Ruthenium precursor compound

The chemical valences of ruthenium range from +1 to +8 and the common valences are +2, +3 and +4. The main ruthenium compounds are as follows  

Ruthenium dioxide (RUO2) is a yellow square crystal. The relative molecular weight is 133.07 and the density is 6.97. It does not dissolve in water, but dissolves in molten alkali. 

The above mentioned four kinds of ruthenium compounds can be divided into two groups One is chlorine-containing and another is chlorine-free. Both of them can be used as the precursor of ruthenium in catalysts. 

RuCls 3H2O is the most common ruthenium compound containing chlorine with stable properties. It easily dissolves in water and is cheaper than other ruthenium compounds. In the past, the ruthenium catalysts were prepared by impregnation with RuCIs as the precursor and water as solvent. However, the chlorine of remnant after reduction can poison the ruthenium catalysts when a metal oxide is adopted as a support. The poison effect of chlorine is not so obvious for ruthenimn catalysts with activated carbon as support.  

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Ruthenium cluster compounds (143) and (144) have been identified that may play a role in the catalysis when Ru3(CO)12 was used as the precursor.540-543 The use of [(dppe)Ru(CO)3] as a catalyst including the intermediates (145) and (146) in the catalytic cycles, have been studied in detail by Gladfelter and co-workers.544-550... 

Reaction of the arene ruthenium precursor 200 with polystyrene and hydrogen leads to the loss of both cycloolefins and gives a polymeric ruthenium complex, used for catalytic hydrogenation, for which EXAFS indicated a Ru—C distance of 2.05 A. A similar reaction of derivative 200 with 1,3-diphenylpropane gives complex 203 and a compound of composition (diphenylpropane)Ru2 (204) (129,130) [Eq. (18)]. 

Abstract Ruthenium holds a prominent position among the efficient transition metals involved in catalytic processes. Molecular ruthenium catalysts are able to perform unique transformations based on a variety of reaction mechanisms. They arise from easy to make complexes with versatile catalytic properties, and are ideal precursors for the performance of successive chemical transformations and catalytic reactions. This review provides examples of catalytic cascade reactions and sequential transformations initiated by ruthenium precursors present from the outset of the reaction and involving a common mechanism, such as in alkene metathesis, or in which the compound formed during the first step is used as a substrate for the second ruthenium-catalyzed reaction. Multimetallic sequential catalytic transformations promoted by ruthenium complexes first, and then by another metal precursor will also be illustrated. 

Ruthenium compounds have been extensively studied as catalysts for the aerobic oxidation of alcohols [142]. They operate under mild conditions and offer possibilities for both homogeneous and heterogeneous catalysts. The activity of common ruthenium precursors such as RuCl2PPh3, can be increased by the use of ionic liquids as solvents (Fig. 4.58). Tetramethylammoniumhydroxide and aliquat 336 (tricaprylylmethylammonium chloride) were used as solvent and rapid conversion of benzyl alcohol was observed [145]. Moreover the tetra-methylammonium hydroxide/RuCl2(PPh3)3 could be reused after extraction of the product. 

For early examples of the reactions of diazo compounds with ruthenium precursors, see France, M.B. Ph. D. Thesis, California Institute of Technology, 1995. 

Unsymmetrically substituted ruthenocenes may also be prepared using gas-phase electrocyclic reactions of penta-dienylruthenium complexes. The precursor compounds are obtained by zinc reduction of either ruthenium trichloride in the presence of 5,5-dimethylcyclohexadiene to give bis(6,6-dimethylcyclohexadienyl)ruthenium or Cp RuClala in the presence of 2,4-di-/l r -butyl-l,3-pentadiene to give (pentamethylcyclopentadienyl)(2,4-di-/ r7-butylpentadienyl)ruthenium or dimethylcyclohexadiene to give (pentamethylcyclopentadienyl)(6,6-dimethylcyclo-hexadienyl)ruthenium. Sublimation of these compounds at 400-450 °C afforded the ruthenocenes 6-8. ... 

Van der Schaaf et al. described a synthesis of the 14-electron complex [RuHCl(PPr13)2] (32) from [RuCl2(COD)]A.,PPr31,isopropanol,and abase.Compound 32 is a suitable precursor for ruthenium carbene complex 33, as outlined in Scheme 10. Although 32 was isolated and structurally characterized, it may also be generated in situ for the preparation of the carbene complex 33 [18]. 

Alternatively, arene displacement can also be photo- rather than thermally-induced. In this respect, we studied the photoactivation of the dinuclear ruthenium-arene complex [ RuCl (rj6-indane) 2(p-2,3-dpp)]2+ (2,3-dpp, 2,3-bis(2-pyridyl)pyrazine) (21). The thermal reactivity of this compound is limited to the stepwise double aquation (which shows biexponential kinetics), but irradiation of the sample results in photoinduced loss of the arene. This photoactivation pathway produces ruthenium species that are more active than their ruthenium-arene precursors (Fig. 18). At the same time, free indane fluoresces 40 times more strongly than bound indane, opening up possibilities to use the arene as a fluorescent marker for imaging purposes. The photoactivation pathway is different from those previously discussed for photoactivated Pt(IV) diazido complexes, as it involves photosubstitution rather than photoreduction. Importantly, the photoactivation mechanism is independent of oxygen (see Section II on photoactivatable platinum drugs) (83). 

This article presents the principles known so far for the synthesis of metal complexes containing stable carbenes, including the preparation of the relevant carbene precursors. The use of some of these compounds in transition-metal-catalyzed reactions is discussed mainly for ruthenium-catalyzed olefin metathesis and palladium-Znickel-catalyzed coupling reactions of aryl halides, but other reactions will be touched upon as well. Chapters about the properties of metal- carbene complexes, their applications in materials science and medicinal chemistry, and their role in bioinorganic chemistry round the survey off. The focus of this review is on ZV-heterocyclic carbenes, in the following abbreviated as NHC and NHCs, respectively. 

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