Hydroformylation of higher olefin in halogen-free ionic liquids catalyzed by water-soluble rhodium–phosphine complexes Original Research Article

The biphasic hydroformylation of higher olefins was performed efficiently in the halogen-free ionic liquids 1-n-alkyl-3-methylimidazolium p-toluenesulfonate ([Rmim][p-CH3C6H4SO3]) using Rh-TPPTS [TPPTS: trisodium salt of tri(m-sulphonylphenyl)phosphine] complexes as catalyst. The catalytic system offers high activity and chemoselectivity for aldehyde with a good retention of the catalyst in ionic liquid phase. The ionic liquid containing catalyst can be easily separated and reused several times without a significant decrease in the activity and selectivity. The results indicated that the cation and anion of ionic liquids strongly influenced the reaction rate. Furthermore, the reaction rate was markedly accelerated when the chain-length of alkyl in ionic liquids was comparable with that of olefin. A “matching effect” between the chain-length of alkyl in ionic liquids and that of olefins was firstly reported.