ACID-BASE EQUILIBRIA IN AQUEOUS-SOLUTION OF CIS-BIS(TRIMETHYLPHOSPHINE)PLATINUM(II) DINITRATE AT 25-DEGREES-C, 0.2 M IONIC-STRENGTH - A POTENTIOMETRIC STUDY

Acid-base equilibria in aqueous solutions of cis-bis(trimethylphosphin e)platinum(II) dinitrate at 25 degrees C, 0.2 M ionic strength (KNO3), have been investigated by potentiometry with a glass electrode. The p rocedure consisted of multiple addition of the investigated analyte to a supporting electrolyte solution (''multiple sample addition'') and subsequent titration with strong base. For the treatment of potentiome tric multiple sample addition data, a new linearization procedure, sui table for an acid dissociation equilibrium whose product dimerizes, ha s been devised and tested. The potentiometric results have been interp reted with the support of NMR data. By dissociation of the first acidi c function of the solute diaquo cation, cis-[(PMe(3))(2)Pt(OH2)(2)](2), a dimeric ampholite, cis-[(PMe(3))(2)Pt(mu-OH)](2+)(2), is quantita tively formed which, in turn, can be converted into the di-hydroxo der ivative cis-(PMe(3))(2)Pt(OH)(2). The two acid dissociation steps invo lving two molecules of solute and condensation of ampholyte have pK(a1 (c)) = 3.89 and pK(a2(c)) = 22.17.