Metallaborane Heteroatom Incorporation Reactions:  Enyne Insertion into arachno-[(CO)(PMe3)2HIrB8H12]

arachno-[(CO)(PMe3)2HIrB8H12] (1) reacts with HC⋮C−C(CH3)CH2 in xylene at 138 °C to afford [7-{C(CH3)CH2}-9,9,9-(CO)(PMe3)2-nido-9,7,8-IrC2B8H10] (2; 10%) together with traces of [5,5,5-(CO)(PMe3)2-μ-6,7-{CHC(CH3)CH2}-nido-5,6-IrCB8H11] (3, <1%). Compound 2 is a conventional nido 11-vertex metallacarborane with the {C2Ir} three-atom string in the open face of the cluster, whereas compound 3 is based on a nido 10-vertex {5,6-IrCB8} skeleton with C(2) of the original butyne bridging adjacent B(7) and C(6) cluster open-face positions. Compounds 2 and 3 are characterized by 1H, 31P, and 11B NMR spectroscopy and by single-crystal X-ray diffraction analysis.