Ruthenium complexes reaction

Figure 6.14 Production of NH3 on tungsten with H2 provided by a ruthenium complex. Reaction as described in reference 36.

Consiglio and Morandini and co-workers (67) have investigated the stereochemistry involved in the addition of acetylenes to chiral ruthenium complexes. Reaction of propyne with the separated epimer of the chiral ruthenium phosphine complex 34 at room temperature results in the chemo- and stereospecific formation of the respective propylidene complex 64. An X-ray structure of the product (64) proves that the reaction proceeds with retention of configuration at the ruthenium center. The identical reaction utilizing the epimer with the opposite configuration at ruthenium (35) also proceeded with retention of configuration at the metal center, proving that the stereospecificity of the reaction in not under thermodynamic control [Eq. (62)]. 

Like the 2-hydroxy-2,2-di-methylethyl radical, C02 can add to the reduced 2,2 -bipyridyl ligand in the ruthenium complex (reaction 33). In contrast to the electron-transfer reaction, the addition reaction is nearly diffusion controlled. Rates of many of the electron-transfer reactions of C02 are sufficiently below... 

High-valent ruthenium oxides (e. g., Ru04) are powerful oxidants and react readily with olefins, mostly resulting in cleavage of the double bond [132]. If reactions are performed with very short reaction times (0.5 min.) at 0 °C it is possible to control the reactivity better and thereby to obtain ds-diols. On the other hand, the use of less reactive, low-valent ruthenium complexes in combination with various terminal oxidants for the preparation of epoxides from simple olefins has been described [133]. In the more successful earlier cases, ruthenium porphyrins were used as catalysts, especially in combination with N-oxides as terminal oxidants [134, 135, 136]. Two examples are shown in Scheme 6.20, terminal olefins being oxidized in the presence of catalytic amounts of Ru-porphyrins 25 and 26 with the sterically hindered 2,6-dichloropyridine N-oxide (2,6-DCPNO) as oxidant. The use... 

The pentammine aqua ion [Ru(NH3)j(H20)]2+, best made by zinc amalgam reduction and aquation of [Ru(NH3)5C1]2+, undergoes extensively studied substitution reactions first order in both the ruthenium complex and the incoming ligand (e.g. NH3, py) and is a convenient source of other... 

Let us now examine sample sets of data. We shall consider two reactions, the formation of a biradical1 [Eq. (7-10)] and an electron transfer reaction between two ruthenium complexes [Eq. (7-11)], in which LN represent nitrogen-donor ligands specified in the original reference.2 The chemical equations are... 

The three steps 32-34 have been suggested77 to be equilibria, and the overall equilibrium must lie far to the left because no adduct 23 is found in the reaction mixture when the reaction of sulfonyl chloride with olefin is carried out in the absence of a tertiary amine. A second possible mechanism involving oxidative addition of the arenesulfonyl halide to form a ruthenium(IV) complex and subsequent reductive elimination of the ruthenium complex hydrochloride, [HRulvCl], was considered to be much less likely. 

Keywords Alkenes Alkynes Carbene complexes Ruthenium Tandem reactions... 

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