The formation and structure of the self-assembling transition metal complex [Os(bpy)(2)(dipy)Cl](PF6) (bpy is 2,2’-bipyridine, dipy is trimethylene-4,4’-bipyridine) adsorbed onto a Pt(111) substrate was studied using scanning tunneling microscopy (STM) and electrochemical scanning tunneling microscopy (ECSTM). The growth of a spread submonolayer was observed in real time while simultaneously measuring the adsorbate coverage using cyclic voltammetry. Molecularly resolved images of the monolayer crystallized onto the Pt(111) surface, taken in air and showing a rectangular close-packed structure, were compared with images of the monolayer obtained in-situ in electrolyte solution and under potential control.