Indacyclopentadienes and Aromatic Indacyclopentadienyl Dianions: Synthesis and Characterization

A series of unprecedented metallacycles of indium, including indacyclopentadienes ( 2 ), spiro indacyclopentadienes ( 3 ), aromatic indacyclopentadienyl dianions with an In−Li bond ( 4 ), and aromatic indacyclopentadienyl dianions with an In−In bond ( 5 ), were synthesized and structurally characterized by single‐crystal X‐ray structural analysis for the first time. Both indacyclopentadienes 2 and 3 were synthesized by reaction of 1,4‐dilithio‐1,3‐butadienes with InCl 3 . Structural transformations between 2 and 3 were observed. Reduction of indacyclopentadienes 2 with an excess amount of lithium afforded aromatic indacyclopentadienyl dianions 4 with an In−Li bond or 5 with an In−In bond, respectively, depending on the substituents on the ring. The aromatic character of 4 and 5 was confirmed by both experimental measurements and theoretical analysis.