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

The square-planar palladium complexes trans-[PdCl2(PPh2-CH2-2,4,6-C6H2Me3)2] (1) and trans-[PdCl2(η2-PPh2-CH2-2,4,6-C6HMe3-CH2-2,4,6-C6HMe3-CH2-PPh2)] (2) 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 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.

Graphical abstractThe square-planar palladium complexes trans-[PdCl2(PPh2-CH2-2,4,6-C6H2Me3)2] (1) and trans-[PdCl2(η2-PPh2-CH2-2,4,6-C6HMe3-CH2-2,4,6-C6HMe3-CH2-PPh2)] (2) have been synthesized from [PdCl2(cod)] (cod = 1,5-cyclooctadiene) and the corresponding new phosphine or diphosphine ligands. Both complexes are found to catalyze Suzuki cross-coupling reactions of deactivated and even bulky aromatic substrates.Figure optionsDownload full-size imageDownload as PowerPoint slide