First-row transition-metal complexes of corroles: synthesis and characterization of oxotitanium(IV) and oxovanadium(IV) complexes of β-alkylcorroles
Abstract
Oxotitanium and oxovanadium β-alkylcorrolates have been synthesized by reaction of corroles H3L with different metal carriers. These complexes retain an aromatic π-electron system and exist as mononuclear species [MO(HL)] containing a MO double bond. Optical and NMR spectroscopy indicated reaction with base leading to the formation of anionic species [MOL]–. Titanyl corrolates represent the first examples of diamagnetic neutral complexes where the corrole acts as a dianionic ligand. Spectral characterization reveals that the location of the proton of HL is at the N22 or N23 inner nitrogen atoms and that the complexes are present in two tautomeric forms. In contrast to derivatives of Cr or Mo where the metals are in the +5 oxidation state, the EPR spectra of the vanadyl corrolates confirm the +4 oxidation state for the co-ordinated metal. These new complexes complete the series of first-row transition-metal derivatives of corrole.