The X-ray structure of Fe(fulvene)2: The missing link in the direct synthesis of ansa- and Cpi-metallocenes (Cpi = C5H4CHMe2)

The compound (ethene) 2 (toluene)iron ( 1 ) is prepared by cocondensation of iron and toluene and subsequent treatment with ethene. Reaction of ( 1 ) with 6,6-dimethylfulvene leads to the known products ansa-ferrocens and 1,1′-bis(isopropyl)ferrocene. Reaction of ( 1 ) with 6,6-diphenylfulvene ( 2 ) gives 1,1′-bis(benzhydryl)ferrocene ( 3 ). The intermediate in the formation of ( 3 ), bis(diphenylfulvene)iron ( 4 ) was isolated. ( 4 ) was characterized by MS and a X-ray structure determination and its structure compared with the structure of the free ligand ( 2 ). The structure of ( 4 ) was also determined by DFT-ab-initio calculations.