ic0343713_si_002.cif (26.85 kB)
Chemically Induced Cyclometalation of 2-(Arylazo)phenols. Synthesis, Characterization, and Redox Properties of a Family of Organoosmium Complexes
dataset
posted on 2003-07-25, 00:00 authored by Parna Gupta, Ray J. Butcher, Samaresh BhattacharyaReaction of 2-(arylazo)phenols (H2ap-R; R = OCH3, CH3, H, Cl, and NO2) with [Os(PPh3)2(CO)2(HCOO)2] affords
a family of organometallic complexes of osmium(II) of type [Os(PPh3)2(CO)(ap-R)] where the 2-(arylazo)phenolate
ligand 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 diamagnetic
and show characteristic 1H NMR signals and intense MLCT transitions in the visible region. They also show emission
in the visible region at ambient temperature. Cyclic voltammetry on the [Os(PPh3)2(CO)(ap-R)] complexes shows
a reversible Os(II)−Os(III) oxidation within 0.39−0.73 V vs SCE, followed by a reversible Os(III)−Os(IV) oxidation
within 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 as
1:1 electrolytes and show intense LMCT transitions in the visible region. The [OsIII(PPh3)2(CO)(ap-R)]PF6 complexes
have been observed to serve as mild one-electron oxidants in a nonaqueous medium.
