2-Methyl-1,4-Benzodioxan Substituted Ag(I)-N-Heterocyclic Carbene Complexes and Ru(II)-N-Heterocyclic Carbene Complexes: Synthesis, Crystal Structure and Transfer Hydrogenation of Aromatic Ketones

Abstract

In this study a series of unsymmetrically silver(I)-N-heterocyclic carbene (NHC) and ruthenium(II)-NHC complexes were synthesised. The Ag(I)-NHC complexes (1a-f) were synthesized in dichloromethane at room temperature from the imidazolium salts and Ag2O. The Ru(II)-NHC complexes (2a-f) were prepared from Ag(I)-NHC complexes by using transmetallation method. All compounds were characterized by spectroscopic techniques (NMR and FT-IR) and elemental analyses. The catalytic activities of the Ru(II)-NHC complexes that were investigated in the transfer hydrogenation reactions showed excellent activity. Also, the 2a complex was characterized by single crystal X-ray crystallography. The Ru atom in the 2a complex, [RuCl2(η6-C10H14)(C19H20N2O2)] exhibit a pseudo-octahedral geometry, with the arene occupying three adjacent sites of the octahedron, two Cl atoms and one carbene group. The six-membered ring of the p-cymene is essentially planar [rms deviation=0.008 A].