Clamshell Palladium(II) Complexes: Suitable Precursors for Photocatalytic Hydrogen Production from Water

A series of carboxylato-bridged dinuclear palladium(II) complexes with cyclopalladated 2-phenylbenzothiazole ligands were prepared and characterized by elemental analyses, NMR, IR, and UV-vis spectroscopies, cyclic voltammetry, and X-ray crystallography. All the complexes have clamshell structures in which two cyclopalladated 2-phenylbenzothiazole ligands bound to palladium atoms are in the anti-configuration arranging the ligands in opposite orientations from each other. The Pd-Pd distances of these complexes are shorter than the sum of the van der Waals radii, indicative of the presence of metal-metal bonding interactions. These dinuclear complexes were used as water reduction catalysts in the photocatalytic system for hydrogen evolution and regarded as precatalysts that are converted into highly catalytically active species.