Département de chimie moléculaire

Whereas the reaction of norbornadiene with terminal alkynes in the presence of a phosphapalladacycle catalyst gives hydroalkynation products, the use of phosphinous acid-phosphinito-contg. palladium complexes gives rise to formal [2+1] cycloadducts. An exptl. and computational approach was employed to study the mechanisms of the palladium-promoted hydroalkynation and [2+1] cycloaddn. On the one hand, expts. highlight the crucial role of acidolysis steps on the catalytic activities. However, DFT calcns. demonstrate the specificity of the phosphinito-phosphinous acid ligands, i.e., the nonequivalence of the two phosphorus atoms but the interchangeability of their properties. These results may have important implications for the mechanism of other palladium-catalyzed transformations esp. those involving phosphapalladacycles and phosphinous acid-phosphinito-contg. palladium complexes.