Triazine-Based Polyfluorinated Triquaternary Liquid Salts:  Synthesis, Characterization, and Application as Solvents in Rhodium(I)-Catalyzed Hydroformylation of 1-Octene

Silylation of N -(2-hydroxyethyl)imidazole, HOCH 2 CH 2 Im ( 1 ), with hexamethyldisilazane gave N -(2-trimethylsilyloxyethyl)imidazole, Me 3 SiOCH 2 CH 2 Im ( 2 ), which underwent quaternization reactions with the alkyl halides and gave three new N -(trimethylsilyloxyethyl) imidazolium halides, Me 3 SiOCH 2 CH 2 Im + RX -, where Im + = imidazolium and R/X = Me/I ( 3 ), CH 2 CH 2 F/Br ( 4 ), and CH 2 CH 2 CF 3 /I ( 5) . The ethyl ether, 6, formed from 1 and ethyl bromide was quaternized with CF 3 CH 2 CH 2 I to obtain 7, followed by anion exchange with LiN(SO 2 CF 3 ) 2 to obtain 8 . The metathesis reactions of 3 − 5 with cyanuric fluoride in acetonitrile at 25 °C gave tris[2-( N ‘-alkylimidazolium)ethoxy] triazine trihalides, N 3 C 3 (OCH 2 CH 2 Im + RX - ) 3, where R/X = Me/I ( 9 ), CH 2 CH 2 F/Br ( 10 ), and CH 2 CH 2 CF 3 /I ( 11 ). Two neutral trimeric compounds, N 3 C 3 (OCH 2 CH 2 Im) 3 ( 12 ) and N 3 C 3 (OCH 2 CH 2 NMe 2 ) 3 ( 14 ), were prepared from reactions of cyanuric fluoride and Me 3 SiOCH 2 CH 2 NMe 2 ( 13 ), or 2, respectively. The quaternization of 12 with MeI gave tris[oxoethyl(trimethyl)ammonium]triazine, N 3 C 3 (OCH 2 CH 2 N + Me 3 I - ) 3 ( 14 ). Subsequent exchange of the halides in 9 − 11 and 15 with the weakly coordinating anions of AgOSO 2 CF 3, LiN(SO 2 CF 3 ) 2, AgNO 3, or AgClO 4 resulted in new triquaternary salts, 16 − 23, that were characterized by NMR, elemental analyses, and, for some of the compounds, mass spectroscopy. Physical (melting point and density) and thermal properties of 9 − 23 determined with a differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA) are reported. In Rh(I)-catalyzed hydroformylation of 1-octene, with Ph 2 P(NMPBTA) ( 26 ) [NMPBTA = N -methylpyridinium bis(trifluoromethanesulfonyl)amide] as ligand, the turnover frequency (TOF), conversion, isomer selectivity (n/i), and recyclability were compared when triquaternary salts 17 and 20 or monoquaternary 8 were used as solvents in the biphasic hydroformylation process. A change of 26 /Rh(I) ratio from 4 to 20 resulted in a significant increase of n/i selectivity with 17 or 20, but was marginal with 8 as solvent.