A new mode of binding of a beta-diketone has been established. Two oxygen atoms and a sulfur atom at the gamma-position of the beta-diketone bind to two ruthenium atoms with the sulfur forming the bridge. A mononuclear complex has also been isolated in which the P-diketone binds through O and S atoms. The syntheses of mononuclear complex [Ru(acac)(2)(topd-O,S)] (1) and binuclear complexes [{Ru(acac)(2)}(2)(mu-topd-O,S,O')] (2, racemic form), [{Ru(acac)(2)}(2)(mu-topd-O,S,O')] (2', meso form), [{Ru(phpa)(2)}(2)(mu-topd-O,S,O')] (3, racemic form), and [{Ru(phpa)(2)}(2)(mu-topd-O,S,O')] (3', meso form) have been described. The crystal and molecular structures of 2 and 2' have been solved by single-crystal X-ray diffraction studies. Crystal data for 2 (Ru2C25H34O10S) : space group P2(1)/n, a = 11.388(3) Angstrom, b = 23.390(3) Angstrom, c = 11.978(3) Angstrom, beta = 93.06(2)degrees, Z = 4, R = 0.056, R-w = 0.042. Crystal data for 2' (Ru2C25H34O10S) : space group P2(1)/n, a 16.281(3) Angstrom, b = 21.195(2) Angstrom, c = 21.465(3) Angstrom, p = 105.75(1)degrees, Z = 4, R = 0.049, R-W = 0.042. The C-13 NMR spectra indicate the difference between the mononuclear (1) and the binuclear complex (2') in their topd-CS signals for the presence of two types of bonding modes for the topd ligand. There is no difference in the electronic spectra of the meso and racemic isomers of the binuclear complexes. The X-ray photoelectron spectrum (XPS) of 1 resembles that of Ru-III whereas the spectra of all of the binuclear complexes indicate the presence of both Ru-III and Ru-II. Cyclic voltammetric studies also corroborate the findings of XPS that the monomeric complex 1 contains Ru-III and all of the binuclear complexes have in them both Ru-III and Ru-II. The electronic structures of the complexes have been discussed on the bases of photoelectron spectra, electronic spectra, and magnetic measurements and electrochemistry.