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The role of alkane coordination in C–H bond cleavage at a Pt(II) center

Chen, George S. and Labinger, Jay A. and Bercaw, John E. (2007) The role of alkane coordination in C–H bond cleavage at a Pt(II) center. Proceedings of the National Academy of Sciences of the United States of America, 104 (17). pp. 6915-6920. ISSN 0027-8424. PMCID PMC1855376. https://resolver.caltech.edu/CaltechAUTHORS:CHEpnas07a

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Abstract

The rates of CFormula H bond activation for various alkanes by [(N–N)Pt(Me)(TFEd3)]+ (N Formula N = ArFormula NFormula C(Me)Formula C(Me)Formula NFormula Ar; Ar = 3,5-di-tert-butylphenyl; TFE-d3 = CF3CD2OD) were studied. Both linear and cyclic alkanes give the corresponding alkene-hydride cation [(N–N)Pt(H)(alkene)]+ via (i) rate determining alkane coordination to form a CFormula H {sigma} complex, (ii) oxidative cleavage of the coordinated CFormula H bond to give a platinum(IV) alkyl-methyl-hydride intermediate, (iii) reductive coupling to generate a methane {sigma} complex, (iv) dissociation of methane, and (v) beta-H elimination to form the observed product. Second-order rate constants for cycloalkane activation (CnH2n), are proportional to the size of the ring (k ~ n). For cyclohexane, the deuterium kinetic isotope effect (kH/kD) of 1.28 (5) is consistent with the proposed rate determining alkane coordination to form a CFormula H {sigma} complex. Statistical scrambling of the five hydrogens of the Pt-methyl and the coordinated methylene unit, via rapid, reversible steps ii and iii, and interchange of geminal CFormula H bonds of the methane and cyclohexane CFormula H {sigma} adducts, is observed before loss of methane.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1855376/PubMed CentralArticle
https://doi.org/10.1073/pnas.0610981104DOIUNSPECIFIED
https://doi.org/10.1073/pnas.0610981104DOIUNSPECIFIED
ORCID:
AuthorORCID
Labinger, Jay A.0000-0002-1942-9232
Additional Information:© 2007 by the National Academy of Sciences. Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved February 15, 2007 (received for review December 11, 2006). Published online before print April 6, 2007, 10.1073/pnas.0610981104 We thank Dr. Travis Williams and Bo-Lin Lin for useful discussions and assistance in preparing the manuscript. This work was supported by British Petroleum as part of the Methane Conversion Consortium and a National Science Foundation Graduate Research Fellowship (to G.S.C.). Coordination Chemistry of Saturated Molecules Special Feature. Author contributions: G.S.C., J.A.L., and J.E.B. designed research; G.S.C. performed research; G.S.C. contributed new reagents/analytic tools; G.S.C., J.A.L., and J.E.B. analyzed data; and G.S.C., J.A.L., and J.E.B. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/cgi/content/full/0610981104/DC1.
Funders:
Funding AgencyGrant Number
BP MC2 programUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:alkane functionalization; C–H activation; catalysis; organometallic chemistry
Issue or Number:17
PubMed Central ID:PMC1855376
Record Number:CaltechAUTHORS:CHEpnas07a
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:CHEpnas07a
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9384
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:17 Dec 2007
Last Modified:02 Oct 2019 23:59

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