Coupling of benzyl halides with aryl Grignard reagents catalyzed by iron(III) amine-bis(phenolate) complexes

• A tridentate amine-bis(phenol) ligand containing bulky tert-pentyl groups is prepared.
• New five-coordinate iron(III) complexes are synthesized in high yield.
• Fe-catalyzed C–C cross-coupling of Grignard reagents and alkyl halides is studied.

Reaction of benzylamino-N,N-bis(2-methylene-4,6-di-tert-amylphenol), H2L1, with anhydrous ferric chloride in the presence of a base yields FeCl(THF)L1 (1). In the solid state, complex 1 exists as a monomeric iron(III) species with a distorted trigonal bipyramidal geometry. Complex 1 is an air-stable, non-hygroscopic, single-component catalyst for C–C cross-coupling of aryl Grignard reagents with benzyl halides, including chlorides. Moderate to good yields of cross-coupled products can be obtained in diethyl ether at room temperature. Preliminary investigations include the screening of electron-donating and electron-withdrawing groups on both the benzylic substrate and the aryl Grignard reagent.

The synthesis of iron(III) complexes of tert-pentyl functionalized amine-bis(phenolate) ligands, and their application for C–C cross-coupling of Grignard reagents with benzyl halides is described.Figure optionsDownload as PowerPoint slide