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[Br8 TPC]) and β-octakis(trifluoromethyl)- meso -tris( p -methoxyphenyl)corrole (Cu[(CF3 )8 T p OMePC]). Unlike reductive demetalation, which affords the free-base β-octabromocorrole, demetalation of Cu[Br8 TPC] under non- reductive conditions (CHCl3 /H2 SO4 ) 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 )8 T p OMePC], affording a highly saddled, hydrated corrole, H3 [5-OH,10-H-(CF3 )8 T p OMePC], 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 )8 T p OMePC], 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.