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]

Abstract

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)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-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].