Deuterium kinetic isotope effects and H/D exchange in dimerization of acetylene with a Nieuwland catalyst in aqueous media

Deuterium kinetic isotope effects were observed in the dimerization of acetylene with a Nieuwland catalyst in an aqueous media, where the copper–acetylene and copper–monovinylacetylene (MVA) π ‐complexes were detected as intermediates by 1 H NMR. The copper–acetylene π ‐complex is responsible for an efficient H/D exchange between acetylene and proton (or deuteron) of water, which occurs rapidly with a Nieuwland catalyst. The deuterium kinetic isotope effects and the rapid H/D exchange reaction together with the detection of the copper–acetylene and copper–MVA π ‐complexes provide deeper insight into the catalytic mechanism of the Nieuwland catalysis for the dimerization of acetylene. Copyright © 2008 John Wiley & Sons, Ltd.