Steric and electronic influence on Cu-Cu short contacts in β-thioketiminato tricopper(I) clusters.

A series of β-thioketiminate copper(I) complex trimers [LCu I ] 3 were synthesized by modifying the ligand framework with electron-withdrawing groups (F and Cl) or electron-donating groups ( i Pr and Me) at the N -aryl ring as well as with CF 3 groups on the chelating backbone. This ligand modification significantly impacts the enhancement of Cu⋯Cu short contacts, which can be rationalized by using steric and electronic factors of the chelated ligand. We observed that this intramolecular cuprophilicity among [LCu I ] 3 complexes is primarily governed by the size of N -aryl ortho -substituents. These findings were well supported by X-ray crystallography, Raman spectroscopy, and Mayer bond order analysis. The electronic effects induced by the ligand modification on the LCu I fragment were investigated using CO and 2,4,6-CNC 6 H 2 Me 3 as probe molecules. Corroborated by the FTIR and CV measurements, our results reveal that the β-thioketiminate SN chelators induce more pronounced changes in the electronic character of the LCu I fragment due to the presence of CF 3 groups on the chelating backbone in comparison with the F or Cl substituents on the N -aryl ring.