1. Introduction
Since its discovery at the end of the 19th century [1,2], iron pentacarbonyl has
played a central role in the field of transition metal carbonyl chemistry [3–6 ]. Its
early use as additive for fuels and as a source of very pure iron for the manufacture
of magnets made this compound commercially available in large amounts, thus
encouraging chemists to study its possible applications in chemical synthesis [4–6].
It was soon recognized that Fe(CO)5, which is insoluble in water, reacts with
aqueous alkali metal hydroxides to yield solutions which exhibit reducing properties.
It was postulated early that these solutions contained mixtures of dianionic and
hydridoanionic iron carbonyl complexes. The most famous application of this property
is the so-called ‘‘Reppe-modification of the hydroformylation reaction’’ which
has been used for the industrial production of butanols [7].