Abstract Dinitrogentrioxide reacts with tetrakis(triphenylphosphine) platinum and palladium under nitrogen to give dinitrobis(triphenylphosphine) platinum(II) and palladium(II) complexes, respectively. In the presence of oxygen these reactions afford the formation of nitro‐nitrato complexes of platinum(II) and palladium(II). The products are characterized by the elemental analyses, i.r. spectra, conductivity and magnetic measurements.