Calculation by the ab initio effective core potentials method on the M2(O2CR)4L2 species (M = Mo, Tc, Ru, Rh) was performed and the electronic structure of these mols. is discussed. There are not only localized s, p bonds, but also delocalized bonds between metals in these mols. The delocalized bonds consist of two metal atoms and four carboxyl ligands.a

Key words: HYDROXY GROUP, MOLYBDENUM COMPLEX, CHEMICAL BONDS, ELECTRONIC STRUCTURE, AB INITIO CALCULATION, TRANSITION METAL COMPLEX, DINUCLEAR COMPLEX, BRIDGE COMPOUNDS, RUTHENIUM COMPLEX