Solid samples isolated from solutions of a platinum superoxo hydroxo comple
x are studied by EPR and X-ray powder diffraction techniques. The short-liv
ed superoxo complex is found to form upon dissolution of the solid samples
in concentrated acids. Magnetic resonance parameters of the platinum supero
xo complexes in the solid state and in acidic solutions are determined. The
structures of the inner coordination sphere of the found superoxo complexe
s are discussed.