| Chemical Properties | Iron pentacarbonyl reacts with cyclopentadiene at 135° in an autoclave to give the
binuclear complex [(π-C5H5)Fe(CO)2]2 as deep reddish-purple crystals which are stable to
air and water. The crystal structure determination shows this molecule to be centrosymmetric with two bridging carbonyls forming a plane with the two iron atoms [Fig. 19(a)]. The rather short Fe-Fe distance of 2-49 ? and the diamagnetism of the compound indicate
the presence of the Fe-Fe bond. In solution, however, it tautomerizes to the structure believed to be that shown in Fig.19(b),in which the two rings lie on one side of the mean
plane formed by the bridging carbonyl groups and the iron atoms and the two terminal CO
groups lie on the other side.
 |
| Chemical Properties | Mobile, yellow liquid.Evolves carbon monoxide on exposure to air or light. Soluble in nickel
tetracarbonyl and most organic solvents; soluble
with decomposition in acids and alkalies; insoluble in water. |
| Uses | Catalyst in organic reactions, carbonyl iron for
high-frequency coils. |
| Uses | Iron pentacarbonyl is a useful dehalogenating and carbonylating agent. |
| Hazard | Flammable, dangerous fire risk. Toxic by
ingestion, inhalation, and skin absorption. |
| Structure and conformation | The trigonal
bipyramidal structure has been preferred to the square pyramidal one in the interpretation of electron diffraction, Raman and infrared and thermodynamic data; the apparently
contradictory dipole moment of 0-8 D being attributed to atom polarization. A single
crystal X-ray structure determination at - 80°C has confirmed the trigonal bipyramidalstructure. |
