Formation of nitrite palladium complexes in nitric acid media

The interaction of solvated Pd2+ ions with molecular HNO2 in aqueous 2-3 M nitric acid at 24degreesC was studied by potentiometric titration. The formation constants of [PdNO2](+) and [Pd(NO2)(2)] were determined at the ionic strength I = 2.5 (HNO3): logbeta(1)* = 3.6 +/- 0.1 and logbeta(2)* = 7.69 +/- 0.03. Four stepwise formation constants for the nitrite palladium complexes were estimated with the use of literature data. The stepwise effects are characterized by a specific feature (logK(2) greater than or equal to log K-1 and log (K3K4) much less than log (K1K2)), which is qualitatively analogous to that previously found for hydroxo complexes. For halide complexes, similar effects are lacking.