Metallaaromaticity involving a d 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 a simple one-pot process by sequential treatment of tantalum methyl complex [η:σ-MeC(CH)(CBH)]TaMe 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.