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Electron counting and bonding analysis in triruthenium clusters containing sulfoximido ligands : true or false electron-deficient systems ?
Auteur(s)
Saillard, Jean-Yves
Kahlal, Samia
Ferrand, Vincent
Date de parution
2001-02-15
In
Journal of Organometallic Chemistry, 2001/620/119-126
Résumé
Triruthenium clusters containing a methylphenylsulfoximido cap or bridge, Ru<sub>3</sub>(CO)<sub>9</sub>(μ<sub>2</sub>-H)[μ<sub>3</sub>-NS(O)MePh] (<b>1</b>), Ru<sub>3</sub>(CO)<sub>10</sub>(μ<sub>2</sub>-H)[μ<sub>3</sub>-NS(O)MePh] (<b>2</b>), Ru<sub>3</sub>(CO)<sub>8</sub>(μ<sub>3</sub>-η<sup>2</sup>-CPhCHBu)[μ<sub>3</sub>-NS(O)MePh] (<b>3</b>), Ru<sub>3</sub> (CO)<sub>9</sub>(μ<sub>3</sub>-η<sup>2</sup>-PhCCCCHPh)[μ<sub>2</sub>-NS(O)MePh] (<b>4</b>), and Ru<sub>3</sub>(CO)<sub>7</sub>(μ<sub>2</sub>-CO)(μ<sub>3</sub>-η<sup>2</sup>-PhCCCCHPh)[μ<sub>3</sub>-NS(O)MePh] (<b>5</b>) have been examined by EHT and DFT calculations in order to analyze the bonding present in the clusters and to establish the electron counting. They clearly show that a μ<sub>3</sub>-sulfoximido group is not a 3e<sup>−</sup> ligand as one may be led to think at first sight, but rather acts as a three-orbital/5e<sup>−</sup> system, i.e. should be considered as isolobal to an N---R<sup>−</sup> ligand. Because of some delocalization of its π-type orbitals on the sulfur and oxygen atoms, it is expected to bind slightly less strongly to metal atoms than classical imido ligands. Once in a μ<sub>2</sub> coordination mode, the sulfoximido ligand retains a lone pair on its pyramidalized N atom and becomes a two-orbital/3e<sup>−</sup> ligand. It follows that clusters <b>1</b>, <b>2</b>, <b>4</b> and <b>5</b> are electron-precise, whereas cluster <b>3</b> is electron deficient with respect to the 18e<sup>−</sup> rule but obeys the polyhedral skeletal electron pair electron-counting rules. Consistently, all the calculated clusters exhibit large HOMO–LUMO gaps and no trace of electron deficiency can be found in their electronic structures.
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Type de publication
journal article
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