in hexane 1,2-W2Me2(O-t-Bu)4(pyridine)2/hexane was frozen at -198°C. Addn. of 1.0 equiv. of ethyne, quickly warmed to 0°C; evapn. at 0°C; extn.(dimethoxyethane); cooled to -20°C for 24 h; removing of the supernatant liquid and drying in vacuo. Detected by IR and elem. anal.;