Alkyne reactions with trimethylphosphine complexes of iridium: Lessons for the catalysis of vinyl ester formation and alkyne dimerization

The combination of iridium with trimethylphosphine ligands yields very electron rich iridium compounds that are active for terminal alkyne dimerization chemistry as well as the addition of carboxylic acids to alkynes. The structures, catalytic and stoichiometric chemistry of some iridium tris-trimethlyphosphine compounds with benzoate ligands are detailed in this paper. The roles that these compounds may play in the catalytic cycles involved in the dimerization of terminal alkynes and the addition of benzoic acid to terminal alkynes are examined and possible mechanisms for these catalytic reactions are proposed.