1H dynamic NMR study of benzyltris(9-triptycyl)stannane (4) using two probes, the benzylic methylene and the aromatic peri-proton signals, revealed that the enantiomerization of the chiral conformers took place with ΔG‡ of 64.2 kJ mol−1 at 300 K.
Static and dynamic stereochemistry of several tris(9-triptycyl)stannane derivatives Tp 3 SnX (X = H, halogens, and alkyl groups) were studied. X-ray crystallography of the bromo and methyl compounds showed that the Sn atomwas fundamentally tetrahedral and that the three Tp groups meshed with each other like bevel gears and formed a near-C 3 chiral conformation. The rate constants for enantiomerization
研究了几种三(9-三苯乙烯基)锡烷衍生物 Tp 3 SnX(X = H、卤素和烷基)的静态和动态立体化学。溴和甲基化合物的 X 射线晶体学表明,Sn 原子基本上是四面体,三个 Tp 基团像锥齿轮一样相互啮合并形成近 C 3 手性构象。溶液中手性构象对映异构化的速率常数可以通过芳族质子信号的线形分析获得,即使不存在对映异构化的直接探针,如苄基。随着取代基 X 变得更大,对映异构化的能垒降低,这表明在引入更大的基团后,基态比过渡态更不稳定。