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Catalytic consequences of open and closed grafted Al(III)-calix[4]arene complexes for hydride and oxo transfer reactions

Nandi, Partha and Tang, Wenjie and Okrut, Alexander and Kong, Xueqian and Hwang, Son-Jong and Neurock, Matthew and Katz, Alexander (2013) Catalytic consequences of open and closed grafted Al(III)-calix[4]arene complexes for hydride and oxo transfer reactions. Proceedings of the National Academy of Sciences of the United States of America, 110 (7). pp. 2484-2489. ISSN 0027-8424. PMCID PMC3574915. https://resolver.caltech.edu/CaltechAUTHORS:20130328-100051607

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Abstract

An approach for the control and understanding of supported molecular catalysts is demonstrated with the design and synthesis of open and closed variants of a grafted Lewis acid active site, consisting of Al(III)-calix[4]arene complexes on the surface of silica. The calixarene acts as a molecular template that enforces open and closed resting-state coordination geometries surrounding the metal active sites, due to its lower-rim substituents as well as site isolation by virtue of its steric bulk. These sites are characterized and used to elucidate mechanistic details and connectivity requirements for reactions involving hydride and oxo transfer. The consequence of controlling open versus closed configurations of the grafted Lewis acid site is demonstrated by the complete lack of observed activity of the closed site for Meerwein-Ponndorf-Verley (MPV) reduction; whereas, the open variant of this catalyst has an MPV reduction activity that is virtually identical to previously reported soluble molecular Al(III)-calix[4]arene catalysts. In contrast, for olefin epoxidation using tert-butyl-hydroperoxide as oxidant, the open and closed catalysts exhibit similar activity. This observation suggests that for olefin epoxidation catalysis using Lewis acids as catalyst and organic hydroperoxide as oxidant, covalent binding of the hydroperoxide is not required, and instead dative coordination to the Lewis acid center is sufficient for catalytic oxo transfer. This latter result is supported by density functional theory calculations of the transition state for olefin epoxidation catalysis, using molecular analogs of the open and closed catalysts.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1073/pnas.1211158110DOIArticle
http://www.pnas.org/content/110/7/2484PublisherArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3574915/PubMed CentralArticle
ORCID:
AuthorORCID
Okrut, Alexander0000-0002-0689-4346
Hwang, Son-Jong0000-0002-3210-466X
Katz, Alexander0000-0003-3487-7049
Additional Information:© 2013 National Academy of Sciences. Edited by Mark E. Davis, California Institute of Technology, Pasadena, CA, and approved November 12, 2012 (received for review July 11, 2012). Published online before print January 28, 2013. A.K. acknowledges helpful conversations with Dr. Karl Mueller and Dr. Nancy Walton (Pacific Northwest National Laboratory) regarding interpretation of ^(27)Al MAS NMR spectra. W.T. acknowledges the Texas Advanced Computing Center for Extreme Science and Engineering Discovery Environment (XSEDE) computing resources. The authors thank Prof. Jeffrey A. Reimer (University of California, Berkeley) for his expertise with liquid-phase ^(27)Al NMR experiments and the Office of Basic Energy Sciences of the US Department of Energy (Grant DE-FG02-05ER15696) for support of this work. The Caltech Solid-State NMR Facility is supported by the National Science Foundation (NSF) under Grant 9724240 and is partially supported by the Materials Research Science and Engineering program of NSF (Grant DMR-520565). Author contributions: P.N., W.T., A.O., X.K., S.-J.H., M.N., and A.K. designed research; P.N., W.T., A.O., X.K., S.-J.H., and M.N. performed research; P.N., W.T., A.O., X.K., S.-J.H., M.N., and A.K. contributed new reagents/analytic tools; P.N., W.T., M.N., and A.K. analyzed data; and P.N., W.T., M.N., and A.K. wrote the paper.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-05ER15696
NSFDMR-9724240
NSFDMR-520565
Subject Keywords:molecular catalysis; single-site catalysts; MPVO reaction; organic-inorganic interface; selective oxidation
Issue or Number:7
PubMed Central ID:PMC3574915
Record Number:CaltechAUTHORS:20130328-100051607
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130328-100051607
Official Citation:Partha Nandi, Wenjie Tang, Alexander Okrut, Xueqian Kong, Son-Jong Hwang, Matthew Neurock, and Alexander Katz Catalytic consequences of open and closed grafted Al(III)-calix[4]arene complexes for hydride and oxo transfer reactions PNAS 2013 110 (7) 2484-2489; published ahead of print January 28, 2013, doi:10.1073/pnas.1211158110
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37669
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:11 Apr 2013 18:18
Last Modified:09 Mar 2020 13:19

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