Dehydrogenation of ketones by pincer-ligated iridium: Formation and reactivity of novel enone complexes

Xiawei Zhang; David Y. Wang; Thomas J. Emge; Alan S. Goldman

doi:10.1016/j.ica.2010.11.016

Dehydrogenation of ketones by pincer-ligated iridium: Formation and reactivity of novel enone complexes

Xiawei Zhang, David Y. Wang, Thomas J. Emge, Alan S. Goldman

School of Arts and Sciences, Chemistry & Chemical Biology

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

29 Scopus citations

Abstract

The transfer dehydrogenation of several ketones by (PCP)IrH₂ (PCP = κ³-C₆H₃-2,6-(CH₂P ^tBu₂)₂) (1) has been observed. Catalytic turnover was inhibited in most cases by the formation of stable metallacycles or the O-H oxidative addition of phenolic products. Catalytic transfer dehydrogenation of 3,3-dimethylcyclohexanone was achieved, giving the corresponding α,β-enone. The transfer dehydrogenation reaction of cycloheptanone with 1 was found to generate a surprisingly stable PCP-iridium troponyl hydride (9), which is stabilized by conjugation and possibly represents an unusual bicyclo[5.2.0]troponyliridium metalloaromatic structure. Complex 9 was found to catalyze the dimerization of tropone to give a fused tricyclic dihydrodicycloheptafuranol. A mechanism for this reaction is proposed wherein the coordinated troponyl group nucleophilically attacks a free tropone molecule.

Original language	English (US)
Pages (from-to)	253-259
Number of pages	7
Journal	Inorganica Chimica Acta
Volume	369
Issue number	1
DOIs	https://doi.org/10.1016/j.ica.2010.11.016
State	Published - Apr 15 2011

All Science Journal Classification (ASJC) codes

Physical and Theoretical Chemistry
Inorganic Chemistry
Materials Chemistry

Keywords

Organometallic homogeneous catalysis
PCP pincer-ligated iridium complexes
Transfer dehydrogenation of ketones
Tropone dimerization
X-ray crystal structures

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10.1016/j.ica.2010.11.016

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title = "Dehydrogenation of ketones by pincer-ligated iridium: Formation and reactivity of novel enone complexes",

abstract = "The transfer dehydrogenation of several ketones by (PCP)IrH2 (PCP = κ3-C6H3-2,6-(CH2P tBu2)2) (1) has been observed. Catalytic turnover was inhibited in most cases by the formation of stable metallacycles or the O-H oxidative addition of phenolic products. Catalytic transfer dehydrogenation of 3,3-dimethylcyclohexanone was achieved, giving the corresponding α,β-enone. The transfer dehydrogenation reaction of cycloheptanone with 1 was found to generate a surprisingly stable PCP-iridium troponyl hydride (9), which is stabilized by conjugation and possibly represents an unusual bicyclo[5.2.0]troponyliridium metalloaromatic structure. Complex 9 was found to catalyze the dimerization of tropone to give a fused tricyclic dihydrodicycloheptafuranol. A mechanism for this reaction is proposed wherein the coordinated troponyl group nucleophilically attacks a free tropone molecule.",

keywords = "Organometallic homogeneous catalysis, PCP pincer-ligated iridium complexes, Transfer dehydrogenation of ketones, Tropone dimerization, X-ray crystal structures",

author = "Xiawei Zhang and Wang, {David Y.} and Emge, {Thomas J.} and Goldman, {Alan S.}",

note = "Funding Information: We thank the National Science Foundation (Grant CHE-0719307 ) for support of this work. ",

year = "2011",

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doi = "10.1016/j.ica.2010.11.016",

language = "English (US)",

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T2 - Formation and reactivity of novel enone complexes

AU - Zhang, Xiawei

AU - Wang, David Y.

AU - Emge, Thomas J.

AU - Goldman, Alan S.

N1 - Funding Information: We thank the National Science Foundation (Grant CHE-0719307 ) for support of this work.

PY - 2011/4/15

Y1 - 2011/4/15

N2 - The transfer dehydrogenation of several ketones by (PCP)IrH2 (PCP = κ3-C6H3-2,6-(CH2P tBu2)2) (1) has been observed. Catalytic turnover was inhibited in most cases by the formation of stable metallacycles or the O-H oxidative addition of phenolic products. Catalytic transfer dehydrogenation of 3,3-dimethylcyclohexanone was achieved, giving the corresponding α,β-enone. The transfer dehydrogenation reaction of cycloheptanone with 1 was found to generate a surprisingly stable PCP-iridium troponyl hydride (9), which is stabilized by conjugation and possibly represents an unusual bicyclo[5.2.0]troponyliridium metalloaromatic structure. Complex 9 was found to catalyze the dimerization of tropone to give a fused tricyclic dihydrodicycloheptafuranol. A mechanism for this reaction is proposed wherein the coordinated troponyl group nucleophilically attacks a free tropone molecule.

AB - The transfer dehydrogenation of several ketones by (PCP)IrH2 (PCP = κ3-C6H3-2,6-(CH2P tBu2)2) (1) has been observed. Catalytic turnover was inhibited in most cases by the formation of stable metallacycles or the O-H oxidative addition of phenolic products. Catalytic transfer dehydrogenation of 3,3-dimethylcyclohexanone was achieved, giving the corresponding α,β-enone. The transfer dehydrogenation reaction of cycloheptanone with 1 was found to generate a surprisingly stable PCP-iridium troponyl hydride (9), which is stabilized by conjugation and possibly represents an unusual bicyclo[5.2.0]troponyliridium metalloaromatic structure. Complex 9 was found to catalyze the dimerization of tropone to give a fused tricyclic dihydrodicycloheptafuranol. A mechanism for this reaction is proposed wherein the coordinated troponyl group nucleophilically attacks a free tropone molecule.

KW - Organometallic homogeneous catalysis

KW - PCP pincer-ligated iridium complexes

KW - Transfer dehydrogenation of ketones

KW - Tropone dimerization

KW - X-ray crystal structures

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Dehydrogenation of ketones by pincer-ligated iridium: Formation and reactivity of novel enone complexes

Abstract

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