The bigger, the better: Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts

Yu Liu, Jonathan Rawlston, Andrew T. Swann, Tait Takatani, C. David Sherrill, Peter J. Ludovice, Marcus Weck

Research output: Contribution to journalArticle

Abstract

Macrocyclic oligomeric Co(III)-salen complexes derived from cyclooctene salen monomers are among the most active catalysts for asymmetric epoxide ring-opening reactions. Due to the uncontrollable feature of the ring-expanding olefin metathesis step during catalyst synthesis, the macrocyclic oligomeric Co(III)-salen complexes are produced as mixtures of oligomers with different ring sizes. We rationalize that the ring size of the Co(III)-salen oligomers might have a significant effect on the catalytic efficiency and selectivity and report here a purification protocol to isolate macrocyclic dimers, trimers, tetramers and oligomeric mixtures with larger size rings. Hydrolytic kinetic resolution (HKR) tests using allyl glycidyl ether as substrate show that the dimer is inactive at a catalyst loading of 0.01 mol%. Increasing ring size shows a remarkable effect on reaction rates with the largest ring-size species exhibiting superior selectivities and activities. NMR studies reveal that the dimeric catalyst is strained which is not observed for the larger ring-size catalysts. Computational modeling studies indicate that the dimer is lacking the flexibility to allow adjacent Co(III)-salen groups to form a bimetallic complex. Further catalytic tests of larger ring-size Co(III)-salen complexes (tetramer to hexamer mixture) by investigating the HKR of various racemic terminal epoxides and the asymmetric epoxide ring-opening with different nucleophiles demonstrate the superior catalytic activity of large ring-size macrocyclic catalysts. Furthermore, this study demonstrates again the structural (or configurational) sensitivity of Co(III)-salen catalyst towards the selectivity and efficiency of cooperative bimetallic reactions.

Original languageEnglish (US)
Pages (from-to)429-438
Number of pages10
JournalChemical Science
Volume2
Issue number3
DOIs
StatePublished - 2011

Fingerprint

Catalysts
Epoxy Compounds
Dimers
Oligomers
Nucleophiles
Kinetics
Catalyst selectivity
Alkenes
disalicylaldehyde ethylenediamine
Reaction rates
Purification
Catalyst activity
Monomers
Nuclear magnetic resonance
Substrates

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Liu, Y., Rawlston, J., Swann, A. T., Takatani, T., Sherrill, C. D., Ludovice, P. J., & Weck, M. (2011). The bigger, the better: Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts. Chemical Science, 2(3), 429-438. https://doi.org/10.1039/c0sc00517g

The bigger, the better : Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts. / Liu, Yu; Rawlston, Jonathan; Swann, Andrew T.; Takatani, Tait; Sherrill, C. David; Ludovice, Peter J.; Weck, Marcus.

In: Chemical Science, Vol. 2, No. 3, 2011, p. 429-438.

Research output: Contribution to journalArticle

Liu, Y, Rawlston, J, Swann, AT, Takatani, T, Sherrill, CD, Ludovice, PJ & Weck, M 2011, 'The bigger, the better: Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts', Chemical Science, vol. 2, no. 3, pp. 429-438. https://doi.org/10.1039/c0sc00517g
Liu Y, Rawlston J, Swann AT, Takatani T, Sherrill CD, Ludovice PJ et al. The bigger, the better: Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts. Chemical Science. 2011;2(3):429-438. https://doi.org/10.1039/c0sc00517g
Liu, Yu ; Rawlston, Jonathan ; Swann, Andrew T. ; Takatani, Tait ; Sherrill, C. David ; Ludovice, Peter J. ; Weck, Marcus. / The bigger, the better : Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts. In: Chemical Science. 2011 ; Vol. 2, No. 3. pp. 429-438.
@article{002dc14656e44bcebcfb3d0620801ea0,
title = "The bigger, the better: Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts",
abstract = "Macrocyclic oligomeric Co(III)-salen complexes derived from cyclooctene salen monomers are among the most active catalysts for asymmetric epoxide ring-opening reactions. Due to the uncontrollable feature of the ring-expanding olefin metathesis step during catalyst synthesis, the macrocyclic oligomeric Co(III)-salen complexes are produced as mixtures of oligomers with different ring sizes. We rationalize that the ring size of the Co(III)-salen oligomers might have a significant effect on the catalytic efficiency and selectivity and report here a purification protocol to isolate macrocyclic dimers, trimers, tetramers and oligomeric mixtures with larger size rings. Hydrolytic kinetic resolution (HKR) tests using allyl glycidyl ether as substrate show that the dimer is inactive at a catalyst loading of 0.01 mol{\%}. Increasing ring size shows a remarkable effect on reaction rates with the largest ring-size species exhibiting superior selectivities and activities. NMR studies reveal that the dimeric catalyst is strained which is not observed for the larger ring-size catalysts. Computational modeling studies indicate that the dimer is lacking the flexibility to allow adjacent Co(III)-salen groups to form a bimetallic complex. Further catalytic tests of larger ring-size Co(III)-salen complexes (tetramer to hexamer mixture) by investigating the HKR of various racemic terminal epoxides and the asymmetric epoxide ring-opening with different nucleophiles demonstrate the superior catalytic activity of large ring-size macrocyclic catalysts. Furthermore, this study demonstrates again the structural (or configurational) sensitivity of Co(III)-salen catalyst towards the selectivity and efficiency of cooperative bimetallic reactions.",
author = "Yu Liu and Jonathan Rawlston and Swann, {Andrew T.} and Tait Takatani and Sherrill, {C. David} and Ludovice, {Peter J.} and Marcus Weck",
year = "2011",
doi = "10.1039/c0sc00517g",
language = "English (US)",
volume = "2",
pages = "429--438",
journal = "Chemical Science",
issn = "2041-6520",
publisher = "Royal Society of Chemistry",
number = "3",

