Liberating the Anion: Evaluating Weakly Coordinating Cations

A series of commonly used weakly coordinating cations (WCCs) including tetraalkylammonium, bis­(triphenylphosphine)­iminium (PPN), P2 and P5 phosphazenium, and tetraphenylphosphonium ions were investigated along with five additional tetraarylphosphonium ions [Ar = 4-Me, 4-t-Bu, 3,5-Me2, 4-Me2N, and...

Full description

Saved in:
Bibliographic Details
Published in:Journal of organic chemistry 2022-11, Vol.87 (22), p.15466-15482
Main Authors: Dempsey, Stephen H., Kass, Steven R.
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A series of commonly used weakly coordinating cations (WCCs) including tetraalkylammonium, bis­(triphenylphosphine)­iminium (PPN), P2 and P5 phosphazenium, and tetraphenylphosphonium ions were investigated along with five additional tetraarylphosphonium ions [Ar = 4-Me, 4-t-Bu, 3,5-Me2, 4-Me2N, and 3,5-(MeO)2 phenyl derivatives]. Dissociation enthalpies of their chloride complexes were computed in the gas phase and in dichloromethane. These results are compared to infrared spectra of these salts in chloroform-d which provide free and bound C–D stretches, 19F NMR spectra of the corresponding tetrafluoroborate salts, ion-pair equilibrium constants, and reaction rates of the chlorides and acetates with 1-iodooctane. The latter transformation was also carried out under catalytic conditions. Substituted tetraphenylphosphonium ion derivatives are found to be surprisingly good WCCs that function as well or better than the P2 and P5 phosphazenium ions, the current WCC gold standard.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.2c02001