Dual Pathways in the Oxidation of an Osmium(III) Guanidine Complex. Formation of Osmium(VI) Nitrido and Osmium Nitrosyl Complex

Jing Xiang; Qian Wang; Shek-Man Yiu; Tai-Chu Lau

doi:10.1021/acs.inorgchem.6b02645

Dual Pathways in the Oxidation of an Osmium(III) Guanidine Complex. Formation of Osmium(VI) Nitrido and Osmium Nitrosyl Complex

Inorg Chem. 2017 Feb 20;56(4):2022-2028. doi: 10.1021/acs.inorgchem.6b02645. Epub 2017 Jan 31.

Authors

Jing Xiang^{1

2}, Qian Wang^{2

3}, Shek-Man Yiu², Tai-Chu Lau²

Affiliations

¹ College of Chemistry and Environmental Engineering, Yangtze University , Jingzhou 434020, Hubei, P. R. China.
² Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Kowloon Tong, Hong Kong.
³ School of Chemical Engineering, Shandong University of Technology , Zibo 255049, P. R. China.

PMID: 28140572
DOI: 10.1021/acs.inorgchem.6b02645

Abstract

The guanidine moiety of arginine is involved in the active sites of a variety of enzymes, such as nitric oxide synthase (NOS) and NiFe hydrogenase. In this paper we aim to investigate the effects of a metal center on the oxidation of guanidine, which should provide an interesting comparison with the biological aerobic oxidation of arginine catalyzed by NOS. We studied the oxidation of an osmium(III) guanidine complex, mer-[Os(L){N(H)C(NH₂)₂}(CN)₃]^-, (OsG, HL = 2-(2-hydroxyphenyl)benzoxazole) by m-chloroperbenzoic acid (m-CPBA), which is potentially an O atom transfer reagent, and by (NH₄)₂[Ce^IV(NO₃)₆], which is a one-electron oxidant. With m-CPBA, mer-[Os(NO)(L)(CN)₃]^- (mer-OsNO) is the product, while with Ce^IV, mer-[Os^VI(N)(L)(CN)₃]^- (mer-OsN) is formed instead. The crystal structures of mer-OsNO and mer-OsN were determined by X-ray crystallography. The mechanisms for the oxidation of OsG by m-CPBA and Ce^IV are proposed.