Platinum acetate blue (PAB) of the empirical formula Pt(OOCMe)2.5±0.25, a byproduct in the synthesis of crystalline platinum(II) acetate Pt4(OOCMe)8, is an X-ray amorphous substance containing platinum in the oxidation state between (II) and (III). Typical PAB samples were studied with X-ray diffraction, differential thermal analysis-thermogravimetric, extended X-ray absorption fine structure, scanning electron microscopy, transmission electron microscopy, magnetochemistry, and combined quantum chemical density functional theory-molecular mechanics modeling to reveal the main structural features of the PAB molecular building blocks. The applicability of PAB to the synthesis of platinum complexes was demonstrated by the preparation of the new homo- and heteronuclear complexes Pt(II)(dipy)(OOCMe)2 (1), Pt(II)(μ-OOCMe)4Co(II)(OH2) (2), and Pt(III)2(OOCMe)4(O3SPhMe)2 (3) with the use of PAB as starting material.