Rhodium-sulfoxantphos complex

The first fixed-bed application of a supported ionic liquid-phase catalyst was hydroformylation of propylene, with the reactants concentrated in the gas phase (265). The catalyst was a rhodium-sulfoxantphos complex in two ionic liquids on a silica support. The supported ionic liquid phase catalysts were conveniently prepared by impregnation of a silica gel with Rh(acac)(CO) and ligands in a mixture of methanol and ionic liquids, [BMIMJPFg and [BMIM][h-C8Hi70S03], under an argon atmosphere. 

These diphosphine ligands are often suitable or can be modified for use in biphasic systems. Sulfonation of xantphos led to a suitable water-soluble ligand [2,7-bis(S03Na)-xantphos], which was employed for hydroformylation of propylene, 1-hexene, and 4-styrene sulfonate. " HP-NMR confirmed that the diphosphine adopted the desired ee configuration. A rhodium-sulfoxantphos complex was employed for hydroformylation of 1-octene in [bmim]PF6, where bmim= l-butyl-3-methyl-imidazolium. " High pressure studies showed that the ee-ea ratio was sensitive to temperature and syngas pressure variations, but not to hydrogen partial pressure. 

A heterogenized version of homogeneous ionic-liquid catalyst system in which the catalyst remains active, highly selective, and stable over extended periods in a continuous gas-phase hydroformylation process was described. Thus, using a rhodium-sulfoxantphos complex in [bmim][n-C8Hi70S03] on a partly dehydrogenated silica support gave a >20 normal/iso butyraldehyde ratio, TON = 2600, TOP = 44h over at least 60 h [88]. 

IR spectroscopy has proved that SILP catalysts have metalorganic complexes dissolved in the liquid layer, which then worked as a homogeneous catalyst Riisager et al. [12] have made spectroscopic measurements of a rhodirun-sulfoxantphos complex which was immobilized in an SILP system. This SILP catalyst was tested in the continuous-flow fixed-bed hydroformylation of propene. Spectroscopy of the SILP system was performed in situ under conditions closely related to the reaction conditions, that is, imder various gas atmospheres and at 100 °C. The result was that the Rh-sulfoxantphos complex of the SILP catalyst behaved similar to an analogous rhodium-xanthene catalyst dissolved in the homogeneous phase. Analysis of the CO stretching band showed that the catalyst was in equilibrium between a dimeric form and two monomeric forms (Scheme 8.3) and, consequently, that the hydroformylation reactions were indeed homogeneously catalyzed. 

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