Reactions of Grignard Reagents with Tin-Corrole Complexes: Demetalation Strategy and σ‑Methyl/Phenyl Complexes

An efficient, mild, and one-step methodology for the conversion of tin-corroles to the corresponding free base corroles has been developed. The Grignard reagent, namely, methylmagnesium chloride, is responsible for the facile demetalation of tin-corroles. In an optimized reaction, almost complete destannation is observed using methylmagnesium chloride in a representative corrolato-Sn­(IV)-chloride complex. This particular protocol has also been proven to be versatile on a wide variety of corrolato-Sn­(IV)-chloride substrates. Similar Grignard reagents, namely, methyl/phenylmagnesium bromides, however, failed to perform the desired demetalation reaction and rather resulted in the usual σ-methyl/phenyl complexes in good yields. In addition to two novel σ-phenyl complexes and three novel σ-methyl complexes, one new A₃-corrole and one new corrolato Sn­(IV)­chloride have also been synthesized. All the complexes have been thoroughly characterized by various spectroscopic techniques, including single-crystal X-ray structural analysis of the representative complexes. In the single-crystal X-ray data analyses, it was observed that the Sn–N and Sn–C bond distances are shorter than those in the similar tin porphyrin analogues. The ¹H NMR spectrum of a representative σ-methyl complex exhibits peaks corresponding to σ-bonded methyl groups in the high field regions at −3.39 ppm.