Reactivity studies of cyclopentadienyl ruthenium(II), osmium(II) and pentamethylcyclopentadienyl iridium(III) complexes towards 2-(2′-pyridyl)imidazole derivatives

The reaction of [CpRu(PPh₃)₂Cl] and [CpOs(PPh₃)₂Br] with chelating 2-(2′-pyridyl)imidazole (N ∩ N) ligands and NH₄PF₆ yields cationic complexes of the type [CpM(N ∩ N)(PPh₃)] ⁺ (<b>1</b>: M = Ru, N ∩ N = 2-(2′-pyridyl)imidazole; <b>2</b>: M = Ru, N ∩ N = 2-(2′-pyridyl)benzimidazole; <b>3</b>: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-dimethylimidazole; <b>4</b>: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-diphenylimidazole; <b>5</b>: M = Os, N ∩ N = 2-(2′-pyridyl)imidazole; <b>6</b>: M = Os, N ∩ N = 2-(2′-pyridyl)benzimidazole). They have been isolated and characterized as their hexafluorophosphate salts. Similarly, in the presence of NH4PF6, [Cp*Ir(μ-Cl)Cl]₂ reacts in dry methanol with N ∩ N chelating ligands to afford in excellent yield [Cp*Ir(N ∩ N)Cl]PF₆ (<b>7</b>: N ∩ N = 2-(2′-pyridyl)imidazole; <b>8</b>: N ∩ N = 2-(2′-pyridyl)benzimidazole). All the compounds have been characterized by infrared and NMR spectroscopy and the molecular structure of [<b>1</b>]PF₆, [<b>2</b>]PF₆ and [<b>7</b>]PF₆ by single-crystal X-ray structure analysis.