Radical metallacyclopropene: synthesis, structure and aromaticity

Abstract

Metallaaromatics are an important class of aromatic compounds, showing diverse and interesting aromatic properties. Radical rhenabenzofurans 1–3 with a fused metallacyclopropene unit are reported, containing d¹ Re centers. Computational studies show that the three-membered rhenacyclopropene ring is σ-aromatic, while the rhenafuran ring is nonaromatic. These complexes represent the first radical metallacyclopropenes. α-Metallabenzofuran complexes 4–5 with d⁰ Re centers and 6 with a d² Re center are also synthesized. α-Metallabenzofurans 1–6 have adjacent oxidation states (Re(III), Re(IV), and Re(V)). Both the structure and aromatic nature of these metallacycles are affected by the change of oxidation states of the metal center.