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.