A series of iron(III)-containing imidazolium salts of the general formula [DRim][FeX 4 ] (R=2,6-diisopropylphenyl, IPr, X=Cl, 1; R=IPr, X=Br, 2; R=tertbutyl, t Bu, X=Cl, 3; R=isopropyl, i Pr, X=Cl, 4; R=benzyl, Bn, X=Cl, 5; R=Bn, X=Br, 6) have been prepared in high yields via reactions of anhydrous ferric halides with equivalent of the corresponding N,N-dihydro- carby-limidazolium halides, where 2-6 are novel ones. All of the complexes were characterized by elemental analysis, Raman spectroscopy, electrospray ionization mass spectroscopy, and X-ray crystallography for 1 and 2. All of them were non-hygroscopic and air-stable, with four of them existing as solids (1-4) and two as liquids (5 and 6) at room temperature. A preliminary catalytic study on the coupling of 4-tolylmagnesium bromide with cyclohexyl bromide revealed that 1 and 3 possessed the highest activity. In comparison, 2, 4 and 5 exhibited moderate activity and the least active complex was 6.
A series of Fe(Ⅲ)-containing imidazolium-based ionic liquids containing ether substituents,including[C3OMim][FeCl4](1,[C3OMim]=1-(2-methoxyethyl)-3-methylimidazolium),[C3OiPim][FeCl4](2,[C3OiPim]=1-isopropyl-3-(2-methoxyethyl)imidazolium),[C3OBim][FeCl4](3,[C3OBim]=1-butyl-3-(2-methoxyethyl)imidazolium),[(C3O)2im][FeCl4](4,[(C3O)2im]=1,3-bis(2-methoxyethyl)imidazolium),[C3OMim][FeBr4](5)and[(C3O)2im][FeBr4](6),were prepared and characterized by elemental analysis,Raman spectroscopy and electrospray ionization mass spectrometry.The catalytic performances of 1–6 and related Fe(III)-based catalysts in the cross-coupling of aryl Grignard reagents with alkyl halides bearing-hydrogens were studied,revealing that mono(ether)functionality improves the catalytic activity and that bis(ether)functionality improves the reusability.After simply decanting the product contained in the ethereal layer,complex 4,which containing bis(ether)-functionalized imidazolium cation,could be successfully recycled seven times.
A novel phenol-linked bis(imidazolium) salt,H3LCl2(L = O-4-C(CH3)3-C6H2-2,6-di[CH2{C(NCHCHNAr)}]2, Ar = 2,6-diisopropylphenyl, 1), was designed and used to prepare an ionic iron(III) complex [H2L][Fe Cl4](2).Complex 2 was a highly efficient catalyst for aryl Grignard cross-coupling of alkyl chlorides bearing b-hydrogens.Furthermore, complex 2 was reusable and could be reused in at least eight times without significant loss in catalytic activity.
