Molecule-Bridged Mixed-Valent Intermediates Involving the RuI Oxidation State

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Journal of the American Chemical Society, 126 (45): 14706--14707 (2004)
DOI: 10.1021/ja046397e


Binuclear diruthenium cymene complexes bridged by azobis(pyridine) and pyrazine-bis-imine ligands are prepd. and studied by cyclic voltammetry. The diruthenium(II) complexes (m-L)RuCl(h6-MeC6H4iPr-4)2(PF6)n, (1, L = 2,2'-azobispyridine (abpy), n = 1; 2, L = 2,5-bis(1-phenyliminoethyl)pyrazine (bpip), n = 2) were prepd. and characterized by NMR and EPR spectroscopy. Whereas the complex 1 has the structure of radical-anion-bridged RuIIRuII complex, the three-electron redn. under loss of both chloride ions produces the ions (m-L)Ru(Cym)2+, which could be identified as RuI(4d7)-contg. mixed-valent species (Ru0RuI or RuIRuII) by its intervalence charge-transfer bands around 1500 nm in UV-vis-NIR spectroelectrochem. and EPR, which shows rhombic g tensor anisotropy. The weak metal-metal interaction of the ds electrons from the eg set is responsible for the small electrochem. coupling with comproportionation consts. Kc $\approx$ 102. on SciFinder(R)



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