Trioxatriangulenium (TOTA+) as a Robust Carbon-based Lewis Acid in Frustrated Lewis Pair Chemistry

09 October 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We report the reactivity between the Lewis acidic trioxotriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzed via variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a stable Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P(tBu)3. The TOTA+-P(tBu)3 FLP was characterized as an encounter complex, and was found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of C–Br bond, and interception of Staudinger reaction intermediate. Moreover, TOTA+ and NHC was found to first undergo single-electron transfer (SET) to form [TOTA][NHC] •+, which was confirmed via electron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA-NHC]+ adduct or a mixture of products depending the reaction condition used.

Keywords

carbon-based frustrated Lewis pair
trioxaatrianguleniums
Carbenium Ions
Single electron transfer
FLP

Supplementary materials

Title
Description
Actions
Title
Gianetti - Carbocation FLPs - ESI
Description
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.