Steric and Electronic Influences 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 (iPr and Me) at the N-aryl ring as well as with CF₃ groups on the chelating backbone. This ligand modification significantly impacts on 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 LCuI fragment were investigated using CO and 2,4,6-CNC₆H₂Me₃ 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 LCu^I fragment due to the presence of CF₃ groups on the chelating backbone in comparison to the F or Cl substituents on the N-aryl ring.