Abstract

The scandium hydride complex [(Cp*SiNR)(PMe_3)Sc(µ-H)]_2 (1), ((Cp*SiNR) = ((η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}) is prepared by hydrogenation of (Cp*SiNR)ScCH(SiMe_3)_2 in the presence of trimethylphosphine. The hydride complex is a catalyst precursor for the polymerization of α-olefins, yielding atactic products of low molecular weight (M, = 3000-7000). GC/MS analysis of volatile, oligomeric products revealed that all scandium centers are active during the polymerization. Selectivity for head-to-tail insertion is high (>99%) and for the tetramer, pentamer, and hexamer formed during propene polymerization, the maximum theoretical numbers of head-to-tail stereoisomers are observed by capillary GC. The stoichiometric reaction between 1 and 2 equiv of ethylene produces the unusual ethylene-bridged dimer [(Cp*SiNR)(PMe_3)Sc]_2(µ,η^2,η^2-C_2H_4) (2) and an equivalent of ethane, whereas the same reaction with propene affords the phosphine-free, alkyl-bridged scandium dimer [(Cp*S~NR)Sc]_2(µ-CH_2CH_2CH_3)_2 (3). The absence of coordinating phosphine allows the latter complex to function as a more active olefin polymerization catalyst precursor. 1 reacts with styrene to form a unique double-insertion product arising from sequential 1,2- and 2,1-styrene insertion. The structure of the catalytic intermediate in solution was determined by low-temperature ^(13)C-NMR studies of the model complexes (Cp*SiNR)(P(^(13)CH_3)_3]ScCH_2CH(CH_3)CHCH_2CH_2CH_3 and (Cp*SiNR)(PMe_3)Sc^(13)CH_2CHCH(^(13)CH_3)_2. One phosphine-bound species is observed in equilibrium with only one phosphine-free species. The symmetry properties of the latter indicate that it is a monomeric, hence 12-electron, scandium alkyl complex. Semiquantitative treatment of equilibrium concentration data supports this conclusion.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/ja00090a011DOIArticle
https://pubs.acs.org/doi/suppl/10.1021/ja00090a011PublisherSupporting Information
ORCID:
AuthorORCID
Labinger, Jay A.0000-0002-1942-9232
Alternate Title:Model Ziegler-Natta .alpha.-Olefin Polymerization Catalysts Derived from[{(.eta.5-C5Me4)SiMe2(.eta.1-NCMe3)}(PMe3)Sc(.mu.2-H)]2 and[{(.eta.5-C5Me4)SiMe2(.eta.1-NCMe3)}Sc(.mu.2-CH2CH2CH3)]2. Synthesis, Structures, and Kinetic and Equilibrium Investigations
Additional Information:© 1994 American Chemical Society. Received November 18, 1993. This work has been supported by USDOE Office of Basic Energy Sciences (Grant No. DE-FG03-85ER113431) and by Exxon Chemicals America.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-85ER113431
Exxon Chemicals AmericaUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Arnold and Mabel Beckman Laboratories of Chemical Synthesis8894
Issue or Number:11
Record Number:CaltechAUTHORS:20180530-134833370
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180530-134833370
Official Citation:Model Ziegler-Natta .alpha.-Olefin Polymerization Catalysts Derived from[{(.eta.5-C5Me4)SiMe2(.eta.1-NCMe3)}(PMe3)Sc(.mu.2-H)]2 and[{(.eta.5-C5Me4)SiMe2(.eta.1-NCMe3)}Sc(.mu.2-CH2CH2CH3)]2. Synthesis, Structures, and Kinetic and Equilibrium Investigations of the Catalytically Active Species in Solution Pamela J. Shapiro, William P. Schaefer, Jay A. Labinger, John E. Bercaw, and W. Donald Cotter Journal of the American Chemical Society 1994 116 (11), 4623-4640 DOI: 10.1021/ja00090a011
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86721
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:01 Jun 2018 21:42
Last Modified:03 Oct 2019 19:47

Repository Staff Only: item control page