 The Bailey system utilized a mixture of tungsten and silicon oxides at temperatures as high as 450 °C.In 1974 Mortreux reported the use of a homogeneous catalyst—molybdenum hexacarbonyl at 160 °C—to observe an alkyne scrambling phenomenon, in which an unsymmetrical alkyne equilibrates with its two symmetrical derivatives.The Mortreux system consists of the molybdenum precatalyst molybdenum hexacarbonyl Mo(CO)6 and resorcinol cocatalyst.