A new, highly potent activator for molybdenum hexacarbonyl and 2-fluorophenol is described. An “instant” catalyst formed in situ from molybdenum hexacarbonyl and 2- fluorophenol shows high activity for cross-and ring-closing alkyne metathesis reaction. The use of 2-fluorophenol can be combined with other activation methods to allow alkyne metathesis at relatively low temperature (80° C).
