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Uncommon cis Configuration of a Metal-Metal Bridging Noninnocent Nindigo Ligand

, , , , , and . Inorganic Chemistry, 53 (17): 9348--9356 (2014)
DOI: 10.1021/ic501460d

Abstract

In contrast to several reported coordination compds. of trans-Nindigo ligands Nindigo = indigo-bis(N-phenylimine) = LH2 with one or two six-membered chelate rings involving one indole N and one extracyclic N for metal binding, the new diruthenium complex ion (acac)2Ru(m,h2:h2-L)Ru(bpy)22+ = (2)2+ exhibits edge-sharing five- and seven-membered chelate rings in the 1st documented case of asym. bridging by a Nindigo ligand in the cis configuration L2- = indigo-bis(N-phenylimine)dianion. The dication in 2(ClO4)2 displays one Ru(a-diimine)3 site and one Ru center with three neg. charged chelate ligands. 2(ClO4)2 was obtained from the Ru(bpy)22+ contg. cis precursor (LH)Ru(bpy)2ClO4 = 1ClO4, which exhibits cation intramol. H-bonding. Four accessible oxidn. states each were characterized for the 1n and 2n redox series with respect to metal- or ligand-centered electron transfer, based on x-ray structures, ESR, and UV-visible-near-IR spectroelectrochem. in conjunction with d. functional theory calcn. results. The structural asymmetry in the RuIII/RuII system 22+ is reflected by the electronic asymmetry (class I mixed-valence situation), leaving the noninnocent Nindigo bridge as the main redox-active site. on SciFinder(R)

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