Issue 33, 2018
From the journal:

Dalton Transactions

Probing steric influences on electrophilic phosphonium cations: a comparison of [(3,5-(CF3)2C6H3)3PF]+ and [(C6F5)3PF]+†

James H. W. LaFortune, ORCID logo a   Kevin M. Szkop, ORCID logo a   Farah E. Farinha,a   Timothy C. Johnstone, ORCID logo a   Shawn Postlea  and  Douglas W. Stephan ORCID logo *a  

* Corresponding authors

a Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario, Canada M5S 3H6
E-mail: dstephan@chem.utoronto.ca

Abstract

The electrophilic phosphonium cation (EPC) salt [(3,5-(CF3)2C6H3)3PF][B(C6F5)4] (2) is prepared via oxidation of the precursor phosphine with XeF2 and subsequent abstraction of fluoride with [Et3Si(tol)][B(C6F5)4]. The Lewis acidity of 2 is evaluated by experimental and computational methods and by preliminary catalysis testing. Exchange reactions of 2 and [(C6F5)3PF][B(C6F5)4] with their respective difluorophosphoranes are studied by 2D 19F–19F NOESY/EXSY and selective 1D 19F NMR exchange spectroscopy (SEXSY) experiments affording comparative rates of fluoride exchange. Collectively, although these data show that 2 is less Lewis acidic than [(C6F5)3PF][B(C6F5)4], the improved access to the P center of 2 provides a kinetic acceleration for fluoride exchange and catalysis where the transition states are more sterically demanding.

Graphical abstract: Probing steric influences on electrophilic phosphonium cations: a comparison of [(3,5-(CF3)2C6H3)3PF]+ and [(C6F5)3PF]+

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Article information

DOI
https://doi.org/10.1039/C8DT02594K
Article type
Paper
Submitted
25 Jun 2018
Accepted
20 Jul 2018
First published
23 Jul 2018

Dalton Trans., 2018,47, 11411-11419

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Probing steric influences on electrophilic phosphonium cations: a comparison of [(3,5-(CF3)2C6H3)3PF]+ and [(C6F5)3PF]+

J. H. W. LaFortune, K. M. Szkop, F. E. Farinha, T. C. Johnstone, S. Postle and D. W. Stephan, Dalton Trans., 2018, 47, 11411 DOI: 10.1039/C8DT02594K

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