Scalar Coupling Across [CH⋅⋅⋅FC] Interactions in (σ-Aryl)-Chelating Post-Metallocenes

The nature and importance of CH⋅⋅⋅FC interactions is a topical yet controversial issue, and the development of spectroscopic methods to probe such contacts is therefore warranted. A series of Group 4 bis(benzyl) complexes supported by (σ‐aryl)‐2‐phenolate‐6‐pyridyl [O,C,NR1] ligands bearing a fluorinated R1 group (CF3 or F) in the vicinity of the metal has been prepared. The X‐ray crystal structure of the CF3‐substituted Hf derivative features intramolecular C‐H⋅⋅⋅F‐C and Hf⋅⋅⋅F‐C contacts. All complexes have been characterized by multinuclear NMR spectroscopy. The 1H and 13C NMR spectra of [M(O,C,NCF3)(CH2Ph)2] derivatives display coupling (assigned to 1hJHF and 2hJCF for Ti; 3JHF and 2JCF (through M⋅⋅⋅F) for Hf and Zr) between the benzyl CH2 and CF3 moieties. [1H,19F]‐HMBC NMR experiments have been performed for the M‐[O,C,N‐R1] complexes and their [O,N,C] counterparts, revealing significant scalar coupling across the CH⋅⋅⋅FC interactions for Ti‐[O,C,N] and [O,N,C] species. Genuinely attractive! The titled complexes have been characterized by multinuclear NMR (including [1H,19F]‐HMBC) experiments, which for the first time confirm that the observed 1H–19F coupling occurs with chemical connectivity across CH⋅⋅⋅FC interactions for Ti complexes (see scheme); differences in coupling patterns for Zr and Hf congeners are also rationalized.