Iron-based Phenol-bridged Imidazolium-containing Complexes: Synthesis, Characterization And Catalysis

A series of Phenol-bridged imidazolinium salts （1-3） have been prepared accordingto improving the method reported; A new Phenol-bridged imidazolinium salt4has beenprepared by introducing2,6-diisopropylphenylimidazole; These imidazolinium saltswere employed to construct a series of ionic iron（III） complexes （5-10） by reactions ofthemselves with anhudrous iron salts FeX₃（X=Cl, Br）, respectively; The studiesfocusing on the catalytic activity of these complexes for the cross-coupling reaction ofaryl Grignard reagents with alkyl halides bearing-H have been investigated; Threekinds of bisnuclear phenoxo-functionalized N-heterocyclic carbene iron（II） alkoxides（11-13） were synthesized; Preliminary studies show that these iron（II） complexes can beused as a single component catalyst for ring-opening polymerization of ε-caprolactoneand lactide.1. Reactions of4-（tert-butyl）-2,6-bis（chloromethyl）phenol with differentimidazoles afforded Phenol-bridged imidazolinium salts （1-3） in shorter time, all ofthem have been characterized by melting point, elemental analysis and1H NMR spectra.2. Reaction of4-（tert-butyl）-2,6-bis（chloromethyl）phenol with2,6-diisopropylphenylimidazole afforded a new Phenol-bridged imidazolinium salt4,this compound has been characterized by melting point, elemental analysis and1HNMR spectra.4haven’t been reported in literature.3. Reactions of Phenol-bridged imidazolinium salts with one equivalent ofanhydrous FeX₃（X=Cl, Br） afforded ionic iron（III） complexes5-10, all of them havebeen characterized by melting point, Raman spectra and elemental analysis. Thestructure of complex6has been determined by X-ray single crystal diffraction.4. It was found that complexes5-10could be used as efficient catalysts for thecross-coupling reaction of aryl Grignard reagents with alkyl halides bearing-H.Furthermore, the reusability of complex8together with the catalytic mechanism of this reaction have been primarily investigated.5. Reactions of NaFe（O^tBu）₃、NaO^tBu with Phenol-bridged imidazolinium saltsH₃L²Cl₂（2）, H₃L³Cl₂（3） and H₃L₄Cl₂（4） afforded three bisnuclearphenoxo-functionalized N-heterocyclic carbene iron（II） alkoxides （L₂FeO^tBu）₂（11）,（L³FeO^tBu）₂（12） and （L⁴FeO^tBu）₂（13）, respectively. The catalytic activity of iron（II）complexes11-13for ring-opening polymerization （ROP） of ε-caprolactone and lactidewas studied in turn, it was found that complexes11-13could be used assingle-component initiator for the ROP of ε-caprolactone and L-lactide.