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

摘要

The reaction of α,β-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[RNC(H)-C(H)C(Ph) ]2}. In these complexes the imine ligands are deprotonated in β-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 α,β-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. [(COD)Ru(2-methylallyl)_2] acts as a substrate for the synthesis of the first structurally characterized mononuclear ruthenium complexes of the general formula [(COD)Ru([RNC(H)-C(H)C(Ph)]_2 in which the imine coordinate as enyl-imino ligands. In addition, [(COD)Ru(2-methylallyl) _2] turns out to be a highly effective precatalyst in catalytic C-H activation/C-C coupling reactions of the same imines.