Palladium-Catalyzed Ethylene/Methyl Acrylate Cooligomerization : Effect of a New Nonsymmetric alpha-Diimine

A new nonsymmetric bis(aryl-imino)acenaphthene (Ar-BIAN) ligand, featured by a subtle steric and electronic unbalance of the N-donor atoms, is reported. With the new ligand and the corresponding symmetrically substituted derivatives, both neutral and monocationic PdCH3 compounds have been synthesized and characterized. The series of the monocationic complexes [Pd(CH3)(L)(Ar-BIAN)][PF6] (L=CH3CN, dmso) has been extended to dimethyl sulfoxide derivatives. The monocationic complexes are tested as precatalysts for the ethylene/methyl acrylate cooligomerization under mild reaction conditions of temperature and ethylene pressure. The catalytic product is a mixture of ethylene/acrylate cooligomers and higher alkenes. The catalysts containing the new nonsymmetric ligand are found to be more productive than those with the symmetric Ar-BIANs. The Pddmso catalysts are more productive and show a longer lifetime than their PdNCCH3 counterparts.