Edge-sharing bi-octahedral diruthenium(IV,IV) compounds containing Ru-Ru bonds chelated and bridged by two carbonate and two oxo groups.

From paddle-wheel starting material Na 3 Ru 2 (CO 3 ) 4 ·6H 2 O, a family of edge-sharing bi-octahedral (ESBO) diruthenium(IV,IV) compounds formulated as Ru 2 O 2 (CO 3 ) 2 (H 2 O) 2 L 2 · n H 2 O [L = piperazine (1) or 2-methylpiperazine (2), n = 4, and L = 2,2-dimethylpiperazine (3), n = 12] and Ru 2 O 2 (CO 3 ) 2 (OH) 4 {M(H 2 O) 4 } 2 · n H 2 O [M = Mg (4), n = 4, and Ni (5), n = 2] were prepared and structurally characterized. The Ru 2 8+ dimer is chelated and bridged by two CO 3 2- and two μ-O in a trans manner, and the Ru-Ru distances fall in the range 2.3808(6)-2.4001(4) Å. Compound 2 shows the shortest Ru-Ru distance for all known ESBO Ru 2 compounds reported thus far. Increasing -CH 3 groups of terminal piperazine ligands coordinated to the Ru(μ-O) 2 (μ-O 3 C) 2 Ru core, and according to Raman spectra experiments combined with theoretical calculations, the intense bands of compounds 1-3 appearing at ∼360 cm -1 can be assigned to the stretching of Ru-Ru bonds.