Nickel(II) and palladium(II) complexes with an alkane-bridged macrocyclic ligand: Synthesis, characterization, and polymerization tests

An efficient synthetic route to a novel macrocyclic aryl alpha-diimine ligand bearing C-6 hydrocarbon bridges connecting the aryl ortho positions is described. Pd(II) and Ni(II) complexes with the new macrocyclic ligand (10 and 14) were successfully synthesized and characterized. The X-ray crystal structures of complexes 10 and 14 show that the complexes exhibit coordination geometry similar to that of their acyclic analogues and the alkyl bridges do not introduce significant ring strain into the complexes. The preactivated Pd(II) complex 12 and the allyl nickel complex 14 were tested for ethylene polymerization. Potential reasons for the low catalytic activities are discussed.