# The Effect of a Single Trifluoromethyl Substituent on the Reactivity of Chelating C 2 and C s‑Symmetric Bis(alkoxide) Ligands on a Terphenyl Platform

## TL;DR

This paper studies how adding a trifluoromethyl group affects the reactivity of specific bis(alkoxide) ligands on a terphenyl platform.

## Contribution

The study introduces new C2- and Cs-symmetric ligands and reveals their unique coordination behavior with chromium.

## Key findings

- The new ligands form square-planar Cr(II) complexes, unlike typical Y-shaped dimers.
- DFT calculations explain the distinct dimeric species formed with racemic and meso ligands.
- The ligands show different coordination chemistry compared to all-phenyl bis(alkoxide) ligands.

## Abstract

Herein we describe the synthesis and preliminary reactivity
studies
of new racemic C
2-symmetric and meso C
s-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 C
2-symmetric and C
s-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.