Nitric oxide monooxygenation (NOM) reaction of cobalt-nitrosyl {Co(NO)}(8) to Co(II)-nitrito {Co(II)(NO(2)(−))}: base induced hydrogen gas (H(2)) evolution

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