STRUCTURE AND MOSSBAUER-EFFECT STUDY OF [ET4N]2[FE2(CO)8]

The reduction of [Et4N]2[Pb{Fe(CO)4}3] leads to the well known [Et4N]2[Fe2(CO)8] as determined by single crystal X-ray crystallography. The bis(tetraethylammonium)bis[tetracarbonylferrate(1 -)], C24H40Fe2N2O8, FW = 596.28 g/mol, monoclinic, P2(1)/n (#14), a = 9.492(3), b = 13.793(5), c = 11.870(4) angstrom, beta = 112.81(2)-degree, V = 1432.5(8) angstrom3, D(X) = 1.38 g/cm3, Z = 2, mu = 10.56 cm-1, lambda(Mo-K(alpha) = 0.71069 angstrom, F(000) = 628, T = 296 K, R = 0.032, R(W) = 0.043 for 1869 unique reflections with I > 3-sigma(I). As in other salts, the anion of [Et4N],2[Fe2(CO)8] consists of two iron atoms situated about a crystallographic inversion center, each of which is coordinated to four carbonyls in a trigonal bipyramidal fashion with the Fe-Fe bond in an axial site. Unexpectedly, the Fe-Fe distance, 2.841(1) angstrom, is significantly longer than reported for the [PPN]+.2CH3CN, [PPh4]+.2CH3CN and [Fe(pyridine)6]2+ salts. The Mossbauer effect spectra of the [Et4N]+ and [PPN]+ salts, which have been measured at 78 and 296 K, are presented and discussed.