Syntheses and Crystal Structures of Disulfide-Bridged Binuclear Ruthenium Compounds:  The First UV−Vis, Raman, ESR, and XPS Spectroscopic Characterization of a Valence-Averaged Mixed-Valent Ru^IIISSRu^II Core

Abstract

Disulfide-bridged binuclear ruthenium complexes, [{RuCl(P(OMe) 3 ) 2 } 2 (µ-Cl) 2 (µ-S 2 )] ( 1), [{RuCl-(P(OMe) 3 ) 2 }(µ-Cl) 2 (µ-S 2 ){Ru(CH 3 CN)(P(OMe) 3 ) 2 ] + ([2] + ), [{Ru(CH 3 CN) , and [{Ru(CH 3 CN) 3 (P(OMe) 3 ) 2 } 2 (µ-S 2 )] 4+ ([5] 4+ ), have been synthesized, and their crystal structures have been solved. Compounds 1, [2] + , and [4] 2+ have a triply bridged Ru III (µ-Cl) 2 (µ-S 2 )Ru III core, in which the S 2 2ligand bridges the two Ru atoms in a cis configuration. Compounds [3] 3+ and [5] 4+ have a singly bridged trans-RuSSRu core, whereby [3] 3+ corresponds to a one-electron reduced form of [5] 4+ . Compound [3] 3+ is the first example of a well-characterized mixed-valent compound with a trans-MSSM core, where M is any metal. All the compounds have intense absorption bands at around 700 nm, which can be explained for [3] 3+ and [5] 4+ as a π-π* transition of the distinct trans-RuSSRu core. Resonance Raman spectroscopy of 1, [2] + , and [3] 3+ and comparison with several literature values for cis-RuSSRu compounds show that only [3] 3+ exhibits a strong ν(S-S) Raman band, when excited by λ e ) 647.1 nm, whereas all the others show strong to medium ν-(Ru-S) and very weak ν(S-S) bands. The ESR spectrum of [3] 3+ shows a rhombic signal with g 1 ) 2.12, g 2 ) 2.05, and g 3 ) 1.995. This anisotropy is unusually small, compared to most mononuclear and binuclear Ru(III) compounds with various ligands. Analysis of the g values by use of the matrix of spin-orbit coupling Hamiltonian has revealed a very small spin-orbit coupling constant of 100 cm -1 , which is a result of the extensive covalency of the metal-disulfide bond. The X-ray photoelectron spectrum of [3] 3+ did not give any of the expected double peaks of the Ru(II) and Ru(III) components; the observed peaks are Ru 3d 5/2 281.0 eV, 3P 3/2 462.4 eV, S(S 2 2-) 2P 3/2 162.7 eV. Compound [3] 3+ does not give any intervalence-transition band in the longer-wavelength visible to near-IR region, other than the UV-vis band similarly observed in the one-electron oxidized compound [5] 4+ . These characteristics are reasonably understood, if [3] 3+ is regarded as a mixed-valent complex with valence-averaged ground state (class III of the Robin and Day classification).

Hydrothermal synthesis of highly crystalline RuS2 nanoparticles as cathodic catalysts in the methanol fuel cell and hydrochloric acid electrolysis

“…XPS was used to qualitatively determine surface oxidation state and composition of RuS 2 nanoparticles prepared at 400 C. is consistent with that observed for S 2 À2 2p 3/2 band [27]. And another peak at 163.7 eV is assigned to the washing residual CS 2 .…”

Oxidative dimerization of Ru(III)-EDTA complex on the surface of functionalized silica gel

“…The rhombic anisotropy in Figure 1 indicates that the unpaired electron is substantially delocalized in the bridging ligand. 29 The thermoanalytical data obtained by TGA analysis of silicas SPA, SF-AEATS and SF-AEATS/(EDTA) 2 Ru 2 (III 1/2 , III 1/2 ) indicate a similar thermal behavior in an N 2 atmosphere. The mass loss occurs in two steps: up to 400.0 ± 0.5 K, which is attributed to the loss of H 2 O and between 453.0 ± 0.5 and 813.0 ± 0.5 K, attributed to the loss of the organofuntional groups.…”

Organometallic-like C−H Bond Activation and C−S Bond Formation on the Disulfide Bridge in the RuSSRu Core Complexes

“…This small anisotropy is a remarkable contrast to the highly anisotropic axial or rhombic symmetry of usual monomeric low-spin Ru III species and suggests that the unpaired electron of 5 is delocalized over the two metals and the bridging disulfide ligand. 21 Reactions of the RuSSRu Core with Conjugated Dienes. The reactions of the disulfide ligand in the dinuclear Ru III complexes with dienes give a clue to the long-standing discussion about the electronic structure of the RuSSRu 4+ core, [17][18][19] namely, whether it should be formulated as (i) two Ru III centers bridged by a disulfide S 2 2-, (ii) two Ru II centers bridged by a singlet disulfur S 2 0 , or (iii) an Ru II center and an Ru III center bridged by a supersulfide S 2 -• .…”