Facile synthesis, X-ray analysis, and spectroscopic studies of di-iron propanedithiolate complexes with tris(aromatic)phosphine ligands

Abstract

Three new propanedithiolate-type iron–sulfur complexes containing tris(aromatic)phosphine ligands, [{(μ-SCH2)2CH2}Fe2(CO)5L] (L = P(PhOMe-p)3, 1; P(PhMe-p)3, 2; P(PhF-p)3, 3), have been prepared through carbonyl substitution in the presence of Me3NO. The new complexes 1–3 were characterized by elemental analysis, IR, 1H, 13C{1H}, and 31P{H} NMR spectra. The molecular structures of 1–3 were unequivocally determined by single crystal X-ray diffraction, in which the tris(aromatic)phosphine coordinated to Fe resides in an apical position of the pseudo-square-pyramidal geometry. IR spectroscopy and X-ray crystallographic analysis for 1–3 have indicated that the highly electron rich tris(aromatic)phosphine ligands (where the corresponding electron-donating abilities display the following order of P(PhOMe-p)3 > P(PhMe-p)3 > P(PhF-p)3) result in a considerable red shift of the CO-stretching frequencies and a clear change of the Fe–Fe bond distances in 1–3.