Scalar coupling across [C-H···F-C] interactions in (σ-aryl)-chelating post-metallocenes

Area of Science:

• Organometallic Chemistry
• Supramolecular Chemistry
• Spectroscopy

Background:

• C-H···F-C interactions are topical but debated in chemistry.
• Developing spectroscopic methods to study these interactions is crucial.
• Fluorinated ligands offer a unique handle for probing non-covalent interactions.

Purpose of the Study:

• To synthesize and characterize Group 4 bis(benzyl) complexes with fluorinated ligands.
• To investigate the presence and nature of C-H···F-C interactions using spectroscopic techniques.
• To establish the utility of NMR spectroscopy in detecting and quantifying these interactions.

Main Methods:

• Synthesis of Group 4 bis(benzyl) complexes featuring fluorinated (σ-aryl)-2-phenolate-6-pyridyl ligands.
• X-ray crystallography to determine the solid-state structure of a representative complex.
• Multinuclear NMR spectroscopy, including (1)H, (13)C, and [(1)H,(19)F]-HMBC experiments.

Main Results:

• The X-ray structure of a Hf complex revealed intramolecular C-H···F-C and Hf···F-C contacts.
• NMR spectra showed characteristic coupling between benzyl and CF(3) groups for Ti, Zr, and Hf complexes.
• [(1)H,(19)F]-HMBC NMR confirmed scalar coupling across C-H···F-C interactions in Ti complexes.

Conclusions:

• The study provides spectroscopic evidence for C-H···F-C interactions in Group 4 metal complexes.
• NMR spectroscopy, particularly HMBC, is effective for probing these non-covalent interactions.
• The findings contribute to understanding the role and detection of C-H···F-C interactions in organometallic chemistry.