Chemistry of some ruthenium phenolates: synthesis, structure and redox properties
نویسندگان
چکیده
Reaction of three phenolate ligands, viz. 2,4,6-tribromophenol (HL, where H stands for the phenolic proton), 2-nitrophenol (HL) and 2,4,6-trinitrophenol (HLO), with [Ru(PPh3)3Cl2] in a 2:1 molar ratio in the presence of a base gives complexes of type [Ru(PPh3)2(L)2] (L=L , L and L). The 2,4,6-tribromophenolate ligand (L) binds to ruthenium as a bidentate O,Br-donor, while the 2-nitrophenolate ligand (L) acts as a bidentate O,O-donor. 2,4,6-Trinitrophenol (HLO) undergoes oxygen loss from one nitro group at the ortho position and coordinates to ruthenium in the 2-nitroso-4,6-dinitrophenolate (L) form through the nitroso nitrogen and phenolate oxygen. The structures of the [Ru(PPh3)2(L )2] and [Ru(PPh3)2(L )2] complexes have been solved by X-ray crystallography. In [Ru(PPh3)2(L )2] the coordination sphere around ruthenium is O2P2Br2 with a trans–cis–cis disposition of the three sets of donor atoms, respectively. In [Ru(PPh3)2(L )2] ruthenium has a N2O2P2 coordination sphere with a cis–cis– trans arrangement of the three sets of donor atoms, respectively. The [Ru(PPh3)2(L)2] complexes are diamagnetic (low-spin d , S=0) and in acetonitrile solution show intense MLCT transitions in the visible region. Cyclic voltammetry on the [Ru(PPh3)2(L)2] complexes shows a reversible ruthenium(II)–ruthenium(III) oxidation within 0.63–0.71 V versus SCE followed by an irreversible ruthenium(III)–ruthenium(IV) oxidation near 1.5 V versus SCE. © 2000 Elsevier Science Ltd. All rights reserved.
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