A 10-Vertex Iron−Dicarbollide System Formed by Insertion of {Fe(CO)4} into 8-Vertex [closo-1-CB7H8]−: Synthesis and Reactivity Studies

Reaction of [NBun4][closo-1-CB7H8] with [Fe2(CO)9] in refluxing THF (tetrahydrofuran) gives the neutral ferradicarborane [2,2,2-(CO)3-1-OH-closo-2,1,10-FeC2B7H8] (3), which, upon treatment with PEt3 in the presence of Me3NO, yields [2,2-(CO)2-2-PEt3-1-OH-closo-2,1,10-FeC2B7H8] (4). In 3 and 4 the 10-vertex {FeC2B7} cluster has two carbon vertices in antipodal, four-connected positions and the iron atom in a five-coordinate site adjacent to a carbon vertex that bears an OH substituent. Treatment of 4 in THF with NaH and then R−X (X = Br, I) affords [2,2-(CO)2-2-PEt3-1-OR-closo-2,1,10-FeC2B7H8] (R = Me (5), CH2CH═CH2 (6), CH2C≡CH (7), CH2C≡CMe (8)). The pendant allyl group in 6 becomes η2-bonded to the iron center upon treatment with Me3NO in CH2Cl2, giving [2-CO-2-PEt3-1,2-σ:η2-OCH2CH═CH2-closo-2,1,10-FeC2B7H8] (9), which then with CNXyl (Xyl = C6H3Me2-2,6) in the presence of PEt3 gives [2,2-(CNXyl)2-2-PEt3-1-OCH2CH═CH2-closo-2,1,10-FeC2B7H8] (10). Reaction between compound 7 and [Co2(CO)8] in petroleum et...