Molecular recognition in Mn-catalyzed C-H oxidation. Reaction mechanism and origin of selectivity from a DFT perspective

David Balcells, Pamela Moles, James D. Blakemore, Christophe Raynaud, Gary W Brudvig, Robert H. Crabtree, Odile Eisenstein

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Experimental studies have shown that the C-H oxidation of Ibuprofen and methylcyclohexane acetic acid can be carried out with high selectivities using [(terpy')Mn(OH2)(μ-O)2Mn(OH2)(terpy')] 3+ as catalyst, where terpy' is a terpyridine ligand functionalized with a phenylene linker and a Kemp's triacid serving to recognize the reactant via H-bonding. Experiments, described here, suggest that the sulfate counter anion, present in stochiometric amounts, coordinates to manganese in place of water. DFT calculations have been carried out using [(terpy')Mn(O)(μ-O) 2Mn(SO4)(terpy')]+ as a model catalyst, to analyze the origin of selectivity and its relation to molecular recognition, as well as the mechanism of catalyst inhibition by tert-butyl benzoic acid. The calculations show that a number of spin states, all having radical oxygen character, are energetically accessible. All these spin states promote C-H oxidation via a rebound mechanism. The catalyst recognizes the substrate by a double H bond. This interaction orients the substrate inducing highly selective C-H oxidation. The double hydrogen bond stabilizes the reactant, the transition state and the product to the same extent. Consequently, the reaction occurs at lower energy than without molecular recognition. The association of the catalyst with tert-butyl benzoic acid is shown to shield the access of unbound substrate to the reactive oxo site, hence preventing non-selective hydroxylation. It is shown that the two recognition sites of the catalyst can be used in a cooperative manner to control the access to the reactive centre.

Original languageEnglish
Pages (from-to)5989-6000
Number of pages12
JournalDalton Transactions
Issue number30
DOIs
Publication statusPublished - 2009

Fingerprint

Molecular recognition
Discrete Fourier transforms
Oxidation
Catalysts
Benzoic Acid
Substrates
Hydroxylation
Catalyst selectivity
Ibuprofen
Manganese
Acetic Acid
Sulfates
Anions
Reactive Oxygen Species
Hydrogen bonds
Association reactions
Ligands
Water
Experiments

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Molecular recognition in Mn-catalyzed C-H oxidation. Reaction mechanism and origin of selectivity from a DFT perspective. / Balcells, David; Moles, Pamela; Blakemore, James D.; Raynaud, Christophe; Brudvig, Gary W; Crabtree, Robert H.; Eisenstein, Odile.

In: Dalton Transactions, No. 30, 2009, p. 5989-6000.

Research output: Contribution to journalArticle

Balcells, David ; Moles, Pamela ; Blakemore, James D. ; Raynaud, Christophe ; Brudvig, Gary W ; Crabtree, Robert H. ; Eisenstein, Odile. / Molecular recognition in Mn-catalyzed C-H oxidation. Reaction mechanism and origin of selectivity from a DFT perspective. In: Dalton Transactions. 2009 ; No. 30. pp. 5989-6000.
@article{65930a656a224370b4cf2e1d0af4b004,
title = "Molecular recognition in Mn-catalyzed C-H oxidation. Reaction mechanism and origin of selectivity from a DFT perspective",
abstract = "Experimental studies have shown that the C-H oxidation of Ibuprofen and methylcyclohexane acetic acid can be carried out with high selectivities using [(terpy')Mn(OH2)(μ-O)2Mn(OH2)(terpy')] 3+ as catalyst, where terpy' is a terpyridine ligand functionalized with a phenylene linker and a Kemp's triacid serving to recognize the reactant via H-bonding. Experiments, described here, suggest that the sulfate counter anion, present in stochiometric amounts, coordinates to manganese in place of water. DFT calculations have been carried out using [(terpy')Mn(O)(μ-O) 2Mn(SO4)(terpy')]+ as a model catalyst, to analyze the origin of selectivity and its relation to molecular recognition, as well as the mechanism of catalyst inhibition by tert-butyl benzoic acid. The calculations show that a number of spin states, all having radical oxygen character, are energetically accessible. All these spin states promote C-H oxidation via a rebound mechanism. The catalyst recognizes the substrate by a double H bond. This interaction orients the substrate inducing highly selective C-H oxidation. The double hydrogen bond stabilizes the reactant, the transition state and the product to the same extent. Consequently, the reaction occurs at lower energy than without molecular recognition. The association of the catalyst with tert-butyl benzoic acid is shown to shield the access of unbound substrate to the reactive oxo site, hence preventing non-selective hydroxylation. It is shown that the two recognition sites of the catalyst can be used in a cooperative manner to control the access to the reactive centre.",
author = "David Balcells and Pamela Moles and Blakemore, {James D.} and Christophe Raynaud and Brudvig, {Gary W} and Crabtree, {Robert H.} and Odile Eisenstein",
year = "2009",
doi = "10.1039/b905317d",
language = "English",
pages = "5989--6000",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "30",

