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

Abstract

The reaction of [CpRu(PPh 3) 2Cl] and [CpOs(PPh 3) 2Br] with chelating 2-(2′-pyridyl)imidazole (N ∩ N) ligands and NH 4PF 6 yields cationic complexes of the type [CpM(N ∩ N)(PPh 3)] + ( 1: M = Ru, N ∩ N = 2-(2′-pyridyl)imidazole; 2: M = Ru, N ∩ N = 2-(2′-pyridyl)benzimidazole; 3: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-dimethylimidazole; 4: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-diphenylimidazole; 5: M = Os, N ∩ N = 2-(2′-pyridyl)imidazole; 6: M = Os, N ∩ N = 2-(2′-pyridyl)benzimidazole). They have been isolated and characterized as their hexafluorophosphate salts. Similarly, in the presence of NH 4PF 6, [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]PF 6 ( 7: N ∩ N = 2-(2′-pyridyl)imidazole; 8: N ∩ N = 2-(2′-pyridyl)benzimidazole). All the compounds have been characterized by infrared and NMR spectroscopy and the molecular structure of [ 1]PF 6, [ 2]PF 6 and [ 7]PF 6 by single-crystal X-ray structure analysis.