Sesquicaesium hemisodium tetra-cyanidoplatinate(II) sesquihydrate.

The title compound, Cs(1.5)Na(0.5)[Pt(CN)(4)]·1.5H(2)O, was isolated from solution as a salt. The tetra-cyanidoplatinate (TCP) anions are stacked in a linear quasi-one-dimensional arrangement along the b axis, with Pt⋯Pt inter-actions of 3.6321 (5) Å. The mixed alkali metal TCP contains three distinct alkali metal positions in the structure that do not show any mixed occupancy: Cs1 (site symmetry 2), Cs2 (general position) and Na1 (site symmetry ). The Na(+) ion contains an octa-hedral coordination environment composed of two water mol-ecules and four N-terminal cyanides, which serve to bridge TCP anions. The Cs(+) cations contain mono- and bicapped square-prismatic environments, where the square prisms are formed from cyanide N atoms with water mol-ecules capping the faces. The 1.5 water mol-ecules per formula unit are a result of two fully occupied sites, one on a general position and one on a twofold rotation axis. Weak hydrogen-bonding inter-actions are observed between one water mol-ecule and terminal N-atom acceptors from TCP, while the second water mol-ecule is not involved in hydrogen bonding.