Stabilization of highly reactive cyclic polyolefins by coordination to iron carbonyls

Thermolysis of (cis-bicyclo[6.1.0]nonatriene)diiron hexacarbonyl (FeFe) involves rearrangement of the starting organic moiety with formation of four iron carboyl complexes. The major product is the known cis-8,9-dihydroindeneiron tricarbonyl complex (VI). Two complexes have the same formula, C9H8Fe2(CO)5 (VII and VIII); VII can be also obtained by reaction of VI with Fe2(CO)9, while VIII is a methylpentalenediiron pentacarbonyl complex and represents a further example of stabilization of this reactive organic molecule by coordination; IX is probably a polycyclic cyclopentadienyl derivative [C9H9Fe(CO)2]2. Possible mechanisms for the formation of the four compounds are discussed.