Synthesis, Characterization, and Detailed Electrochemistry of Binuclear Ruthenium(III) Complexes Bridged by Bisacetylacetonate. Crystal and Molecular Structures of [{Ru(acac)₂}₂(tae)] (acac = 2,4-Pentanedionate Ion, tae = 1,1,2,2-Tetraacetylethanate Dianion)

Abstract

Binuclear beta-diketonatoruthenium(III) complexes [[Ru(acac)(2)](2)(tae)], [[Ru(phpa)(2)](2)(tae)], and [(acac)(2)Ru(tae)Ru(phpa)(2)] and binuclear and mononuclear bipyridine complexes [[Ru(bpy)(2)](2)(tae)](PF(6))(2) and [Ru(bpy)(2)(Htae)]PF(6) (acac = 2,4-pentanedionate ion, phpa = 2,2,6,6-tetramethyl-3,5-heptanedionate ion, tae = 1,1,2,2-tetraacetylethanate dianion, and bpy = 2,2'-bipyridine) were synthesized. The new complexes have been characterized by (1)H NMR, MS, and electronic spectral data. Crystal and molecular structures of [[Ru(acac)(2)](2)(tae)] have been solved by single-crystal X-ray diffraction studies. Crystal data for the meso isomer of [[Ru(acac)(2)](2)(tae)] have been confirmed by the dihedral angle result that two acetylacetone units of the bridging tae ligand are almost perpendicular to one another. A detailed investigation on the electrochemistry of the binuclear complexes has been carried out. The electrochemical behavior details of the binuclear complexes have been compared with those of the mononuclear complexes obtained from the half-structures of the corresponding binuclear complexes. Studies on the effects of solvents on the mixed-valence states of Ru(II)-Ru(III) and Ru(III)-Ru(IV) complexes have been carried out by various voltammetric and electrospectroscopic techniques. A correlation between the comproportionation constant (K(c)) and the donor number of the solvent has been obtained. The K(c) values for the binuclear complexes have been found to be low because of the fact that two acetylacetone units of the bridging tae ligand are not in the same plane, as revealed by the crystal structure of [[Ru(acac)(2)](2)(tae)].

Experimental and DFT Evidence for the Fractional Non‐Innocence of a β‐Diketonate Ligand

“…The 1 H NMR spectra of diamagnetic compounds [ 1 ]ClO 4 and 2 in [D 6 ]DMSO display partially overlapping signals within the chemical‐shift range δ =6.5–9 ppm. The 1 H NMR resonances of complex 3 in CDCl 3 appear within a wide range of δ =−30 to +15 ppm, owing to the paramagnetic contact shift effect7 (see the Supporting Information, Figure S2 and the Experimental Section).…”

Valence‐State Analysis through Spectroelectrochemistry in a Series of Quinonoid‐Bridged Diruthenium Complexes [(acac)2Ru(μ‐L)Ru(acac)2]n (n=+2, +1, 0, −1, −2)

“…[3v, 34,35] The 1 H NMR spectra of the complexes 3 and 4 were too broad and complicated to be analyzed. The NMR spectra of 1, 2, and 6 in CDCl 3 exhibit signals corresponding to half of the molecules, indicating formation of only the meso isomers.…”

Tris(β-diketonato) Ru(III) Complexes as Chiral Dopants for Nematic Liquid Crystals: the Effect of the Molecular Structure on the Helical Twisting Power

“…Bulky groups introduced at the 3-position of the acac ligands are often stabilized at the almost orthogonal position because of the steric hindrance by the methyl groups. 42 We further performed the density functional theory (DFT) calculations for the model compounds, [Ru(acac) 2 (acacPh)] (acacPh = 3-phenyl-pentane-2,4-dionato) and [Ru-(acac) 2 (acacC 2 Ph)] ((acacPh = 3-phenylalkynyl-pentane-2,4-dionato)), to clarify the role of the alkyne spacer in the acacC 8 ligand. The complexes could be regarded as the simplified structure of Ru-para and RuC 8 -1 without terminal alkoxy chains, respectively.…”