Synthesis, Crystal Structure, and Properties of Polymeric Rb12Nb6Se35, a Novel Ternary Niobium Selenide Consisting of Infinite Anionic Chains Built Up by Nb2Se11Units Containing an Uncommon Se4−3-Fragment

Abstract

Rb12Nb6Se35is the first ternary niobium polyselenide composed of infinite anionic chains. These are well separated by rubidium cations. It crystallizes in the orthorhombic space groupPbcnwith unit cell dimensionsa=8.5811(1) Å,b=13.7152(1) Å,c=56.5225(4) Å, andZ=4. The least-squares refinement againstF2with anisotropic displacement parameters for all atoms yieldsR1=5.78 and wR2=12.81. The anionic polymeric chains are arranged in layers parallel to the (010) plane, and successive planes are rotated by 35° against each other. Nb2Se11units composed of two face-sharing NbSe7pentagonal bipyramids are the building blocks of the structure. They are interconnected by Se2−2and Se2−3polyanions, giving rise to infinite1∞[Nb6Se35]12−chains. Within the Nb2Se11units an unusual nearly linear Se3fragment is found which must be formulated as Se4−3.