Chromium Corroles in Four Oxidation States

Abstract

We have isolated and characterized chromium complexes of 5,10,15-tris(pentafluorophenyl)corrole [(tpfc)H_3] (1) in four oxidation states:  [(tpfc•)CrO][SbCl_6] (6); [(tpfc)CrO] (2); [(tpfc)CrO][Cp_2Co] (4); and [(tpfc)Cr(py)_2] (3). Complex 6 was prepared both by electrochemical and chemical oxidation of 2; its formulation as a Cr^VO ligand−radical species is based on UV−visible absorption as well as EPR measurements. Cobaltocene reduction of 2 gave 4; it was identified as a diamagnetic d^2 Cr^(IV)O complex from its sharp ^1H NMR spectrum. Reaction of 2 with triphenylphosphine yielded a chromium(III) corrole, [(tpfc)Cr(OPPh_3)_2] (5). Owing to its air sensitivity, 5 could not be isolated in the absence of excess OPPh_3. The structure of the Cr^(III) bis-pyridine complex (3) was determined by X-ray crystallography (Cr−N distances:  1.926−1.952 Å, pyrrole; 2.109, 2.129 Å, pyridine).