Mono- and binuclear ruthenium corroles: Synthesis, spectroscopy, electrochemistry, and structural characterization

The aim of this research was to prepare mononuclear ruthenium corroles, because of the well-documented potency of analogous porphyrin complexes in catalysis. The syntheses of the mononuclear nitrosyl complexes [Ru(tpfc)(NO)] and [Ru(tdcc)(NO)] (tpfc=trianion of 5,10,15-tris(pentafluorophenyl)corrole, tdcc=trianion of 5,10,15-tris(2,6-dichlorophenyl)corrole), and of the binuclear [{Ru(tpfc)}₂] were achieved by using [{Ru(cod)Cl₂}_x] (cod=cyclooctadiene) as the metal source. The NMR spectra of all three complexes clearly demonstrate that they are diamagnetic; this is consistent with a triple bond between the metal ions in [{Ru(tpfc)}₂] and is expected for classical {MNO}⁶ complexes. These features were further substantiated by the stretching frequencies of the {MNO} moieties, electrochemical measurements on all complexes, and the X-ray crystal structures of [Ru(tpfc)(NO)] and [{Ru(tpfc)}₂]. A comparison of the spectroscopic and structural characteristics of these new complexes with analogous iron corroles, as well as with iron and ruthenium porphyrins, suggests that it will be hard to obtain mononuclear ruthenium corroles without π-accepting ligands.