13C NMR Relaxation Study of Molecular Motions in Tetraphenyltin and Tetra(p-tolyl)tin in Solution

Autor:	Henry F. Schaefer, Yaoming Xie, Kong Mun Lo, Renuka V. Sathasivam, Soon Ng
Rok vydání:	2005
Předmět:	Chemistry Relaxation (NMR) chemistry.chemical_element Hyperconjugation Rotation Ring (chemistry) Rotational energy chemistry.chemical_compound Crystallography Computational chemistry Moiety Physical and Theoretical Chemistry Tin Methyl group
Zdroj:	The Journal of Physical Chemistry A. 109:12059-12063
ISSN:	1520-5215 1089-5639
DOI:	10.1021/jp058135k
Popis:	The Woessner approach is applied to the 13C 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.
Databáze:	OpenAIRE
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