New polynuclear compounds of iron(II) chloride with oxygen donor ligands Part I. Fe4Cl8(THF)6: synthesis and a single crystal X-ray structure determination

A new polynuclear compound of Fe(II) chloride with oxygen donor ligands has been isolated as a colorless crystalline solid, Fe4Cl8(THF)6 (1), by the reaction of FeCl3 and Fe in THF. 1 consists of centrosymmetric, tetranuclear molecules with two different types of Fe atoms, two (Fe(1) and Fe(1)′) in trigonal bipyramidal environments and the others (Fe(2) and Fe(2)′) in octahedral environments. Each trigonal bipyramidally coordinated iron atom is linked through doubly- and triply-shared chlorine atoms to an iron atom in an octahedral environment. The magnetic moment of 1, per iron atom, at room temperature is 5.40 BM, which is a reasonable value for high spin Fe2+. The Fe…Fe distances are 3.656(1) and 3.750(1) A for Fe(1)…Fe(2) and Fe(2)…Fe(2)′, respectively. The order of FeCl distances, Fe(μ3-Cl)>Fe(μ2-Cl)>FeClt is as expected. The FeClt distance is 2.244(1) ]A, the Fe(μ2-Cl) distances are 2.355(1)–2.488(2) A and the Fe(μ3-Cl) distances are 2.506(1)–2.737(1) A. The average FeO distance is 2.135(9) A. Crystallographic data: 1, triclinic, space group P 1 , a = 10.607(2), b = 10.993(3), c = 10.038(2) A, α = 111.84(3)°, β = 98.28(3)°, γ = 63.18(3) °, V = 969.2(6) A3, Z = 1, R = 0.048 (Rw = 0.069) for 188 parameters and 2616 unique data having Fo2>3σ(Fo2).