A Novel Method for the Demetalation of Tricarbonyliron-Diene Complexes by a Photolytically Induced Ligand Exchange Reaction with Acetonitrile.

The photochemical exchange of all three carbonyl ligands with acetonitrile converts tricarbonyliron-diene complexes into the very labile triacetonitrile-iron-diene complexes. These easily demetalate in high yields to the corresponding free ligands on injection of air at -30°C [Eq. (1)]. The novel demetalation procedure is applied to the tricarbonyliron complexes of cyclopentadienones, cyclohexa-1,3-dienes, and buta-1,3-dienes.

Demetalation of Tricarbonyl(cyclopentadienone)iron Complexes Initiated by a Ligand Exchange Reaction with NaOH-X-Ray Analysis of a Complex with Nearly Square-Planar Coordinated Sodium.

A sequential exchange of one carbonyl ligand by a hydrido ligand with NaOH, and then by an iodo ligand with iodopentane and finally treatment with acid transforms tricarbonyl(η4-cyclopentadienone)iron complexes into dicarbonyl(η5-hydroxycyclopentadienyl)iodoiron complexes. These iodo complexes demetalate with high selectivity to the corresponding free ligands on contact with air in daylight. Under basic reaction conditions at the stage of the iodo complex an anionic dicarbonyl(η4-cyclopentadienone)iodoiron complex is generated, which is dimeric in the solid state and has an almost square-planar arrangement of the ligands at the sodium counterion.