Spin-orbit effects on electronic delocalization. Aromaticity in a discrete square tetrapalladium sandwich complex.
In this article, we report the relativistic electronic structure, including spin-orbit interaction, employing all-electron density functional theory calculations on the multimetallic sandwich compound [(CNT)Pd(4)(COT)](1+) (1), which can be considered as a [Pd(4)](2+) fragment flanked by two ring-ligands, namely, cyclononatetraenyl (CNT(1-)) and cyclooctatetraene (COT), as well as the dimer of 1, hereafter 2. The calculations suggest that the Pd(4)-ligand interaction is mainly electrostatic, being the main responsible term for the stabilization of the almost fully occupied 4d shell [Pd(4)](2+) fragment. The ring currents and electronic delocalization estimated via the nuclear independent chemical shifts indices and electron localization function, allow us to describe a significant sigma-aromaticity at the center of the Pd(4) square in 1, which in conjunction with the aromaticity arising from the ligands induce considerable aromatic character inside of the multimetallic metallocene.
Muñoz-Castro
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Departamento de Ciencias Quimicas, Relativistic Molecular Physics Group, Universidad Andres Bello, Republica 275, Santiago, Chile.
Mac-Leod Carey
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Arratia-Pérez
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R