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Nitric Oxide Dioxygenation (NOD) Reactions of CoIII-peroxo and NiIII-peroxo Complexes: NOD Versus NO Activation

Abstract

Here, we report the nitric oxide dioxygenation (NOD) reactions of NiIII-peroxo, [(12-TMC)NiIII(O22)]+ (NiIII-O22, 1), and CoIII-peroxo, [(12-TMC)CoIII(O22)]+ (CoIII-O22, 2), complexes bearing N-tetramethylated cyclam (TMC) ligands. The reaction of complex 1 with nitric oxide (NO) generates NiII-nitrato complex [(12-TMC)NiII(NO3)]+ (NiII-NO3, 3). However, in contrast to the NOD reaction of 1, compound 2 produces CoII-nitrito complex, [(12-TMC)CoII(NO2)]+ (CoII-NO2, 4) with O2 gas formation. Results suggested the formation of a presumptive Ni-peroxynitrite ([Ni-PN]+, [Ni-ONOO]+) intermediate, in the NOD reaction of 1, prior to the generation of NiII-NO3 (3). Although the end-products of the reaction of 2 with NO is different from that of 1, the mechanistic study explored by using 2,4-di-tert-butylphenol (2,4-DTBP), suggested that the reaction of 2 with NO  is also going through a presumed Co-peroxynitrite ([Co-PN]+, [Co-ONOO]+) intermediate. Further, exploring these NOD reactions and tracking the oxygen atom using 18O-labeled hydrogen peroxide (H218O2) revealed that two oxygen atoms of 3 (NiII-18O2N16O) and one oxygen atom of 4 (CoII-18ON16O) derives from peroxo (O22) moieties of 1 and 2, respectively. In continuation, we have explored the M-peroxo regeneration from NOD products (3 and 4), and for the first time, we have observed the formation of MIII-O22 complexes, 1 and 2, upon treatment with H2O2 and triethylamine (TEA), respectively. This work is the first-ever report, which showed the exact NO dioxygenase (NODs) enzyme catalytic cycle. Furthermore, we have also explored the NO activation of 3 and 4, and surprisingly, we observed the formation of Co-nitrosyl (5) from 4 upon reaction with NO; on the contrary, 3 was unreactive towards NO. Evidence supporting the formation of [Ni-PN]+ and [Co-PN]+ intermediates are also presented.

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Supplementary files

Article information


Submitted
23 Aug 2020
Accepted
07 Oct 2020
First published
10 Oct 2020

Inorg. Chem. Front., 2020, Accepted Manuscript
Article type
Research Article

Nitric Oxide Dioxygenation (NOD) Reactions of CoIII-peroxo and NiIII-peroxo Complexes: NOD Versus NO Activation

M. Yenuganti, S. Das, K. kulbir, S. GHOSH, P. Bhardwaj, S. S. Pawar, S. C. Sahoo and P. Kumar, Inorg. Chem. Front., 2020, Accepted Manuscript , DOI: 10.1039/D0QI01023E

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