Heterometallic Co III Zn II schiff base catalyst for mild hydroxylation of C(sp 3 )–H bonds of unactivated alkanes: Evidence for dual mechanism controlled by the promoter

Oksana V. Nesterova, Katerina V. Kasyanova, Elena A. Buvaylo, Olga Yu Vassilyeva, Brian W. Skelton, Dmytro S. Nesterov, Armando J.L. Pombeiro

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The novel Schiff base complex [Co III Zn II L 3 Cl 2 ]·CH 3 OH (1) was synthesized by interaction of zinc powder, cobalt(II) chloride and methanol solution of the pre-formed HL in air (HL is the product of condensation of o-vanillin and methylamine) and characterized by IR, UV-Vis and NMR spectroscopy, ESI-MS and single crystal X-ray diffraction analysis. In the heterometallic core of 1 the two metal centers are bridged by deprotonated phenoxy groups of the L ligands with the cobalt-zinc separation of 3.123 Å. Catalytic investigations demonstrated a pronounced activity of 1 towards mild alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as the model substrate. The influence of the nature of different promoting agents of various acidities (from HOTf to pyridine) on the catalytic process was studied in detail and a pronounced activity of 1 in the presence of nitric acid promoter was found, also showing a high retention of stereoconfiguration of the substrate (>99% for cis-1,2-DMCH). The best achieved yield of tertiary cis-alcohol based on the oxidant was 61%, with a turnover number (TON) of 198 for nitric acid as promoter. The 18 O-incorporations into the alcohols when the reactions were performed under 18 O 2 atmosphere using acetic and nitric acid promoters, suggest that the cis-1,2-DMCH hydroxylation proceeds by two distinct pathways, a non-stereoselective and a stereoselective one (with and without involvement of a long-lived free carbon radical, respectively). The former dominates in the case of acetic acid promoter and the latter is realized in the case of HNO 3 promoter.

Original languageEnglish
Article number209
JournalCatalysts
Volume9
Issue number3
DOIs
Publication statusPublished - 1 Mar 2019

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Nitric Acid
Hydroxylation
Alkanes
Schiff Bases
nitric acid
Nitric acid
Paraffins
imines
alkanes
Oxidants
acetic acid
catalysts
Acetic acid
Catalysts
Zinc
Cobalt
alcohols
Alcohols
cobalt
zinc

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Nesterova, Oksana V. ; Kasyanova, Katerina V. ; Buvaylo, Elena A. ; Vassilyeva, Olga Yu ; Skelton, Brian W. ; Nesterov, Dmytro S. ; Pombeiro, Armando J.L. / Heterometallic Co III Zn II schiff base catalyst for mild hydroxylation of C(sp 3 )–H bonds of unactivated alkanes : Evidence for dual mechanism controlled by the promoter. In: Catalysts. 2019 ; Vol. 9, No. 3.
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abstract = "The novel Schiff base complex [Co III Zn II L 3 Cl 2 ]·CH 3 OH (1) was synthesized by interaction of zinc powder, cobalt(II) chloride and methanol solution of the pre-formed HL in air (HL is the product of condensation of o-vanillin and methylamine) and characterized by IR, UV-Vis and NMR spectroscopy, ESI-MS and single crystal X-ray diffraction analysis. In the heterometallic core of 1 the two metal centers are bridged by deprotonated phenoxy groups of the L − ligands with the cobalt-zinc separation of 3.123 {\AA}. Catalytic investigations demonstrated a pronounced activity of 1 towards mild alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as the model substrate. The influence of the nature of different promoting agents of various acidities (from HOTf to pyridine) on the catalytic process was studied in detail and a pronounced activity of 1 in the presence of nitric acid promoter was found, also showing a high retention of stereoconfiguration of the substrate (>99{\%} for cis-1,2-DMCH). The best achieved yield of tertiary cis-alcohol based on the oxidant was 61{\%}, with a turnover number (TON) of 198 for nitric acid as promoter. The 18 O-incorporations into the alcohols when the reactions were performed under 18 O 2 atmosphere using acetic and nitric acid promoters, suggest that the cis-1,2-DMCH hydroxylation proceeds by two distinct pathways, a non-stereoselective and a stereoselective one (with and without involvement of a long-lived free carbon radical, respectively). The former dominates in the case of acetic acid promoter and the latter is realized in the case of HNO 3 promoter.",
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Heterometallic Co III Zn II schiff base catalyst for mild hydroxylation of C(sp 3 )–H bonds of unactivated alkanes : Evidence for dual mechanism controlled by the promoter. / Nesterova, Oksana V.; Kasyanova, Katerina V.; Buvaylo, Elena A.; Vassilyeva, Olga Yu; Skelton, Brian W.; Nesterov, Dmytro S.; Pombeiro, Armando J.L.

