The reactions of diselenophosphates, [dsep, (RO)₂PSe₂⁻; R = Et, ⁿPr and ⁱPr] with cadmium(II) and mercury(II) perchlorates in a 2 : 1 molar ratio formed compounds of stoichiometry M[Se₂P(OR)₂]₂ {M = Cd, R = Et (1), ⁿPr (2), ⁱPr (3); Hg, Et(4), ⁿPr (5), ⁱPr (6)}, and with zinc(II) perchlorates, chalcogen centered tetranuclear clusters, [Zn₄(μ₄-E){Se₂P(OR)₂}₆] {E = Se, R = Et (7), ⁿPr (8), ⁱPr (9); E = O, R = Et (10), ⁿPr (11), ⁱPr (12)} were formed. All these complexes have been characterized with the help of analytical data, X-ray crystallography (1, 3, 6, 10, 11 and 12), and FAB-mass spectrometry (7–12). Compound 1 is a linear double-chain polymer, in which each pair of Cd atoms is bridged by two dsep ligands; the mercury polymer 6 has a helical chain structure, in which two Hg atoms are bridged by one dsep ligand, and the other ligand chelates the Hg atom. The chelating dsep ligands lie on either side of the helical chain. Compound 3 exists as a dimer in which two cadmium atoms are connected by two bridging dsep ligands, and each cadmium atom is further chelated by a dsep ligand. The metal atoms in 1, 3 and 6 are each coordinated by four selenium atoms in a distorted tetrahedral geometry. Clusters 10–12 have tetrahedral array of zinc atoms with an oxygen atom in the center with edge-bridging dsep ligands. Positive FAB-mass spectra support the formation of selenium-centered clusters, 7–9, of which the cluster 8 was structurally confirmed earlier. The solution state behavior of compounds 1–12 has been studied by using multinuclear NMR spectroscopy. Dimer 3 in CD₂Cl₂ showed monomer–dimer exchange equilibrium in the temperature range 20 to −90 °C and the free energy of activation is calculated from the coalescence temperature as ΔG^‡_{(223 K)} = 38.5 kJ mol⁻¹. Polymer 6 undergoes depolymerization in CDCl₃ and exhibits monomer–dimer exchange equilibrium in the temperature range 20 to −60 °C.