β‐Octabromo‐ and β‐Octakis(trifluoromethyl)isocorroles: New Sterically Constrained Macrocyclic Ligands

Presented herein is a study of the acid-induced demetalation of two sterically hindered copper corroles, Cu β-octabromo-meso-triphenylcorrole (Cu[Br8TPC]) and β-octakis(trifluoromethyl)-meso-tris(p-methoxyphenyl)corrole (Cu[(CF3)8TpOMePC]). Unlike reductive demetalation, which affords the free-base β-octabromocorrole, demetalation of Cu[Br8TPC] under non- reductive conditions (CHCl3/H2SO4) resulted in moderate yields of free-base 5- and 10-hydroxy isocorroles. The isomeric free bases could be complexed to CoII and NiII, affording stable complexes. Only reductive demetalation was found to work for Cu[(CF3)8TpOMePC], affording a highly saddled, hydrated corrole, H3[5-OH,10-H-(CF3)8TpOMePC], where the elements of water had added across C5 and C10. Interaction of this novel free base with CoII resulted in Co[iso-10-H-[CF3)8TpOMePC], a CoII 10-hydro isocorrole. The new metal complexes were all characterized by single-crystal X-ray diffraction analysis and, despite their sterically hindered nature, were found to exhibit almost perfectly planar isocorrole cores.