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Title: Experimental and DFT Computational Study of β-Me and β-H Elimination Coupled with Proton Transfer: From Amides to Enamides in Cp* 2 MX (M = La, Ce)

Abstract

The thermal rearrangement of the f-block metallocene amides Cp*2MNR1R2, where R1 is CHMe2, R2 is either CHMe2 or CMe3, and M is either La or Ce, to the corresponding enamides Cp*2MNR1[C(Me)=CH2] and H2 or CH4, respectively, occurs when the solid amides are heated in sealed evacuated ampules at 160–180 °C for 1–2 weeks. The net reaction is a β-H or β-Me elimination followed by a γ-abstraction of a proton at the group from which the β-elimination occurs. When R1 is either SiMe3 or SiMe2CMe3 and R2 is CMe3, the enamide Cp*2MNR1[C(Me)=CH2] is isolated, the result of β-Me elimination, but when R2 is CHMe2, the enamides Cp*2MNR1[C(Me)=CH2] and Cp*2NR1[C(H)=CH2] are isolated, the result of β-H and β-Me elimination. In the latter cases, both enamides are formed in similar amounts and the rates of the β-H and β-Me elimination steps must be similar. A two-step mechanism is developed from DFT calculations. The first step is migration of a hydride or a methyl anion to the Cp*2M fragment, forming M–H or M–Me bonds as the N=C bond in the intermediate imine forms. Furthermore, the enamide evolves from the metal-coordinated imine by abstraction of a proton from the γ-carbon of the intermediate imine. Themore » two elementary steps involve significant geometrical changes within the NαCβCγ set of atoms during the two-step elimination process that are in large part responsible for the relatively high activation barriers for the net reaction, which may be classified as a proton-coupled hydride or methyl anion transfer reaction.« less

Authors:
 [1];  [2];  [3];  [1]
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  1. Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
  2. Université Lyon 1, CNRS UMR 5246, Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne, France
  3. Institut Charles Gerhardt, CNRS UMR 5253, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier, France
Publication Date:
Research Org.:
Univ. of California, Berkeley, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1330108
Alternate Identifier(s):
OSTI ID: 1339954
Grant/Contract Number:  
AC02- 05CH11231; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Organometallics
Additional Journal Information:
Journal Name: Organometallics Journal Volume: 36 Journal Issue: 1; Journal ID: ISSN 0276-7333
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Rozenel, Sergio S., Perrin, Lionel, Eisenstein, Odile, and Andersen, Richard A. Experimental and DFT Computational Study of β-Me and β-H Elimination Coupled with Proton Transfer: From Amides to Enamides in Cp* 2 MX (M = La, Ce). United States: N. p., 2016. Web. doi:10.1021/acs.organomet.6b00677.
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Rozenel, Sergio S., Perrin, Lionel, Eisenstein, Odile, & Andersen, Richard A. Experimental and DFT Computational Study of β-Me and β-H Elimination Coupled with Proton Transfer: From Amides to Enamides in Cp* 2 MX (M = La, Ce). United States. https://doi.org/10.1021/acs.organomet.6b00677
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Rozenel, Sergio S., Perrin, Lionel, Eisenstein, Odile, and Andersen, Richard A. Wed . "Experimental and DFT Computational Study of β-Me and β-H Elimination Coupled with Proton Transfer: From Amides to Enamides in Cp* 2 MX (M = La, Ce)". United States. https://doi.org/10.1021/acs.organomet.6b00677.
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@article{osti_1330108,
title = {Experimental and DFT Computational Study of β-Me and β-H Elimination Coupled with Proton Transfer: From Amides to Enamides in Cp* 2 MX (M = La, Ce)},
author = {Rozenel, Sergio S. and Perrin, Lionel and Eisenstein, Odile and Andersen, Richard A.},
abstractNote = {The thermal rearrangement of the f-block metallocene amides Cp*2MNR1R2, where R1 is CHMe2, R2 is either CHMe2 or CMe3, and M is either La or Ce, to the corresponding enamides Cp*2MNR1[C(Me)=CH2] and H2 or CH4, respectively, occurs when the solid amides are heated in sealed evacuated ampules at 160–180 °C for 1–2 weeks. The net reaction is a β-H or β-Me elimination followed by a γ-abstraction of a proton at the group from which the β-elimination occurs. When R1 is either SiMe3 or SiMe2CMe3 and R2 is CMe3, the enamide Cp*2MNR1[C(Me)=CH2] is isolated, the result of β-Me elimination, but when R2 is CHMe2, the enamides Cp*2MNR1[C(Me)=CH2] and Cp*2NR1[C(H)=CH2] are isolated, the result of β-H and β-Me elimination. In the latter cases, both enamides are formed in similar amounts and the rates of the β-H and β-Me elimination steps must be similar. A two-step mechanism is developed from DFT calculations. The first step is migration of a hydride or a methyl anion to the Cp*2M fragment, forming M–H or M–Me bonds as the N=C bond in the intermediate imine forms. Furthermore, the enamide evolves from the metal-coordinated imine by abstraction of a proton from the γ-carbon of the intermediate imine. The two elementary steps involve significant geometrical changes within the NαCβCγ set of atoms during the two-step elimination process that are in large part responsible for the relatively high activation barriers for the net reaction, which may be classified as a proton-coupled hydride or methyl anion transfer reaction.},
doi = {10.1021/acs.organomet.6b00677},
journal = {Organometallics},
number = 1,
volume = 36,
place = {United States},
year = {Wed Oct 26 00:00:00 EDT 2016},
month = {Wed Oct 26 00:00:00 EDT 2016}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1021/acs.organomet.6b00677
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Cited by: 12 works
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Figures / Tables:

