It was found that Heck reaction with PdCl2 in diethanolamine and N,N-diethylethanolamine ionic liquids (ILs) is more efficient than analogous reactions performed in classical organic solvents. The used Its facilitate solubility of the Pd(II) precatalysts, increase catalyst stability during the reaction, and function as reaction media, bases, precatalyst-precursors, good coordinating ligands, and mobile support for active Pd species. Thus, Heck reaction occurs without additional solvents, ligands and bases, that makes experimental procedure much simpler. Our DFT investigation provides mechanistic insight into the formation of the trans-[PdCl2(DEA)(2)] complex that acts as a precatalyst. (C) 2010 Elsevier B.V. All rights reserved.