Structure and Mössbauer Effect Study of [Et₄N]₂[Fe₂(CO)₈]

The reduction of [Et4N]2[PbFe(CO)43] leads to the well known [Et4N]2[Fe2(CO)8] as determined by single crystal X- bis[tetracarbonylferrate(1 -)], C24H40Fe2N2O8, FW = 596.28 g/mol, monoclinic, P21/n (#14), a = 9.492(3), b (2)°, V = 1432.5(8) Å3, Dx = 1.38 g/cm3, Z = 2, μ = 10.56 cm-1, λ(Mo-Kα) = 0.71069 Å, F(000) = 62 for 1869 unique reflections with I \u3e 3σ(I). As in other salts, the anion of [Et4N]2[Fe2(CO)8] consists of two iron atoms situ each of which is coordinated to four carbonyls in a trigonal bipyramidal fashion with the FeFe bond in an axial site. Unexpectedly, the Fe longer than reported for the [PPN]+·2CH3CN, [PPh4]+·2CH3CN and [Fe(pyridine)6]2+ salts. The Mössbauer effect spectra have been measured at 78 and 296 K, are presented and discussed. bl]. © 1992