Complexation of monosulfonated triphenylphosphine with chemically modified β-cyclodextrins:: Effect of substituents on the stability of inclusion complexes

Interactions between the meta-substituted monosulfonated triphenylphosphine and chemically modified beta-cyclodextrins were investigated in aqueous solution by NMR and UV-vis spectroscopy. Titration and continuous variation plots obtained from P-31 NMR data indicate that the monosulfonated triphenylphosphine forms 1:1 inclusion complexes with the 2-hydroxypropylated beta-cyclodextrin, the methylated beta-cyclodextrin and the (2-hydroxy-3-trimethylammoniopropyl)-beta-cyclodextrin chloride. These inclusion complexes are more stable that those formed with native beta-cyclodextrin, confirming that poisoning of the chemically modified beta-cyclodextrins by the hydrosoluble phosphine occurs when modified cyclodextrins are used as mass transfer promoters in aqueous-phase organometallic catalysis.