Formation by Five-Membered Ring Systems

Complex Formation by Five-Membered Ring Systems 

The first group of workers observed the formation of this compound by the action of cyclopentadiene on reduced iron at 300°. The latter group described an entirely different approach it was expected that a coupling reaction of a solution of cyclopentadienyl magnesium bromide containing ferric chloride would yield the (unknown) hydrocarbon ful-valene, CioHs instead, the reaction 

The field of metal complexes of cyclopentadiene has subsequently been extended mainly by the two groups of workers who elucidated the structure of ferrocene. New methods for the preparation of such compounds were essential to further progress. 

By this method, which had formerly been employed only for the alkali metals and iron, the magnesium derivative, Mg(C5H6)2, has recently been prepared in the vapor phase. Cyclopentadiene vapor was passed over magnesium powder at 500-600° and under suitable conditions crystals of mp 176° were obtained (4). Thallium and indium reacted similarly with cyclopentadiene vapor at 350°, giving the compounds TlCsHs and InCgH (55). Attempts to develop a more general method of preparation from cyclopentadiene and molten metals met with no success 121). 

Interaction of Metal Salts and Cyclopentadienyl Magnesium Bromide 

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II. Complex Formation by Five-Membered Ring Systems... 

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