Solution nuclear magnetic resonance spectral characterization of iron(II) porphyrin complexes of weakly coordinating anions

Weakly coordinating anions show little affinity for binding to unfunctionalized iron(II) porphyrins. The electron-deficient 5, 10, 15, 20-tetrakis(pentafluorophenyl)porphinatoiron(II) compound is utilized in this study to demonstrate solution coordination by chloride, bromide and acetate ions. The binding strength of anions to the iron(II) porphyrin is reflected by a systematic change in pyrrole proton chemical shift in H-1 NMR spectra; the pyrrole resonance moves downfield when the sigma-donor ability of anions is decreased.