Copper(II) complexes derived from substituted 2,2′-bis-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one) ligands:: Synthesis, structure and catalytic activity

New chiral N,N-bidentate 2,2-bis-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5.-one) ligands have been prepared and characterised by their H-1 and C-13 NMR spectra and/or optical rotation. The ligands prepared were then tested for their ability to form complexes with copper(II) salts. It was found that the most stable complex is formed from the 2, 2'-bis-(4-isopropyl-1,4-dimethyl-4,5-dihydro-1H-imidazol-5-one) ligand and copper(II) chloride. The structure of this complex was determined by means of quantum-chemical computations at the B3LYP or UB3LYP/6-31G(d,p) level. According to the computations, the geometry of the copper atom most resembles a tetrahedral arrangement, which was also confirmed by means of X-ray structural analysis. It was found that the structure of this copper(II) complex does not allow the copper atom to coordinate to additional ligands; therefore, it is catalytically inactive in the asymmetric Henry reaction. (C) 2007 Elsevier Ltd. All rights reserved.