A strongly coupled mixed valence state between Ru3 clusters. Intramolecular electron transfer on the infrared vibrational time scale in a pyrazine (pz) bridged dimer of triruthenium clusters, [{Ru33-O) (μ- CH3CO2)6(CO)(abco)}2(μ-pz)] (abco = 1-azabicyclo[2,2,2]octane)

Tadashi Yamaguchi, Naoyuki Imai, Tasuku Ito, Clifford P. Kubiak

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Abstract

A pyrazine bridged dimer of triruthenium clusters [{(Ru(III)2Ru(II)(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)] (abco = 1- azabicyclo[2,2,2]octane, pz = pyrazine) gives an inter-cluster mixed valence state upon one electron reduction. The splitting of the reduction waves in cyclic voltammetry, ΔE, was 470 mV. This corresponds to a comproportionation constant for formation of the mixed valence state of 9.0 x 107. The IR spectrum of the mixed valence species in the ν(CO) region, measured by reflectance IR spectroelectrochemistry, showed a completely coalesced ν(CO) band. This represents delocalized redox behavior on the infrared vibrational timescale. The rate constant for intramolecular electron transfer was estimated to be 1 x 1012 s-1 at -18 °C by simulating the ν(CO) absorption bandshape. The mixed valence complex showed an intervalence charge transfer (ICT) band at 12500 cm-1. Hush analysis provides a spectroscopic estimate of H(AB) to be 2490 cm-1. Crystal structures of [{(Ru(III)2Ru(II)(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)]·2CH2Cl2 and its precursor, [Ru(III)2Ru(II)(μ3- O)(CH3CO2)6(CO)(abco)2]·CH2Cl2, were determined by X-ray crystallography. Trends in Ru-O(oxo) and Ru-O(acetate) distances in these compounds show that the divalent site is localized on the Ru center attached to the carbonyl ligand.

Original languageEnglish
Pages (from-to)1205-1212
Number of pages8
JournalBulletin of the Chemical Society of Japan
Volume73
Issue number5
DOIs
Publication statusPublished - 2000 May 1

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ASJC Scopus subject areas

  • Chemistry(all)

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