Uranocene – The Trend Setting Aromatic Actinide Sandwich Compound

Chemistry, Technology
Uranocene, U(C₈H₈)₂, or biscyclooctatetraenyl uranium, is a most interesting aromatic organometallic sandwich compound.1 Notice its dumbbell-like shape. By no means is its shape uranocene's only claim to fame. But before we get into that, it would be helpful to explain terms. We can guess why it's an organometallic compound, just as we can guess why it's called a sandwich compound. Let us, however, discuss what we mean by the term aromatic. Aromaticity in a Nutshell An aromatic structure is a molecule or ion that is cyclic and flat and that incorporates 4n+2 conjugated (alternating) sp2 (double) bonds, where n is some small integer. It displays increased stability over non-aromatic structures. Despite possessing double bonds, aromatic structures tend to undergo substitution rather than addition reactions. It requires considerable energy to disrupt…
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The Iron Sandwich Compound Ferrocene

[caption id="attachment_6151" align="alignright" width="440"] Ferrocene - an Iron Sandwich Compound[/caption] Who doesn't love a ham and cheese sandwich? Or a peanut butter and jelly sandwich? Well, there are special chemical substances that resemble sandwiches. There is, for example, the sandwich compound ferrocene, (C₅H₅)₂Fe. It consists of an atom of iron "sandwiched" between two cyclopentadiene molecules. Sandwich Compound The classification of such metallic organic compounds is metallocene. D-orbital electrons in the iron atom add to the pi-electrons of two cyclopentadiene molecules. This stabilizes the structure, since the cyclopentadienyl anion (-1 charge) has aromatic properties. The iron atom adopts, in effect, a ferrous (+2) electrical charge. Other Metallocenes In general, metallocenes have mostly been of laboratory interest. Some do exhibit a marked level of importance. One application is in catalysis. Other metallocenes…
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