Oxidation of aliphatic and aromatic CH bonds by t-BuOOH catalyzed by μ-nitrido diiron phthalocyanine

Abstract

Low temperature selective transformation of alkanes to useful products continues to be an important challenge in chemistry and industry. μ-Nitrido diiron phthalocyanines in combination with H₂O₂ have been recently identified as powerful oxidation catalysts for these challenging reactions due to the formation of ultra-high valent diiron oxo species PcFe(IV)μNFe(IV)O(Pc⁺). This very strong two-electron oxidizing species is generated from peroxo complex PcFe(IV)μNFe(III)OOR(Pc) (RH in the case of H₂O₂) via heterolytic OO bond cleavage. Therein we show that the evolution of the peroxo diiron complex depends on the peroxide structure. Using ^tBuOOH we have demonstrated the formation of an one-electron oxidizing PcFe(IV)μNFe(IV)O(Pc) and ^tBuO radical via homolytic OO cleavage of the peroxocomplex. The reactivity of the μ-nitrido diiron tetra-t-butylphthalocyanine − ^tBuOOH catalytic system was investigated in the oxidation of different CH bonds in alkanes, olefins, aromatic and alkylaromatic compounds. The main products of cyclohexane oxidation were cyclohexanone and cyclohexanol whereas bicyclohexyl was formed in minor amounts even in the presence of O₂ and ^tBuOOH. Under optimal conditions, the turnover numbers of almost 5300 have been achieved.