Mechanistic Investigation and New Catalyst Design in Palladium- and Platinum-Catalyzed Se−Se Bond Addition to Alkynes

The present study explains the different catalytic activities of platinum and palladium in Se−Se addition reactions with alkynes. Under the catalytic conditions cis -[Pt(SePh) 2 (PPh 3 ) 2 ] undergoes fast isomerization to the trans isomer, which does not react with alkynes. Palladium complexes maintain their catalytic activity, due to the formation of the dinuclear structure [Pd 2 (SePh) 4 (PPh 3 ) 2 ]. It was shown that the palladium intermediate involved in the catalytic cycle can be prepared directly in the reaction mixture starting from the simple [PdCl 2 (PPh 3 ) 2 ] precursor, thus allowing replacement for the traditional Pd(PPh 3 ) 4 catalyst. X-ray analysis shows that the products of Se−Se addition reactions with alkynes possess the necessary geometry parameters for coordination as bidentate ligands.