Successful stabilization of the elusive species {FeNO}8 in a heme model

PELLEGRINO, JUAN; BARI, SARA E.; BIKIEL, DAMIÁN E.; DOCTOROVICH, F.A.

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

AMER CHEMICAL SOC

Lugar: Washington, DC, USA; Año: 2010 vol. 132 p. 989 - 995

0002-7863

Abstract: Nitroxyl (HNO/NO-) heme-adducts have been postulated as intermediates in a variety of catalyticprocesses carried out by different metalloenzymes. Hence, there is growing interest in obtaining andcharacterizing heme model nitroxyl complexes. The one-electron chemical reduction of the {FeNO}7 nitrosylderivative of FeIII(TFPPBr8)Cl, FeII(TFPPBr8)NO (1) (TFPPBr8 ) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-[Tetrakis-(pentafluorophenyl)]porphyrin) with cobaltocene yields the significantly stable {FeNO}8 complex,[Co(C5H5)2]+[Fe(TFPPBr8)NO]- (2). Complex 2 was isolated and characterized by UV-vis, FTIR, 1H and15N NMR spectroscopies. In addition, DFT calculations were performed to get more insight into the structureof 2. According to the spectroscopic and DFT results, we can state unequivocally that the surprisinglystable complex 2 is the elusive {FeNO}8 species. Both experimental and computational data allow to assignthe electronic structure of 2 as intermediate between FeIINO- and FeINO, which is contrasted with thepredominant FeIINO- character of known nonheme {FeNO}8 complexes. The enhanced stability achievedfor a heme model {FeNO}8 is expected to allow further studies related to the reactivity of this elusive species.