Synthesis, Structure, and Catalytic Studies of Palladium and Platinum Bis-Sulfoxide Complexes

The bis-sulfoxide ligand <i>p</i>-tolyl-binaso and its derivatives can be used to synthesize neutral and cationic palladium and platinum complexes. Various Pt bis-sulfoxide complexes could be made by using the precursor Pt­{(<i>M</i>,<i>S</i>_<i>S</i>,<i>S</i>_<i>S</i>)-<i>p</i>-tolyl-binaso}­Cl₂ (<b>5a</b>) and abstracting the chlorides with silver salts. The Pd analogue of this compound (<b>4</b>) could not be used in the same way. In this case, the sulfoxides appear to be very weakly coordinated and different methods to make stable Pd bis-sulfoxide complexes had to be found. The nature of the bonding in the synthesized compounds was studied through analysis of their IR and NMR spectra and X-ray crystal structures. These studies revealed that the <i>trans</i> effect of other ligands in the complex is quite significant in determining the lability of the metal–sulfoxide bond. Some of the more stable platinum structures were then tested for their activity as catalysts in hydroboration and diboration reactions