Ruthenium hydroformylation using

Hydroformylation Using Other Metals. Ruthenium, as a hydroformy-lation catalyst, has an activity significantly lower than that of rhodium and even cobalt. 

Triphenylphosphine-Modified Ruthenium Catalyst. The mechanism of olefin hydroformylation using Ru(CO)3(P(C6H5)3)2 as the catalyst precursor has been explained by the classical hydride-, alkyl-, and acyl-complex sequence involving Ru(H)2(CO)(P(C6H5)3) as the principal active catalytic species (125). 

The first example of homogeneous transition metal catalysis in an ionic liquid was the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate (mp. 78 °C), described by Parshall in 1972 (Scheme 5.2-1, a)) [1]. In 1987, Knifton reported the ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [Bu4P]Br, a salt that falls under the now accepted definition for an ionic liquid (see Scheme 5.2-1, b)) [2]. The first applications of room-temperature ionic liquids in homogeneous transition metal catalysis were described in 1990 by Chauvin et al. and by Wilkes et ak. Wilkes et al. used weekly acidic chloroaluminate melts and studied ethylene polymerization in them with Ziegler-Natta catalysts (Scheme 5.2-1, c)) [3]. Chauvin s group dissolved nickel catalysts in weakly acidic chloroaluminate melts and investigated the resulting ionic catalyst solutions for the dimerization of propene (Scheme 5.2-1, d)) [4]. 

Small amounts of hydrocarbons added to the normal tetrahydrofuran or diglyme solvent system result in improved WGSR activity, but larger quantities inhibit the reaction (Table II). When 1-butene or 1-hexene is used, hydroformylation competes with the WGSR (4 ), but the rate of this process is small compared with the rate of H2 production. With pentane, no olefin or aldehyde products could be detected. Calderazzo (29) has reported that Ru(C0) is the principal product when the acetylacetonate of ruthenium is treated with synthesis gas in heptane,... 

Given the previous discussion on reductive amination, it is surprising that the potentially more complicated domino hydroformylation-reductive amination reactions have been more thoroughly developed. The first example of hydroaminomethylation was reported as early as 1943 [83]. The most synthetically useful procedures utilize rhodium [84-87], ruthenium [88], or dual-metal (Rh/Ir) catalysts [87, 89, 90]. This area was reviewed extensively by one of the leading research groups in 1999 [91], and so is only briefly outlined here as the second step in the domino process is reductive amination of aldehydes. Eilbrachfs group have shown that linear selective hydroaminomethylation of 1,2-disubstituted alkenes... 

Another possible reason that ethylene glycol is not produced by this system could be that the hydroxymethyl complex of (51) and (52) may undergo preferential reductive elimination to methanol, (52), rather than CO insertion, (51). However, CO insertion appears to take place in the formation of methyl formate, (53), where a similar insertion-reductive elimination branch appears to be involved. Insertion of CO should be much more favorable for the hydroxymethyl complex than for the methoxy complex (67, 83). Further, ruthenium carbonyl complexes are known to hydro-formylate olefins under conditions similar to those used in these CO hydrogenation reactions (183, 184). Based on the studies of equilibrium (46) previously described, a mononuclear catalyst and ruthenium hydride alkyl intermediate analogous to the hydroxymethyl complex of (51) seem probable. In such reactions, hydroformylation is achieved by CO insertion, and olefin hydrogenation is the result of competitive reductive elimination. The results reported for these reactions show that olefin hydroformylation predominates over hydrogenation, indicating that the CO insertion process of (51) should be quite competitive with the reductive elimination reaction of (52). 

Hydroformylation - [CARBON MONOXIDE] (Vol 5) - [OXO PROCESS] (Vol 17) -of allyl alcohol [ALLYL ALCOHOL AND MONOALLYL DERIVATIVES] (Vol 2) -catalysts for [CATALYSIS] (Vol 5) -C-19 dicarboxylic acids from [DICARBOXYLIC ACIDS] (Vol 8) -of ethylene [ETHYLENE] (Vol 9) -of ethylene [PROPYL ALCOHOLS - N-PROPYLALCOLHOL] (Vol 20) -of maleate and fumarate esters [MALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) -phosphine catalyst [PHOSPHORUS COMPOUNDS] (Vol 18) -platinum-group metal catalysts for [PLATINUM-GROUP METALS] (Vol 19) -rhodium catalysis [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -ruthenium cmpds or catalyst [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -use of coordination compounds [COORDINATION COMPOUNDS] (Vol 7)... 

The results of the hydroformylation of internal olefins are reported in Table 9. In the case of (Z)- and (E)-2-butene, the same fare of the unsaturated carbon atom is formylated with either a rhodium- or platinum (—)-DIOP-containing catalytic system. With the rhodium catalyst, when an acyclic olefin is used as the substrate, the same fare is always attacked, and it is only the notation but not the geometric requirement that is different for (E)-l-phenyl-1-propene. The only exception is represented by bicyclo[2,2,l]heptene. However, using (—)-CHIRAPHOS instead of (—)-DIOP, also bieyelo[2,2,l]heptene behaves like internal butenes. No regularity is observed for the cobalt or ruthenium (—)-DIOP catalytic systems. With the same system, only in 3 cases out of 15 the face of the prochiral atom preferentially formylated has different geometric requirements. 

In hydroformylation, several metals have high catalytic activity. Roelen discovered hydroformylation by using cobalt as the catalyst metal. Cobalt catalysts need relatively harsh conditions with high pressures and temperatures. A more active catalyst metal is rhodium, which enables working under milder conditions. Other metals which can be employed in hydroformylation are ruthenium, palladium, iridium, or platinum-tin catalysts however, only the most active rhodium and cobalt systems are industrially relevant. The development of hydroformylation catalysts in industry progressed through several steps. 

