The electron transfer (ET) reaction between bis(butylcyclopentadienyl)iron(II) ([Fe-II(C5H4Bu)(2)]) in 1,2-dichloroethane (1,2-DCE) and the hexacyanoferrate redox couple ([Fe-II/III(CN)(6)](4-/3-)) in water (W) at the 1,2-DCE vertical bar W interface has been studied by use of normal pulse voltammetry and cyclic voltammetry. In normal pulse voltammetry, S-shaped current vs. potential curves with well-defined limiting currents attributable to the interfacial ET reaction were observed. The voltammetric results can be explained well by the theoretical equations [M. Senda, Rev. Polarogr. (Jpn), 49 (2003) 219; 50 (2004) 60] according to a so-called IT-mechanism, that is, the [Fe-II(C5H4Bu)(2)] Molecule is transferred from the 1,2-DCE to the W phase across the interface, then the ET reaction takes place homogeneously in the W phase between [Fe-III(CN)(6)](3-)(W) and [Fe-II(C5H4Bu)(2)](W) to produce [Fe-II(CN)(6)](4-)(W) and [Fe-III(C5H4Bu)(2)](+)(W), which is followed by the transfer of the [Fe-III(C5H4Bu)(2)](+) ion from the W to the 1,2-DCE phase across the interface to give the voltammetric current. Experimental results from cyclic voltammetry are also explained well by the IT-mechanism. (c) 2004 Elsevier B.V. All rights reserved.