Nitric Oxide Release from a Nickel Nitrosyl Complex Induced by One-Electron Oxidation

• Published in: Inorganic chemistry Vol. 52; no. 6; pp. 3207 - 3216
• Main Authors: Wright, Ashley M, Zaman, Homaira T, Wu, Guang, Hayton, Trevor W
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18-03-2013
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic302697v

Reaction of [Ni(NO)(bipy)][PF6] (2) with AgPF6 or [NO][PF6] in MeCN results in formation of [Ni(bipy) x (MeCN) y ]2+ and release of NO gas in moderate yields. In contrast, the addition of the inner sphere oxidant Ph2S2 to 2 does not result in denitrosylation. Instead, the diphenyldisulfide adduct [{(bipy)(NO)Ni}2(μ-S2Ph2)][PF6]2 (3) is formed in good yield. However, oxidation of 2 with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) does results in cleavage of the Ni–NO bond and generation of NO. The metal-containing product, [(bipy)Ni(η2-TEMPO)][PF6] (4), can be isolated as an orange-brown solid in excellent yields. In the solid state, complex 4 contains a side-on bound TEMPO– ligand, which is characterized by a long N–O bond length [1.383(2) Å]. The contrasting reactivity of Ph2S2 and TEMPO likely relates to their different redox potentials, as Ph2S2 is a relatively weak oxidant. Finally, the addition of pyridine-N-oxide to 2 results in the formation of the adduct, [(bipy)Ni(NO)(ONC5H5)][PF6] (5). No evidence of NO release is observed in this reaction, probably because of the low one-electron (1e–) reduction potential of pyridine-N-oxide.