Reactions of Platina-β-diketones with 2-Aminopyridines: Synthesis and Characterization of Aminocarbene Complexes of Platinum(II)

Reactions of the dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) with 2-aminopyridine and 2-(N-methylamino)pyridine resulted in the formation of cyclic aminocarbene complexes of platinum(II) [Pt(COMe)Cl{2-(CMeNR)C5H4N-κC,N}] (R = H, 3a; Me, 3b). Constitution of these complexes was confirmed by microanalysis and IR and NMR (1H, 13C) spectroscopy. Single-crystal X-ray diffraction analyses of 3a and 3b showed them to be monomeric square-planar platinum complexes with the chloro ligand trans to the carbene ligand (configuration index SP-4-4). The five-membered platinacycles are planar in good approximation. The bond lengths Pt−Ccarbene (1.943(6)−1.950(9) Å) and N−Ccarbene (1.31(1)−1.340(7) Å) indicate some double-bond character as further established by DFT calculations. A tentative mechanism for the formation of the aminocarbene complexes 3a/b is discussed.