Description:
<jats:title>Abstract</jats:title><jats:p>RbNb<jats:sub>4</jats:sub>Br<jats:sub>11</jats:sub> was obtained by a solid state reaction of niobium powder, NbBr<jats:sub>5</jats:sub> and RbBr in a sealed niobium tube at 500 °C. It crystallizes in the orthorhombic space group <jats:italic>Pmma</jats:italic> with <jats:italic>a</jats:italic> = 1699.5(1), <jats:italic>b</jats:italic> = 726.7(1), <jats:italic>c</jats:italic> = 694.5(1) pm, <jats:italic>V</jats:italic> = 857.6(1)·10<jats:sup>6</jats:sup> pm<jats:sup>3</jats:sup>, <jats:italic>Z</jats:italic> = 2 and is isotypic with CsNb<jats:sub>4</jats:sub>Br<jats:sub>11</jats:sub>. Four niobium atoms build a cluster in the shape of a rhombus with bonding distances of 295 pm (Nb1–Nb2) and 304 pm (Nb2–Nb2), respectively. The structure consists of [{Nb<jats:sub>4</jats:sub>}Br<jats:sub>6</jats:sub><jats:sup>i</jats:sup>Br<jats:sub>10/2</jats:sub><jats:sup>a–a</jats:sup>]<jats:sup>–</jats:sup>cluster complex anions that are interconnected by two common edges and two faces to the next cluster complexes, thus forming a 2D undulated layer structure. The Rb<jats:sup>+</jats:sup> ion is coordinated by 12 Br<jats:sup>–</jats:sup> ions in the shape of an anticuboctahedron. Electronic structure calculations indicate the presence of a band gap of approximately 0.33 eV. This is experimentally confirmed by an electrical conductivity measurement revealing a slightly higher gap of 0.46 eV.</jats:p>