Reaction of [Te₆Fe₈(CO)₂₄]^2- with Dihaloalkanes: A New Route to Organotellurium Complexes of Iron

Organotellurium hexacarbonyldiiron complexes, Fe₂(CO)₆(μ-Te(CH₂)_nTe) (n = 1, n = 2, 2; n = 3, 3), are synthesized by the reaction of [Te₆Fe₈(CO)₂₄]^2- (1) with appropriate dihaloalkanes. When [Et₄N]₂[1] is treated with Br(CH₂)₂Br, an anionic cluster [Et₄N] [BrTe₂Fe₂(CO)₆] (4) is obtained. Clusters 2–4 were characterized by spectroscopic data and single-crystal X-ray analysis. Compound 2 crystallizes in the monoclinic space group P2₁/n with a = 7.194(1) Å, b = 13.179(4) Å, c = 14.644(3) Å, β = 91.57(2)°, V = 1387.9(6) ų, and Z = 4. Compound 3 is isomorphous with 2: monoclinic, space group P2₁/n with a = 7.455(1) Å, b = 13.312(1) Å, c = 15.097(3) Å, β = 91.48(2)°, V = 1497.7(4) ų, and Z = 4. Crystals of 4 are monoclinic, space group P2₁/n with a = 13.304(2) Å, b = 13.022(3) Å, c = 13.372(5) Å, β = 93.70(2)°, V = 2311.6(1) ų, and Z = 4. Compound 2 or 3 displays a Te₂Fe₂ butterfly geometry with the Te atoms bridged by a –(CH₂)_n– (n = 2, 3) group while the anionic cluster 4 exhibits a Te₂Fe₂ tetrahedral core with one Te bonded to an external Br atom. The anionic 1 has been shown to be a source of the dianion, [Te₂Fe₂(CO)₆]^2-, and provides a useful reagent for the preparation of organotellurium hexacarbonyldiiron complexes, Fe₂(CO)₆(μ-Te(CH₂)_nTe).