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Updated: Mar 18, 2026

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
Experimental Basicities of Superbasic Phosphonium Ylides and Phosphazenes
Jaan Saame1, Toomas Rodima1, Sofja Tshepelevitsh1
1Institute of Chemistry, University of Tartu , 14a Ravila Str, 50411 Tartu, Estonia.
Abstract:
Experimental basicities of some of the strongest superbases ever measured (phosphonium ylides) are reported, and by employing these compounds, the experimental self-consistent basicity scale of superbases in THF, reaching a pKα (estimate of pKa) of 35 and spanning more than 30 pKa units, has been compiled. Basicities of 47 compounds (around half of which are newly synthesized) are included. The solution basicity of the well-known t-Bu-N═P4(dma)9 phosphazene superbase is now rigorously linked to the scale. The compiled scale is a useful tool for further basicity studies in THF as well as in other solvents, in particular, in acetonitrile. A good correlation between basicities in THF and acetonitrile spanning 25 orders of magnitude gives access to experimentally supported very high (pKa > 40) basicities in acetonitrile, which cannot be directly measured. Analysis of structure-basicity trends is presented.
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