Novel organotin halides. Organometallic substituted stannoles and alkene derivatives with tinchlorine and tinbromine bonds—exceptionally small magnitude of coupling constants ∣1J(119Sn, 13C)∣

Exchange reactions of spirocyclic stannoles with boron, tin and phosphorus halides lead to stannoles 4, 5 and 6, 7, in which the tin atoms bear two chloro or two bromo ligands. The same stannoles 4 and 5 were prepared by 1,1-ethylboration of bis(trimethylsilylethynyl)tin dichloride (8) or -dibromide (9), prepared in situ from tetrakis(trimethylsilylethynyl)tin and tin tetrachlodide or -tetrabromide. Alkenes with a similar pattern of substituents at the CC bond were prepared either by 1,1-ethylboration of the trimethylsilylethynyltin trihalides (10, 11, leading to 12, 13) or by exchange reactions of organotin substituted alkenes with tin tetrachloride (leading to 14). All compounds, in which a trimethylsilyl and an SnX2 moiety (in the stannoles 4, 5) or an SnX3 group (in the alkenes 12, 13) are in geminal positions at the olefinic carbon atoms, decompose already at room temperature by elimination of SnX2 (X=Cl, Br). Exceptionally small coupling constants ∣1J(119Sn, 13C)∣ are observed for these compounds. The comparable derivatives, in which the trimethylsilyl groups are replaced by propyl (stannoles 6, 7, and the alkene 14), are much more stable, and the magnitude of ∣1J(119Sn, 13C)∣ is found in the expected range.