Chemically Induced Cyclometalation of 2-(Arylazo)phenols. Synthesis, Characterization, and Redox Properties of a Family of Organoosmium Complexes
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- 作者：Parna Gupta ; Ray J. Butcher ; and Samaresh Bhattacharya
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：August 25, 2003
- 年：2003
- 卷：42
- 期：17
- 页码：5405 - 5411
- 全文大小：134K
- 年卷期：v.42,no.17(August 25, 2003)
- ISSN：1520-510X
文摘
Reaction of 2-(arylazo)phenols (H2ap-R; R = OCH3, CH3, H, Cl, and NO2) with [Os(PPh3)2(CO)2(HCOO)2] affordsa family of organometallic complexes of osmium(II) of type [Os(PPh3)2(CO)(ap-R)] where the 2-(arylazo)phenolateligand is coordinated to the metal center as a tridentate C,N,O-donor. Structure of the [Os(PPh3)2(CO)(ap-H)]complex has been determined by X-ray crystallography. All the [Os(PPh3)2(CO)(ap-R)] complexes are diamagneticand show characteristic 1H NMR signals and intense MLCT transitions in the visible region. They also show emissionin the visible region at ambient temperature. Cyclic voltammetry on the [Os(PPh3)2(CO)(ap-R)] complexes showsa reversible Os(II)-Os(III) oxidation within 0.39-0.73 V vs SCE, followed by a reversible Os(III)-Os(IV) oxidationwithin 1.06-1.61 V vs SCE. Coulometric oxidation of the [Os(PPh3)2(CO)(ap-R)] complexes generates the [OsIII(PPh3)2(CO)(ap-R)]+ complexes, which have been isolated as the hexafluorophosphate salts. The [OsIII(PPh3)2(CO)(ap-R)]PF6 complexes are one-electron paramagnetic and show axial ESR spectra. In solution they behave as1:1 electrolytes and show intense LMCT transitions in the visible region. The [OsIII(PPh3)2(CO)(ap-R)]PF6 complexeshave been observed to serve as mild one-electron oxidants in a nonaqueous medium.