In: Catalysts, Vol. 9, No. 3, 209, 01.03.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Heterometallic Co III Zn II schiff base catalyst for mild hydroxylation of C(sp 3 )–H bonds of unactivated alkanes

T2 - Evidence for dual mechanism controlled by the promoter

AU - Nesterova, Oksana V.

AU - Kasyanova, Katerina V.

AU - Buvaylo, Elena A.

AU - Vassilyeva, Olga Yu

AU - Skelton, Brian W.

AU - Nesterov, Dmytro S.

AU - Pombeiro, Armando J.L.

PY - 2019/3/1

Y1 - 2019/3/1

N2 - The novel Schiff base complex [Co III Zn II L 3 Cl 2 ]·CH 3 OH (1) was synthesized by interaction of zinc powder, cobalt(II) chloride and methanol solution of the pre-formed HL in air (HL is the product of condensation of o-vanillin and methylamine) and characterized by IR, UV-Vis and NMR spectroscopy, ESI-MS and single crystal X-ray diffraction analysis. In the heterometallic core of 1 the two metal centers are bridged by deprotonated phenoxy groups of the L − ligands with the cobalt-zinc separation of 3.123 Å. Catalytic investigations demonstrated a pronounced activity of 1 towards mild alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as the model substrate. The influence of the nature of different promoting agents of various acidities (from HOTf to pyridine) on the catalytic process was studied in detail and a pronounced activity of 1 in the presence of nitric acid promoter was found, also showing a high retention of stereoconfiguration of the substrate (>99% for cis-1,2-DMCH). The best achieved yield of tertiary cis-alcohol based on the oxidant was 61%, with a turnover number (TON) of 198 for nitric acid as promoter. The 18 O-incorporations into the alcohols when the reactions were performed under 18 O 2 atmosphere using acetic and nitric acid promoters, suggest that the cis-1,2-DMCH hydroxylation proceeds by two distinct pathways, a non-stereoselective and a stereoselective one (with and without involvement of a long-lived free carbon radical, respectively). The former dominates in the case of acetic acid promoter and the latter is realized in the case of HNO 3 promoter.

AB - The novel Schiff base complex [Co III Zn II L 3 Cl 2 ]·CH 3 OH (1) was synthesized by interaction of zinc powder, cobalt(II) chloride and methanol solution of the pre-formed HL in air (HL is the product of condensation of o-vanillin and methylamine) and characterized by IR, UV-Vis and NMR spectroscopy, ESI-MS and single crystal X-ray diffraction analysis. In the heterometallic core of 1 the two metal centers are bridged by deprotonated phenoxy groups of the L − ligands with the cobalt-zinc separation of 3.123 Å. Catalytic investigations demonstrated a pronounced activity of 1 towards mild alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as the model substrate. The influence of the nature of different promoting agents of various acidities (from HOTf to pyridine) on the catalytic process was studied in detail and a pronounced activity of 1 in the presence of nitric acid promoter was found, also showing a high retention of stereoconfiguration of the substrate (>99% for cis-1,2-DMCH). The best achieved yield of tertiary cis-alcohol based on the oxidant was 61%, with a turnover number (TON) of 198 for nitric acid as promoter. The 18 O-incorporations into the alcohols when the reactions were performed under 18 O 2 atmosphere using acetic and nitric acid promoters, suggest that the cis-1,2-DMCH hydroxylation proceeds by two distinct pathways, a non-stereoselective and a stereoselective one (with and without involvement of a long-lived free carbon radical, respectively). The former dominates in the case of acetic acid promoter and the latter is realized in the case of HNO 3 promoter.

KW - O isotopic labelling

KW - Metal complex catalysis

KW - Stereoselective C-H oxidation

UR - http://www.scopus.com/inward/record.url?scp=85063493031&partnerID=8YFLogxK

U2 - 10.3390/catal9030209

DO - 10.3390/catal9030209

M3 - Article

VL - 9

JO - Catalysts

JF - Catalysts

SN - 2073-4344

IS - 3

M1 - 209

ER -