Here, we report the nitric oxide dioxygenation (NOD) reactions of two MnIII-peroxo (MIII-O22−) complexes, [(3PYENMe)MnIII(O22–)]+ (1) and [(N3PY)MnIII(O22–)]+ (2), bearing the pentadentate ligands. Complexes 1 & 2 showed the generation...

Here, we report a comparative study of nitric oxide oxidation (NOO) reactions of Co III -peroxo (Co III −O 2 2− ) and Co-nitrosyl ({CoNO} 8 ) complexes bearing the same N 4 -donor ligand (HMTETA) framework. In this regard, we prepared and characterized two new [(HMTETA)Co III (O 2 2− )] + (2, S = 2) and [(HMTETA)Co(NO)] 2+ (3, S = 1) complexes from [(HMTETA)Co II (CH 3 CN) 2 ] 2+ (1). Both complexes (2 and 3) are characterized by different spectroscopic measurements, including their DFT-optimized structures. Complex 2 produces Co II -nitrato [(HMTETA)Co II (NO 3 − )] + (Co II −NO 3 − , 4) complex in the presence of NO. In contrast, when 3 reacted with a superoxide (O 2 •− ) anion, it generated Co II -nitrito [(HMTETA)-Co II (NO 2 − )] + (Co II −NO 2 − , 5) with O 2 evolution. Experiments performed using 18/16 O-labeled superoxide ( 18 O 2 •− / 16 O 2 •− ) showed that O 2 originated from the O 2 •− anion. Both the NOO reactions are believed to proceed via a presumed peroxynitrite (PN) intermediate. Although we did not get direct spectral evidence for the proposed PN species, the mechanistic investigation using 2,4di-tert-butylphenol indirectly suggests the formation of a PN intermediate. Furthermore, tracking the source of the N-atom in the above NOO reactions using 15 N-labeled nitrogen ( 15 NO) revealed N-atoms in 4 (Co II − 15 NO 3 − ) and 5 (Co II − 15 NO 2 − ) derived from the 15 NO moiety.