Linear-to-branched

Ru(1PP)2(00)2, at 2000 ppm mthenium and 1-hexene as substrate, gives only an 86% conversion and a 2.4 1 linear-to-branched aldehyde isomer ratio. At higher temperatures reduced conversions occur. High hydrogen partial pressures increase the reaction rate, but at the expense of increased hydrogenation to hexane. Excess triphenylphosphine improves the selectivity to linear aldehyde, but at the expense of a drastic decrease in rate. 

High conversion rates and high selectivity of linear to branch aldehyde. 

The 1-octene conversions averaged 50% at the current flow rate (residence time 30 minutes). We believe the scatter in the data is due to the drift in the pump flow rate, which alters the residence time, and not to a change in the catalyst itself. In all cases the linear to branch aldehyde selectivity was very high in the range of 5 1 linear to branch aldehyde. The reaction was ran under thermomorphic conditions for over 400 hours and we found that we maintained good conversion and good selectivity. 

Similarly, enolsilanes 44 and 45 are afforded when silyl-protected alcohols and alkynes are reacted with ruthenium catalyst 41 (Equation (27)).40 The linear to branched ratio typically ranged from 2-4 1, except when the alkyne terminus was substituted with a TMS group. These internal alkynes afforded only the branched products. 

There was a thermodynamic preference for the reaction to take place at the terminal alkene carbon, which favors the yield of linear aldehyde, but the TS to linear aldehyde path was higher than the TS for the branched aldehyde path. Regioselectivity was evaluated from the products relative stability, i.e. considering that the reaction is under thermodynamic rather than under kinetic control. The linear to branched ratio (l b) of 94 6 was in excellent agreement with the ratio 95 5 reported for PPh3 [25], However, this nice coincidence must be viewed cautiously because the model is simple, reaction paths were partially considered, so a subtle cancellation of errors may have been made. 

Subtle electronic effects were also observed for the Sasol ligands, as in the series X = CN, Ph, OBz, Me a decrease in the rate of reaction was found while the linearity followed the reverse trend the better donor gives the highest linear to branched ratio (4.9, very similar to the best Shell catalyst 170 °C, 85 bar). As the authors remarked, this is not an intrinsic ligand effect on the reaction it is a measure of the amount of phosphine-free catalyst 5 that is present in the equilibrium. Thus the weaker donor ligands give more 5 and thus a higher rate and a lower l b ratio. This was supported by IR and NMR measurements. 

I isom = selectivity for 2-octene. lib = linear to branched ratio of... 

The selectivity to the linear product nonanal vas strongly dependent on the CO pressure (see Table 6.4). The linear to branched ratio drops from 29 at Pco = 5 bar to 4 at Pco = 40 bar. Part of this selectivity change can be ascribed to enhanced isomerization at lower CO pressure, but faster P-hydride elimination cannot account completely for the increased formation of the branched aldehyde. The reduced selectivity was attributed to partial ligand dissociation resulting in less selective rhodium monophosphites and/or ligand-free complexes. 

The discovery and use of fluorophosphites and chlorophosphites as trivalent phosphorus ligands in the rhodium catalyzed, low-pressure hydroformylation reaction are described. The hydroformylation reaction with halophosphite ligands has been demonstrated with terminal and internal olefins. For the hydroformylation of propylene, the linear to branched ratio of the butyraldehyde product shows a strong dependency on the ligand to rhodium molar ratios, the reaction temperature, and the carbon monoxide partial pressure. 

The molar ratio of the phosphorus ligand to rhodium has pronounced effects on catalyst activity and selectivity. It is well established that increasing the molar ratio of the ligand to the rhodium leads to a higher linear to branched isomer ratio at the... 

Regioselectivity linear to branched, determined by GC analysis and or H NMR spectroscopy. 

For the hydroformylation, (PPli j) Rli( H)(CO) with host 11 was used as the catalyst. An excess of PPhj (stemming from the catalyst precursor) was needed to avoid isomerization, as was found when phosphine-free precursors were used (at the concentrations used even bidentates should be added in excess to prevent substantial exchange with carbon monoxide). Linear to branched ratios of 2 1 were obtained and no isomerized alkene could be detected. These results are similar to those obtained by Kalck and coworkers [41]. As expected, catalysis for 11 is slower than that for (PPh3)3Rh(H)(CO) as the host is a bidentate phosphine catalysis with (PPh3)3Rh (H)(CO) strongly depends on the concentrations of rhodium and PPh3 and comparison of the rates of the two systems does not make sense. 

The first-generation catalyst, a cobalt carbonyl ligand, was employed in the BASF process. In the next generation, phosphine species were added to milden the reaction conditions and to optimize the linear to branched ratio. In the third... 

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