Phosphines with 2-imidazolium and para-phenyl-2-imidazolium moieties - synthesis and application in two-phase catalysis

Deprotonation of 1-n-butyl-3-methyl-imidazolium chloride or hexafluorophosp hate with n-butyl lithium and subsequent reaction of the intermediate 2,3-d ihydro-imidazol-2-ylidene with diphenylchlorophosphine affords the 2-imidaz olium phosphines 3a or 3b. The phosphine 4 with a para-phenylene spacer bet ween the imidazolyl moiety and the phosphorus atom has been obtained by Kos ugi-Stille coupling between 2-tri-n-butyl-stannyl-1-methylimidazole and 4-f luoroiodobenzene followed by nucleophilic substitution of fluorine with PPh 2K. The X-ray structure of 4 (space group P1) has been determined. Selectiv e N-protonation or N-quaternization of 4 affords the corresponding imidazol ium phosphines 5a-5c. The ligands 3b and 5c have been tested in the biphasi c Rh-catalyzed hydroformylation of 1-octene employing the ionic liquid 1-bu tyl-3-methylimidazolium hexafluorophosphate as catalyst solvent. (C) 2001 E lsevier Science B.V. All rights reserved.