Efficient Synthesis of Water-Soluble Alkyl-bis(m-sulfonated-phenyl)- and Dialkyl-(m-sulfonated-phenyl)-phosphines and Their Evaluation in Rhodium-Catalyzed Hydrogenation of Maleic Acid in Water

The combined application of 31 P NMR and pH measurements during the tri-isooctylamine-assisted aqueous/organic separation and purification steps after the sulfonation of diphenyl-alkyl-phosphines (Ph 2 PR; R = Me, n-Bu) and phenyl-dialkyl-phosphines (PhPR 2; R = Me, n-Bu) resulted in the preparation of water-soluble alkyl-bis( m -sulfonated-phenyl)- (C 6 H 4 - m -SO 3 Na) 2 PR; R = Me, n-Bu) and dialkyl-( m -sulfonated-phenyl)- (C 6 H 4 - m -SO 3 Na)PR 2; R = Me, n-Bu) phosphines in the presence of less than 0.5% phosphine oxides. When 2 equiv of the water-soluble phosphines were used per rhodium atom, no significant effect on the turnover frequency of the hydrogenation of maleic acid can be observed by using these phosphines.