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The crystal structures of three isotypic orthorhombic dihydrogendiphosphates, namely dipotassium copper(II)/nickel(II)/zinc(II) bis(dihydrogendiphosphate) dihydrate, K2M(H2P2O7)2.2H2O (M = Cu, Ni and Zn), have been refined from single-crystal data. The M2+ and K+ cations are located at sites of m symmetry, and the P atoms occupy general positions. These compounds also exist in triclinic forms with very similar structural features. The structures of both forms are compared, as well as the geometry of the MO6 octahedron, which is considerably elongated towards the water molecules for M = Ni and Cu. Such elongation has not been observed among the other representatives of the family. A Raman study of the whole series K2M(H2P2O7)2.2H2O (M = Mn, Co, Ni, Cu, Zn and Mg) is reported.

The title compound, [Ag(C(3)H(5)OS(2))](n), is polymeric in the solid state and adopts a layered structure in which each Ag atom is five-coordinated in a distorted trigonal-bipyramidal geometry defined by four S atoms belonging to four different xanthate groups and by a neigbouring Ag atom [Ag.Ag = 3.0540 (8) A]. Each S atom is three-coordinated to one C and two Ag atoms. The structure can be envisaged as being formed by Ag(2)(S(2)COEt)(2) units in which every S atom is bonded to another Ag atom from a different unit and the Ag atoms are also bonded to two different S atoms of two other units. The result is a two-dimensional network of condensed metallacycles of six or eight atoms.

The Pd atom in the title compound, [Pd(C(3)H(5)OS(2))(2)], lies on an inversion center and adopts a square-planar coordination geometry defined by the four S atoms of the two dithiocarbonate (xanthate) ligands. In the solid state, the molecules aggregate into layers in which the rows of molecules alternate their orientation to allow each Pd atom to interact with two symmetry-equivalent S atoms of the xanthate ligands of adjacent molecules, generating a pseudo-octahedral environment around each Pd atom. This weak interaction of 3.3579 (7) A can be classified as a closed-shell electrostatic intermolecular interaction.

A new triclinic polymorphic modification of the title compound, [Ag(C(3)H(5)OS(2))(C(18)H(15)P)(2)], has been found and compared with the previously known orthorhombic modification [Tiekink (1988). Coord. Chem. 17, 239-243]. The two polymorphs have the same molecular shape, viz. a distorted tetrahedral geometry, with a chelating dithiocarbonate (xanthate) and two PPh(3) ligands bonded to the Ag atom. However, in this new polymorph, the xanthate ligand is bonded asymmetrically to the Ag atom, with Ag-S distances of 2.5489 (6) and 2.8055 (7) A, while for the orthorhombic polymorph these distances are 2.686 (4) and 2.601 (4) A. The Ag-P distances are similar in both structures.