Bis(Phenol)-functionalized Imidazole/Imidazoline Cations-based Ionic Iron(Ⅲ) Complexes As Efficiently Recyclable Catalysts For Coupling Of Aryl Grignard Reagents With Alkyl Halides

1. Bis(phenol)-functionalized benzimidazolium salt1has been synthesized by two-step reactions of2-chloromethyl-4,6-di-ter?-butylphenol with benzimidazole. Analogous imidazolium salt2has been synthesized by the reaction of catechol, tert-butanol, oxalic aldehyde and paraformaldehyde. Bis(phenol)-functionalized imidazolinium salt3has been synthesized by the reaction of catechol, tert-butanol, ethylene diamine and triethyl orthoformate. All of them have been characterized by melting point, elemental analysis and1H NMR spectra. Among them,1and2have not been reported in literatures.2. Reactions of1-3with one equivalent of anhydrous FeX3(X=Cl, Br) or FeCl3-6H2O afforded the cooresponding ionic iron(Ⅲ) complexes4-9, respectively. Complex6is the first example of imidazolinlium cation-based iron(Ⅲ) complex. All of them have been characterized by Raman spectra, melting point and elemental analysis. The structures of complexes4and6have been determined by X-ray single crystal diffraction.3. It was found that complexes4-9could be used as efficient catalysts for the cross-coupling reaction of aryl Grignard reagents with alkyl halides bearing β-H, especially the alkyl chlorides-mediated couplings. Furthermore, the reusability of some complexes together with the catalytic mechanism have been primarily investigated.4. The iron(Ⅲ) chloride10has been prepared by the reaction of FeCl3with in situ generated carbine derived from3. The synthesis of iron(Ⅲ) aryloxides of NHCs (11and12) have been attempted using10as starting malterials. The reaction of3with FeCl2and excess NEt3afforded a iron(Ⅱ) carbene complex13. Among them, complexes10,12and13have been characterized by elemental analysis. A novel ionic iron(Ⅱ) complex [NEt3]2[FeCl4] was isolated from the reaction of3with FeCl2in the presence of excess of NEt3, which had been characterized by X-ray single crystal diffraction. 5. It was found that complex10could be used as efficient catalysts for the cross-coupling reaction of4-tolylmagnesium bromide with chlorocyclohexane. The catalytic activity of complex10was higher than that of complex6in the same experimental condition.