Does cyclopentadienyl iron dicarbonyl dimer have a metal–metal bond? Who's asking?

Abstract

In a 2012 essay, Green, Green and Parkin noted that certain bridged carbonyl complexes, including [CpFe(CO)_2]_2 (Cp = η^5-cyclopentadienyl), are commonly depicted with an explicitly-drawn metal–metal bond in textbooks, and presented a rationale for why that constitutes a misrepresentation. Here I briefly summarize the history of that compound, in which Cotton played a major part, and try to show that there are at least equally valid justifications for keeping the M–M bond in the picture. More generally, I will argue against the idea of a single "best" representation of a complex molecule, by drawing upon analogies to literary translation.

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