Binuclear oxalamidinate complexes (MePd)2(oxam) and homoleptic complexes of the type [(THF)nLi4(Me8)M2] and [(THF)4Li2(Ph4)M] (M=Pd, Ni): synthesis, structures and catalytic CC linking reactions

The dinuclear methyl complexes 1 and 2 of the type [CH3Pd(oxam)PdCH3] were obtained by reaction of (COD)PdCH3(Cl) with the corresponding dilithium oxalic amidinates, prepared from LiBu and the oxalic amidines H2Y or H2Z (H2Y=N,N′-bis(2-pyridylethyl)-1,2-bis-(2,4,6-trimethylphenyl-imino)-ethane-1,2-diamine; H2Z=N,N′-bis(diphenylphosphino-3-propyl)-1,2-bis-(2,4,6-trimethylphenyl-imino)-ethane-1,2-diamine). Reaction of both 1 and 2 with an excess of LiCH3 results in the formation of the dimeric compound [(THF)4Li4(CH3)8Pd2] (3). Similarly, monomeric phenyl complexes of the composition [(THF)4Li2M(C6H5)4] (M=Pd (4), Ni (5)) were prepared. The complexes were characterized by elemental analysis, mass spectroscopy, 1H-NMR, 13C-NMR and 7Li-NMR spectroscopy, and by X-ray single-crystal diffraction analysis in the solid state. All complexes contain the metals in a planar-square environment. Compounds 1–3 and 4 are highly active, selective and long-living catalysts in the Heck reaction of 4-bromoacetophenone and n-butyl acrylate. Compound 5 and the related neutral ligand-free Ni complex [(THF)4Li4(CH3)8Ni2] (6) are active catalysts for the Kumada cross-coupling of MesitylMgBr with 4-bromotoluene and are even able to couple the corresponding aryl chloride or aryl fluoride with MesitylMgBr.