Abstract
Some bacterial heme proteins catalyze the coupling of two NO molecules to generate N(2) O. We previously reported that a heme Fe-NO model engages in this N-N bond-forming reaction with NO. We now demonstrate that (OEP)Co(II) (NO) similarly reacts with 1 equiv of NO in the presence of the Lewis acids BX(3) (X=F, C(6) F(5) ) to generate N(2) O. DFT calculations support retention of the Co(II) oxidation state for the experimentally observed adduct (OEP)Co(II) (NO⋅BF(3) ), the presumed hyponitrite intermediate (P(.+) )Co(II) (ONNO⋅BF(3) ), and the porphyrin π-radical cation by-product of this reaction, and that the π-radical cation formation likely occurs at the hyponitrite stage. In contrast, the Fe analogue undergoes a ferrous-to-ferric oxidation state conversion during this reaction. Our work shows that cobalt hemes are chemically competent to engage in the NO-to-N(2) O conversion reaction.