Abstract: The reaction of platinum acetate blue, empirically described as Pt(OOCMe) 2.50 , with palladium(II) acetate Pd 3 (μ-OOCMe) 6 gave the first heterometallic acetate-bridged platinum(II) and palladium(II) complex Pd 2 Pt(μ-OOCMe) 6 (I) as co-crystallizates 17Pd 2 Pt(μ-OOCMe) 6 ⋅ 4Pd 3 (μ-OOCMe) 6 ⋅ 42C 6 H 6 (IIa) and 17Pd 2 Pt(μ-OOCMe) 6 ⋅ 4 Pd 3 (μ-OOCMe) 6 (IIb). Single crystal X-ray diffraction (CIF files CCDC nos. 1568105 and 1852744), EXAFS, and quantum chemical studies (DFT and QTAIM) of complex I revealed a slightly distorted triangular structure similar to the structure of palladium(II) acetate Pd 3 (μ-OOCMe) 6 and hypothetical platinum(II) complex Pt 3 (μ-OOCMe) 6 . The thermal decomposition of complex IIa gives the bimetallic alloy PtPd 2 . A combined X-ray diffraction and EXAFS study demonstrated that the obtained material consists of core (Pt)–shell (Pd) particles with an average size of ~28 nm and a minor amount of smaller (~5 nm) PdO nanoparticles on the surface. The obtained results are useful for the understanding of the nature and structure of the supported phase of heterogeneous Pt–Pd catalysts. © 2019, Pleiades Publishing, Ltd.