Equilibrium study on the reactions of boric acid with some cis-diaqua CrIII-complexes

tSubstitution inert cis-diaqua CrIII complexes: cis-[(Lx–)CrIII(H2O)2](3–x)+ derived from N-donor ligands (Lx–) viz., bipyridine and 1,10-phenanthroline (x = 0) and N,O-donor ligands viz., nitrilotriacetate and anthranilate N,N-diacetate (x = 3) titrate as diprotic acids in aqueous solution and enhance the acidity of otherwise weakly acidic boric acid (H3BO3) producing mononuclear and binuclear mixed ligand CrIII-borate complexes: [(L)Cr(H2BO4)]x– and [(L)Cr(BO4)Cr(L)](1–2x)+ respectively through coordination of the H2O and/or OH– ligands, cis-coordinated in the CrIIIcomplexes on the electron deficient BIII-atom in H3BO3 with release of protons. Deprotonation of the parent CrIII-complexes and their reactions with H3BO3 have been investigated by potentiometric method in aqueous solution, I = 0,1 mol dm–3 (NaNO3) at 25 plus-minus0,1C. The equilibrium constants have been evaluated by computerized methods and the tentative stoichiometry of the reactions have been worked out on the basis of the speciation curves.