Cyclopentadienylaluminum complexes are of interest due to their practical application in various technological processes as well as their versatile bonding modes with metallic center observed. The analysis of the factors influencing the electronic structure of the cyclopentadienyl ring in aluminum complexes of general formulae Cp_xAlL_y is the subject of this contribution.

The electronic structure of the cyclopentadienyl ligand bonded to metallic center can be regarded as intermediate between the highly aromatic, uncomplexed cyclopentadienyl anion and the structure of the cyclopentadiene, CpH, exhibiting antiaromatic character. Basing on the crystal structure of the newly characterized aluminum complexes and the data deposited in CSD the relationship between the Cp ligand aromaticity (described by HOMA index [1]) and the Cp bond-mode with aluminum will be discussed. The impact of both the negative hyperconjugation and steric effects will be shown. The nature of the effects observed will be supported and explained by DFT calculations (B3LYP/6-311G**) and NBO analysis [2].

[1] T. M. Krygowski, J. Chem. Inf. Comput. Sci. 1993, 33, 70.
[2] J. P. Foster, F. Weinhold, J. Am. Chem. Soc. 1980, 102, 7211.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/8556 must be provided.