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Electrochemical studies of molybdenum-ethylenediaminetetraacetic acid complexes

1968; Elsevier BV; Volume: 17; Issue: 1-2 Linguagem: Inglês

10.1016/s0022-0728(68)80047-6

2590-2954

Franklin A. Schultz, Donald T. Sawyer,

Electrocatalysts for Energy Conversion

Summary Among the chelates formed by ethylenediaminetetraacetic acid (EDTA), those with Mo(VI) and Mo(V) are unusual because the metal-to-ligand ratio is two-to-one. Coulometry, chronopotentiometry and cyclic voltammetry have been used to investigate the electrochemistry of these compounds with the intention of establishing a correlation between the electrochemical results and the unique structural features of the chelates. In the presence of EDTA, the overall reduction of Mo(VI) involves three electrons. The initial electrode reaction, however, is the reduction of Mo(VI) to Mo(IV), which is followed by a disproportionation reaction to give Mo(V) and Mo(III). The two-to-one Mo(V)-EDTA chelate (a diamagnetic, dioxo-bridged species) is reduced through a series of parallel, but entirely independent steps. A third series of compounds arises from the Mo(III) species produced coulometrically from Mo(VI)-EDTA. The uniqueness of the various molybdenum-EDTA species can be seen from cyclic voltammetric experiments and the differences in the rate of Mo(IV) disproportionation. The rate of disproportionation of Mo(IV) is considerably slower for those compounds having oxygen bridges between molybdenum atoms.