Ruthenium carbonylation catalysts

This research was supported by the Department of Energy, Office of Basic Energy Sciences. Initial studies on the acidic ruthenium carbonyl catalyst system were carried out by Dr. Charles Ungermann in this group, Professor R.G. Rinker and his research group of the UCSB Chemical Engineering Department contributed significantly to the discussion and interpretation of these results. 

Although related reactions have also been done under low pressures/ very low rates of product formation are observed (8/10/11). We have found/ however, that a ruthenium carbonyl catalyst is quite active for converting H2/CO to methanol under moderate pressures (below 340 atm). More significantly, we also discovered that an ethylene glycol product could be obtained from this catalyst by use of carboxylic acid promoters or solvents (12) This remarkable and intriguing promoter effect deserved, we felt, further mechanistic investigation... 

The reactions with ruthenium carbonyl catalysts were carried out in pressurized stainless steel reactors glass liners had little effect on the activity. When trimethylamine is used as base, Ru3(CO) 2> H Ru4(CO) 2 an< H2Ru4(CO)i3 lead to nearly identical activities if the rate is normalized to the solution concentration of ruthenium. These results suggest that the same active species is formed under operating conditions from each of these catalyst precursors. The ambient pressure infrared spectrum of a typical catalyst solution (prepared from Ru3(CO)i2> trimethylamine, water, and tetrahydrofuran and sampled from the reactor) is relatively simple (vq q 2080(w), 2020(s), 1997(s), 1965(sh) and 1958(m) cm ). However, the spectrum depends on the concentration of ruthenium in solution. The use of Na2C(>3 as base leads to comparable spectra. 

Organometallic compounds often show unique catalytic properties that may also allow their use as potential drug candidates. The cyclopentadienyl-ruthenium carbonyl catalyst 75, that bears a quinoline-based bidentate ligand, was found to be a potent inhibitor of certain protein kinases <2006AGE1504>. 

Hydroxycarbonylation of olefins (Scheme 5.11) in fully aqueous solution was studied using a ruthenium-carbonyl catalyst with no phosphine ligands [35]. In a fine mechanistic study it was shown, that (the WGS) reaction of /ac-[Ru(C0)3(H20)3]2+ and water provided /ac-[RuH(CO)2(H20)3]+. At 70 °C and in the presence of CF3S03H the latter compound reacted with ethene (10 bar) giving a a-alkylruthenium complex, solutions of which absorbed CO and yielded the corresponding acyl-derivative ... 

Fujita, S. I. Okamuta, S. Akiyama, Y Arai, M. Hydroformylation of Cyclohexene with Carbon Dioxide and Hydrogen Using Ruthenium Carbonyl Catalyst Influence of Pressures of Gaseous Components. Int. J. Mol. Sci. 2007,8,749-759. 

Ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [PBuJBr was reported by Knifton as early as in 1987 [2]. The author described a stabilization of the active ruthenium-carbonyl complex by the ionic medium. An increased catalyst lifetime at low synthesis gas pressures and higher temperatures was observed. 

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. 

Fischer-Tropsch synthesis could be "tailored by the use of iron, cobalt and ruthenium carbonyl complexes deposited on faujasite Y-type zeolite as starting materials for the preparation of catalysts. Short chain hydrocarbons, i.e. in the C-j-Cq range are obtained. It appears that the formation and the stabilization of small metallic aggregates into the zeolite supercage are the prerequisite to induce a chain length limitation in the hydrocondensation of carbon monoxide. However, the control of this selectivity through either a definite particle size of the metal or a shape selectivity of the zeolite is still a matter of speculation. Further work is needed to solve this dilemna. 

