Arylation of aldehydes catalyzed by fluorinated NHC–Rh(i) complexes

Abstract

The synthesis and characterization of twelve Rh(I) complexes with fluorinated NHC ligands are described. Seven molecular structures of these complexes were unequivocally elucidated by single crystal X-ray diffraction techniques. In all cases the metal center showed a distorted square planar geometry; including a chloride, a 1,5-cyclooctadiene and an NHC ligand coordinated to the Rh(I) center. Furthermore, the catalytic activity of the series of complexes was explored in the arylation of aldehydes, finding that the catalytic activity of the complexes is related to the number of fluorine atoms present on their structures, showing that as more fluorine atoms are found in the NHC ligand, the complexes become more active. This observation can be correlated with the fact that increasing the number of fluorine atoms in the NHC makes it a less electron-donating ligand, thus favoring the arylation of aldehydes.