Synthesis and structure of Fe 4(CO) 10( μ2-CO)( μ4-Te) 2 and 57Fe Mössbauer spectra of Fe 3(CO) 9( μ3-Te) 2 and Fe 4(CO) 10( μ2-CO)( μ4-Te) 2

Abstract

The compound Fe 4(CO) 10( μ 2-CO)( μ 4-Te) 2 ( 1) has been prepared by the reaction of Fe 3(CO) 9Te 2 ( 2) and Fe 2(CO) 9 in toluene. Compound 1 is also formed by UV light irradiation of 2 and Fe(CO) 5 in THF. The structure of 1 was established by single-crystal analysis. Crystal data: orthorhombic, Pccn, a=6.843(1), b=15.814(1), c=17.436(1) Å; V=1887 Å 3; Z=4; T=293 K, R 1=0.040. 1 consists of a planar array of four iron atoms with a quadruply bridging telluro ligand on each side of the plane. The shortest metalmetal bond contains a bridging carbonyl ligand, semi-bridging carbonyl ligands bridge the two adjacent metalmetal bonds. 125Te-NMR investigations show a conversion from 1 to 2 within several hours. 57Fe Mössbauer spectra show two doublets for 1 and only one broadened doublet for 2. The ratio of the intensities of the doublets of 1 is found close to unity and confirms the existence of two equipopulated crystallographic sites of iron. On the contrary, in the case of 2, the analysis of the spectra does not allow the expected correlation with the results of the crystal structure determination. The same difficulty was previously encountered in the case of the isostructural selenide Fe 3(CO) 9Se 2.