title: Aqueous-phase hydroformylation of 1-octene using hydrophilic sulfonate salicylaldimine dendrimers.
abstract: Water-soluble dendritic ligands based on tris-2-(5-sulfonato salicylaldimine ethyl)amine (5) and DAB-(5-sulfonato salicylaldimine) (6) (DAB = diaminobutane) were synthesized by means of Schiff base condensation and sulfonation reactions. These dendritic ligands were fully characterized by (1)H NMR, (13)C NMR and FT-IR spectroscopy, elemental analysis and mass spectrometry. Dendritic ligands (5 and 6) in combination with [RhCl(COD)](2) (COD = 1,5-cyclooctadiene) were evaluated in aqueous biphasic hydroformylation of 1-octene. New water-soluble mononuclear 5-sulfonato propylsalicylaldimine Rh(i) complexes (7 and 8) were synthesized and characterized using (1)H NMR, (13)C NMR and FT-IR spectroscopy, elemental analysis as well as mass spectrometry. These complexes were applied as catalyst precursors in aqueous biphasic hydroformylation reactions. All the catalyst precursors were active in the hydroformylation of 1-octene under the investigated conditions. Optimal conditions were realized at 75 °C (40 bars), where the best selectivity for aldehydes was noticed. Catalyst recycling was achieved up to 5 times with minimal loss in conversion and consistent chemoselectivities and regioselectivities. Less Rh leaching was observed in the dendritic systems (5 and 6)/[RhCl(COD)](2) as compared to mononuclear catalyst precursors (7 and 8) as determined by inductively coupled plasma-mass spectrometry (ICP-MS).
authors.affiliation: Department of Chemistry, University of Cape Town, South Africa.
authors.forename: Emma B
authors.initials: EB
authors.lastname: Hager
authors.forename: Banothile C E
authors.initials: BC
authors.lastname: Makhubela
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Smith
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D050091:Dendrimers / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry; D012459:Salicylates / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000447:Aldehydes; D000475:Alkenes; D050091:Dendrimers; D009942:Organometallic Compounds; D012459:Salicylates; D014867:Water; D012238:Rhodium; C037690:1-octene