Treatment of the pyrazole sulfoxide, 1,1′-(2,2′- sulfoneinylbis(ethanediyl))bis(3,5-dimethyl-1-pyrazole) (L1), and pyrazole sulfone, 1,1′-(2,2′-sulfoneonylbis(ethanediyl))bis(3,5-dimethyl-1- pyrazole) (L2) ligands, with [PdCl<inf>2</inf>(CH<inf>3</inf>CN)<inf>2</inf>] in a 1:1 M:L ratio, yields two kinds of complexes, monomer or dimer, depending on the solvent of the reaction. Monomeric complexes [PdCl<inf>2</inf>(L)] (L = L1 (1) or L2 (3)) are obtained when the solvent is acetonitrile, whereas when the reaction takes place in tetrahydrofuran, dimeric complexes [PdCl <inf>2</inf>(L)]<inf>2</inf> (L = L1 (2) or L2 (4)) are obtained. Diffusion NMR studies have been performed to characterize a mixture of the monomeric/dimeric species in CD<inf>3</inf>CN solution. The solid-state structures of 3 and 4 have been determined by single-crystal X-ray diffraction methods. The extended structures allowed the study of the effects of the structure of the ligands on the topology and interpenetration form (two-dimensional layer polymers and three-dimensional networks). Finally, it has been observed that dimers are converted into the corresponding monomers under continuous acetonitrile reflux conditions, thus indicating that the latter are thermodynamically more stable than dimers. © The Royal Society of Chemistry.