Coia, George M. and Demadis, Konstantinos D. and Meyer, Thomas J. (2000) Oxidation of Ammonia in Osmium Polypyridyl Complexes. Inorganic Chemistry, 39 (10). pp. 2212-2223. ISSN 0020-1669. doi:10.1021/ic0000505. https://resolver.caltech.edu/CaltechAUTHORS:20170424-122539672
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Abstract
The oxidations of cis- and trans-[Os^(III)(tpy)(Cl)_2(NH_3)](PF_6), cis-[Os^(II)(bpy)_2(Cl)(NH_3)](PF_6), and [Os^(II)(tpy)(bpy)(NH_3)](PF_6)_2 have been studied by cyclic voltammetry and by controlled-potential electrolysis. In acetonitrile or in acidic, aqueous solution, oxidation is metal-based and reversible, but as the pH is increased, oxidation and proton loss from coordinated ammonia occurs. cis- and trans-[Os^(III)(tpy)(Cl)_2(NH_3)](PF_6) are oxidized by four electrons to give the corresponding Os^(VI) nitrido complexes, [Os^(VI)(tpy)(Cl)_2(N)]^+. Oxidation of [Os(tpy)(bpy)(NH_3)](PF_6)_2 occurs by six electrons to give [Os(tpy)(bpy)(NO)](PF_6)_3. Oxidation of cis-[Os^(II)(bpy)_2(Cl)(NH_3)](PF_6) at pH 9.0 gives cis-[Os^(II)(bpy)_2(Cl)(NO)](PF_6)_2 and the mixed-valence form of the μ-N_2 dimer {cis-[Os(bpy)_2(Cl)]_2(μ-N_2)}(PF_6)_3. With NH_4^+ added to the electrolyte, cis-[Os^(II)(bpy)_2(Cl)(N_2)](PF_6) is a coproduct. The results of pH-dependent cyclic voltammetry measurements suggest Os^(IV) as a common intermediate in the oxidation of coordinated ammonia. For cis- and trans-[Os^(III)(tpy)(Cl)_2(NH_3)]^+, Os^(IV) is a discernible intermediate. It undergoes further pH-dependent oxidation to [Os^(VI)(tpy)(Cl)_2(N)]^+. For [Os^(II)(tpy)(bpy)(NH_3)]_2^+, oxidation to Os^(IV) is followed by hydration at the nitrogen atom and further oxidation to nitrosyl. For cis-[Os^(II)(bpy)_2(Cl)(NH_3)]^+, oxidation to Os^(IV) is followed by N−N coupling and further oxidation to {cis-[Os(bpy)_2(Cl)]_2(μ-N_2)}^(3+). At pH 9, N−N coupling is competitive with capture of Os^(IV) by OH- and further oxidation, yielding cis-[Os^(II)(bpy)_2(Cl)(NO)]^(2+).
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Additional Information: | © 2000 American Chemical Society. Received 18 January 2000. Published online 26 April 2000. Published in print 1 May 2000. The authors acknowledge the National Science Foundation for funding this research under Grant CHE-9503738 and Dr. Martin Devenney for obtaining the Raman spectrum of cis,cis-[(bpy)_2(Cl)Os^(II)(N⋮N)Os^(II)(Cl)(bpy)_2]^(2+). | ||||||||||||
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Issue or Number: | 10 | ||||||||||||
DOI: | 10.1021/ic0000505 | ||||||||||||
Record Number: | CaltechAUTHORS:20170424-122539672 | ||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20170424-122539672 | ||||||||||||
Official Citation: | Oxidation of Ammonia in Osmium Polypyridyl Complexes George M. Coia, Konstantinos D. Demadis, and Thomas J. Meyer Inorganic Chemistry 2000 39 (10), 2212-2223 DOI: 10.1021/ic0000505 | ||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||
ID Code: | 76854 | ||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||
Deposited By: | Ruth Sustaita | ||||||||||||
Deposited On: | 24 Apr 2017 20:31 | ||||||||||||
Last Modified: | 15 Nov 2021 17:03 |
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