A family of edge-sharing bi-octahedral diruthenium(iii,iii) compounds containing Ru–Ru single bonds†
Abstract
From paddlewheel starting reactants Ru2(R′CO2)4+, a family of edge-sharing bi-octahedral (ESBO) diruthenium(III,III) compounds has been prepared, formulated as Ru2(μ-O2CR′)2(μ-OR)2(η-L)2 (1–10) [R′ = CH3, R = CH3, L = acac (1), tfac (2); R′ = CH3, R = CH2CH3, L = hfac (3); R′ = CH2CH3, R = CH3, L = acac (4), tfac (5); R′ = CH2CH3, R = CH2CH3, L = hfac (6); R′ = CH2Cl, R = CH3, L = tfac (7); R′ = CH2Cl, R = CH2CH3, L = hfac (8); R′ = C6H5, R = CH3, L = tfac (9); and R′ = H, R = CH3, L = acac (10); here, acac, tfac and hfac represent acetylacetone, trifluoroacetylacetone and hexafluoroacetylacetone, respectively]. Compounds 1–10 have a similar ESBO coordination geometry of the Ru(μ-O2CR′)2(μ-OR)2Ru core with a Ru–Ru center chelated and bridged by two μ-O2CR′ and two μ-OR in a trans manner, and each Ru center is also coordinated with a η2-L bidentate ligand. The Ru–Ru distances fall in the range of 2.4560(9)–2.4771(4) Å. The investigation of the electronic spectra and vibrational frequencies as well as theoretical studies with density functional theory (DFT) reveal that compounds 1–10 are ESBO bimetallic species of d5–d5 valence electron counts showing a σ2π2δ2δ*2π*2 electronic configuration. Varying –CH3 to –CF3 groups on the η2-L bidentate ligands coordinating to the Ru(μ-O2CR′)2(μ-OR)2Ru core, and according to Raman spectrum measurements combined with theoretical calculations, the intense bands of compounds 1–10 appearing at ∼345 cm−1 in the small-wavenumber region can be assigned to the stretching of the Ru–Ru single bond.