Synthesis of Tridentate 2,6-Bis(imino)pyridyl Ruthenium(II) Complexes with N‑Heterocyclic Carbene Ligands: Activation of Imidazolium Salts

Low-valent Ru(0) complexes, [η²-N₃]­Ru­(η⁶-Ar) (<b>1</b>) or {[N₃]­Ru}₂­(μ-N₂) (<b>2</b>), where Ar = C₆H₆ or C₆H₅Me, and [N₃] = 2,6-(2,4,6-(CH₃)₃­C₆H₂NCCH₃)₂­C₅H₃N, activate C–H bonds in imidazolium salts to produce bis­(imino)­pyridyl ruthenium–(imida­zolidin-2-ylidene) complexes, [N₃]­Ru­(H)­(X)­(NHC) (<b>4</b>) (X = halides and tosylate). Formation of <b>4</b> is most likely to proceed via C–H oxidative addition, followed by anion coordination, which is expected to be a useful pathway in synthesizing new complexes with both N-heterocyclic carbene (NHC) and hydride ligands. A zwitterionic ruthenium complex with an ylidic ligand, bis­(imino)­pyridyl ruthenium–(2-methylene­imida­zoline) complex, <b>7</b>, was also successfully isolated and fully characterized. The ¹H NMR spectra and the solid-state structure confirm that complex <b>7</b> is an ylidic transition-metal complex with both NHC and hydride ligands, which was formed through the activation of imidazolium salts