Cyclopalladated complexes of 3-thiophosphorylbenzoic acid thioamides: Hybrid pincer ligands of a new type. Synthesis, catalytic activity, and photophysical properties

Treatment of the 3-diphenylphosphorylbenzoic acid amides 3a,b with the Lawesson reagent resulted in 3-diphenylthiophosphorylbenzoic acid thioamides 4a,b, which easily underwent cyclopalladation at the C-2 position of the central benzene ring to give new hybrid pincer complexes 5a,b with kappa(3)-SCS coordination. Molecular structures of the complexes were characterized by X-ray diffraction. The peculiarities of chemical bonding in 5a were investigated via topological analysis of charge density in the crystal. The palladium complexes 5a,b demonstrated high catalytic activity for the Suzuki cross-coupling reactions of aryl bromides with phenylboronic acid and exhibited luminescence at 77 and 300 K.