Neutron diffraction study of the electrochemical passivation of nickel powder

With the aid of the Yamaoka mechanism and a.c. polarographic observables, rate constants for the homogeneous reduction of Co(III)pentammine complexes by Eu(II) are measured. Where comparison is possible, rate parameters obtained by this electrochemical procedure are found to be in good agreement with previous measurements by stopped-flow and pulse radiolysis procedures, with one exception. The order of reactivity for the halopentammineCo(III) complexes is found to follow the sequence RF²⁺>RCl²⁺>RBr²⁺>RI²⁺, where R=Co(III)(NH₃)₅³⁺. This and a pH dependence noted for the RF²⁺ case are suggestive of a predominantly inner sphere reaction pathway.