Treatment of 7-(CH3)3N-7-CB10H12 with triethylamineborane(3) at 180-200 °C proceeds under splitting off one methyl group and inserting one boron vertex to obtain 1-(CH3)2NH-1-CB11H11. Methylation of the latter compound produces 1-(CH3)3N-1-CB11H11 which can be reduced to the parent 1-CB11H12- anion with sodium in liquid ammonia. The constitution of all compounds was established by NMR and mass spectroscopy.

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Reaction of [Ir(CO)Cl(PPh3)2] with the [closo-CB7H8]- anion in dichloromethane solution at room temperature results in oxidative insertion into the cluster to give the novel nine-vertex closo-type species [(CO)(PPh3)2IrCB7H8] in 87% yield as a pale-yellow air-stable solid. Crystals (from hexane-benzene) are orthorhombic, space group P212121, with a = 1056.7(1), b = 1597.6(2), c = 2150.5(2) pm, and Z = 4. The crystal and molecular structure was refined to R (Rw) = 0.0244 (0.0250) for 3338 observed reflections with F0 > 4.0σ(F0). The cluster structure is based on a tricapped trigonal prismatic arrangement of the {IrCB7} atoms, with the iridium atom at a five-connected cluster-vertex position, and the carbon at a non-adjacent four-connected capping site. In this formally closo cluster, the distance between the two boron atoms that are bound to both iridium and carbon atoms is markedly long at 219.0(14) pm, an instance of a generally unrecognized phenomenon which is briefly discussed in the context of the other partially opened, though formally closo, nine-, ten- and eleven-vertex boron-containing cluster compounds.

Two representatives of the 10-vertex family of tricarbaboranes, arachno-p6,9-RCH-9-R-5,6,9-C3B7Hll (R = H o r Me) and nido-5,6,1 0-Me3-5,6,1 0-C3B7H8, arise f r o m two different modes of al kyne insertion (acetylene and but-2-yne) into the cage of arachno-4,5-C2B7HI3.