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. 2026 Feb 2;65(4):2110-2116.
doi: 10.1021/acs.inorgchem.5c05470. Epub 2026 Jan 15.

The Effect of a Single Trifluoromethyl Substituent on the Reactivity of Chelating C2 and Cs-Symmetric Bis(alkoxide) Ligands on a Terphenyl Platform

Ruwandhi Jayasundara  1 , Lakshani W Kulathungage  1 , Benjamin J Baillie  1 , Cassandra L Ward  2 , Richard L Lord  3 , Stanislav Groysman  1
Affiliations

The Effect of a Single Trifluoromethyl Substituent on the Reactivity of Chelating C2 and Cs-Symmetric Bis(alkoxide) Ligands on a Terphenyl Platform

Ruwandhi Jayasundara et al. Inorg Chem. .

Abstract

Herein we describe the synthesis and preliminary reactivity studies of new racemic C2-symmetric and meso Cs-symmetric bis(alkoxide) ligands on a para-terphenyl platform. The ligands were synthesized by reaction of 2,2'-dilithium-p-terphenyl with trifluoroacetophenone, separated by column chromatography, and obtained in 36% (racemic, rac-Lig2H2) and 26% (meso, meso-Lig2H2) isolated yields. The reaction with n-butyl-sec-butylmagnesium led to formation of the expected C2-symmetric and Cs-symmetric mononuclear magnesium complexes. In contrast, the reaction with Cr(N(SiMe3)2)2(THF)2 exhibited a profoundly different coordination chemistry from that of all-phenyl chelating bis(alkoxide) or monodentate alkoxides. While the latter generally form Cr2(OR)4 dimers in which the geometry at Cr(II) is Y-shaped, these new ligands lead to square-planar Cr(II) complexes. DFT calculations help rationalize the distinct dimeric species Cr2(rac-Lig2)2(THF)4 and Cr2(meso-Lig2)2 observed for these new ligands.

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Figures

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1
Previous design of C 2v-symmetric complexes with chelating bis­(alkoxide) on a terphenyl platform (Lig1), and current design of C 2-symmetric chelating bis­(alkoxide).
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Top: Synthesis and isolated yields of Lig2H2. Middle: 1H NMR of the OH protons of the mixture of diastereomers (center), separated racemic (homochiral, left) and meso (right) diastereomers. Bottom: X-ray structures (ORTEP drawings, 50% probability ellipsoids, side and top view) of rac-Lig2H2 and meso-Lig2H2.
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VT NMR spectra of rac-Lig2H2, demonstrating (1) two isomers at low temperature and (2) equilibration above room temperature.
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Reactions of rac/meso-Lig2H2 to produce the corresponding mononuclear Mg­(II) and dinuclear Cr­(II) products. X-ray structures of 1–4 are drawn using ORTEP, with 50% probability ellipsoids.
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Optimized structures of 3 rac (top left) and 3 meso (top right), with side-on views of the Cr–arene interaction, with distances (Å) below each structure. Hydrogens omitted for clarity.
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Ligand conformations of rac-Lig2 (left) and meso-Lig2 (right) from 4 rac and 4 meso , respectively. Full dimer structures are in the Supporting Information ().
See this image and copyright information in PMC

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