Dinuclear ruthenium carboxylates are unique compounds, showing paramagnetic properties irrespective of the lantern-type (or paddlewheel-type) dinuclear core with metal-metal bonding (Fig. 1) [1].  Especially, interesting feature is that mixed-valent dinuclear ruthenium(II,III) carboxylates have three unpaired electrons in the metal-metal bonding orbitals with large zero-field splitting and can be considered to be useful as building block for constructing magnetic materials.  We reported magnetic properties and crystal structures of some molecule-assembled complexes from dinuclear ruthenium complexes to one-dimensional polymeric chain compounds with bidentate linking ligands L.  In these compounds, magnetic interaction between the dinuclear units depends on the linking ligands and mostly antiferromagnetic [1,2].   Ferrimagnetic behavior was observed for mixed-metal systems of dinuclear ruthenium with hexacyanidoferrate(III) and octacyanidotungstate(V) [1,3].  We extended these systems to mixed-metal complexes with dicyanidoargentate(I) [4] and tetracyanidonickelate(II) [5] .  In this study, we prepared new mixed-metal complexes by using tetracyanidoplatinate(II) [Pt(CN)4]2– in order to obtain further information.  Herein, we report on the magnetic properties of these complexes. Fig. 1.  Dinuclear ruthenium carboxylates.