150666-59-4Relevant articles and documents
Routes to Stannoles, Stannolenes and 1-Stanna-4-bora-2,5-cyclohexadienes - Crystal Structure of a Triorganotin Cation Stabilized by ?-Coordination
Wrackmeyer, Bernd,Kundler, Sabine,Boese, Roland
, p. 1361 - 1370 (2007/10/02)
Di-1-alkynyltin compounds (1) react with triorganoboranes R3B to give (η2-alkynyl)tin compounds 3 (R = Et) and 4 (R = iPr) in which a cationic three-coordinate tin centre is stabilized by intramolecular side-on coordination to the CC bond of an alkynylborate fragment.An X-ray analysis of 3e, prepared from Me2Sn(CCiPr)2 (1e) and Et3B, proves the coordination of the tin atom to the CC bond as well as a weak B-C bond.An important dynamic process, i.e. exchange of the alkynyl group between boron and tin, is shown by 11B and 119Sn NMR at variable temperature.Most of the intermediates 3 react with an excess of Et3B by a second intramolecular 1,1-ethyloboration to dialkenyltin derivatives 7 which readily rearrange to the 3-stannolenes, 8.Without an excess of Et3B, intramolecular 1,1-vinyloboration (leading to stannoles 5) competes with intramolecular 1,1-ethylboration (leading to 1-stanna-4-bora-2,5-cyclohexadienes 9).The latter route is preferred in the case of most of the intermediates 4 (intramolecular 1,1-isopropyloboration) and affords the six-membered rings 10 (R = iPr). 11B- and 13C-NMR data indicate that the heterocycles 9 (R = Et) adopt a flatter conformation than 10 (R = iPr). Key Words: 1,1-Organoboration / Alkynyltin compounds / Tin cations, triorgano- / ?-Coordination