The hydroformylation of alkenes to give linear aldehydes constitutes the most important homogeneously catalyzed process in industry today [51]. The hydroformylation of propene is especially important for the production of n-bu-tyraldehyde, which is used as a starting material for the manufacture of butanol and 2-ethylhexanol. Catalysts based on cobalt and rhodium have been the most intensively studied for the hydroformylation of alkenes, because they are industrially important catalysts. While ruthenium complexes have also been reported to be active catalysts, ruthenium offers few advantages over cobalt or... 

As early as 1938, Roelen discovered the cobalt-catalyzed hydroformylation of olefins, then known as the oxo reaction, which allowed the synthesis of aldehydes by addition of carbon monoxide and hydrogen to alkenes. Not long after this discovery it was found that cobalt, rhodium, ruthenium and platinum are also suitable as catalysts. However, because of the considerable price advantage for large scale applications in industry, cobalt catalysts are mostly used. Rhodium complexes, however, are... 

A number of metals catalyze the hydroformylation reaction, of which rhodium is by far the most active, Rh >> Co > Ir, Ru > Os > Pt. Platinum and ruthenium are mainly of academic interest, although L2PtCl(SnCl3) complexes with chiral ligands find use in asymmetric alkene hydroformylations.59 In most cases, and certainly in industrial processes, cobalt has now been replaced by rhodium. 

Hydroformylation can also be achieved using ruthenium complexes such as Ru(CO)3(PPh3)2, by platinum-tin catalysts,59 and by PtH(Ph2POH)(PPh3) made from Pt(COD)2, PPh3, and Ph2POH. The latter system yields ketones when under high ethylene pressure. Ketone formation can also be observed in other systems and occurs by the reaction sequence ... 

Ruthenium-catalyzed hydroformylation of alkenes was also studied using charged tags [84]. A unique permanently-charged version of a self-assembling bidentate ligand (Fig. 15) was synthesized to study the catalytic mechanism. 

Metal enolates have played a Umited role in the metal-catalyzed isomerization of al-kenes . As illustrated in a comprehensive review by Bouwman and coworkers, ruthenium complex Ru(acac)3 (51) has been used to isomerize a wide range of substituted double bonds, including aUylic alcohols (131), to the corresponding ketones (132) (equation 38) . The isomerization of aUylic alcohols affords products that have useful applications in natural product synthesis and in bulk chemical processes. An elegant review by Fogg and dos Santos shows how these complexes can be used in tandem catalysis, where an alkene is subjected to an initial isomerization followed by a hydroformylation reaction ... 

In addition to hydroformylation, metal catalysed hydrogenation processes have been studied at length including hydrogenation of a-olefins, aromatics and asymmetric hydrogenations of more complex substrates. Benzene can be selectively fully hydrogenated by using a ruthenium cluster catalyst in [Bmim][BF4]. ... 

One of the most significant processes that involve CO in organic industrial chemistry is the hydroformylation of alkene, or the 0x0 process, in which rhodium and cobalt complex catalysts are used. Ruthenium is a strong candidate for replacing the very expensive rhodium catalyst. Further, ruthenium complexes are excellent catalysts for the addition of formyl groups of aldehydes, formates and formamides to alkenes. 

The hydroformylation reaction or 0x0 process is an important industrial synthetic tool. Starting from an alkene and using syngas, aldehydes with one or more carbon atoms are obtained. In almost all industrial processes for the hydroformylation of alkenes, rhodium or cobalt complexes are used as catalysts [33]. A number of studies on ruthenium complex-catalyzed hydroformylation have been reported [34]. One of the reasons for the extensive studies on ruthenium complex catalysts is that, although the rhodium catalysts used in industry are highly active, they are very expensive, and hence the development of a less-expensive catalytic system is required. Since inexpensive ruthenium catalysts can achieve high selectivity for desired u-alde-hydes or n-alcohols, if the catalytic activity can be improved to be comparable with that of rhodium catalysts, it is possible that a ruthenium-catalyzed 0x0 process would be realized. 

The hydroformylation of alkenes using CO2 instead of CO is an attractive target reaction. Since ruthenium complexes are active catalysts for the reduction of CO2 to CO and also for hydroformylation, it is expected that the hydroformylation of an alkene with CO2 would be successful. Indeed, Sasaki and coworkers found that Ru4H4(CO)i2/LiCl catalyzed the hydroformylation of cyclohexene to give (hydroxymethyl) cyclohexane in 88% yield [141]. 

Although ruthenium is significantly less expensive than rhodium and although its use has been recommended since 1960 (7) for the oxo synthesis, complexes of this metal have not been developed as catalysts. However, many papers and patents have referred to the results obtained employing various ruthenium complexes. The purpose of this article is to analyze the work done involving ruthenium compounds, restricting the scope only to the hydroformylation reaction and not to the carbonylation reaction, which would demand to too lengthy an article. In this review we examine successively mononuclear ruthenium complexes, ruthenium clusters as precursors, photochemical activation, and supported catalysis. 

The same catalyst precursor, generated from [(EDTA)RuCI] which is also water soluble, was used for the hydroformylation of allylic alcohol under the same reaction conditions (//). At 50 bar and 130°C, in water as solvent, 4-hydroxybutanal was produced [Eq. (5)], together with about 2% of formaldehyde. However, the reaction proceeded further to give butane-1,4-diol by hydrogenation and y-butyrolactone as well as dihydrofuran by cyclization [Eq. (6)]. The same catalytic cycle as that proposed in Scheme 3 can be considered. A kinetic investigation revealed a first-order dependence on the ruthenium complex concentration and on the allyl alcohol... 

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