Multiple N–H and C–H Hydrogen Atom Abstractions Through Coordination-Induced Bond Weakening at Fe-Amine Complexes

We report the use of the reported Fe-phthalocyanine complex, PcFe ( 1 ; Pc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine), to generate PcFe-amine complexes 1-(NH 3 ) 2 , 1-(MeNH 2 ) 2 , and 1-(Me 2 NH) 2 . Treatment of 1 or 1-(NH 3 ) 2 o an excess of the stable aryloxide radical, 2,4,6-tri er -butylphenoxyl radical ( Bu ArO • ), under NH 3 resulted in catalytic H atom abstraction (HAA) and C-N coupling to generate the product 4-amino-2,4,6-tri er -butylcyclohexa-2,5-dien-1-one ( 2 ) and Bu ArOH. Exposing 1-(NH 3 ) 2 o an excess of the trityl (CPh 3 ) variant, 2,6-di- er -butyl-4-tritylphenoxyl radical ( Tr ArO • ), under NH 3 did not lead to catalytic ammonia oxidation as previously reported in a related Ru-porphyrin complex. However, pronounced coordination-induced bond weakening of both α N-H and β C-H in the alkylamine congeners, 1-(MeNH 2 ) 2 and 1-(Me 2 NH) 2 , led to multiple HAA events yielding the unsaturated cyanide complex, 1-(MeNH 2 )(CN) , and imine complex, 1-(MeN═CH 2 ) 2 , respectively. Subsequent C-N bond formation was also observed in the latter upon addition of a coordinating ligand. Detailed computational studies support an alternating mechanism involving sequential N-H and C-H HAA to generate these unsaturated products.