Electrochemical quartz crystal microbalance studies of partially oxidized tetracyanoplatinum salts

The electrochemical quartz crystal microbalance (EQCM) has been used to study electrocrystallization and dissolution of the partially oxidized cyanoplatinum complexes K1.75Pt(CN)(4)(H2O)(1.5) and K2Pt(CN)(4)Cl-0.3(H2O)(3). Electrocrystallization from aqueous solutions of K2Pt(CN)(4) was found to proceed with low efficiency (5-20%) by progressive nucleation and one-dimensional growth. SEM photographs show hollow needle-like crystals with a distribution of lengths. EDAX data for cation-deficient crystals prepared in the absence of chloride show the expected decreased K/Pt value with respect to the starting material; in the presence of chloride, the anion-rich crystals have, as expected, a K:Pt ratio similar to that of the starting material. At potentials below 0.8 V, both cation-deficient and chloride-containing materials dissolve in aqueous media; EQCM data suggest a uniform dissolution rate for individual crystals.