Successful Stabilization of the Elusive Species {FeNO}8 in a Heme Model

摘要

Abstract: Nitroxyl (HNO/NO ) heme-adducts have been postulated as intermediates in a variety of catalyticnprocesses carried out by different metalloenzymes. Hence, there is growing interest in obtaining andncharacterizing heme model nitroxyl complexes. The one-electron chemical reduction of the {FeNO}n7 nitrosylnderivative of FeIIIn(TFPPBr8)Cl, FeIIn(TFPPBr8)NO (1) (TFPPBr8 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-n[Tetrakis-(pentafluorophenyl)]porphyrin) with cobaltocene yields the significantly stable {FeNO}n8 complex,n[Co(C5H5)2] [Fe(TFPPBr8)NO] (2). Complex 2 was isolated and characterized by UV vis, FTIR,n1H andn15N NMR spectroscopies. In addition, DFT calculations were performed to get more insight into the structurenof 2. According to the spectroscopic and DFT results, we can state unequivocally that the surprisinglynstable complex 2 is the elusive {FeNO}n8 species. Both experimental and computational data allow to assignnthe electronic structure of 2 as intermediate between FeIInNO and FeInNO, which is contrasted with thenpredominant FeIInNO character of known nonheme {FeNO}n8 complexes. The enhanced stability achievednfor a heme model {FeNO}n8 is expected to allow further studies related to the reactivity of this elusive species.