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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >C-13 NMR relaxation study of molecular motions in tetraphenyltin and tetra(p-tolyl)tin in solution
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C-13 NMR relaxation study of molecular motions in tetraphenyltin and tetra(p-tolyl)tin in solution

机译：溶液中四苯基锡和四（对甲苯基）锡中分子运动的C-13 NMR弛豫研究

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摘要

The Woessner approach is applied to the C-13 relaxation data for tetraphenyltin (1) and tetra(p-tolyl)tin (2) in CDCl3 solution over the temperature range 5-42 degrees C to obtain correlation times for rotational motions and hence the activation barriers. Quantum mechanical computations were carried out to obtain the rotational energy barriers for comparison. For 2 the relaxation data indicate (1) slower ring rotation than in 1, (2) highly hindered internal rotation of the methyl group. IR and chemical shift data support the hypothesis of hyperconjugation of the methyl correlated with interaction between the pi-electrons and the 5d orbitals of tin in the (p-tolyl)Sn moiety to account for the hindrances to the rotations of the ring and the methyl. The activation barrier for the tolyl group rotation is found to be much higher than that for the phenyl rotation. However, the Woessner approach yields an anomalously high barrier for the methyl rotation. An explanation based on correlated rotations of the tolyl ring and the methyl is offered.
机译：Woessner方法适用于温度范围为5-42摄氏度的CDCl3溶液中四苯基锡（1）和四（对甲苯基）锡（2）的C-13弛豫数据，以获得旋转运动的相关时间，因此获得了激活障碍。进行了量子力学计算以获得旋转能垒以进行比较。对于2，弛豫数据表明（1）环旋转慢于1，（2）严重阻碍了甲基的内部旋转。红外和化学位移数据支持以下假设：甲基的超共轭与π电子和（对-甲苯基）Sn部分中锡的5d轨道之间的相互作用有关，从而解释了环和甲基旋转的障碍。发现甲苯基基团旋转的活化屏障比苯基旋转基团的活化屏障高得多。但是，Woessner方法对甲基旋转产生异常高的势垒。提供了基于甲苯基环和甲基的相关旋转的解释。

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