Influence of strong transannular N → P interaction on acidity of cyclenphosphine sulfide
Résumé
The acid-base behavior of cyclenphosphine sulfide (cyclenPS) is appreciably different from that of cyclamphosphine sulfide (cyclamPS). The cyclenPS shows five acid functionalities compared to four for cyclamPS. The fifth acidic group in cyclenPS corresponds to the formation of a stable amidure in aqueous solution (pK(a5) = 12.3). This behavior is due to the strong transannular N → P interaction. The deprotonation sequences were established by 31P-NMR and confirmed by modelling of cyclenPS.