Abstract The complex bis (acetonitrile) bis (triphenylphosphine) ruthenium (II) sulfate [Ru (PPh 3) 2 (NCCH 3) 2 (SO 4)], fully characterized spectroscopically and by a single crystal X- ray study, catalyzes at 110 C the direct transformation of primary alcohols to the corresponding acetals with liberation of molecular hydrogen. The formation of acetals proceeds via direct substitution of the hydroxy group of the hemiacetal intermediate by an ...