Ferric nitrosyl hemes are important intermediates in biology. We reported, in 2016, the preparation of stable synthetic ferric nitrosyl porphyrins of the form [(por)Fe(NO)L]OTf (por = porphyrinato dianion; L = axial imidazole-based ligand). These compounds were stable to NO loss for extended periods in solution and in the solid state, allowing for a systematic study of their chemical reactivity. For example, we showed that hydride attack on these compounds generated the nitroxyl derivatives (por)Fe(HNO)(L) with characteristic IR and 1H NMR spectroscopic signals for the bound HNO ligands. We have extended this reactivity to include nucleophilic attack of C-based and N-based nucleophiles at the bound ferrric-NO groups. Specifically, reactions of the stable ferric nitrosyls [(por)Fe(NO)L]OTf with PhLi generated the nitrosobenzene (por)Fe(PhNO)L products. The analogous reactions with the Ru congener provided the (por)Ru(PhNO)L product that was characterized by spectroscopy and by X-ray crystallography. Interestingly, reactions of the ferric nitrosyls [(por)Fe(NO)L]+ with diethylamide results in the generation of the carcinogenic diethylnitrosamine Et2NNO resulting from N-N bond formation. The preparation, characterization, and reactivity of these species will be presented and discussed. These results provide the first documented cases of nucleophilic attack at bound ferric nitrosyls by C-based and organic N-based reagents; the resulting C-N and N-N bond formation reactions have relevance to heme-based nitrosations of significance to human health and the global N-cycle in general.

Nucleophilic attack at the bound NO of stable ferric nitrosyl porphyrins

255th National Meeting (2018)

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