The clean formation of the 3-boryl-1-stannacyclopentane (2) is observed from the monohydroboration of divinyldimethyltin with 9-BBN-H, a previously unknown process. This heterocyclic system undergoes expected organoborane reactions with the notable exception of the Suzuki-Miyaura coupling where, with bromobenzene, 3-butenyl(dimethyl)phenyltin (16) is the exclusive coupling product, evidently forming through an unprecedented stanna-Heck process.