Semiconducting Niobium Oxyiodide Cluster Compounds from Heterogenous Solid-State Reactions

Abstract

The use of lithium cyanamide (Li2CN2) as an unconventional reducing agent gave access to the synthesis of a variety of previously unknown niobium oxyiodide phases, which could not be obtained by conventional reduction methods of niobium iodides. These compounds are predominantly formed through an gaseous intermediate phase, from which diverse cluster species were isolated depending on the specific thermal conditions applied during the reaction. The resulting clusters exhibit a wide range of structural motifs, such as framework-like, layered, and chain-like architectures. As a result, the previously limited Nb–O–I system, formerly represented by the compounds NbOI2, NbOI3, and NbO2I, is now significantly expanded by the addition of several metal-rich niobium oxyiodide phases. These new phases are exclusively accessible through the reduction of NbI4 by Li2CN2 under controlled thermal conditions.