Synthesis and structure of rare zwitterionic complexes involving the presence of N(py)MCl3− moieties (M = Pt(II), Pd(II))

The monocation 2,3-dicyano-5-[(N-methyl)-2-pyridyl-6-(2-pyridyl)pyrazine, [(CN)2(2-Mepy)PyPyz]+ (1) reacts, as the iodide salt (2), under mild experimental conditions, with dichloro-di(benzonitrile)platinum(II), [(C6H5CN)2PtCl2], forming trans-diiodo-di(benzonitrile)platinum(II), [(C6H5CN)2PtI2] (3), and the complex [(CN)2Py(2-Mepy)PyzPtCl3]∙CH3CN (4), both structurally elucidated by single-crystal X-ray work. Using a parallel procedure, reaction of 2 with dichloro-di(benzonitrile)palladium(II), [(C6H5CN)2PdCl2], results in the formation of complex 5, [(CN)2Py(2-Mepy)PyzPdCl3]∙CH3CN, isostructural with 4. Complex 5 is also formed by reaction of the same reactant 2 with PdCl2. Complexes 4 and 5, further characterized by IR and UV–vis spectral data, are neutral stable zwitterions presenting both a +1 pyridinium component neutralized by rare N(py)PtCl3− and N(py)PdCl3− anionic moieties, respectively (py = 2-pyridyl group). DFT calculations fit reasonably well with the observed UV–vis absorptions and provide information on the localization of the HOMO and LUMO within the species 4 and 5.