Ruthenium carbonyl clusters reactions

Reactive Intermediates in the Thermal and Photochemical Reactions of IHnuclear Ruthenium Carbonyl Clusters... 

The dominant role of copper catalysts has been challenged by the introduction of powerful group VIII metal catalysts. From a systematic screening, palladium(II) and rhodium(II) derivatives, especially the respective carboxylates62)63)64-, have emerged as catalysts of choice. In addition, rhodium and ruthenium carbonyl clusters, Rh COJjg 65> and Ru3(CO)12 e6), seem to work well. Tables 3 and 4 present a comparison of the efficiency of different catalysts in cyclopropanation reactions with ethyl diazoacetate under standardized conditions. 

Table 12. Amount (%) of mono-, di- and trisubstituted ruthenium carbonyl clusters obtained by reaction of [Ru3(CO)i2] with 3 equiv. FDPP and use of 10 % iron(I) electrocatalyst. The standard redox potentials of [Fe Cp(C6H6 Me )] in THF + -Bu4NPF6, 0.1 m, are E° = -(1.745 0.032n)...

Treatment of (80) and (81) with Ru3(CO)12 gave the >/4-silatrimethylenemethane-ruthenium complexes in 9% and 22% yield, respectively. The major product of the Z-alkylidenesilacyclopropane reaction was trinuclear ruthenium carbonyl cluster (82), whose structure was established by x-ray diffraction (Equation (37)). This appears to be the first example of a main group metal-bound carbonyl inserting into a silacyclopropane <9lJA279i, 94OM4606). 

A particularly broad potential for application in syngas reactions is shown by ruthenium carbonyl clusters. Iodide promoters seem to favor ethylene glycol (155,156) the formation of [HRu3(CO),]- and [Ru(CO)3I3]- was observed under the catalytic conditions. These species possibly have a synergistic effect on the catalytic process. Imidazole promoters have been found to increase the catalytic activity for both methanol and ethylene glycol formation (158-160). Quaternary phosphonium salt melts have been used as solvents in these cases the anion [HRu3(CO)u] was detected in the mixture (169). Cobalt iodide as cocatalyst in molten [PBu4]Br directs the catalytic synthesis toward acetic add (163). With... 

Table 1 lists alkyne hydrogenation reactions which use ruthenium carbonyl cluster complexes as catalyst precursors. The contents of the table are discussed in the following paragraphs, which are classified according to the type of metal cluster complex used as catalyst precursor. 

Although C-S bond cleavage reactions between thiophenes and osmium clusters have not been observed, selenophene and tellurophene undergo ring opening reactions with [Os3(CO)io(NCMe)2] to give complexes 28a and 28b (Scheme T). " It is likely that the sulfur-extrusion reactions of iron and ruthenium carbonyl clusters with thiophenes proceed via ring-opened intermediates of this type. 

E3.19 Base-promoted ruthenium carbonyl cluster complexes from fundamental reactions to catalysis... 

E3.25 Reactions of ruthenium carbonyl clusters with alkynes... 

More recently, catalytic hydrogenations of alkenes by other catalysts in water have been explored. For example, water-soluble ruthenium complex RuCl2(TPPTS)3 has been used for the catalytic hydrogenation of unsaturated alkenes (and benzene). Hydrogenation of nonactivated alkenes catalyzed by water-soluble ruthenium carbonyl clusters was reported in a biphasic system. The tri-nuclear clusters undergo transformation during reaction but can be reused repeatedly without loss of activity. The organometallic aqua complex [Cp Ir (H20)3] " ... 

Complexes of other transition metals have been reported to catalyze Pauson-Khand reactions. Buchwald reported intramolecular PKRs with 1.2 atm of CO at 90 °C in the presence of CpjTi(CO)2. " However, most other catalytic Pauson-Khand reactions have been conducted with late transition metal catalysts. Murai and Mitsudo simultaneously reported intramolecular PKRs catalyzed by ruthenium carbonyl clusters in dioxane or DMAc at 140-160 °C under 10-15 atm of CO. The first Rli-catalyzed PKR was reported by Narasaka. ° In this case, the reaction occurred with acceptable rates, even with CO pressures less than 1 atm. Shibata reported PKRs in refluxing xylenes under 1 atm of CO in the presence of catalytic amounts of PPli and [Ir(COD)Cl]2. Adrio and Carretero showed that the solvated molybdenum carbonyl complex Mo(DMF)3(CO)3 catalyzed intramolecular PKRs with monosubstituted olefins, as well as with disubstituted electron-poor olefins, and Hoye showed that W(CO)5(THF) catalyzes intramolecular PKRs. Iron and palladium complexes have also been reported to catalyze the PKR. 

CO2MC] were obtained by metal exchange liom (he same ruthenium-dicobalt precursor and analogous functionalized (cyclopentadienyl)metal carbonyl Related reactions of the selenido-containing cluster RuCo2(/r rSe)... 

However, while ruthenium carbonyl was found to decompose the formate ion in basic media, the rate was slower (<0.1 mmol trimethyl ammonium formate to H2 and C02 per hour) than the rate of the water-gas shift reaction (>0.4 mmol H2/hr) at 5 atm CO and 100 °C. Increasing CO pressure decreased the formate decomposition rate. However, it was observed that increasing the CO pressure from 5 atm CO to 50 atm increased the H2 production rate to 10 mmol/hr. They proposed, in a similar manner to Pettit et al.,34 a mechanism that involved nucleophilic attack by amine (instead of hydroxide). Activation of the metal carbonyl (e.g., Ru3(CO) 2 cluster to Ru(CO)5) was suggested to be favored by dilution, increases in CO pressure, or, in the case of Group VIb metal carbonyl complexes, photolytic promotion. The mechanism is shown below in Scheme 9 ... 

The formation of carbido-carbonyl cluster compounds with ruthenium and osmium appears to be common in pyrolysis reactions the basic reaction may be viewed as the transformation of the coordinated carbon monoxide to carbide and carbon dioxide. Small variations in... 

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