Mechanistic Studies of Ethylene Hydrophenylation Catalyzed by Bipyridyl Pt(II) Complexes

Description:

This article discusses mechanistic studies of ethylene hydrophenylation catalyzed by bipyridyl Pt(II) complexes.

Creator(s):
Creation Date: November 8, 2011
Partner(s):
UNT College of Arts and Sciences
Collection(s):
UNT Scholarly Works
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Creator (Author):
McKeown, Bradley A.

University of Virginia

Creator (Author):
Gonzalez, Hector Emanuel

University of North Texas

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Friedfeld, Max R.

University of Virginia

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Gunnoe, T. Brent

University of Virginia

Creator (Author):
Cundari, Thomas R., 1964-

University of North Texas

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Sabat, Michal

University of Virginia

Publisher Info:
Publisher Name: American Chemical Society
Place of Publication: [Washington, DC]
Date(s):
  • Creation: November 8, 2011
Description:

This article discusses mechanistic studies of ethylene hydrophenylation catalyzed by bipyridyl Pt(II) complexes.

Degree:
Department: Chemistry
Note:

Reprinted with permission from the Journal of the American Chemical Society. Copyright 2011 American Chemical Society.

Note:

Abstract: Cationic platinum (II) complexes [(ᵗbpy)Pt(Ph)-(L)]⁺[ᵗbpy=4,4'-di-tert-butyl-2,2'-bipyridyl; L = THF, NC₅F₅, or NCMe] catalyze the hydrophenylation of ethylene to generate ethylbenzene and isomers of diethylbenzene. Using ethylene as the limiting reagent, an 89% yield of alkylarene products is achieved after 4 h at 120 ˚C. Catalyst efficiency for ethylene hydrophenylation is diminished only slightly under aerobic conditions. Mechanistic studies support a reaction pathway that involves ethylene coordination to Pt(II), insertion of ethylene into the Pt-phenyl bond, and subsequent metal-mediated benzene C-H activation. Studies of stoichiometric benzene (C₆H₆ or C₆D₆) C-H/C-D activation by [(ᵗbpy)Pt(Ph-dn)-(THF)]⁺ (n = 0 or 5) indicate a kʜ/kᴅ = 1.4(1), while comparative rates of ethylene hydrophenylation using C₆H₆ and C₆D₆ reveal kʜ/kᴅ = 1.8(4) for the overall catalytic reaction. DFT calculations suggest that the transition state for benzene C-H activation is the highest energy species along the catalytic cycle. In CD₂Cl₂, [(ᵗbpy)Pt(Ph)(THF)][BAr'₄] [Ar' = 3,5-bis(trifluoromethyl)phenyl] reacts with ethylene to generate [(ᵗbpy)Pt(CH₂CH₂Ph)(ɳ²-C₂H₄)][BAr'₄] with kobs = 1.05(4) x 10⁻³ s⁻¹ (23 ˚C, [C₂H₄] = 0.10(1) M). In the catalytic hydrophenylation of ethylene, substantial amounts of diethylbenzenes are produced, and experimental studies suggest that the selectivity for the monoalkylated arene is diminished due to a second aromatic C-H activation competing with ethylbenzene dissociation.

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22 p.

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Subject(s):
Keyword(s): ethylene | ethylbenzene | hydrophenylation | catalytic reactions
Source: Journal of the American Chemical Society, 2011, Washington DC: American Chemical Society, pp. 19131-19152
Partner:
UNT College of Arts and Sciences
Collection:
UNT Scholarly Works
Identifier:
  • DOI: 10.1021/ja206064v |
  • ARK: ark:/67531/metadc107788
Resource Type: Article
Format: Text
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Access: Public
Citation:
Publication Title: Journal of the American Chemical Society
Volume: 133
Issue: 47
Page Start: 19131
Page End: 19152
Peer Reviewed: Yes