Aerobic Oxidation of an Osmium(III) N-Hydroxyguanidine Complex To Give Nitric Oxide

Jing Xiang, Qian Wang, Shek Man Yiu, Wai Lun Man, Hoi Ki Kwong, Tai Chu Lau*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

The aerobic oxidation of the N-hydroxyguanidinum moiety of N-hydroxyarginine to NO is a key step in the biosynthesis of NO by the enzyme nitric oxide synthase (NOS). So far, there is no chemical system that can efficiently carry out similar aerobic oxidation to give NO. We report here the synthesis and X-ray crystal structure of an osmium(III) N-hydroxyguanidine complex, mer-[OsIII{NH═C(NH2)(NHOH)}(L)(CN)3]− (OsGOH, HL = 2-(2-hydroxyphenyl)benzoxazole), which to the best of our knowledge is the first example of a transition metal N-hydroxyguanidine complex. More significantly, this complex readily undergoes aerobic oxidation at ambient conditions to generate NO. The oxidation is pH-dependent; at pH 6.8, fac-[Os(NO)(L)(CN)3]− is formed in which the NO produced is bound to the osmium center. On the other hand, at pH 12, aerobic oxidation of OsGOH results in the formation of the ureato complex [OsIII(NHCONH2)(L)(CN)3]2– and free NO. Mechanisms for this aerobic oxidation at different pH values are proposed.
Original languageEnglish
Pages (from-to)5056–5061
Number of pages6
JournalInorganic Chemistry
Volume55
Issue number10
DOIs
Publication statusPublished - 16 May 2016
Externally publishedYes

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