SYNTHESIS AND CHARACTERIZATION OF TRIAMMINE-TRIAQUARUTHENIUM(III) TRIFLUOROMETHANESULFONATE

[Ru(NH3)3(OH2)3](CF3SO3)3 was prepared from RuCl3(NH3)3 by using trifluoromethanesulfonic acid and Ag2CO3, and characterized by microanalytical, electrochemical and spectroscopic techniques. The complex is soluble in water and in many organic solvents and is a convenient starting material for the preparation of triammine complexes. [Ru(NH3)3(OH2)3]3+ has pK(a1) 3.77+/-0.04 and pK(a2) 6.93+/-0.04 at 25-degrees-C, and an E1/2 of -120 mV at pH 1.5 and -190 mV at pH 5. In the u.v. spectrum lambda(max) is at 251 nm (epsilon 1150 mol-1 dm3 cm-1) in 0.1 m H+ and at 296 nm (epsilon 1760 mol-1 dm3 cm-1) at pH 5. [Ru(NH3)4(OH2)2]3+ has pK(a1) 3.96+/-0.4 and pK(a2) 7.09+/-0.04 and E1/2 of -140 mV at pH 1 and -200 mV at pH 5. In the u.v. spectrum lambda(max) is at 254 nm (epsilon 1200 mol-1 dm3 cm-1) in 0.1 m H+ and at 296 nm (epsilon 2650 mol-1 dm3 cm-1) at pH5. [Ru(NH3)3(OH2)3]2+ can be prepared in situ by reduction with Zn(Hg) or H-2/Pt black; at high pH, the reduction proceeds via a blue mixed-oxidation-state intermediate.