Metal Influence over Decker Complexes.
Could the Metals be Communicated through Aromatic Rings or Create Aromaticity?

David Arias-Olivaresa, Julia Contreras-Garcíab, and Dayán Páez-Hernándezc
aUniversidad Andres Bello, Santiago, Chile
bLaboratoire de Chimie Théorique, Sorbonne Université & CNRS, Paris, France
cCenter of Applied Nanoscience, Universidad Andres Bello, Santiago, Chile

Mercredi 20 Février 2019, 11h00
bibliothèque LCT, tour 12 - 13, 4ème étage

One of the most interesting topics in chemistry is aromaticity, represented by the major breakthrough developed by Kekulé. Its analogues and derivatives paved the way for theoreticians and experimental chemists to understand how aromaticity works, what type of molecules could be aromatic and how aromaticity could be affected by the environment (i.e., magnetic fields or ligands) [1]. In this way, benzene-stacked system or Metallabenzene-like molecules have been studied showing some physical chemical properties like the aromatic ones, such as the existence of homologous molecular orbitals (compared with benzene), the planarity on the ring, the bond length between C-C [2]. Furthermore, in some systems, the rings proposed are purely from transition metals like the tri-platinum clusters but it is not already known if it is possible to have a Pt-Pt covalent bond as well as the interaction between transition metals with d10 configuration, or aromatic behaviour [3]. In some of the previous cases, a possible communication (isotropic interaction) between the metals through the ring is observed. An Uranium (open Shell) system is proposed to measure the isotropic interaction theoretically, nevertheless, is computationally expensive in the CASSCF framework. To reduce this cost, the error bars from HF to BS-DFT for J-Coupling are proposed for an organometallic database.

[Picture]

Figure 1. (a) Triple Decker Metal-Benzene, (b) C5H5Pt - Cp Metallabenzene, (c), Pt3 model ring and (d) U2Benzene model.


In the current work, the aromaticity of benzene and how it is affected by a metallic environment is studied by means of NICS and the induced magnetic field (Bind) as a consequence of the change of transition metal atoms (Figure 1a). This study is extended to metallabenzene complexes to understand the insertion of the metal into the ring (Figure 1b) and finally a ring fully composed of transition metals (Figure 1c). In the last two cases, the ring currents are measured as well as topological analyses carried out to reveal the interactions among metals (or between metals and the organic structure). In the open Shell cases (Figure 1d), the CASSCF framework was used to measure the isotropic coupling whereas the BS-DFT models were used for the rest of the organometallic database.
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References :
[1] H.-F. Li, X.-Y. Kuang, and H.-Q. Wang, Dalton Trans., 2011, 40, 4578-4589.
[2] M. A. Iron, A. C. B. Lucassen, H. Cohen, M. E. van der Boom, and J. M. L. Martin, J. Am. Chem. Soc., 2004, 126, 11699-11710.
[3] R. Bender, P. Braunstein, S.-E. Bouaoud, N. Merabet, D. Rouag, P. Zanello, and M. Fontani, New J. Chem., 1999, 23, 1045-1047.