Metallaborane Chemistry.  Part 14.  Icosahedral h⁶-Arene Carbametallaboranes of Iron and Ruthenium; Molecular Structures of closo-[1-(h⁶-C₆H₅Me)-2,4-Me₂-1,2,4-FeC₂B₉H₉] and closo-[3-(h⁶-C₆H₆)-3,1,2-RuC₂B₉H₁₁]

Icosahedral 2,4-dicarba-1-ferraboranes with η⁶-bonded benzene, toluene, o-xylene, or naphthalene ligands have been synthesised in moderate yields by reaction of [Fe(cod)(η⁵-C₅H₅)] (cod = cyclo-octa-1,5-diene) with 2,3-Me₂-2,3-C₂B₉H₉ in the presence of the appropriate arene. In addition, the toluene derivative, closo-[1-(η⁶-C₆H₅Me)-2,4-Me ₂-1,2,4-FeC₂B₉H₉] (2), has also been obtained by treatment of the carbaborane with [Fe₂(μ-η-C₆Me₆) (η⁵-C₅H₅)₂] in toluene. Reaction of [RuCl₂(η⁶-C₆H₆)₂] with Tl[TlC₂B₉H₁₁] affords closo-[3-(η⁶-C₆H₆)-3,1,2-RuC ₂B₉H₁₁] (7). Complexes (2) and (7) have been characterised by single-crystal X-ray diffraction. Crystals of (2) are orthorhombic, space group Pna2₁, with a = 21.793(4), b = 8.6274(15), c = 8.636(3) Å, and Z = 4; R = 0.0499 for 1 676 reflections. Complex (7) is also orthorhombic, space group Pnam, with a = 18.477(2), b = 9.191(4), and c = 7.704(1) Å, and Z = 4; R = 0.0223 for 1 723 data. Both species have slightly distorted Icosahedral cage geometries and overall C_s molecular symmetry, space group imposed for (7). The naphthalene derivative [1-(η⁶-C₁₀H₈)-2,4-Me ₂-1,2,4-FeC₂B₉H₉] undergoes substitution of the arene ligand by CO at 100 bar and 50 °C, to afford the complex [1,1,1-(CO)₃-2,4-Me₂-1,2,4 FeC₂B₉H₉].