The Mortreux system consists of the molybdenum catalyst molybdenum hexacarbonyl Mo(CO)6 and resorcinol cocatalyst. In 1975 T.J. Katz proposed a metal carbyne and a metallacyclobutadiene as an intermediate and in 1981 R.R. Schrock characterized several metallacyclobutadiene complexes that were capable of catalytic turnover.
The Schrock catalyst system Tris(t-butoxy)(2,2-dimethylpropylidyne)(VI)tungsten  is based on tungsten . This catalyst is not reactive towards<unk> s in olefin<unk> . On the other hand Fischer carbenes have no value in<unk> .
The Schrock catalyst is commercially available and is prepared by amidation of tetrachloro tungsten with lithium dimethylamide to a di-tungsten complex followed by replacing the amide groups with tert-butoxy groups with tert-butanol.
This organometallic<unk>  then undergoes a<unk>  reaction with neoheptyne to the final product. In 2001 A. Fürstner developed a new molybdenum catalyst replacing carbon monoxide with aniline ligands .
Alkyne metathesis
Fischer esterification
Carboxylation
Glucuronidation
Hydroxylation
Alkylation
Biotinylation
Radical polymerization