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Title: Metal–Ligand Bifunctional Catalysis: The “Accepted” Mechanism, the Issue of Concertedness, and the Function of the Ligand in Catalytic Cycles Involving Hydrogen Atoms

For years, following the ideas of Shvo and Noyori, the core assumption of metal–ligand bifunctional molecular catalysis has relied on the direct involvement of the chelating ligand in the catalytic reaction via a reversible proton (H +) transfer through cleavage/formation of one of its X–H bonds (X = O, N, C). A recently revised mechanism of the Noyori asymmetric hydrogenation reaction (Dub, P. A. et al. J. Am. Chem. Soc. 2014, 136, 3505) suggests that the ligand is rather involved in the catalytic reaction via the stabilization of determining transition states through N–H···O hydrogen-bonding interactions (HBIs) and not via a reversible H + transfer, behaving in a chemically intact manner within the productive cycle or predominantly in a chemically intact manner within productive cycles. By reexamining selected examples of computational mechanistic studies involving bifunctional catalysts from the literature in the years between 2012–2017, the purpose of this paper is to point out common misconceptions in modeling concerted reactions and show that the actual stepwise nature of key transition states unveils a more complicated catalytic reaction pool (all conceivable catalytic pathways and their crossovers). Such a realization can not only potentially result in a reconsideration of the “accepted” mechanism but alsomore » lead us to a new conceptual understanding of the role that the ligand plays in the reaction. Finally, the ultimate goal of this paper is, therefore, to encourage the reader to reconsider the function of the ligand in catalytic cycles of hydrogenation/dehydrogenation with bifunctional catalysts, which until recently has relied almost exclusively on a chemically noninnocent ligand.« less
Authors:
ORCiD logo [1] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-24272
Journal ID: ISSN 2155-5435
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 7; Journal Issue: 10; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE; LANL Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Inorganic and Physical Chemistry
OSTI Identifier:
1409775

Dub, Pavel A., and Gordon, John C.. Metal–Ligand Bifunctional Catalysis: The “Accepted” Mechanism, the Issue of Concertedness, and the Function of the Ligand in Catalytic Cycles Involving Hydrogen Atoms. United States: N. p., Web. doi:10.1021/acscatal.7b01791.
Dub, Pavel A., & Gordon, John C.. Metal–Ligand Bifunctional Catalysis: The “Accepted” Mechanism, the Issue of Concertedness, and the Function of the Ligand in Catalytic Cycles Involving Hydrogen Atoms. United States. doi:10.1021/acscatal.7b01791.
Dub, Pavel A., and Gordon, John C.. 2017. "Metal–Ligand Bifunctional Catalysis: The “Accepted” Mechanism, the Issue of Concertedness, and the Function of the Ligand in Catalytic Cycles Involving Hydrogen Atoms". United States. doi:10.1021/acscatal.7b01791. https://www.osti.gov/servlets/purl/1409775.
@article{osti_1409775,
title = {Metal–Ligand Bifunctional Catalysis: The “Accepted” Mechanism, the Issue of Concertedness, and the Function of the Ligand in Catalytic Cycles Involving Hydrogen Atoms},
author = {Dub, Pavel A. and Gordon, John C.},
abstractNote = {For years, following the ideas of Shvo and Noyori, the core assumption of metal–ligand bifunctional molecular catalysis has relied on the direct involvement of the chelating ligand in the catalytic reaction via a reversible proton (H+) transfer through cleavage/formation of one of its X–H bonds (X = O, N, C). A recently revised mechanism of the Noyori asymmetric hydrogenation reaction (Dub, P. A. et al. J. Am. Chem. Soc. 2014, 136, 3505) suggests that the ligand is rather involved in the catalytic reaction via the stabilization of determining transition states through N–H···O hydrogen-bonding interactions (HBIs) and not via a reversible H+ transfer, behaving in a chemically intact manner within the productive cycle or predominantly in a chemically intact manner within productive cycles. By reexamining selected examples of computational mechanistic studies involving bifunctional catalysts from the literature in the years between 2012–2017, the purpose of this paper is to point out common misconceptions in modeling concerted reactions and show that the actual stepwise nature of key transition states unveils a more complicated catalytic reaction pool (all conceivable catalytic pathways and their crossovers). Such a realization can not only potentially result in a reconsideration of the “accepted” mechanism but also lead us to a new conceptual understanding of the role that the ligand plays in the reaction. Finally, the ultimate goal of this paper is, therefore, to encourage the reader to reconsider the function of the ligand in catalytic cycles of hydrogenation/dehydrogenation with bifunctional catalysts, which until recently has relied almost exclusively on a chemically noninnocent ligand.},
doi = {10.1021/acscatal.7b01791},
journal = {ACS Catalysis},
number = 10,
volume = 7,
place = {United States},
year = {2017},
month = {8}
}