Reactions of anionic carborane nucleophiles with chromium-coordinated haloarenes

Article abstract of DOI:10.1021/om00042a057

Lithiated C-methyl-o-carborane, LiC₂B₁₀H₁₀-(CH₃), reacts with the complexes (η⁶-arene)Cr(CO)₃ to yield C-methyl-C′-aryl-substituted carboranes. With the complexes (η⁶-o-C₆H₄X₂)Cr(CO)₃, the carborane displaces either a hydrogen atom (X = Cl) or a halide (X = F) from the arene ring to give 1-(1′-closo-2′-CH₃-1′,2′-C₂B ₁₀H₁₀)-2,3-Cl₂C₆H₃ (1) or 1-(1-closo-2′-CH₃-1′,2′-C₂B ₁₀H₁₀)-2-FC₆H₄ (2), respectively. Reaction of 2 equiv of LiC₂B₁₀H₁₀(CH₃) with (η⁶-p-C₆H₄F₂)Cr(CO)₃ results in the displacement of both fluoride atoms on the arene ring to yield the p-phenylene compound 1,4-(1′-closo-2′-CH₃-1′,1′-C ₂B₁₀H₁₀)₂C₆H₄ (3). Compounds 1 and 3 have been characterized by X-ray crystallography. 1 crystallized in the monoclinic space group P2₁ with a = 7.2516 (7), b = 7.7424 (8), and c = 13.4028 (13) A?; β= 97.389 (3)°; V = 750 A?³; and Z = 2. Data were collected at 128 K on a modified Picker FACS-1 diffractometer, using Mo Kα radiation, to a maximum 2θ = 50°, giving 1421 unique reflections, and the structure was solved by direct methods. The final discrepancy index was R = 0.038, R_w = 0.051 for 1355 independent reflections with I > 3σ(I). The C-C bond in the carborane is unusually long, 1.706 (5) A?, but it is the shortest interatomic distance within the icosahedron. 3 crystallized in the monoclinic space group P2₁/n with a = 7.024 (1), b = 13.764 (4), and c = 12.335 (4) A?; β = 90.99 (1)°; V = 1192 A?³; and Z = 2. Data were collected on a modified Syntex P1 diffractometer, using Cu Kα radiation, to a maximum 2θ = 100°, giving 1219 unique reflections, and the structure was solved by direct methods. The final discrepancy index was R = 0.061, R_w = 0.086 for 1020 independent reflections with I > 2σ(I). The molecule is centrosymmetric. The C-C bond in the carborane is rather long, 1.684 (5) A?, but it is the shortest interatomic distance in the icosahedron.