Metalation of Bis(meta-carborane)

The first metallacarborane derivatives of 1,1′-bis(meta-carborane), specifically [1-(1′-closo-1′,7′-C₂B₁₀H₁₁)-2-(p-cymene)-closo-2,1,7-RuC₂B₉H₁₀] (2), [1-(1′-closo-1′,7′-C₂B₁₀H₁₁)-2-(p-cymene)-6-OEt-closo-2,1,7-RuC₂B₉H₉] (3), [1-(1′-closo-1′,7′-C₂B₁₀H₁₁)-2-(C₆Me₆)-closo-2,1,7-RuC₂B₉H₁₀] (4), [1-(1′-closo-1′,7′-C₂B₁₀H₁₁)-2-(C₆Me₆)-6-OEt-closo-2,1,7-RuC₂B₉H₉] (5), [1-(1′-closo-1′,7′-C₂B₁₀H₁₁)-2-Cp-closo-2,1,7-CoC₂B₉H₁₀] (6) and [1-(1′-closo-1′,7′-C₂B₁₀H₁₁)-2-Cp*-closo-2,1,7-CoC₂B₉H₁₀] (7), have been prepared by deboronation of one cage and subrogation of the {BH} fragment removed by an isolobal {Ru(arene)}, {CoCp} or {CoCp*} fragment. In the case of the {Ru(arene)} species, attack on the products 2 and 4 by EtO⁻ resulted in derivatives 3 and 5, respectively, in which an OEt group is attached to B6 of the metallacarborane cage. All products were characterised by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. All are of the form the 2,1,7-MC₂B₉-1′,7′-C₂B₁₀, and even though the structural studies reveal clear evidence of steric crowding between the arene or Cp/Cp* ligand on the metal and the pendant carborane cage, no isomerisation of the metallacarborane to either 2,1,8-MC₂B₉ or 2,1,12-MC₂B₉ occurs, even on heating to reflux in toluene.