Metallaaromaticity involving a d 0 early transition metal centre: synthesis, structure, and aromaticity of tantallapyridinazirine complexes.

Though late transition metal aromatic metallabenzenes and related heteroatom-containing analogues have been well studied, the corresponding aromatic early transition metal complexes remain elusive. Herein, we demonstrate the synthesis of aromatic, planar, and delocalised organotantallapyridinium complexes via a simple one-pot process by sequential treatment of tantalum methyl complex [η 5 :σ-Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )]TaMe 3 with alkynes and isocyanide. Single-crystal X-ray analyses, NMR spectroscopic data and DFT calculations suggest that they are aromatic tantallapyridinium complexes, a class of long-sought-after molecules. This work would shed some light on the preparation of metallaaromatics involving early transition metals.