Rhodium hydroformylation using

The reaction with dihydrogen could not be tracked down in this study. Iridium forms much more stable complexes than rhodium and therefore it has been studied to obtain more details about the complexes and the mechanism of rhodium hydroformylation. Using an iridium complex, Eisenberg and Deutsch [34] succeeded in the identification by NMR of all species involved in the catalytic cycle the ethyl complex (i) (Fig. 6.8) the propionyl complex (j) (including X-ray structure determination), and, moreover, the dihydride adduct (k). The latter... 

There are currentiy no commercial producers of C-19 dicarboxyhc acids. During the 1970s BASF and Union Camp Corporation offered developmental products, but they were never commercialized (78). The Northern Regional Research Laboratory (NRRL) carried out extensive studies on preparing C-19 dicarboxyhc acids via hydroformylation using both cobalt catalyst and rhodium complexes as catalysts (78). In addition, the NRRL developed a simplified method to prepare 9-(10)-carboxystearic acid in high yields using a palladium catalyst (79). 

A method has been developed for the continuous removal and reuse of a homogeneous rhodium hydroformylation catalyst. This is done using solvent mixtures that become miscible at reaction temperature and phase separate at lower temperatures. Such behavior is referred to as thermomorphic, and it can be used separate the expensive rhodium catalysts from the aldehydes before they are distilled. In this process, the reaction mixture phase separates into an organic phase that contains the aldehyde product and an aqueous phase that contains the rhodium catalyst. The organic phase is separated and sent to purification, and the aqueous rhodium catalyst phase is simply recycled. 

A phosphite degradation reaction that occurs during hydroformylation using an aryl-phosphite-modified rhodium catalyst involves replacement of one of the aryl groups with an alkyl group corresponding to the alkyl group of the hydroformylation prod-uct[.[27] This is illustrated in Equation 2.7... 

Figure 3.9. Sol-gel processed rhodium complexes using various procedures. These catalysts gave different results in the hydroformylation...

Rhodium Catalysed Hydroformylation Using Supported Ionic Liquid Phase SILP) Catalysis... 

In rhodium hydroformylations, highly efficient separation and recovery of catalyst becomes imperative, because of the very expensive nature of the catalyst. Any loss, by trace contamination of product, leakage, or otherwise, of an amount of rhodium equivalent to 1-2 parts per million (ppm) of aldehyde product, would be economically severe. The criticalness of this feature has contributed to some pessimism regarding the use of rhodium in large hydroformylation plants (63). However, recent successful commercialization of rhodium-catalyzed processes has proved that with relatively simple process schemes losses are not a significant economic factor (103, 104). 

Table 8.6. Hydroformylation using rhodium bulky diphosphite catalysts3...

For instance, catalysis in liquid/liquid two phases is generally referred to as biphasic catalysis and has widened the practical scope of homogeneous catalysis the catalyst is present in one liquid phase, while reactants and products are present in the other liquid phase. Thus, the catalyst can be separated by simple phase separation. Celanese is operating a 300 000 t/a plant for propylene hydroformylation using a water-soluble rhodium phosphine complex in a biphasic mode of operation at the Ruhrchemie site in Oberhausen [142],... 

The 2D property can be used to increase filtering efficiently [62]. We have filtered FTIR data from the homogeneous catalyzed rhodium hydroformylation of alkenes using a variety of ID and 2D filters. On blocks of 100-1000 spectra, the ID filters i. e. SG, fft, cubic spline, can reduce noise by ca. 10-50%, but the 2D filters, i. e. 2D fft, can reduce the noise level even further, to ca. 85 %+ [63]. The procedure for each block of spectroscopic data can be viewed as Eq. (7)... 

The automatic procedure for reference spectra generation was first demonstrated for the start-up of a homogeneous catalyzed rhodium hydroformylation of cyclo-octene using Rh4(CO)i2 as precursor, n-hexane as solvent and FTIR as the in situ spectroscopy at 298 K [63]. The first n spectra were (i) empty spectrometer compartment (background), (ii) n-hexane at 0.2 MPa in a high pressure thermostatically controlled cell fitted with Cap2 windows (iii) system equilibrated with 2.0 MPa CO, (iv) system upon addition of cyclo-octene, and (v) system upon addition of Rh4(CO)i2. The n=l reference spectrum, which contained atmospheric... 

