Numerous aryl and alkenyl chromium and molybdenum carbene complexes are prepared, and their reactions with trienyne 2 are examined. With chromium as the metal, insertion of carbon monoxide occurs leading to the formation of hydroquinones. When carbene complexes of molybdenum are employed, the product distribution is highly dependent on the alkyl substituent of the carbene complex. Aryl substituted molybdenum carbene complexes produce hexahydroazulenes while alkenyl substituted molybdenum carbene complexes generate hydroquinones or cyclopentadiene derivatives. The mechanisms of these reactions with respect to the partitioning between the different reaction pathways is discussed.