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 Na3Ru2(CO3)4·6H2O, a family of edge-sharing bi-octahedral (ESBO) diruthenium(IV,IV) compounds formulated as Ru2O2(CO3)2(H2O)2L2·nH2O [L = piperazine (1) or 2-methylpiperazine (2), n = 4, and L = 2,2-dimethylpiperazine (3), n = 12] and Ru2O2(CO3)2(OH)4{M(H2O)4}2·nH2O [M = Mg (4), n = 4, and Ni (5), n = 2] were prepared and structurally characterized. The Ru28+ dimer is chelated and bridged by two CO32- 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 Ru2 compounds reported thus far. Increasing -CH3 groups of terminal piperazine ligands coordinated to the Ru(µ-O)2(µ-O3C)2Ru 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.