For spontaneously adsorbed monolayers of [Os(bpy)(2)Cl(p2p)](+), where p2p is 1,2-bis(4-pyridyl)ethane and bpy is 2,2’-dipyridyl, reduction induces rapid loss of the chloride Ligand. Cyclic voltammetry and chronoamperometry in DMF reveal that two sequential, one-electron ligand-based reductions lead to exchange of chloride for solvent at the metal center. High speed chronoamperometry has been used to probe the kinetics of this coupled electron-transfer chemical reaction. The heterogeneous electron transfer rate constant for the second electron transfer (k), linking charge states 0 and 1-, has been evaluated using nanosecond time scale chronoamperometry. The rate constant depends exponentially on overpotential for absolute overpotentials less than 0.200 V, and transfer coefficients (alpha) of 0.500+/-0.08 are observed. The standard heterogeneous rate constant increases with increasing supporting electrolyte concentration over the range 0.01-0.5 M, and a limiting value of 7.8+/-0.6 x 10(4) s(-1) is observed for high electrolyte concentrations. The structure of the monolayer and the potential distribution at the modified interface have been probed from the electrolyte concentration dependence of the interfacial capacitance. These data suggest that, for some electrolyte concentrations, the electric field decays linearly over at least part of the monolayer thickness, leading to a large interfacial electric field at the reaction site. The kinetics of chloride elimination have been probed by monitoring the charge recovered during monolayer reoxidation as the reducing potential triggering chloride ligand loss is held for various times. These studies revealed that chloride elimination is a first-order process that occurs on a microsecond time scale. The rate of chloride loss (k(elim)) increases linearly with an increasingly more negative potential, and k(elim) also increases linearly with increasing square root of the supporting electrolyte concentration. Temperature-resolved measurements of the elimination rate reveal that not only does the activation energy depend on the field strength but so too does the pre-exponential factor.