Rhodium and iridium complexes of N-(2′-hydroxyphenyl)pyrrole-2- aldimine: Synthesis, structure, and spectral and electrochemical properties

Reaction of N-(2'-hydroxyphenyl)pyrrole-2-aldimine (H₂L) with [M(PPh₃)₃Cl] (M = Rh, Ir) affords complexes of type [M(PPh₃)₂(L)Cl]. Structures of both complexes have been determined by X-ray crystallography. In both complexes, the N-(2'- hydroxyphenyl)pyrrole-2-aldimine ligand is coordinated to the metal centre, via dissociation of the acidic protons, as a dianionic tridentate N,N,O-donor. The M(L)C1 fragment constitutes an equatorial plane with the metal at the centre and the two PPh₃ ligands occupying axial positions. The complexes are diamagnetic (low-spin d⁶, S = 0) and show intense MLCT transitions in the visible region. Cyclic voltammetry of the [M(PPh₃) ₂(L)CI] complexes shows reversible M(III)-M(IV) oxidation near 0-5 V vs SCE and quasi-reversible ligand-centred oxidative response near 1.0 V vs SCE. © Indian Academy of Sciences.