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(CI) with the corresponding dilithium oxalic amidinates, prepared from LiBu and the oxalic amidines H2Y or H(2)Z (H2Y = N,N'-bis(2-pyridylethyl)-1,2-bis-(2,4,6-trimethylphenyl-imino)-ethane-1,2-diamine; H(2)Z = 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)(4)Li-4(CH3)(8)Pd-2] (3). Similarly, monomeric phenyl complexes of the composition [(THF)(4)Li2M(C6H5)(4)] (M = Pd (4), Ni (5)) were prepared. The complexes were characterized by elemental analysis, mass spectroscopy, H-1-NMR, C-13-NMR and Li-7-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)(4)Li-4(CH3)(8)Ni-2] (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. (C) 2003 Elsevier B.V. All rights reserved.