Singlet diradical complexes of ruthenium and osmium: geometrical and electronic structures and their unexpected changes on oxidation

Samanta, Subhas ; Singh, Priti ; Fiedler, Jan ; Zalis, Stanislav ; Kaim, Wolfgang ; Goswami, Sreebrata (2008) Singlet diradical complexes of ruthenium and osmium: geometrical and electronic structures and their unexpected changes on oxidation Inorganic Chemistry, 47 (5). pp. 1625-1633. ISSN 0020-1669

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic702301a?prev...

Related URL: http://dx.doi.org/10.1021/ic702301a

Abstract

Reaction of HL, HLa (2-[(2-N-phenylamino)phenylazo]pyridine), HLb (2-[{2-N-(4-methylphenyl)amino}phenylazo]pyridine), or HLc (2-[{2-N-(4-chlorophenyl)amino}phenylazo]pyridine), with KRuO4 or OsO4 and PPh3 under exhaustive deoxygenation (PPh3 → OPPh3) yields diamagnetic compounds ML2. Crystal structure determination for M(La)2 indicates the radical dianion state, L*2-, for the ligands as evident from the typical N-N bond length of about 1.33 Å for a one-electron reduced azo function. The resulting spin-coupled complexes, MIV(L*2-)2, can be oxidized in two reversible one-electron steps, as probed by cyclic voltammetry and UV-vis-NIR spectroelectrochemistry. The paramagnetic intermediates, [M(La)2]+, are distinguished by intense NIR absorption, largely metal-centered spin as revealed by EPR, and, in the case of [Os(La)2]I3, by crystallographically determined shortening of the N=N bond to about 1.30 Å, corresponding to a coordinated unreduced azo function. Thus, oxidation of the complex MIV(L*2-)2 involves partial reduction of the metal in [MIII(L-)2]+ because intramolecular double electron transfer is offsetting the external charge removal. Density-functional theory calculations were employed to confirm the structural features and to support the spectroscopic assignments.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:12791
Deposited On:11 Nov 2010 08:56
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