Ruthenium carbonyl iodides

Chemical and Catalytic Properties of Ruthenium Carbonyl Iodide Systems during Reactions on Oxygenated Substrates... 

Scheme 1 Lewis acid assisted evolution of alkyl and acyl ruthenium carbonyl iodide intermediates.

These results also demonstrate the ability of the ruthenium carbonyl iodide systems to activate both the alkyl and the acyl part of the formates. The same is true for esters of higher carboxylic acids where new esters of higher homologous acids and alcohols are produced. 

Hieber and Heusinger (3) reported an interesting reaction in which a liquid ammonia solution of ruthenium carbonyl iodide decomposed above — 30 °C to produce free and coordinated formamide ... 

Two carbonyl complexes K2[Ru(CN)2I2(CO)2] (from ruthenium carbonyl iodide and KCN)4 and [RuC1(CN)(NH3)(CO)(PPh3)2] (4) (from treatment of [RuCl2(CCl2)(CO)(PPh3)2] with ammonia) are known. Reaction of the latter with CO gives [RuCl(CN)(CO)2(PPh3)2] (5).49... 

Methanol is protonated to give an ion pair with a ruthenium carbonyl iodide anion. Dehydration by an 5 2 type process gives a methyl complex which undergoes insertion of carbon monoxide to an acetyl intermediate followed by reduction to an alkoxy derivative. Finafly. ethanol is released via hydrogenation of the alkoxy intermediate. 

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

Subsequent insertion of CO into the newly formed alkyl-ruthenium moiety, C, to form Ru-acyl, D, is in agreement with our 13C tracer studies (e.g., Table III, eq. 3), while reductive elimination of propionyl iodide from D, accompanied by immediate hydrolysis of the acyl iodide (3,14) to propionic acid product, would complete the catalytic cycle and regenerate the original ruthenium carbonyl complex. 

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. 

In a more detailed examination of the ruthenium-cobalt-iodide "melt" catalyst system, we have followed the generation of acetic acid and its acetate esters as a function of catalyst composition and certain operating parameters, and examined the spectral properties of these reaction products, particularly with regard to the presence of identifiable metal carbonyl species. 

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... 

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. 

Homogeneous hydrogenation of carbon dioxide to methanol is catalyzed by ruthenium cluster anions in the presence of halide anions. The catalyst system was Ru3(CO)i2 and alkyl iodides in A -methylpyrrolidone (NMP) solution at 513 K. Some methane was also formed. FT-IR spectra of the reactions allowed identification of several ruthenium carbonyl anions. 

It is useful to explore this analogy between known alkyne systems and potential benzyne ones. For example, alkynes react with ruthenium carbonyl to form the Ru4( --alkyne)(CO)i2, which form an octahedral RU4C1 arrangement with the metal atoms in a butterfly geometry. Since the synthesis cannot be adapted to arynes, another method is needed. Oxidative addition of aryl iodides to Ru3(CO)i2 gives the aryl complexes described in Sec. 1.14.4.5. Flowever, we have... 

Data in Table V illustrate the production of acetic acid from 1/1 syngas. A variety of ruthenium-containing precursors - coupled with cobalt halide, carbonate and carbonyl compounds - at different initial Co/Ru atomic ratios, have been found to yield the desired carboxylic acid when dispersed in tetrabutylphosphonium bromide. In a more detailed examination of the ruthenium-cobalt-iodide melt catalyst system, we have followed the generation of acetic acid and its acetate esters as a function of catalyst composition and certain operating parameters, and examined the spectral properties of these reaction products, particularly with regard to the presence of identifiable metal carbonyl species. 

To achieve a high reaction rate at low concentrations of ionic iodide, promoters assisting the removal of free iodide are applied in the process. Possible promoters are simple iodide complexes of zinc, cadmium, and gallium or carbonyl-iodide complexes of osmium, tungsten, and ruthenium (the latter being used preferably). 

The effect of metal promoter species on the rate of carbonylation of [Ir(CO)2l3Me] was tested. Neutral ruthenium iodocarbonyl complexes such as [Ru(CO)3l2]2> [Ru(CO)4l2] or [Ru(CO)2l2]n were found to give substantial rate enhancements (by factors of 15-20 for a Ru Ir ratio of 1 13 at 93 °C, PhCl). Indium and gallium triiodides and zinc diiodide had comparable promotional effects. By contrast, addition of anionic ruthenium(II) species [Ru(CO)3I3] or [Ru(CO)2I4]2 did not lead to any appreciable promotion or inhibition. This behaviour indicates that the ability to accept an iodide ligand is a key property of the promoter. Indeed, it has been demonstrated that an iodide ligand can be transferred from [ Ir(C0)2l3Me] to neutral ruthenium or indium species [73,74],... 

In 1970, the first rhodium-based acetic acid production unit went on stream in Texas City, with an annual capacity of 150 000 tons. Since that time, the Monsanto process has formed the basis for most new capacities such that, in 1991, it was responsible for about 55% of the total acetic acid capacity worldwide. In 1986, B.P. Chemicals acquired the exclusive licensing rights to the Monsanto process, and 10 years later announced its own carbonylation iridium/ruthenium/iodide system [7, 8] (Cativa ). Details of this process, from the viewpoint of its reactivity and mechanism, are provided later in this chapter. A comparison will also be made between the iridium- and rhodium-based processes. Notably, as the iridium system is more stable than its rhodium counterpart, a lower water content can be adopted which, in turn, leads to higher reaction rates, a reduced formation of byproducts, and a better yield on CO. 

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