Reaction of a Co(III)-peroxo complex with nitric oxide: putative formation of a peroxynitrite intermediate.

A Co(II) complex, [Co II (L) 2 (H 2 O) 2 ](ClO 4 ) 2 , 1, having a bidentate ligand L [L = bis(3,5-dimethylpyrazolyl)methane] has been synthesized. Complex 1 in acetonitrile solution at -40 °C, in the presence of H 2 O 2 and NEt 3 , afforded the corresponding Co(III)-peroxo species, [Co III (L) 2 (O 2 2- )] + , as the transient intermediate 1a. Thermal instability precluded its isolation and further characterization. The addition of nitric oxide (NO) gas into the freshly prepared [Co III (L) 2 (O 2 2- )] + in acetonitrile at -40 °C resulted in the corresponding Co(II)-nitrato complex, [Co II (L) 2 (NO 3 )](ClO 4 ) (2). The reaction is proposed to proceed through a putative Co(II)-peroxynitrite intermediate 1b. It was evidenced by the characteristic phenol ring nitration reaction.