Square-planar dichloro palladium complexes with <i>trans</i>-configurated phosphine ligands avoiding <i>ortho</i>-metallation: Ligand design, complex synthesis, molecular structure and catalytic potential for Suzuki cross-coupling reactions

The square-planar palladium complexes trans-[PdCl₂ (PPh₂-CH₂-2,4,6-C₆H₂Me₃)₂] (<b>1</b>) and trans-[PdCl₂ (η²-PPh₂-CH₂-2,4,6-C₆HMe₃-CH₂-2,4,6-C₆HMe₃-CH₂-PPh₂)] (<b>2</b>) have been synthesized from [PdCl₂ (cod)] (cod = 1,5-cyclooctadiene) and the corresponding new phosphine or diphosphine ligands. The single-crystal X-ray structure analysis reveals for both complexes a <i>trans</i> arrangement of the two chlorine and of the two phosphorus atoms. In both cases, <i>ortho</i>-metallation leading to palladacycles is not possible, since all <i>ortho</i> positions in the benzylic rings of <b>1</b> and <b>2</b> are blocked by methyl substituents. Both complexes are found to catalyze Suzuki cross-coupling reactions of deactivated and even bulky arene substrates.