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

Abstract

The square-planar palladium complexes trans-[PdCl 2(PPh 2-CH 2-2,4,6-C 6H 2Me 3) 2] ( 1) and trans-[PdCl 2(η 2-PPh 2-CH 2-2,4,6-C 6HMe 3-CH 2-2,4,6-C 6HMe 3-CH 2-PPh 2)] ( 2) have been synthesized from [PdCl 2(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 trans arrangement of the two chlorine and of the two phosphorus atoms. In both cases, ortho-metallation leading to palladacycles is not possible, since all ortho positions in the benzylic rings of 1 and 2 are blocked by methyl substituents. Both complexes are found to catalyze Suzuki cross-coupling reactions of deactivated and even bulky arene substrates.