Issue 4, 2016

Bond fission in monocationic frameworks: diverse fragmentation pathways for phosphinophosphonium cations

Abstract

A series of phosphinophosphonium cations ([R2PPMe3]+; R = Me, Et, iPr, tBu, Cy, Ph and NiPr2) have been prepared and examined by collision-induced dissociation (CID) to determine the fragmentation pathways accessible to these prototypical catena-phosphorus cations in the gas-phase. Experimental evidence for fission of P–P and P–E (E = P, C) bonds, and β-hydride elimination has been obtained. Comparison of appearance potentials for the P–P bond dissociation fragments [R2P]+ (P–P heterolysis) and [PMe3]+˙ (P–P homolysis) shows that heterolytic P–P cleavage is more sensitive than P–P homolysis towards changes in substitution at the trivalent phosphorus center. The facility of β-hydride elimination increases with the steric bulk of R in [R2PPMe3]+. A density functional theory (DFT) study modelling these observed processes in gas-phase, counterion- and solvent-free conditions, to mimic the mass spectrometric environment, was performed for derivatives of [R2PPMe3]+ (R = Me, Et, iPr, tBu, Ph and NiPr2), showing good agreement with experimental trends. The unusual observation of both homolytic and heterolytic cleavage pathways for the P–P and P–C bonds reveals new insight into the fundamental aspects of bonding in monocations and undermines the use of simplistic bonding models.

Graphical abstract: Bond fission in monocationic frameworks: diverse fragmentation pathways for phosphinophosphonium cations

Supplementary files

Article information

Article type
Edge Article
Submitted
06 Oct 2015
Accepted
05 Jan 2016
First published
05 Jan 2016
This article is Open Access

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

Chem. Sci., 2016,7, 2544-2552

Author version available

Bond fission in monocationic frameworks: diverse fragmentation pathways for phosphinophosphonium cations

K. L. Bamford, S. S. Chitnis, R. L. Stoddard, J. S. McIndoe and N. Burford, Chem. Sci., 2016, 7, 2544 DOI: 10.1039/C5SC03804A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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