CaltechAUTHORS
  A Caltech Library Service

Preparation of ansa-Niobocene and ansa-Tantalocene Olefin Hydride Complexes as Transition State Analogues in Metallocene-Catalyzed Olefin Polymerization

Chirik, Paul J. and Zubris, Deanna L. and Ackerman, Lily J. and Henling, Lawrence M. and Day, Michael W. and Bercaw, John E. (2003) Preparation of ansa-Niobocene and ansa-Tantalocene Olefin Hydride Complexes as Transition State Analogues in Metallocene-Catalyzed Olefin Polymerization. Organometallics, 22 (1). pp. 172-187. ISSN 0276-7333. https://resolver.caltech.edu/CaltechAUTHORS:20170808-142319435

[img] PDF - Supplemental Material
See Usage Policy.

1224Kb
[img] PDF - Supplemental Material
See Usage Policy.

815Kb

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20170808-142319435

Abstract

o examine the effects of cyclopentadienyl and olefin substitution on preferred stereochemistry, a series of singly [SiMe_2]-bridged ansa-niobocene and -tantalocene olefin hydride complexes has been prepared via reduction and alkylation of the corresponding dichloride complexes. In this manner, [Me_2Si(η^5-C_5H_4)(η^5-C_5H_3-3-R)]M(CH_2⚌CHR‘)H (M = Nb, Ta; R = CHMe_2, CMe_3; R‘ = H, C6H5; M = Ta; R = CHMe2, CMe3; R‘ = Me), rac- and meso-[Me_2Si(η^5-C_5H_3-3-R)(η^5-C_5H^3-3-R)]Nb(CH_2⚌CH_2)H (R = CMe_3), and [Me_2Si(η^5-C_5H_4)(η^5-C_5H^2-2,4-(CHMe_2)_2)]Ta(CH_2⚌CHR‘)H (R‘ = H, C_6H_5) have been prepared and characterized by NMR spectroscopy and, in some cases, X-ray diffraction. The doubly [SiMe_2]-bridged ansa-tantalocene ethylene hydride complex [(1,2-SiMe_2)_2(η^5-C_5H-3,5-(CHMe_2)_2)(η^5-C_5H_2-4-CMe_3)]Ta(CH_2⚌CH_2)H has been prepared from thermolysis of the methylidene methyl complex [(1,2-SiMe_2)_2(η^5-C_5H-3,5-(CHMe_2)_2)(η^5-C_5H_2-4-CMe_3)]Ta(CH_2)CH_3. Addition of an excess of propylene or styrene to the tantalocene ethylene hydride results in olefin exchange and formation of the olefin hydride complexes [(1,2-SiMe_2)_2(η^5-C_5H-3,5-(CHMe_2)_2)(η^5-C_5H_2-4-CMe_3)]Ta(CH_2⚌CHR‘)H (R‘ = CH_3, C_6H_5). These compounds serve as stable transition state analogues for the much more kinetically labile group 4 metallocenium cationic intermediates in metallocene-catalyzed olefin polymerization. Characterization of the thermodynamically preferred isomers of metallocene olefin hydride complexes reveals that alkyl substitution on the cyclopentadienyl ligand array may have a significant effect on the stereochemistry of olefin coordination.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/om020628dDOIArticle
http://pubs.acs.org/doi/abs/10.1021/om020628dPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/om020628dPublisherSupporting Information
Additional Information:© 2003 American Chemical Society. Received 2 August 2002. Published online 7 December 2002. Published in print 1 January 2003. This work has been supported by the USDOE Office of Basic Energy Sciences (Grant No. DE-FG03-85ER13431) and Exxon Chemicals America. L.J.A. wishes to thank the National Science Foundation for a Graduate Research Fellowship.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-85ER13431
Exxon Chemicals AmericaUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20170808-142319435
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170808-142319435
Official Citation:Preparation of ansa-Niobocene and ansa-Tantalocene Olefin Hydride Complexes as Transition State Analogues in Metallocene-Catalyzed Olefin Polymerization Paul J. Chirik, Deanna L. Zubris, Lily J. Ackerman, Lawrence M. Henling, Michael W. Day, and John E. Bercaw Organometallics 2003 22 (1), 172-187 DOI: 10.1021/om020628d
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79954
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:09 Aug 2017 18:20
Last Modified:03 Oct 2019 18:26

Repository Staff Only: item control page