Ruthenium complex catalysts hydroformylation

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 ruthenium complex-catalyzed hydroformylation of 1-alkene was first examined by Wilkinson s group. Ru(CO)3(PPh3)2/phosphine catalysts were found to have moderate catalytic activity [35-37]. Ru3(CO)i2 [38] and anionic hydridocluster complexes such as [NEt4][Ru3H(CO)ii] [39] have also been shown to have catalytic activity. In molten phosphonium salt, Ru3(CO)i2/2,2 -bipyridine has high catalytic activity [40]. The Ru3(CO)i2/l,10-phenanthroline catalyst in N,N-dimethylacetamide (DMAC) shows excellent activity and selectivity for u-aldehydes (Eq. 11.10) [41]. 

Ru3(CO)i2 reacts with dppe in benzene solvent to provide Ru(CO)3(dppe) Sanchez-Delgado RA, Bradley JS, Wilkinson G (1976) Further smdies on the homogeneous hydroformylation of alkenes by use of ruthenium complex catalysts. J Chem Soc Dalton Trans 399-404... 

A highly regio- and enantio-selective hydroformylation of alkenes, such as PhCH= CH2, CH2=CHCH2CN, and CH2=CHOAc, catalysed by ruthenium complexes with (g) 2,5-disubstituted phospholane ligands has been reported. With (83) as the ligand, the turnover rates over 4000 h-1 at 80 °C, have been attained.108 (Acac)Rh(CO)2-TangPhos [Tangphos = (84)] has been developed as a new enantioselective catalyst for asymmetric hydroformylation of norbornene and other [2.2.1]-bicyclic alkenes (55-92% ee).109... 

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... 

Ruthenium is not an effective catalyst in many catalytic reactions however, it is becoming one of the most novel and promising metals with respect to organic synthesis. The recent discovery of C-H bond activation reactions [38] and alkene metathesis reactions [54] catalyzed by ruthenium complexes has had a significant impact on organic chemistry as well as other chemically related fields, such as natural product synthesis, polymer science, and material sciences. Similarly, carbonylation reactions catalyzed by ruthenium complexes have also been extensively developed. Compared with other transition-metal-catalyzed carbonylation reactions, ruthenium complexes are known to catalyze a few carbonylation reactions, such as hydroformylation or the reductive carbonylation of nitro compounds. In the last 10 years, a number of new carbonylation reactions have been discovered, as described in this chapter. We ex-... 

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 ... 

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 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... 

If cobalt, rhodium and ruthenium complexes are the most frequently used in hydroformylation reactions, most carbonylation reactions employ palladium catalysts. The active water-soluble complex Pd(TPPTS)3 is easily prepared by reducing in situ PdCl2/TPPTS with CO in water at room temperature. The carbonylation of alcohols and olefins (Scheme 1.24) requires the presence... 

Ru(CO)5 is less frequently used than Fe(CO)5 for organic synthesis or as a starting material as a zero-valent ruthenium complex because of its ease of decomposition to Ru4(CO),2 [99]. Dodecacarbonyltriruthenium is very useful for these purposes. It has been showm to be an active catalyst for the hydrogenation of olefins [100], carbonyla-tion of ethylene [101], hydroformylation of alkenes [102], water-gas shift reaction [103], and reduction of nitro groups [104], and recently, C—H bond activation [105] and coupling of diynes with CO [106]. 

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