Structures of some derivatives of bis-π-cyclopentadienyltetracarbonyl-di-iron

Abstract

The i.r. spectra of a number of [(π-dienyl)Fe(CO)₂]₂ and [(π-dienyl)(π-C₅H₅)Fe₂(CO)₄] complexes [dienyl = CH₃C₅H₄ and C₉H₇(indenyl)] have been investigated between 400 and 700, and 1700 and 2100 cm.^–1. They are solvent-dependent, and it is proposed that these compounds, like [(π-C₅H₅)Fe(CO)₂]₂, exist as their trans-bridged isomers in the solid state, but as a mixture of cis- and trans-bridged forms, together with small amounts of non-bridged species, in solution. The spectra of solutions of [(π-C₉H₇)Fe(CO)₂]₂ in saturated hydrocarbon solvents show two well-resolved bands of comparable intensities at ca. 1790 cm.^–1, thereby confirming that two bridged isomers of this compound exist in solution.