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Abstract: The vibrational and 1H NMR data hints that the coordination of the 2,2′-dithiodipyridine (2-pySS) ligand to the [Ru(CN)5]3− metal center occurs through the sulfur atom instead of the nitrogen atoms which is usually observed for N-heterocyclic ligands. Electrochemical results show that this coordination mode implies an additional thermodynamic stabilization of the RuII over RuIII oxidation state due to a relative stronger π-back-bonding interaction with the empty low-lying dπ orbitals of the sulfur atom. Computational data reinforce the experimental results showing that the 2-pySS Lewis base centers are located on the sulfur atoms. Ligands containing only sulfur atoms as coordination sites (2,2′-dithiodipyridine N-oxide (2-pySSNO), 1,4-dithiane (1,4-dt), and 2,6-dithiaspiro[3.3]heptane (asp)) were also coordinated to the [Ru(CN)5]3− metal center to undoubtedly correlate the electrochemical results with the ligand coordination atom. Among the synthesized compounds, the [Ru(CN)5(1,4-dt)]3− and [Ru(CN)5(asp)]3− complexes showed to be able to form self-assembled monolayers (SAMs) on gold. These SAMs, which were characterized by SERS (surface-enhanced Raman scattering) spectroscopy, successfully assessed the heterogeneous electron transfer reaction of the cytochrome c metalloprotein in physiological medium. [Copyright &y& Elsevier]

Abstract: The [Ru(dppb)(mbt)2], mbt=2-mercaptobenzothiazole, complex, isolated from the reaction of the mer-[RuCl3(dppb)(OH2)] complex with the 2,2′-dithiobis(benzothiazole), mbts, was characterized by spectroscopic and electrochemical techniques (E 1/2 =0.78V versus NHE) and its structure was determined by crystal X-ray analysis. The structural analysis suggests that the S–S bond of the mbts ligand is cleaved, thus forming two four-membered chelate rings coordinated to the ruthenium through the N,S-donor atoms of the mbt reduced ligands, with an average bite angle of 67.295(11)°. The 1H and 13C NMR signals observed for mbts ligand coordinated to the metal center, the changes in the vibrational spectra, and the appearance of a MLCT band in the electronic spectrum of the complex point for the reduced state of the ruthenium metal center, RuII. These reducing processes are suggested to be due to the methanol interference, which is observed to be strongly affected by N-methylmorpholine. The cytochrome c electrochemistry was analyzed by using the SAMs formed by the mbts and the [Ru(dppb)(mbt)2] complex on gold, with only the former presenting electroactivity. [Copyright &y& Elsevier]

Abstract: The catalytic conversion of glycerol to acrolein by liquid-phase dehydration over molecular sieves catalysts was studied. In order to understand the role of the acidity, structure and porosity, five structures were synthesized and evaluated. The lower the Si/Al ratio, the higher the activity; large pore molecular sieves, as HY showed high performance (conversion=89.0%; selectivity to acrolein=99.5%), while siliceous molecular sieves such as SBA-15 possessing weak acidity, exhibited low conversion (40.6%) and decreased selectivity to acrolein (84.0%). The structure and the acidity govern the selectivity to acrolein and hydroxyacetone, the latter being a by-product mainly dependent on the amount of weak and medium strengths acidic sites, as in the case of Hβ. The activity has almost the same order of the acidity: HY>Hβ>Mor>SBA-15>ZSM-23. Modifications of the most acidic and active catalysts by silanation (CVD) or Pt incorporation did not result in an enhanced conversion. The studies of reusability and the nature of the coke deposits indicated that heavy polycondensed and cyclic C6 compounds resulting from the reaction between glycerol and acrolein block the pores and the acidic sites. The blockage was the main cause of deactivation, whereas acidic site poisoning led to a less extensive deactivation of the surface active sites. From these results, it was possible to establish acidity–activity–deactivation relationships that allow to explain the behaviour of the catalysts. [Copyright &y& Elsevier]

