Synthesis of 16-Electron (η³-Cyclooctenyl)metallacarboranes of Rhodium(III) and Iridium(III) with the New Sterically Demanding [(4‘-MeC₆H₄)₂C₂B₉H₉]^2- Carborane Ligand. Molecular Structures of [3-{(1−3-η³)-C₈H₁₃}-1,2-(4‘-MeC₆H₄)₂-3,1,2-pseudocloso-MC₂B₉H₉] (M = Rh, Ir) and [(η⁶-MeC₆H₄)Rh(C₂B₉H₉C₆H₄Me)Rh(η⁴-C₈H₁₂)]₂, a Dimeric Byproduct Containing Distorted 13-Vertex {4,9,1,10-Rh₂C₂B₉} Cluster Units

Reactions of the [K]⁺ salt of the [7,8-(4‘-MeC₆H₄)₂-7,8-nido-C₂B₉H₁₀]^- monoanion with the COD−rhodium and COD−iridium μ-chloride complexes [(η⁴-COD)₂M₂(μ-Cl)₂] proceed in benzene at ambient temperature with the formation of the 16-electron complexes [3-{(1−3-η³)-C₈H₁₃}-1,2-(4‘-MeC₆H₄)₂-3,1,2-pseudocloso-MC₂B₉H₉] (5, M = Rh(III); 6, M = Ir(III)), respectively, whose pseudocloso strucrure has been confirmed by single-crystal X-ray diffraction studies. The major species 5 is formed along with a small amount of the dimeric rhodacarborane [(η⁶-MeC₆H₄)Rh(C₂B₉H₉C₆H₄Me)Rh(η⁴-C₈H₁₂)]₂ (7), which, as found from X-ray structure determinations, is composed of two distorted {4,9,1,10-Rh₂C₂B₉} cluster units joined together through η⁶ coordination of the 4-tolyl cage substituent of one unit to one of the rhodium atoms of the second unit and vice versa.