A series of pyrazine (pz) complexes containing cis-(NH3)(2)Pt-parallel to, (tmeda)Pt-parallel to (tmeda = N, N, N', N'-tetramethylethylenediamine), and trans-(NH3)(2)Pt-parallel to entities have been prepared and characterized by X-ray crystallography and/or H-1 NMR spectroscopy. In these compounds, the pz ligands act as monodentate (1-3) or bidentate bridging ligands (4-7). Three variants of the latter case are described: a dinuclear complex [Pt-parallel to](2) (4b), a cyclic tetranuclear [Pt-parallel to](4) complex (5), and a trinuclear mixed-metal complex [Pt2Ag] (7). Mono- and bidentate binding modes are readily differentiated by H-1 NMR spectroscopy, and the assignment of pz protons in the case of monodentate coordination is aided by the observation of Pt-195 satellites. Formation of the open molecular box cis-[{(NH3)(2)Pt(pz)}(4)](NO3)(8)(.)3.67H(2)O (5) from cis-(NH3)(2)Pt-parallel to and pz follows expectations of the "molecular library approach" for the generation of a cyclic tetramer.