Gupta, Parna ; Das, Anindya ; Basuli, Falguni ; Castineiras, Alfonso ; Sheldrick, William S. ; Mayer-Figge, Heike ; Bhattacharya, Samaresh (2005) Variable coordination mode of chloranilic acid. Synthesis, structure, and electrochemical properties of some osmium complexes Inorganic Chemistry, 44 (6). pp. 2081-2088. ISSN 0020-1669
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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic049149s
Related URL: http://dx.doi.org/10.1021/ic049149s
Abstract
Reaction of chloranilic acid (H2ca) with [Os(bpy)2Br2] (bpy = 2,2′-bipyridine) affords a dinuclear complex of type [{Os(bpy)2}2(ca)]2+, isolated as the perchlorate salt. A similar reaction of H2ca with [Os(PPh3)2(pap)Br2] (pap = 2-(phenylazo)pyridine) affords a dinuclear complex of type [{Os(PPh3)2(pap)}2(ca)]2+ (isolated as the perchlorate salt) and a mononuclear complex of type [Os(PPh3)2(pap)(ca)]. Reaction of H2ca with [Os(PPh3)2(CO)2(HCOO)2] gives a dinuclear complex of type [{Os(PPh3)2(CO)2}2(r-ca)], where r-ca is the two electron reduced form of the chloranilate ligand. The structures of the [{Os(PPh3)2(pap)}2(ca)](ClO4)2, [Os(PPh3)2(pap)(ca)], and [{Os(PPh3)2(CO)2}2(r-ca)] complexes have been determined by X-ray crystallography. In the [{Os(bpy)2}2(ca)]2+ and [{Os(PPh3)2(pap)}2(ca)]2+ complexes, the chloranilate dianion is serving as a tetradentate bridging ligand. In the [Os(PPh3)2(pap)(ca)] complex, the chloranilate dianion is serving as a bidentate chelating ligand. In the [{Os(PPh3)2(CO)2}2(r-ca)] complex, the reduced form of the chloranilate ligand (r-ca4-) is serving as a tetradentate bridging ligand. All the four complexes are diamagnetic and show intense metal-to-ligand charge-transfer transitions in the visible region. The [Os(PPh3)2(pap)(ca)] complex shows an Os(II)-Os(III) oxidation, followed by an Os(III)-Os(IV) oxidation on the positive side of a standard calomel electrode. The three dinuclear complexes show two successive oxidations on the positive side of SCE. The mixed-valent OsII-OsIII species have been generated in the case of the two chloranilate-bridged complexes by coulometric oxidation of the homovalent OsII-OsII species. The mixed-valent OsII-OsIII species show intense intervalence charge-transfer transitions in the near-IR region.
| Item Type: | Article |
|---|---|
| Source: | Copyright of this article belongs to American Chemical Society. |
| ID Code: | 2034 |
| Deposited On: | 08 Oct 2010 09:30 |
| Last Modified: | 21 Jan 2011 10:35 |
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