Synthesis and structure of rare zwitterionic complexes involving the presence of N (py) MCl 3 − moieties (M = Pt(II), Pd(II))

Abstract 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), [(C 6 H 5 CN) 2 PtCl 2 ], forming trans -diiodo-di(benzonitrile)platinum(II), [(C 6 H 5 CN) 2 PtI 2 ] ( 3 ), and the complex [(CN) 2 Py(2-Mepy)PyzPtCl 3 ]∙CH 3 CN ( 4 ), both structurally elucidated by single-crystal X-ray work. Using a parallel procedure, reaction of 2 with dichloro-di(benzonitrile)palladium(II), [(C 6 H 5 CN) 2 PdCl 2 ], results in the formation of complex 5 , [(CN) 2 Py(2-Mepy)PyzPdCl 3 ]∙CH 3 CN, isostructural with 4 . Complex 5 is also formed by reaction of the same reactant 2 with PdCl 2 . 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) PtCl 3 − and N (py) PdCl 3 − 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 .