The 1 : 1 reactions of triphenylborane 1 with monoalkyn-1-yltin compounds Me3Sn-C≡C-R1 2 [R1 = tBu (a), Ph (b), ferrocenyl (c), Si(H)Me2 (d), SnMe3 (e)] afford mainly (> 80 %) the corresponding alkene derivatives 3 by 1,1-phenylboration. Exchange B-Ph/Sn-C≡C-R1 takes place as a side reaction. The corresponding 1 : 2 reaction with 2b leads to the dialkenylborane 4b (R1 = Ph), of which the molecular structure could be determined by X-ray analysis. In contrast, the 1 : 2 reaction with 2e gave an allene derivative 5e. The solution-state structures of compounds 3 - 5 have been confirmed by 1H, 11B, 13C and 119Sn NMR spectroscopy.