Ruthenium complexes reaction with

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

Ruthenium compounds are widely used as catalysts for hydrogen-transfer reactions. These systems can be readily adapted to the aerobic oxidation of alcohols by employing dioxygen, in combination with a hydrogen acceptor as a cocatalyst, in a multistep process. For example, Backvall and coworkers [85] used low-valent ruthenium complexes in combination with a benzoquinone and a cobalt Schiff s base complex. The proposed mechanism is shown in Fig. 14. A low-valent ruthenium complex reacts with the alcohol to afford the aldehyde or ketone product and a ruthenium dihydride. The latter undergoes hydrogen transfer to the benzoquinone to give hydroquinone with concomitant... 

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)]. 

A number of reactions of organothiols with complexes of alkoxycar-benes, isocyanides, or thiocarbonyls, leading to thiocarbene complexes, have been reviewed (4,125,126). Further related examples include the conversion of a chlorocarbene to a dithiocarbene by reaction of the ruthenium complex 154 with RSH (R = Me, p-tolyl) or HSCH2CH2SH to give the dithiocarbene compounds 155 and 156 (82). 

III.B.2), complexes with manganese, chromium, as well as second- and third-row transition metal ions (e.g., ruthenium) oxidation reactions with dioxygen alone or with other peroxides (e.g., ferf-butyl-peroxide) the stabilization and spectroscopic characterization of mononuclear superoxo, peroxo, and oxo complexes other catalytic processes (e.g., the iron-catalyzed aziridination), enantioselective reactions with chiral bispidine ligands and the iron oxidation chemistry continues to produce novel and exciting results. 

Reaction of the dinuclear ruthenium complexes, XXV, with propene gives n-allylruthenium complexes, XXVI. A mechanism is shown in Scheme 3. 

Ruthenium-catalyzed asymmetric reductions of aromatic ketones 180 can be performed under microwave irradiation. Moberg [98] described this reaction using a monomode microwave reactor and ruthenium complexes 182 with enan-tiomerically pure chiral diamines 181 (Scheme 5.51). The reaction is very fast and efficient even sterically hindered tert-butylphenylketone, which is normally quite umeactive, was reduced in almost quantitative yield in 3 minutes. The enantio-selectivity was, however, lower than that obtained under standard conditions similarly to that described by Larhed [77] in the enantioselective Heck reaction between cydopentene 115 and phenyl triflate 116 (Scheme 5.33). 

As carboxylic acid additives increased the efficiency of palladium catalysts in direct arylations through a cooperative deprotonation/metallation mechanism (see Chapter 11) [45], their application to ruthenium catalysis was tested. Thus, it was found that a ruthenium complex modified with carboxylic acid MesC02H (96) displayed a broad scope and allowed for the efficient directed arylation of triazoles, pyridines, pyrazoles or oxazolines [44, 46). With respect to the electrophile, aryl bromides, chlorides and tosylates, including ortho-substituted derivatives, were found to be viable substrates. It should be noted here that these direct arylations could be performed at a lower reaction temperatures of 80 °C (Scheme 9.34). 

In 1999, Fiirstner [33] reported the reaction of the allenylidene ruthenium complex 3 with [RuCl2(p-cymene)]2, which led to the formation of a diruthenium complex bearing chloride bridges and mixed, arene-allenylidene ligands of... 

Oxidative addition reactions to form metal alkyls or aryls have been observed for low-valent rhodium (37, 38), iridium 37, 39, 40), ruthenium 41), nickel 42), and platinum 11, 43, 44) complexes. Reactions with perfluoroalkyl halides extend this list to cobalt 45) and iron 46). Some examples are... 

Cycloaddition reactions across metal/nitrogen bonds are also observed. Nitrene complexes, formed in the reaction of the ruthenium complex 148 with an isocyanate, add a second molecule to give the [2+2] cycloadduct 149. ... 

The Mossbauer etfect has been observed in ruthenium compounds, and this can be exploited because these compounds have similar properties to the corresponding ones of iron. Evidence that (CO) is more efficient than CN at accepting tig electrons back-donated from the metal is obtained from similar isomer shifts for the two compounds Ru"(CO)2Cl2 and Ru"(CN)6 . In fact, it would appear that the isomer shifts for ruthenium complexes correlate with the order of the ligands in the spectrochemical series. The chemical consequences of beta decay for the reaction Os Ir... 

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