Diphosphines rhodium hydroformylation

Diphosphines have also become very popular ligands since the late eighties in rhodium hydroformylation, e.g. Eastman s BISBI. The two-phase system underwent considerable improvements involving diphosphines [9],... 

Electronic effects. To study the nature of the electronic effect in the rhodium diphosphine catalysed hydroformylation, a series of thixantphos 18 ligands with varying basicity was synthesized 25-30 (Figure 8.11). In this series of ligands, steric differences are minimal so purely electronic effects could be investigated. 

A. L. (2000) Origin of the bite angle effect on rhodium diphosphine catalyzed hydroformylation. Organometallics, 19, 872-883. 

Modified Rh systems show considerable activity in the hydroformylation of styrene to the branched aldehydes. Chiral diphosphine rhodium complexes that lead to high activity and high regioselectivity in branched aldehyde have been studied. These systems do not provide high enantioselectivity [2, 3]. Stanley reported that a tetraphosphine hgand can be used to form a bimetallic complex [8] and provide ee s up to 85% using vinyl esters. 

Carbo JJ, Maseras F, Bo C, van Leeuwen WNM (2001) Unraveling the origin of regioselectivity in rhodium diphosphine catalyze hydroformylation. A DFT QM/MM study. J Am Chem Soc 123 7630-7637... 

Cobalt carbonyls are the oldest catalysts for hydroformylation and they have been used in industry for many years. They are used either as unmodified carbonyls, or modified with alkylphosphines (Shell process). For propene hydroformylation, they have been replaced by rhodium (Union Carbide, Mitsubishi, Ruhrchemie-Rhone Poulenc). For higher alkenes, cobalt is still the catalyst of choice. Internal alkenes can be used as the substrate as cobalt has a propensity for causing isomerization under a pressure of CO and high preference for the formation of linear aldehydes. Recently a new process was introduced for the hydroformylation of ethene oxide using a cobalt catalyst modified with a diphosphine. In the following we will focus on relevant complexes that have been identified and recently reported reactions of interest. 

The hydroformylation of styrene using rhodium systems containing the four structurally related diphosphines dppe, dppp, (86), and (87) has been studied. A systematic analysis of the effect of the pressure, temperature, and the ligand metal molar ratio shows that the five- and six-membered ring chelating diphosphines behave differently from one another.347 An analysis of the effect of pressure, temperature, and ligand metal molar ratio on the selectivity of styrene hydroformylation catalyzed... 

It is interesting to note that using the sol-gel procedure (I) the pre-formation of the rhodium diphosphine complex suppressed the formation of ligand free rhodium-cations on the silica surface. This approach gave rise to a well-defined, very selective hydroformylation catalyst. All immobilised catalysts were 10 to 40 times slower than the homogeneous catalyst under the same conditions, the sol-gel procedure yielding the fastest catalyst of this series. 

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