}

TY - JOUR

T1 - Molecular recognition in Mn-catalyzed C-H oxidation. Reaction mechanism and origin of selectivity from a DFT perspective

AU - Balcells, David

AU - Moles, Pamela

AU - Blakemore, James D.

AU - Raynaud, Christophe

AU - Brudvig, Gary W

AU - Crabtree, Robert H.

AU - Eisenstein, Odile

PY - 2009

Y1 - 2009

N2 - Experimental studies have shown that the C-H oxidation of Ibuprofen and methylcyclohexane acetic acid can be carried out with high selectivities using [(terpy')Mn(OH2)(μ-O)2Mn(OH2)(terpy')] 3+ as catalyst, where terpy' is a terpyridine ligand functionalized with a phenylene linker and a Kemp's triacid serving to recognize the reactant via H-bonding. Experiments, described here, suggest that the sulfate counter anion, present in stochiometric amounts, coordinates to manganese in place of water. DFT calculations have been carried out using [(terpy')Mn(O)(μ-O) 2Mn(SO4)(terpy')]+ as a model catalyst, to analyze the origin of selectivity and its relation to molecular recognition, as well as the mechanism of catalyst inhibition by tert-butyl benzoic acid. The calculations show that a number of spin states, all having radical oxygen character, are energetically accessible. All these spin states promote C-H oxidation via a rebound mechanism. The catalyst recognizes the substrate by a double H bond. This interaction orients the substrate inducing highly selective C-H oxidation. The double hydrogen bond stabilizes the reactant, the transition state and the product to the same extent. Consequently, the reaction occurs at lower energy than without molecular recognition. The association of the catalyst with tert-butyl benzoic acid is shown to shield the access of unbound substrate to the reactive oxo site, hence preventing non-selective hydroxylation. It is shown that the two recognition sites of the catalyst can be used in a cooperative manner to control the access to the reactive centre.

AB - Experimental studies have shown that the C-H oxidation of Ibuprofen and methylcyclohexane acetic acid can be carried out with high selectivities using [(terpy')Mn(OH2)(μ-O)2Mn(OH2)(terpy')] 3+ as catalyst, where terpy' is a terpyridine ligand functionalized with a phenylene linker and a Kemp's triacid serving to recognize the reactant via H-bonding. Experiments, described here, suggest that the sulfate counter anion, present in stochiometric amounts, coordinates to manganese in place of water. DFT calculations have been carried out using [(terpy')Mn(O)(μ-O) 2Mn(SO4)(terpy')]+ as a model catalyst, to analyze the origin of selectivity and its relation to molecular recognition, as well as the mechanism of catalyst inhibition by tert-butyl benzoic acid. The calculations show that a number of spin states, all having radical oxygen character, are energetically accessible. All these spin states promote C-H oxidation via a rebound mechanism. The catalyst recognizes the substrate by a double H bond. This interaction orients the substrate inducing highly selective C-H oxidation. The double hydrogen bond stabilizes the reactant, the transition state and the product to the same extent. Consequently, the reaction occurs at lower energy than without molecular recognition. The association of the catalyst with tert-butyl benzoic acid is shown to shield the access of unbound substrate to the reactive oxo site, hence preventing non-selective hydroxylation. It is shown that the two recognition sites of the catalyst can be used in a cooperative manner to control the access to the reactive centre.

UR - http://www.scopus.com/inward/record.url?scp=68149119189&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=68149119189&partnerID=8YFLogxK

U2 - 10.1039/b905317d

DO - 10.1039/b905317d

M3 - Article

C2 - 19623399

AN - SCOPUS:68149119189

SP - 5989

EP - 6000

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 30

ER -