Mössbauer Studies of Iron Organometallic Complexes. I. Iron Tetracarbonyl Complexes

Abstract

Mössbauer absorption spectra at 78°K have been obtained for a series of compounds of the form R:Fe(CO)₄, where R includes triphenylphosphine, triethylphosphite, acenaphthalene, trans‐cinnamaldehyde, maleic anhydride, syn‐syn‐1,3‐dimethyl‐π‐allyl cation, syn‐1‐methyl‐π‐allyl cation, π‐allyl cation, and I₂. The isomer shift increases and the electric quadrupole splitting decreases regularly through this series. The effect is explained in terms of the extent of forward coordination of the ligands, and so forms a basis for measuring Lewis basicity of ligands. The compound I₂:Fe(CO)₄ unexpectedly follows the trend, suggesting there remains appreciable bonding between iodine atoms.