Evaluation of the stereoselectivity for titanium(IV)-based coordination entities induced by the enantiopure diphenylethene-1,2-diamine ligand

Emilie Macker , Laurent Barloy (1) , Alain Chaumont (2) , Nathalie Kyritsakas (3) , Bruno Vincent (4) , Marc Henry (5) , Pierre Mobian

1 CMC - Chimie de la matière complexe
2 Institut de Chimie de Strasbourg
3 Institut Le Bel
4 IRBI - Institut de recherche sur la biologie de l'insecte
5 Départment de sciences économiques

This article describes the formation of neutral TiO 4 N 2-based coordination entities where the titanium centers are coordinated by oxygenated ligands incorporating one or two biphenolato units, i.e. L 1 and L 2 respectively. In these systems, the sixfold coordination spheres of each metallic center are completed by the enantiopure bi-dentate diphenylethene-1,2-diamine compound, abbreviated as dpeda. A solvent dependent diastereomeric ratio is evaluated by 1 H NMR for the monomeric [Ti(L 1) 2 ((1R,2R)-dpeda)] or [Ti(L 1) 2 ((1S,2S)-dpeda)] (abbreviated as [R-Ti] or [S-Ti] respectively) complexes. The highest diastereomeric ratio for [Ti(L 1) 2 (dpeda)] is obtained in chloroform (2 : 1). Energy calculation and circular dichroism spectra simulation, obtained by DFT, permit to assign the configuration of the stereoisomer formed in excess. The (1R,2R)-(+)-dpeda privileges the Δ form and (1S,2S)-(-)-dpeda the Λ form of the [Ti(L 1) 2 (dpeda)] stereoisomers. The helicates formulated as [Ti 2 (L 2) 2 ((1S,2S)-dpeda) 2 ] and [Ti 2 (L 2) 2 (1R,2R)-dpeda) 2 ] (abbreviated as [S-Ti2] or [R-Ti2] respectively) are obtained by following a multi-component self-assembly approach. In this case, the diastereomeric ratios evaluated by 1 H NMR are much lower compared to those determined for the monomeric species, and a privileged P and M configuration for the [Ti 2 (L 2) 2 (1R,2R)-dpeda) 2 ] helicate and the [Ti 2 (L 2) 2 ((1S,2S)-dpeda) 2 ] helicate respectively is assigned through theoretical calculations. Overall, this article describes a strategy to favour handedness in a helicate system where the chiral control is originated from a ligand that is not inscribed within the helical framework of the architecture.

Domaines: Chimie de coordination

Emilie Macker, Laurent Barloy, Alain Chaumont, Nathalie Kyritsakas, Bruno Vincent, et al.. Evaluation of the stereoselectivity for titanium(IV)-based coordination entities induced by the enantiopure diphenylethene-1,2-diamine ligand. Inorganica Chimica Acta, 2019, 498, pp.119119. ⟨10.1016/j.ica.2019.119119⟩. ⟨hal-02353903⟩