Acid–base equilibria of the aqua adducts of Ru(II) arene complexes with functionalised pyridines

Acid–base equilibria of the aqua adducts of Ru(II) arene complexes, general formulae [(η6-p-cymene)Ru (L1−3)Cl2] where L1 = 3-acetylpyridine (1), L2 = 4-acetylpyridine (2) and L3 = 2-amino-5-chloropyridine (3), then [(η6-p-cymene)Ru(HL4)Cl2] with HL4 = isonicotinic acid (4); [(η6-p-cymene)Ru(HL5−8)Cl] where H2L5 = 2,3-pyridine dicarboxylic acid (5), H2L6 = 2,4-pyridine dicarboxylic acid (6), H2L7 = 2,5-pyridine dicarboxylic acid (7) and H2L8 = 2,6-pyridine dicarboxylic acid (8) have been studied. pK a values were determined by potentiometry at 25 °C and constant ionic strength of 0.1 M NaNO3. The assumed equilibria were confirmed by UV and 1H-NMR spectroscopy.