The Rectangular Niobium Oxyiodide Cluster Nb₄OI₁₀ – A Narrow Band‐Gap Semiconductor

A metal‐rich niobium oxyiodide was prepared by soft reduction of NbI 4 . The structure of the new compound Nb 4 OI 10 was determined by single‐crystal X‐ray diffraction and contains a rectangular Nb 4 (μ 4 ‐O) cluster that is interconnected into layers by iodide ligands. The local structure of the Nb 4 OI 10 cluster bears a close relationship to a defect Nb 6 I 11 structure. The two‐dimensional van der Waals material Nb 4 OI 8 I 4/2 ] is a small band‐gap semiconductor (<1 eV), as analysed by electrical conductivity measurements, photoresponse, experimental band gap determination, and band structure calculation.