A family of edge-sharing bi-octahedral diruthenium(III,III) compounds containing Ru-Ru single bonds.

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.