Issue 35, 2018

Facile and systematic access to the least-coordinating WCA [(RFO)3Al–F–Al(ORF)3] and its more Lewis-basic brother [F–Al(ORF)3] (RF = C(CF3)3)

Abstract

By reaction of the Lewis acid Me3Si–F–Al(ORF)3 with a series of [PF6] salts, gaseous PF5 and Me3Si–F are liberated and salts of the anion [F–Al(ORF)3] ([f–al]; RF = C(CF3)3) can be obtained. By addition of another equivalent of Me3Si–F–Al(ORF)3 to [f–al], gaseous Me3Si–F is released and salts of the least coordinating anion [(RFO)3Al–F–Al(ORF)3] ([al–f–al]) are formed. Both procedures work for a series of synthetically useful cations including Ag+, [NO]+, [Ph3C]+ and in very clean reactions with 5 g batch sizes giving excellent yields typically exceeding 90%. In addition, the synthesis of Me3Si–F–Al(ORF)3 has been optimized and scaled up to 85 g batches in an one-pot procedure. These anions could previously only be obtained by difficult to control decomposition reactions of [Al(ORF)4] or by halide abstraction reactions with Me3Si–F–Al(ORF)3, generating relatively large countercations that are unsuited for further use as universal starting materials. Especially [al–f–al] is of interest for the stabilization of reactive cations, since it is even weaker coordinating than [Al(ORF)4] and more stable against strong electrophiles. This bridged anion can be seen as an adduct of [f–al] and Al(ORF)3. Thus, it is similarly Lewis acidic as BF3 and eventually reacts with nucleophiles (Nu) from the reaction environment to yield Nu–Al(ORF)3 and [f–al]. This prevents working with [al–f–al] salts in ethereal or other donor solvents. By contrast, the [f–al] anion is no longer Lewis acidic and may therefore be used for reactions involving stronger nucleophiles than the [al–f–al] anion can withstand. Subsequently it may be transformed into the [al–f–al] salt by simple addition of one equivalent of Me3Si–F–Al(ORF)3.

Graphical abstract: Facile and systematic access to the least-coordinating WCA [(RFO)3Al–F–Al(ORF)3]− and its more Lewis-basic brother [F–Al(ORF)3]− (RF = C(CF3)3)

Supplementary files

Article information

Article type
Edge Article
Submitted
12 Jun 2018
Accepted
31 Jul 2018
First published
01 Aug 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2018,9, 7058-7068

Facile and systematic access to the least-coordinating WCA [(RFO)3Al–F–Al(ORF)3] and its more Lewis-basic brother [F–Al(ORF)3] (RF = C(CF3)3)

A. Martens, P. Weis, M. C. Krummer, M. Kreuzer, A. Meierhöfer, S. C. Meier, J. Bohnenberger, H. Scherer, I. Riddlestone and I. Krossing, Chem. Sci., 2018, 9, 7058 DOI: 10.1039/C8SC02591F

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements