Mixed ligand complexes of iron(ii) as nonaqueous acid-base and aqueous oxidation-reduction indicators

Abstract

The neutral mixed ligand complexes dicyano-bis-(1,10-phenanthroline)-iron(II) and dicyano-bis-(2.2'-bipyridine)-iron(II) are suitable indicators for the titration of various weak bases in nonaqueous solvents, They also serve as practical indicators for certain redox titrations in aqueous solutions; their applicability in the determination of primary aromatic amines is especially noteworthy. Formal potentials of the complexes in different concentrations of sulfuric acid are reported; the results confirm earlier findings that the neutral iron(II) complexes form stable protonated species.