EFFICIENT PALLADIUM CATALYSTS FOR THE CARBONYLATION OF ALKYNES

A class of highly efficient homogeneous palladium catalysts has been d eveloped for the carbonylation of alkynes. One application of interest is the selective production of methyl methacrylate by methoxycarbonyl ation of propyne. The essential feature of the new catalyst systems is that they are formed by the combination of a ligand containing a 2-py ridylphosphine moiety with a palladium(II) species and a proton source containing weakly coordinating anions. High turn-over numbers of more than 40000 mol (mol Pd)-1 h-1 and selectivities towards methyl methac rylate of up to 99.95% can be obtained under mild conditions. It is su ggested that the 2-pyridylphosphine ligand plays an essential role bot h as a chelating P-N ligand in the selectivity-determining step and as a monocoordinated ligand in the rate-determining step of the catalyti c cycle.