Linkage of Alkylidyne, Carbonyl, and Alkyne Ligands at a Tungsten Center to Form a Metallacyclopentadienone and an η³‐Oxocyclobutenyl Complex

The conversion of alkylidyne into alkylidene complexes, which is of interest in connection with the catalysis of acetylene polymerization, is demonstrated by the reaction of 1 with PhCCH. The localized double bonds in 2 lend support to this complex being regarded as an alkylidene complex. The complex 3, which is isomeric with 2 and obtained likewise, is not formed from the five‐membered ring of 2 by reductive elimination of the tungsten center but via an independent route. (Figure Presented.)