The ruthenium(II) compounds cis -[Ru(bpy) 2 (4-bzpy)(CO)](PF 6 ) 2 ( I ) and cis -[Ru(bpy) 2 (4-bzpy)(Cl)](PF 6 ) ( II ) (4-bzpy = 4-benzoylpyridine, bpy = 2,2′-bipyridine) were synthesized and characterized by spectroscopic and electrochemical techniques. The crystal structure of II was determined by X-ray diffraction. The photochemical behavior of I in aqueous solution shows that irradiation with ultraviolet light (365 nm) releases both CO and 4-bzpy leading to the formation of the cis -[Ru(bpy) 2 (H 2 O) 2 ] 2 + ion as identified by NMR and electronic spectroscopy. Carbon monoxide release was confirmed with the myoglobin method and by gas chromatographic analysis of the headspace. CO release was not observed when aqueous I was irradiated with blue light (453 nm). Changes in the electronic and 1 H NMR spectra indicate that I undergoes photoaquation of 4-bzpy to form cis -[Ru(bpy) 2 (CO)(H 2 O)] 2 + . Blue light irradiation of aqueous II released the coordinated 4-bzpy to give the cis -[Ru(bpy) 2 (H 2 O)(Cl)] 2 + ion. When the latter reaction was carried out in the presence of the nucleobase guanine, Ru-guanine adducts were formed, indicating that the metal containing photoproduct may also participate in biologically relevant reactions. The photochemical behavior of I indicates that it can release either CO or 4-bzpy depending on the wavelength chosen, a feature that may have therapeutic application. [ABSTRACT FROM AUTHOR]

Abstract: Ruthenium(II) carbonyl complexes containing triarylphosphines and hybrid ligands PPh2-X (X= o-dimethylaniline – P–N, o-pyridine – P-Py, or o-anisole – P–O) were synthesized and characterized. Six new complexes with the formula cis,trans-[RuCl2(CO)(PPh2-X)(PR3)] (X= o-dimethylaniline, R=Ph 1a; X= o-pyridine, R=Ph 2a; X= o-anisole, R=Ph 3a; X= o-dimethylaniline, R= p-tol 1b; X= o-pyridine, R= p-tol 2b; and X= o-anisole, R= p-tol 3b) were obtained by starting from the appropriate precursors, [RuCl2(CO)(DMF)(PPh3)2] or [RuCl2(CO)(DMF)(P{p-tol}3)2]. The two chlorine atoms are in cis position to each other, and the monophosphine (PPh3 or P{p-tol}3) is in trans position to the nitrogen or oxygen of the PPh2-X ligand. The synthesized complexes were characterized by 1D–1H, 31P{1H} and 2D-correlations HMBC 31P–1H NMR, vibrational spectroscopy, elemental analysis, and X-ray diffraction structural determination (for complexes 1a, 2a·CH2Cl2 , 3a, and 3b·CH2Cl2 ). Only the complexes containing the P–O ligand (3a and 3b) reacted with carbon monoxide (at 1atm and room temperature). The NMR (31P{1H}, 1H) data was compatible with carbon monoxide coordination at the OCH3 position, which led to the formation of dicarbonyl complexes [RuCl2(CO)2(P–O)(PR3)] (R=Ph 4a or p-tol 4b), and proved the hemilabile behavior of the P–O ligand. In addition, the complexes underwent isomerization in solution when exposed to ambient light, and the products were analyzed by 31P{1H} NMR. The X-ray structures and the chemical shift in the 31P NMR spectra were correlated and discussed. [Copyright &y& Elsevier]

Abstract: The “Ru(P–P)” unit (P–P=diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl2Ru-pz-RuCl2(CO)(dppb)] (pz=pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF6 (N–N=diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF6 were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl2(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and 31P{1H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography. [Copyright &y& Elsevier]