Table 6.2 Hydroformylation using rhodium bulky monophosphite catalysts. ...

Figure 6 Union Carbide chiral bis-phosphite-rhodium complexes used as catalysts for the asymmetric hydroformylation.

The potential of QUINAPHOS ligands for asymmetric catalysis was assessed in rhodium-catalyzed enantioselective hydroformylation using styrene as a benchmark substrate (Table 2.1.5.2). The catalysts were prepared in situ from [(acac)Rh(CO)2] and 4 equiv of the diastereomeric mixture or the single diaste-... 

Optical yields up to 17% and 25%, respectively, have been reached in the styrene hydroformylation in the presence of cobalt or rhodium catalysts using N-alkylsalicylaldimine or phosphines as asymmetric ligands. Furthermore the hydroformylation of aliphatic and internal olefins have been achieved using rhodium catalysts in the presence of optically active phosphines. With the same catalysts, cis-butene surprisingly undergoes asymmetric hydroformulation with optical yields up to 27%. On the basis of the results obtained for cis-butene and the asymmetric induction phenomena in dichlor(olefin)(amine)platinum( 11) com-... 

To obtain information about the steps in which the asymmetric induction actually takes place, 1-butene, cis-butene, and trans-butene were hydroformylated using asymmetric rhodium catalyst. According to the Wilkinson mechanism, all three olefins yield a common intermediate, the sec-butyl-rhodium complex, which, if the asymmetric ligand contains one asymmetric center, must exist in the two diastereomeric forms, IX(S) and IX(R),... 

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

Considering isomeric and stereoisomeric composition of the products obtained in the asymmetric hydrocarbalkoxylation investigated using the palladium-(-)DIOP catalytic system, some interesting regularities are apparent. This is also true of the rhodium-(-)DIOP-catalyzed hydroformylation using the same substrates (13). 

The most detailed published study on the kinetics of the hydroformylation using triphenylphosphine containing rhodium catalysts is by Cavalieri d Oro et al. [27]. As the overall kinetic equation they found ... 

Figure 22-7 Simplified catalytic cycle for hydroformylation using rhodium complexes. Note that the configurations of complexes are not known with certainty and that five-coordinate species are fluxional. Rhodium can be added as Rh(acac)(CO)(PPh3), HRh(CO)(PPh3)3, or similar complexes. The solvent in QH4 or CHjCH=CH2 hydroformylation is the aldehyde trimer which is in equilibrium with aldehyde.

The regioselectivity in the hydroformylation of monohydroxyben-zenes was the same for the host catalyst and a triphenylphosphine complex of rhodium (with a molar product ratio linear branched = 2 1) (35). No isomerization was observed. Rates of the conversion of monohydrox-ybenzenes when host-guest catalysis is employed are lower than when a triphenylphosphine complex of rhodium is used. In contrast, dihydroxy substrates, which are more strongly boimd to the host, react at higher rates, with an initial increase by a factor of 4 relative to catalysis by the bare rhodium complex. Dihydroxybenzenes also gave the selectivities to linear products (linear branched molar product ratio > 20 1, see below). At 30% conversion, product inhibition took place. 

The supramolecular binding motifs described here were also used to attach catalysts to solid (silica) supports (128). The active metal complex could be switched from palladium to rhodium by using a polar solvent that breaks up the binding of the supramolecular motif. Allylic alkylation and hydroformylation catalysis could be carried out by using the same support "receptor" material and different "guest" ligands for the two metals a... 

Another similarity between HCo(CO)4 and HRh(CO)4 is that they are only stable under certain reaction conditions. Unlike HCo(CO)4, HRh(CO)4 does not usually precipitate out as metallic rhodium, but rather forms stable rhodium carbonyl clusters such as Rli4(CO)i2 and Rh6(CO)i6- Indeed, just as Co2(CO)g is a common catalyst precursor for cobalt hydroformylation, Rh4(CO)i2 is often used as a starting species for rhodium hydroformylation. 

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