Pyrazine as a Building Block for Molecular Architectures with Pt^II

A series of pyrazine (pz) complexes containing cis-(NH3)2PtII, (tmeda)PtII (tmeda = N,N,N‘,N‘-tetramethylethylenediamine), and trans-(NH3)2PtII entities have been prepared and characterized by X-ray crystallography and/or 1H
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 [PtII]2 (4b), a cyclic tetranuclear [PtII]4
complex (5), and a trinuclear mixed-metal complex [Pt2Ag] (7). Mono- and bidentate binding modes are readily
differentiated by 1H NMR spectroscopy, and the assignment of pz protons in the case of monodentate coordination
is aided by the observation of 195Pt satellites. Formation of the open molecular box cis-[{(NH3)2Pt(pz)}4](NO3)8·3.67H2O (5) from cis-(NH3)2PtII and pz follows expectations of the “molecular library approach” for the generation
of a cyclic tetramer.