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.