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Understanding Trends in 27 Al Chemical Shifts and Quadrupolar Coupling Constants in Chloroalkyl Aluminum [AlCl x (Me) 3 − x ] n = 1 or 2 Compounds
Author(s) -
Lam Erwin,
Copéret Christophe
Publication year - 2018
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201800120
Subject(s) - chemistry , chemical shift , coupling constant , atomic orbital , aluminium , chemical physics , catalysis , molecular orbital , computational chemistry , lewis acids and bases , crystallography , molecule , electron , organic chemistry , physics , particle physics , quantum mechanics
The usage of alkyl aluminum compounds and related structures as co‐catalyst finds a broad range of application in homogeneous and heterogeneous catalysis. While understanding the nature of the aluminum species in solution or in solids can be a challenge, 27 Al solid state NMR is a powerful tool to understand the structures of Al species, but their assignment remains mostly empirical, typically by comparing chemical shifts with known compounds. In this work, the observed trends in 27 Al‐ NMR parameters – chemical shift and quadrupolar coupling constant – of chloroalkyl aluminum compounds, a prototypical class of important Lewis activators, are traced back to their frontier orbitals and electron polarization through a natural localized molecular orbital analysis. This study thus provides guidelines to understand the nature of chemical shift and thereby assignment of possible structure.