Homogeneous catalysis by cationic palladium complexes. Precision catalysis in the carbonylation of alkynes

Article abstract of DOI:10.1016/0022-328X(94)84007-5

A class of highly efficient homogeneous palladium cationic catalysts has been developed for the carbonylation of alkynes.An interesting application is the selective production of methyl methacrylate by methoxycarbonylation of propyne.The essential feature of the new catalyst systems is that they are formed by the combination of a ligand containing a 2-pyridylphosphine moiety with a palladium(II) species and a proton source containing weakly coordinating anions.High turnover numbers of more than 40 000 mol/(mol Pd h) and selectivities to methyl methacrylate of up to 99.95percent can be obtained under mild conditions.It is hypothesized that the 2-pyridylphosphine ligand plays an essential role both as a chelating P-N ligand in the selectivity-determining step and as a mono-coordinated ligand in the protonolysis step of the catalytic cycle.Key words: Palladium; Catalysis; Carbonylation; Alkyne; Methyl methacrylate; 2-Pyridylphosphine