Organic Syntheses via Transition Metal Complexes, 90:1 Novel Route to Cyclopentadienes from (1-Alkynyl)carbene Complexes of Chromium and Tungsten via 2-Amino Metalla-1,3,5-hexatrienes - Aumann, Rudolf; Kößmeier, Michael; Zippel, Frank (Synlett, 1997)