Quenched gas-phase reactions of tetraborane(10), B4H10, with substituted alkynes : new nido-dicarbapentaboranes and arachno-monocarbapentaboranes.

New alkyl derivatives of the nido-dicarbapentaborane, 1,2-C2B3H7, and arachno-carbapentaborane, 1-CB4H10, have been identified as the main volatile carbaborane products in quenched gas-phase reactions of tetraborane(10), B4H10, with alkyl-substituted ethynes RC[triple bond, length as m-dash]CR′ (R = Me, Et, nPr or tBu, R′ = H; R = Me or Et, R′ = Me). The gaseous mixtures were heated at 70 °C, and monitored by gas-phase mass spectrometry. Each reaction was quenched when the ethyne was used up. The quenched gas-phase reaction of B4H10 and Me3SiC[triple bond, length as m-dash]CH gave a single volatile carbaborane product, 1-Me3Si-1,2-C2B3H6