HOMOGENEOUS CATALYSIS BY CATIONIC PALLADIUM COMPLEXES - PRECISION CATALYSIS IN THE CARBONYLATION OF ALKYNES

A class of highly efficient homogeneous palladium cationic catalysts h as been developed for the carbonylation of alkynes. An interesting app lication is the selective production of methyl methacrylate by methoxy carbonylation of propyne. The essential feature of the new catalyst sy stems is that they are formed by the combination of a ligand containin g a 2-pyridylphosphine moiety with a palladium(II) species and a proto n source containing weakly coordinating anions. High turnover numbers of more than 40000 mol/(mol Pd h) and selectivities to methyl methacry late of up to 99.95% can be obtained under mild conditions. It is hypo thesized that the 2-pyridylphosphine ligand plays an essential role bo th as a chelating P-N ligand in the selectivity-determining step and a s a mono-coordinated ligand in the protonolysis step of the catalytic cycle.