Separating Innocence and Non-Innocence of Ligands and Metals in Complexes [(L)Ru(acac)2]n (n = -1, 0, +1; L = o-Iminoquinone or o-Iminothioquinone)

The diamagnetic title complexes were obtained from Ru(acac)2(CH3CN)2 and 2-aminophenol or 2-aminothiophenol. X-ray structure analysis of (L1)Ru (acac)2 (L1 = o-iminoquinone) revealed C-C intra-ring, C-O, and C-N distances which suggest a RuIII-iminosemiquinone oxidation state distribution with antiparallel spin-spin coupling. One-electron oxidation and reduction of both title compounds to paramagnetic monocations [(L)Ru(acac)2]+ or monoanions [(L)Ru(acac)2]- occurs reversibly at widely separated potentials ((delta)E > 1.3 V) and leads to low-energy shifted charge transfer bands. In comparison with clearly established RuII-semiquinone or RuIII-catecholate systems the g tensor components 2.23 > g1 > 2.09, 2.16 > g2 > 2.07, and 1.97 > g3 > 1.88 point to considerable metal contributions to the singly occupied MO, corresponding to RuIII complexes with either o-quinonoid ((right arrow) cations) or catecholate-type ligands ((right arrow)anions) and only minor inclusion of RuIV- or RuII-iminosemiquinone formulations, respectively. The preference for the RuIII oxidation state for all accessible species is partially attributed to the monoanionic 2,4-pentanedionate (acac) co-ligands which favor a higher metal oxidation state than, e.g., neutral 2,2ʹ-bipyridine (bpy).