As shown in Table I, at 0.1 mM Ru (C0) 2 concentration, CO pressure has little if any effect on activity. On the other hand, at fixed pressure, the concentration of ruthenium carbonyl has a dramatic effect on activity (see Figure 2). At 0.1 mM Ru CCO), ruthenium carbonyl is very active for the WGSR, small decreases in catalyst concentration lead to substantial increases in activity, and no activity dependenee on CO pressure is observed. At concentrations of 0.5 mM or more, less activity is observed, changes in concentration cause smaller effects in activity and rate dependence on pressure is manifested. Diffusion effects have been shown to be unimportant (26). 

We found little difference between the activities of this catalyst with K2CO3 and with KOH. However, a pronounced dependence on pressure was seen for a six-fold decrease in CO pressure, the activity increased by a factor of 2.5. This tendency is in marked contrast to the activity increase with increasing CO pressure observed with ruthenium carbonyl. 

I/Ru ratio critical, 34 112 proposed mechanism, 34 112 ruthenium-carbonyl complexes, 34 113 species involved, 34 110-113 -catalyzed homologation, 34 115 proposed mechanism, 34 115 compensation behavior of, 26 285, 286 complex catalyst... 

Butenolides are formed in the alkyne-CH3l--Co2(CO)3 phase transfer reaction. When the latter process is effected in the presence of ruthenium carbonyl, a second metal catalyst, y-keto acids are isolated in good yields(17). 

Alumina-supported Ru catalysts derived from supported ruthenium carbonyls have been reported to be effective for carbon dioxide methanation, showing higher activity than other catalysts prepared from RUCI3. The catalytic activity depended on the nuclearity of the carbonyl precursor [111]. 

Hexaruthenium carbonyl complexes have been used to prepare Ti02-supported mthenium catalysts for the sulfur dioxide reduction with hydrogen [112, 113], A catalyst derived from [Ru6C(CO)i6] showed higher activity in the production of elemental sulfur at low temperatures than that prepared from RUCI3 as precursor. This catalytic behavior is related with the formation of an amorphous ruthenium sulfide phase that takes place during the reaction over the ex-carbonyl catalyst [112]. 

Ruthenium carbonyl-derived catalytic systems have also been studied in hydrodesulfuration [118, 119], Highly active catalysts for the hydrodesulfuration of diben-zothiophene have been obtained by supporting on alumina MHRu3(CO)n (M = group 1 metal), which was the product of the reaction between Ru3(CO)i2 and MOH. The activity increased from Li to Cs [119]. 

A number of ruthenium-based catalysts for syn-gas reactions have been probed by HP IR spectroscopy. For example, Braca and co-workers observed the presence of [Ru(CO)3l3]", [HRu3(CO)ii]" and [HRu(CO)4] in various relative amounts during the reactions of alkenes and alcohols with CO/H2 [90]. The hydrido ruthenium species were found to be active in alkene hydroformylation and hydrogenation of the resulting aldehydes, but were inactive for alcohol carbonylation. By contrast, [Ru(CO)3l3]" was active in the carbonylation of alcohols, glycols, ethers and esters and in the hydrogenation of alkenes and oxygenates. 

Carbonylation of acetic acid to higher carboxylic acids can occur in presence of ruthenium/iodide catalysts. The reaction involves reduction and several carbonylation steps. The overall reaction may be written as follows ... 

Acetic acid has been generated directly from synthesis gas (CO/H2) in up to 95 wt % selectivity and 97% carbon efficiency using a Ru-Co-I/Bu4PBr "melt" catalyst combination. The critical roles of each of the ruthenium, cobalt and iodide catalyst components in achieving maximum selectivity to HOAc have been identified. Ci Oxygenate formation is observed only in the presence of ruthenium carbonyls [Ru(C0)3l3] is here the dominant species. Controlled quantities of iodide ensure that initially formed MeOH is rapidly converted to the more reactive methyl iodide. Subsequent cobalt-catalyzed carbonylation to acetic acid may be preparatively attractive (>80% selectivity) relative to competing syntheses where the [00(00)4] concentration is optimized that is, where the Co/Ru ratio is >1, the syngas feedstock is rich in 00 and the initial iodide/cobalt ratios are close to unity. 

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