{(COD)Ru[RN=C(H)-C(H)=C(Ph)]2} (R=Me, Et): The first structurally characterized mononuclear ruthenium complexes with enyl-imino ligands and their relevance in ruthenium catalyzed C-H activation reactions

The reaction of alpha,beta-unsaturated imines with [(1,5-cyclooctadiene)-bis(2-methylallyl)-ruthenium(II)] leads to the formation of mononuclear ruthenium complexes of the general formula {(COD)Ru[RN=C (H)-C(H)=C(Ph)](2)}. In these complexes the imine ligands are deprotonated in beta-position with respect to the imine double bond and coordinate as an enyl-imino ligand. In the case of R = Me, Et the corresponding compounds have been characterized by X-ray crystallography. The relevance of these complexes with respect to ruthenium catalyzed C-C coupling reactions of the same alpha,beta-unsaturated imines is demonstrated by the structural analysis of another mononuclear ruthenium complex in which two imine ligands are reductively coupled (R = Cy). [(1,5-Cyclooctadiene)-bis(2-methylallyl)-ruthenium (II)] also turns out to be a highly effective precatalyst in the reaction of the respective imines with carbon monoxide and ethylene to produce heterocyclic compounds. (c) 2010 Elsevier B.V. All rights reserved.