Studies on Ru of [Ru(acac)3], [Ru(acac)2(CH3CN)2], [Ru(acac)2(topd-O,S], and [Ru(acac)2(μ-topd-O,S,O′)] (acac = acetylacetonato and topd = 3-thioxo-2,4-pentanedione) by XPS

The XPS of the novel sulfur-bridged binuclear β-diketonatoruthenium complexes of [Ru(acac)2(μ-topd-O,S,O′)] (acac = acetylacetonato and topd = 3-thioxo-2,4-pentanedione) and a monomeric ruthenium complex of [Ru(acac)2(topd-O,S)] were measured in order to obtain the information for the valence of the ruthenium, together with those of [RuII(acac)2(CH3CN)2] and [RuIII(acac)3] as the reference compounds of RuII and RuIII, respectively. The Ru 3d5/2 binding energy of [Ru(acac)2(topd-O,S)] (282.4 eV) is almost the same as that found for [RuIII(acac)3] (282.8 eV). Such an energy value is an indication of the presence of RuIII. However, the binding energy of Ru 3d5/2 for binuclear complex is 282.2 eV which is intermediate between RuII and RuIII found in [RuII(acac)2(CH3CN)2] (281.3 eV) and [RuIII(acac)3]. This means that the binuclear complex contains both RuII and RuIII and there could be some kind of delocalization of electron between the two ruthenium atoms via topd ligand. Alternatively, this can be described as a valence-averaged mixed-valent RuII and RuIII.