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Issue 10, 2013
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Synthesis, structure, and electrochemical characterization of a mixed-ligand diruthenium(III,II) complex with an unusual arrangement of the bridging ligands

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Abstract

A mixed-ligand metal–metal bonded diruthenium complex having the formula Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl where ap is the anilinopyridinate anion was synthesized from the reaction of Ru2(O2CCH3)4Cl and H(2,4,6-(CH3)3ap), after which the isolated product was structurally, spectroscopically and electrochemically characterized. The crystal structure reveals an unusual arrangement of the bridging ligands around the dimetal unit where one ruthenium atom is coordinated to one anilino and two pyridyl nitrogen atoms while the other ruthenium atom is coordinated to one pyridyl and two anilino nitrogen atoms. To our knowledge, Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl is the only example of a mixed-ligand diruthenium complex of the type [Ru2L3(O2CCH3)]+, where L is an unsymmetrical anionic bridging ligand that has been structurally characterized with a “(2,1)” geometric conformation of the bridging ligands, all others being “(3,0)”. The initial Ru25+ compound in CH2Cl2 or CH3CN containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) undergoes up to four one-electron redox processes involving the dimetal unit. The Ru25+/4+ and Ru25+/6+ processes were characterized under N2 using thin-layer UV-visible spectroelectrochemistry and this data is compared to UV-visible spectral changes obtained during similar electrode reactions for related diruthenium compounds having the formula Ru2L4Cl or Ru2L3(O2CCH3)Cl where L is an anionic bridging ligand. Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl was also examined by UV-visible and FTIR spectroelectrochemistry under a CO atmosphere and two singly reduced Ru24+ species, [Ru2(2,4,6-(CH3)3ap)3(O2CCH3)(CO)Cl] and Ru2(2,4,6-(CH3)3ap)3(O2CCH3)(CO) were in situ generated for further characterization. The CO-bound complexes could be further reduced and exhibited additional reductions to their Ru23+ and Ru22+ oxidation states.

Graphical abstract: Synthesis, structure, and electrochemical characterization of a mixed-ligand diruthenium(iii,ii) complex with an unusual arrangement of the bridging ligands

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Publication details

The article was received on 13 Nov 2012, accepted on 14 Dec 2012 and first published on 17 Dec 2012


Article type: Paper
DOI: 10.1039/C2DT32715E
Citation: Dalton Trans., 2013,42, 3571-3580
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    Synthesis, structure, and electrochemical characterization of a mixed-ligand diruthenium(III,II) complex with an unusual arrangement of the bridging ligands

    S. Ngubane, K. M. Kadish, J. L. Bear, E. Van Caemelbecke, A. Thuriere and K. P. Ramirez, Dalton Trans., 2013, 42, 3571
    DOI: 10.1039/C2DT32715E

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