Metallaborane chemistry. Part 14. Icosahedral η6-arena carbametallaboranes of iron and ruthenium; molecular structures of closo-[1-(η6-C6H5Me)-2,4-Me2-1,2,4-FeC2B9H9] and closo-[3-(η6-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-Me2-1,2,4-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-RuC2B9H11](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)A, 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)A, and Z= 4; R= 0.0223 for 1 723 data. Both species have slightly distorted Icosahedral cage geometries and overall Cs molecular symmetry, space group imposed for (7). The naphthalene derivative [1-(η6-C10H8)-2,4-Me2-1,2,4-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].