Anion effects on pKa values of organophosphonium salts in o-difluorobenzene and implications
Year: 2026
Type: preprint
Abstract: Herein, the anion effects on p K a values of organophosphonium salts in o -difluorobenzene are reported. Using the autoprotolysis constants of 2-(4-trifluoromethanesulfonato)phenylmalononitrile as an anchor, the p K a values of eight organophosphonium bistriflimides are experimentally determined in three polar fluorinated arenes via 31 P{ 1 H} NMR spectroscopic titration. Subsequently, the p K a values of eight corresponding organophosphonium tetrafluoroborates and eight corresponding organophosphonium tetraphenylborates soluble in o -difluorobenzene are further experimentally determined. These p K a values show significant differences due to different counter-anions. Further DFT calculations reveals that the anions BF 4 – and NTf 2 – in o-difluorobenzene form hydrogen-bonded contact ion pairs with organophosphonium cation, but BPh 4 – forms contact ion pairs via Coulombic interactions with it. In addition to providing important guidance for future improvement of DFT and AI for predicting p K a values and thermodynamic analyses in low dielectric constant solvents, this work also provides a more comprehensive understanding of anion effects in organic and inorganic X–H bond breaks and formations.
Source: ChemRxiv
Authors: Yunfei Liang, Xiangmei Kong, Zhenbo Guo, Shanhui Zhu, Jun Chen, Tianfei Liu, Jin-Pei Cheng
Institutions: Nankai University, Tsinghua University
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7211886857