cyclo-Tetra-kis(μ2-d-penicillaminato-κ(4) N,S:O,S)tetra-palladium(II) 9.75-hydrate

The asymmetric unit of the title compound, [Pd4(C5H9NO2S)4]·9.75H2O, contains two neutral tetranuclear complex molecules with similar conformations and 19.5 solvent water mol-ecules. Of the 21 independent water molecules, three exhibit an occupancy of one-half. In each tetranuclear complex molecule, the four Pd(II) atoms have a square-planar coordination environment and are spanned by four d-penicillaminate ligands in a κ(4) N,S:S,O coordination mode, forming an eight-membered Pd4S4 metallacycle. In the crystal, two tetra-nuclear mol-ecules are connected to each other through eight N-H⋯O hydrogen bonds between amine and carboxyl-ate groups, constructing a cylindrical dimer. The dimers are further hydrogen-bonded with the solvent water mol-ecules, completing a three-dimensional network.