Scheme 1 Scheme 1: β-Methyl Elimination from an f-Block Metal Alkyl Compound
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Works referencing / citing this record:

CCDC 1483809: Experimental Crystal Structure Determination: RAKHOD : bis(η5-pentamethylcyclopentadienyl)-(t-butyl(isopropyl)amino)-cerium
dataset, June 2016

CCDC 1483823: Experimental Crystal Structure Determination: RAKHUJ : bis(η5-pentamethylcyclopentadienyl)-(bis(trimethylsilyl)amino)-cerium
dataset, June 2016

CCDC 1483836: Experimental Crystal Structure Determination: RAKJIZ : bis(η5-pentamethylcyclopentadienyl)-(isopropyl(dimethylsilyl)amino)-cerium
dataset, June 2016

CCDC 1483848: Experimental Crystal Structure Determination: RAKKEW : bis(η5-pentamethylcyclopentadienyl)-(t-butyl(trimethylsilyl)amino)-cerium
dataset, June 2016

Pentamethylcyclopentadienyl-Supported Cerocene(III) Complexes: Pentamethylcyclopentadienyl-Supported Cerocene(III) Complexes
journal, February 2017

  • Schneider, David; Anwander, Reiner
  • European Journal of Inorganic Chemistry, Vol. 2017, Issue 8
  • DOI: 10.1002/ejic.201601404

Pentamethylcyclopentadienyl-Supported Cerocene(III) Complexes: Pentamethylcyclopentadienyl-Supported Cerocene(III) Complexes
journal, February 2017

  • Schneider, David; Anwander, Reiner
  • European Journal of Inorganic Chemistry, Vol. 2017, Issue 8
  • DOI: 10.1002/ejic.201601404
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    Figures / Tables found in this record:

    Scheme 1 (p. 1)figure
    Scheme 2 (p. 2)figure
    Table 1 (p. 2)table
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    Scheme 3 (p. 4)figure
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    Figure 5 (p. 6)figure
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    Scheme 4 (p. 7)figure
    Table 8 (p. 8)table
    Table 9 (p. 8)table
    Table 10 (p. 9)table
    Figure 6 (p. 10)figure
    Figure 7 (p. 10)figure
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