The Question of Participation in the Bonding of Fluorosubstituted Arenes to Chromium Tricarbonyl. A 19F Nuclear Magnetic Resonance Investigation

I9 F n.m.r. chemical shifts of free fluoroarenes have been correlated with the Swain–Lupton field and resonance parameters. Comparison of these data with the corresponding Cr(CO) 3 complexes shows little change in the transmission of mesomeric effects by para-substituents. Meta-substituents which interact primarily by a field effect have very little influence on the fluorine chemical shift in the complexes suggesting that the σ framework of the ring interacts with the chromium.