Nitric oxide monooxygenation (NOM) reaction of a Cobalt-nitrosyl {Co(NO)}8 to CoII-nitrito {CoII(NO2–)}: Base induced hydrogen gas (H2) evolution

Here, we report the nitric oxide monooxygenation (NOM) reactions of a CoIII-nitrosyl complex (1, {Co-NO}8) in the presence of mono-oxygen reactive species, i.e., base (OH–, tetrabutylammonium hydroxide (TBAOH) or NaOH/15-Crown-5), oxide (O2–, Na2O/15-Crown-5) and water (H2O). The reaction of 1 with OH– produces a CoII-nitrito complex {3, (CoII-NO2–)} and hydrogen gas (H2), via the formation of a putative N-bound Co-nitrous acid intermediate (2, {Co-NOOH}+). The homolytic cleavage of O–H bond of proposed [Co-NOOH]+ releases H2 via a presumed CoIII-H intermediate. In another chemistry, 1 generates CoII-NO2– when reacted with O2– via an expected CoI-nitro (4) intermediate. However, complex 1 is found to be unreactive towards H2O. Mechanistic investigations using 15N-labeled-15NO and 2H-labeled-NaO2H (NaOD) evidently revealed that the N-atom in CoII-NO2– and H-atom in H2 gas are derived from nitrosyl ligand and OH– moiety, respectively.