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Brian Mann
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The Fluxionality of Fe3(CO)12

In 1989, it was shown that the lowest energy fluxional mechanism operating in Fe3(CO)12 and its derivatives is the concerted bridge-opening bridge-closing mechanism.

In this mechanism carbonyls C1O, C11O, C12O, C2O and C7O circulate around the edge of the Fe3 triangle defined by Fe2 and Fe3. There is also a concerted rotation of carbonyls C3O, C5O, C4O, C9O and C8O around the edge of the Fe1 triangle defined by Fe2.

Carbonyls C6O and C10O are brought into the exchange by choosing an alternative of Fe-Fe edge for the circulation axis.

The two sets of carbonyls remain synchronised as they rotate. This has been demonstrated for Fe3(CO)10(CNBut){P(OMe)3}.

Recently the mechanism has been mapped by comparing a series of crystal structures. This has resulted in the generation of a movie which shows the two sets of carbonyls rotating about the axis defined by carbonyls C6O and C10O. The viewpoint is looking down this axis.

[Movie of Fe<SUB>3</SUB>(CO)<SUB>12</SUB> fluxionality]


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Date:- 8 April, 1998