Redox reactions ruthenium salts

An example of the use of direct redox reactions in the preparation of bimetallic catalysts is the modification of copper catalysts by the addition of ruthenium, platinum, gold, or palladium [11-14], Assuming the metallic state for copper atoms on the surface, the redox reaction with the noble metal salts is... 

According to the standard electrochemical potentials (Table 1), with Cu/Cu2+ and Ru/Ru3+ couples, the amount of ruthenium deposited on metallic copper will be small, whereas the redox reaction carried out in presence of platinum or gold salts will occur to a large extent. On the other hand, for electrodes of first type (metal immersed in a solution of a salt of that metal), the standard electrochemical potentials as defined by thermodynamics are calculated with regard to a poly-crystalline metallic phase of infinite size. However, in the case of small metallic particles, characterized by metallic atoms of different coordination numbers, the notion of a local potential can be introduced. That no-... 

In the case of powder bulk catalysts, Cu Raney was modified by direct redox reaction between reduced copper and the salt of a noble metal M (Ru, Pt and Au) [5, 7]. Typically the Cu-M bimetallic catalysts were obtained by mixing a freshly prepared Cu Raney with an aqueous solution of the noble metal salt. When the amount of M is in excess compared to the number of copper surface atoms, it appears that ruthenium deposition is restricted to approximately 1/3 of the copper surface atoms. For platinum and gold, a deposit larger than a monolayer is obtained, indicating that subsurface copper atoms are involved in direct redox reaction. This result is explained by the lower potential difference between copper and rathenium compared to those of copper and platinum or gold [7j. However, the reactions involved in the direct redox reaction may not be as simple as indicated in Section 9.2. A typical time distribution of ion concentrations in solution during the preparation of Cu-Pt is shown in Fig. 9.1. It can be observed that platinum ions disappear very rapidly from the solution while at the same time copper... 

Nitrite Nitrite is an important indicator of fecal pollution in natural waters as well as a potential precursor of carcinogenic species. A rush of flow and sequential injection spectrophotometric method based on Griess-type reactions has been proposed, also coupled to online sorbent enrichment schemes. The catalytic effect of nitrite on the oxidation of various organic species constitutes the basis of fairly sensitive spectrophotometric methods. Fluorometric methods based on the formation of aromatic azoic acid salts, quenching of Rhodamine 6G fluorescence, and direct reaction with substituted tetramine or naphthalene species have been also reported. Indirect CL methods usually involve conversion into nitric oxide and gas-phase detection as mentioned in the foregoing section. The redox reaction between nitrite and iodide in acidic media is the fundamental of a plethora of flow injection methodologies with spectrophotometric, CL, or biamperometric detection. New electrochemical sensors with chemically modified carbon paste electrodes containing ruthenium sites, or platinum electrodes with cellulose or naphthalene films, have recently attracted special attention for amperometric detection. 

Abstract Photoredox catalysis by well-known nithenium(II) polypyridine complexes is a versatile tool for redox reactions in synthetic organic chemistry, because they can effectively catalyze single-electron-transfer (SET) processes by irradiation with visible light. These favorable properties of the catalysts provide a new strategy for efficient and selective radical reactions. Salts of tris(2,2 -bipyridine)mthenium (II), [Ru(bpy)3], were first reported in 1936. Since then, anumber of works related to artificial photosynthesis and photofunctional materials have been reported, but only limited efforts had been devoted to synthetic organic chemistry. Remarkably, since 2008, this photocatalytic system has gained importance in redox reactions. In this chapter, we will present a concise review of seminal works on ruthenium photoredox catalysis around 2008, which will be followed by our recent research topics on trifluoromethylation of alkenes by photoredox catalysis. 

Hydrogen generation requires a photosensitizer, an electron donor, an electron mediator and a multi-electron redox eatalyst. To obtain the polymer the reaction mixture must be refluxed in methanol for 20 hours. This yields a polymer wifli 1% viologen groups. In the system, water donates the protons and electrons are supplied by ethylenediamine tetraacetic acid disodium salt. The viologen groups transport the electrons to the multi-electron redox catalyst (2,2 -bipyridine)ruthenium(ll), Ru(bpy). ... 

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