Oxo-Free Hydrocarbon Oxidation by an Iron(III)-Isoporphyrin Complex

Metal-halides that perform proton coupled electron-transfer (PCET) oxidation are an important new class of high-valent oxidant. In investigating metal-dihalides, we reacted [Fe III (Cl)(T(OMe)PP)] ( 1 , T(OMe)PP = meso -tetra(4-methoxyphenyl)porphyrinyl) with (dichloroiodo)benzene. An Fe III - meso -chloro-isoporphyrin complex [Fe III (Cl) 2 (T(OMe)PP-Cl)] ( 2 ) was obtained. 2 was characterized by electronic absorption, 1 H NMR, EPR, and X-ray absorption spectroscopies and mass spectrometry with support from computational analyses. 2 was reacted with a series of hydrocarbon substrates. The measured kinetic data exhibited a nonlinear behavior, whereby the oxidation followed a hydrogen-atom-transfer (HAT) PCET mechanism. The meso -chlorine atom was identified as the HAT agent. In one case, a halogenated product was identified by mass spectrometry. Our findings demonstrate that oxo-free hydrocarbon oxidation with heme systems is possible and show the potential for iron-dihalides in oxidative hydrocarbon halogenation.