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].