Influence of water-soluble sulfonated phosphine ligands on ruthenium catalyzed generation of hydrogen from formic acid

Hydrogen can be generated from formic acid in aqueous phase homogeneous catalytic reactions using ruthenium catalysts with water-soluble phosphine ligands. A comparison of tri-, di-, and mono-sulfonato triphenylphosphine, disulfonato diphenyl-alkyl-phosphines (Ph2PR; R Me, n-Bu, Cyp), and monosulfonato phenyl-dialkyl-phosphines (PhPR2; R Me, Cyp) is described. Using two equivalents of water-soluble phosphine per ruthenium ion, significant turnover frequencies are observed for the decomposition of formic acid. The influence of basicity, water solubility (related to the structures and behavior in aqueous solution), electronic properties, and steric effects of the phosphines on the rate of the hydrogen generation are investigated.