Preparation, Hydrogen Bonds, and Catalytic Activity in Metal-Promoted Addition of Arylboronic Acids to Enones of a Rhodium Complex Containing an NHC Ligand with an Alcohol Function

The complex RhCl­(COD)­{3-benzyl-1-(2-hydroxy-2-phenylethyl)­imidazol-2-ylidene}
has been prepared by reaction of the dimer [Rh­(μ-OMe)­(COD)]2 with 3-benzyl-1-(2-hydroxy-2-phenylethyl)­imidazolium chloride
and characterized by X-ray diffraction analysis. The structure reveals
that 75% of the molecules are associated through intermolecular O–H···Cl
hydrogen bonds between the OH group of the NHC substituent of one
molecule and the chloride ligand of the adjacent molecule. This complex
catalyzes the addition of arylboronic acids to cyclic and acyclic
enones in anhydrous toluene. The alcohol function of the substituent
of the NHC ligand plays the role assigned to water in previous cases.