- Iridium(III) Complexes Formed by O-H and/or C-H Activation of 2-(Arylazo)phenols
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Reaction of 2-(arylazo)phenols with [Ir(PPh3)3Cl] in refluxing ethanol in the presence of a base (NEt3) affords complexes of three different types, viz. [Ir(PPh3)2(NO-R)(H)Cl] (R = OCH3, CH3, H, Cl and NO2), [Ir(PPh 3)2(NO-R)(H)2] and [Ir(PPh3) 2(CNO-R)(H)]. Structures of the [Ir(PPh3) 2(NO-Cl)(H)Cl], [Ir(PPh3)2(NO-Cl)(H) 2] and [Ir(PPh3)2(CNO-Cl)(H)] complexes have been determined by X-ray crystallography. In the [Ir(PPh3) 2(NO-R)(H)Cl] and [Ir(PPh3)2(NO-R)(H) 2] complexes, the 2-(arylazo)phenolate ligands are coordinated to the metal center as monoanionic bidentate N,O-donors, whereas in the [Ir(PPh3)2(CNO-R)(H)] complexes, they are coordinated to iridium as dianionic tridentate C,N,O-donors. In all three products formed in ethanol, the two PPh3 ligands are trans. Reaction of 2-(arylazo)phenols with [Ir(PPh3)3Cl] in refluxing toluene in the presence of NEt3 affords complexes of two types, viz. [Ir(PPh3)2(CNO-R)(H)] and [Ir(PPh3) 2(CNO-R)Cl]. Structure of the [Ir(PPh3) 2(CNO-Cl)Cl] complex has been determined by X-ray crystallography, and the 2-(arylazo)phenolate ligand is coordinated to the metal center as a dianionic tridentate C,N,O-donor and the two PPh3 ligands are cis. All of the iridium(III) complexes show intense MLCT transitions in the visible region. Cyclic voltammetry shows an Ir(III)-Ir(IV) oxidation on the positive side of SCE and an Ir(III)-Ir(II) reduction on the negative side for all of the products.
- Acharyya, Rama,Basuli, Falguni,Wang, Ren-Zhang,Mak, Thomas C. W.,Bhattacharya, Samaresh
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p. 704 - 711
(2008/10/09)
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