A CN- adlayer on an electrochemical Pt surface produces two detectable vibrational bands. The band at 2160 cm(-1) has previously been assigned to an intermediate species in the electrochemical production of [Pt(CN)(4)](2-). The second mode (approximate to 2100-2140 cm(-1)) is attributed to a co-adsorbed cyanide monolayer. The lifetime of the 2160 cm(-1) mode is approximate to4-6 ps at potentials where the two modes are close in energy and approaches that of freely solvated cyanide ions (approximate to 30 ps) at potentials where the two modes become well separated in energy. This potential dependence is interpreted in the context of a simple dipole-dipole coupling mechanism.