Rhodium Hydroformylation Catalysts with Bidentate Ligands

6 Rhodium Hydroformylation Catalysts with Bidentate Ligands 

---

Even higher linearities are characteristic of modified rhodium catalysts. The effect is most pronounced when hydroformylation is carried out in molten triphe-nylphosphine,41 resulting in linearities as high as 9. The active catalytic species with two phosphine ligands (6) ensures the increased selectivity through steric effects. Platinum complexes with bidentate ligands exhibit the highest linearity to form linear aldehydes with 99% selectivity.27... 

The results of unsymmetrical 7r-acid bidentate ligands, e.g., (81), have in the hydroformylation of ra-octenes was described. The preparation of seven such ligands was described. Thus, [Rh-(acac)(cod)]-catalyzed hydroformylation of ra-octene in the presence of a phosphinite ligand gave 94% ra-nonanal.295 A new upper-rim phosphacalix[4]arene 5,17-bis(diphenylphosphinomethyl)-25,26,27,28-tetrapropoxycalix[4]arene has been prepared. It reacted with [(cod)RhCl]2 to give a dirhodium complex that is an active catalyst for the hydroformylation of 1-octene and styrene.296 Rhodium complexes of [l-propyl-3-methylimidazolium+]2 [PhP(C6H4SO%)2] dissolved in the... 

Soon after the initial discovery of the hydroformylation activity of RhH(CO)(PPh3)3 it was found that ligands have a profound influence on the activity and selectivity of the rhodium catalysts. The majority of the numerous published patents and publications are concerned with the effect of ligands and it is therefore impossible to review this matter here. Instead we have made a choice that includes a study of the electronic and steric effects of phosphines and phosphites and a few examples of bidentate ligands. A few trends will be briefly summarized. 

Bidentate ligands were used by Alper and coworkers. The bis(diphenylphospino-methyl)amine ligands were prepared on primary amine-terminated PAMAM dendrons on silica as well as polyamido dendrons on polystyrene via the double Mannich-like reaction with formaldehyde and diphenylphosphine (Scheme 15.36a). " Subsequently, Alper and coworkers subjected the dendronized ligand-decorated supports to complexation with rhodium and palladium precursors in order to prepare active catalysts for a number of important chemical transformations (Scheme 15.36b). Initially, the dendronized rhodium catalysts were tested in the hydroformylation reaction and carbonylative ring expansion of... 

---