Structure and C-C cross-coupling reactivity of iron(III) complexes of halogenated amine-bis(phenolate) ligands

The preparation of tetradentate amine-bis(phenol) proligands with dichloro and difluoro substituted phenol groups and their reaction with FeX3 (X = Cl or Br) is described. The compounds, 2-pyridylamino-N,N-bis(2-methylene-4,6-dichlorophenol), H-2[L-1]; 2-pyridylamino-N, N-bis(2-methylene-4,6-difluorophenol), H-2[L-2]; dimethylaminoethylamino-N, N-bis(2-methylene-4,6-dichlorophenol), H-2[L-3]; 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4,6-dichlorophenol), H-2[L-4]; and methoxyethylamino-N, N-bis(2-methylene-4,6-dichlorophenol), H-2[L-5] were prepared in aqueous medium and obtained as white powders in good to excellent yield. Ten new iron(III) halide complexes supported by these tetradentate ligands are reported. Representative single crystal X-ray diffraction structures were obtained for H-2[L-1] and a water adduct of the iron(III) complex, aquachloro{2-pyridylamino-N, N-bis(2-methylene-4,6-dichlorophenolato)} iron(III), 2 center dot H2O. The structure of the proligand H-2[L-1] shows intramolecular hydrogen bonding. In the solid-state structure, the iron complex exhibits intermolecular hydrogen bonding between the water ligand and the phenolate oxygen of a neighbouring complex. The anhydrous complexes were studied for catalytic activity towards C-C cross-coupling of Grignard reagent nucleophiles with alkyl halide electrophiles. (C) 2010 Elsevier B.V. All rights reserved.