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

Here, we present a study of the acid-induced demetalation of two sterically hindered copper corroles, Cu β-octabromo-meso-triphenylcorrole (Cu[Br 8TPC]) and β-octakis(trifluoromethyl)-meso-tris(p-methoxyphenyl)corrole (Cu[(CF 3) 8TpOMePC]). Unlike reductive demetalation, which affords the free-base β-octabromocorrole, demetalation of Cu[Br 8TPC] under non- reductive conditions (CHCl 3/H 2SO 4) resulted in moderate yields of free-base 5- and 10-hydroxy isocorroles. The isomeric free bases could be complexed to Co II and Ni II, affording stable complexes. Only reductive demetalation was found to work for Cu[(CF 3) 8TpOMePC], affording a highly saddled, hydrated corrole, H 3[5-OH,10-H-(CF 3) 8TpOMePC], where the elements of water had added across C5 and C10. Interaction of this novel free base with Co II resulted in Co[iso-10-H-[CF 3) 8TpOMePC], a Co II 10-hydro isocorrole. Finally, 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.