title: Dual Pathways in the Oxidation of an Osmium(III) Guanidine Complex. Formation of Osmium(VI) Nitrido and Osmium Nitrosyl Complex.
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[CeIV(NO3)6], which is a one-electron oxidant. With m-CPBA, mer-[Os(NO)(L)(CN)3]-(mer-OsNO) is the product, while with CeIV, mer-[OsVI(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 CeIVare proposed.
authors.affiliation: College of Chemistry and Environmental Engineering, Yangtze University , Jingzhou 434020, Hubei, P. R. China.|Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Kowloon Tong, Hong Kong.
authors.forename: Jing
authors.initials: J
authors.lastname: Xiang
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Kowloon Tong, Hong Kong.|School of Chemical Engineering, Shandong University of Technology , Zibo 255049, P. R. China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Kowloon Tong, Hong Kong.
authors.forename: Shek-Man
authors.initials: SM
authors.lastname: Yiu
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Kowloon Tong, Hong Kong.
authors.forename: Tai-Chu
authors.identifier: http://orcid.org/0000-0002-0867-9746
authors.initials: TC
authors.lastname: Lau