Synthesis and structure of tris(1,2-benzoquinone diimine)osmium(ii) perchlorate, and its redox and spectroelectrochemical series
Journal
Journal of the Chemical Society, Dalton Transactions
Journal Issue
3
Pages
336-340
Date Issued
2001
Author(s)
Abstract
Reaction of [NH 4] 2[Os IVBr 6] with 1,2-diaminobenzene (H 2opda) in aerobic conditions afforded [Os(bqdi) 3][ClO 4] 2 (bqdi = 1,2-benzoquinone diimine), a diamagnetic osmium(II) complex containing three redox non-innocent α,α′-diimine ligands. In the crystal structure the relatively long C=N distances together with short Os-N distances indicate the existence of considerable metal(dπ)-ligand(pπ) interactions. Cyclic voltammetry of [Os(bqdi) 3][ClO 4] 2 shows one electron redox processes at -0.24, -0.67 and -1.78 V versus Fc-Fc + (Fc = ferrocene) which are assigned as successive reductions of the coordinated bqdi, and an irreversible Os II-Os III couple at +0.99 V. The solution electronic spectra of the mixed-valent (ligand) compounds, generated by electrolysis of [Os(bqdi) 3] 2+ in an optically transparent thin-layer electrode cell at potentials past the first and the second cathodic responses, show near-IR transitions at 1405 and 1164 nm, respectively, assignable to inter-valence charge transfer between the reduced 1,2-diiminosemiquinone monoanion (dsq) and non-reduced (bqdi) ligands. The spectrum of the triply reduced form is more consistent with the formulation [Os III(dsq) 2(opda)] - than with the expected formulation [Os(dsq) 3] -, suggesting that an internal redox isomerism has occurred. © The Royal Society of Chemistry 2001.
SDGs
Type
journal article