Ionic Phosphine Ligands with Cobaltocenium Backbone:
Novel Ligands for the Highly Selective, Biphasic,
Rhodium-Catalyzed Hydroformylation of 1-Octene in
Ionic Liquids†
posted on 2000-08-15, 00:00authored byClaudia C. Brasse, Ulli Englert, Albrecht Salzer, Horst Waffenschmidt, Peter Wasserscheid
The use of electron-poor phosphine-substituted cobaltocenium salts as ligands for the
biphasic hydroformylation in ionic liquids has been investigated. Using improved oxidation
methods, 1,1‘-bis(diphenylphosphino)cobaltocenium nitrate, 1,1‘-bis(diphenylphosphino)cobaltocenium hexafluorophosphate, and 1,1‘-bis[1-methyl(1-diphenylphosphino)ethyl]cobaltocenium hexafluorophosphate have been synthesized. 1,1‘-Bis(diphenylphosphinocobaltocenium hexafluorophosphate in particular proved to be a very suitable ligand for the
biphasic hydroformylation of 1-octene in 1-butyl-3-methylimidazolium hexafluorophosphate
(BMIM PF6), enabling high catalyst activity, high selectivity to the n-product, and no
detectable catalyst leaching. In contrast to aqueous biphasic systems, the ionic liquid BMIM
PF6 provides for the rhodium catalyst a low-coordinating medium with limited but sufficient
solubility for 1-octene to allow high reaction rates.