Ruthenium-carbonyl clusters

Figure 1 Synthesis of ruthenium-carbonyl clusters with the 3,5,6-bicyclophosphite-l,2-o-isopropylidene-a-D -glucofuranoside ligand.

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. 

It is proposed that the rate dependence on concentration and pressure involves cluster dissociation and that the monomeric species, Ru(CO), is responsible for the high activity of this system. Dissociation is well known for ruthenium carbonyl clusters (25,27-31). Piacenti and co-workers (31) have demonstrated that at temperatures above 80° and CO pressures greater than 150 psi, monomeric ruthenium carbonyl is observed in significant quantities due to the equilibrium,... 

Cabeza, J.A., in Braunstein, P., Oro, L.A., Raithby, P.R. (Eds.), Homogeneous Catalysis with Ruthenium Carbonyl Cluster Complexes Metal Clusters in Chemistry, Vol. 2. Wiley-VCH GmbH, Weinheim,... 

Scheme 16.4 Pathways for the generation of ruthenium carbonyl clusters on the surface of Si02.

Platinum-ruthenium carbonyl clusters, characteristics, 8, 419 Platinum-sulfur bonds, in platinacycles, 8, 505 Platinum-thallium carbonyl clusters, characteristics,... 

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)...

M. P. Cifuentes, M. G. Humphrey, J. E. McGrady, P. J. Smith, R. Stranger, K. S. Murray, and B. Moubaraki, High Nuclearity Ruthenium Carbonyl Cluster Chemistry. 5. Local Density Functional, Electronic Spectroscopy, Magnetic Susceptibility, and Electron Paramagnetic Resonance Studies on (Carbido)decaruthenium Carbonil Clusters, J. Am. Chem. Soc. 119,2647-2655 1997. 

The coordinatively unsaturated cluster [H20s3(CO),o] is found to be cat-alytically active for hydrogenation of alkynes or isomerization of alkenes in solution. Hydridotriosmium and -ruthenium carbonyl clusters bound to a variety of oxides are summarized in Table VIII. The relative activities for... 

Binsted N, Evans J, Greaves GN, Price RJ (1989) Characterization of supported rhodium and ruthenium carbonyl clusters by EXAFS spectroscopy. Organometallics 8 613... 

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... 

The combination of C H activation and olefin insertion onto C-2 of TP 44, catalyzed by ruthenium carbonyl (cluster catalysis, presents an opportunity for C-C bond formation to yield 2-acyl TP 120 (01AG222). 

It is not surprising that homogeneous WGS catalysts are in two categories—those which operate in acidic and those in basic media. Of the acid-based systems, the most active are the rhodium carbonyl iodide combinations ", the PtCl4 /SnCl3 preparation, and the system based on the ruthenium carbonyl cluster catalyst precursors Ru3(CO)i2 and H4Ru4(CO),2 . The Rh carbonyl iodide system under more vigorous conditions (185°C, 23 atm ) shows a catalytic rate of 400 tumovers/h. 

---