}

TY - JOUR

T1 - The bigger, the better

T2 - Ring-size effects of macrocyclic oligomeric Co(III)-salen catalysts

AU - Liu, Yu

AU - Rawlston, Jonathan

AU - Swann, Andrew T.

AU - Takatani, Tait

AU - Sherrill, C. David

AU - Ludovice, Peter J.

AU - Weck, Marcus

PY - 2011

Y1 - 2011

N2 - Macrocyclic oligomeric Co(III)-salen complexes derived from cyclooctene salen monomers are among the most active catalysts for asymmetric epoxide ring-opening reactions. Due to the uncontrollable feature of the ring-expanding olefin metathesis step during catalyst synthesis, the macrocyclic oligomeric Co(III)-salen complexes are produced as mixtures of oligomers with different ring sizes. We rationalize that the ring size of the Co(III)-salen oligomers might have a significant effect on the catalytic efficiency and selectivity and report here a purification protocol to isolate macrocyclic dimers, trimers, tetramers and oligomeric mixtures with larger size rings. Hydrolytic kinetic resolution (HKR) tests using allyl glycidyl ether as substrate show that the dimer is inactive at a catalyst loading of 0.01 mol%. Increasing ring size shows a remarkable effect on reaction rates with the largest ring-size species exhibiting superior selectivities and activities. NMR studies reveal that the dimeric catalyst is strained which is not observed for the larger ring-size catalysts. Computational modeling studies indicate that the dimer is lacking the flexibility to allow adjacent Co(III)-salen groups to form a bimetallic complex. Further catalytic tests of larger ring-size Co(III)-salen complexes (tetramer to hexamer mixture) by investigating the HKR of various racemic terminal epoxides and the asymmetric epoxide ring-opening with different nucleophiles demonstrate the superior catalytic activity of large ring-size macrocyclic catalysts. Furthermore, this study demonstrates again the structural (or configurational) sensitivity of Co(III)-salen catalyst towards the selectivity and efficiency of cooperative bimetallic reactions.

AB - Macrocyclic oligomeric Co(III)-salen complexes derived from cyclooctene salen monomers are among the most active catalysts for asymmetric epoxide ring-opening reactions. Due to the uncontrollable feature of the ring-expanding olefin metathesis step during catalyst synthesis, the macrocyclic oligomeric Co(III)-salen complexes are produced as mixtures of oligomers with different ring sizes. We rationalize that the ring size of the Co(III)-salen oligomers might have a significant effect on the catalytic efficiency and selectivity and report here a purification protocol to isolate macrocyclic dimers, trimers, tetramers and oligomeric mixtures with larger size rings. Hydrolytic kinetic resolution (HKR) tests using allyl glycidyl ether as substrate show that the dimer is inactive at a catalyst loading of 0.01 mol%. Increasing ring size shows a remarkable effect on reaction rates with the largest ring-size species exhibiting superior selectivities and activities. NMR studies reveal that the dimeric catalyst is strained which is not observed for the larger ring-size catalysts. Computational modeling studies indicate that the dimer is lacking the flexibility to allow adjacent Co(III)-salen groups to form a bimetallic complex. Further catalytic tests of larger ring-size Co(III)-salen complexes (tetramer to hexamer mixture) by investigating the HKR of various racemic terminal epoxides and the asymmetric epoxide ring-opening with different nucleophiles demonstrate the superior catalytic activity of large ring-size macrocyclic catalysts. Furthermore, this study demonstrates again the structural (or configurational) sensitivity of Co(III)-salen catalyst towards the selectivity and efficiency of cooperative bimetallic reactions.

UR - http://www.scopus.com/inward/record.url?scp=79955605425&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79955605425&partnerID=8YFLogxK

U2 - 10.1039/c0sc00517g

DO - 10.1039/c0sc00517g

M3 - Article

VL - 2

SP - 429

EP - 438

JO - Chemical Science

JF - Chemical Science

SN - 2041-6520

IS - 3

ER -