Water-Soluble Triisopropylphosphine Complexes of Ruthenium(II): Synthesis, Equilibria, and Acetonitrile Hydration

The complex [RuCl(NCMe)4(PiPr3)]BF4 (1) and its water-soluble dicationic products of chloride replacement by PiPr3 (2), P(OMe)3 (3), Hpz (4), MeOH (5), and H2O (6) have been prepared and characterized. The chloride dissociation constant of 1 in water (Kd = 2.0 M) and the pKa (10.5) for the deprotonation of the water ligand of 6 have been determined by NMR methods. The conjugate base of 6, [Ru(OH)(NCMe)4(PiPr3)]+ (7), has been observed to isomerize into an amidate complex in route to acetonitrile hydration. Consistently, 6 has been found to catalyze the selective hydration of acetonitrile to acetamide in aqueous solution at pH 10.5 and 353 K, with initial TOF about 50 h−1.