The reduction of the tris-(2,2′-bipyridyl) and the tris-(1,10-phenanthroline) complexes of iron(III) by hydroxide ion

Abstract

The reaction 4[Fe(biL)₃]³⁺+ 4OH^–→ 4[Fe(biL)₃]²⁺+ O₂+ 2H₂O (biL = 1,10-phenanthroline or 2,2′-bipyridyl) occurs in aqueous NaCl–NaOH with the following rate law: d[Fe(biL)₃]³⁺/dt=k[{Fe(biL)₃}³⁺]-[OH^–]. For the bipyridyl complex k= 10^12·54e^{–(65,100 ± 800)J/RT}. for the phenanthroline complex k= 10^14·4e^{–(65,000 ± 2000)J/RT}, both determined in 1 M-NaCl by stopped-flow spectrophotometry. The subsequent and slower re-oxidation of the Fe^II products earlier reported has been confirmed using an oxygen electrode.