Preparation of Low-Dimensional Cluster Materials: Synthesis, Structure, and Properties of A2Ti2Nb6Cl14O5 (A = K, Rb, Cs), a Series of One-Dimensional Titanium Niobium Oxychlorides

Abstract

In the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional compounds, a new series of niobium oxychloride cluster compounds, A2Ti2Nb6Cl14O5 (A = K, Rb, Cs), was obtained from stoichiometric amounts of ACl (A = K, Rb, Cs), Ti, Nb2O5, NbCl5, and Nb, heated at 750 °C. The crystal structures of the series were determined by single-crystal X-ray diffraction techniques. The compounds crystallize in the monoclinic system, space group C2/c, with unit cell parameters a = 21.503(3) A, b = 8.816(1) A, c = 15.710(2) A, β = 116.21(1)°, V = 2672.1(6) A3, and Z = 4 for A = Rb. The full-matrix least-squares refinement against F 2 converged to R1 = 0.043 (Fo > 4σ(Fo)) and wR2 = 0.089 (all data for A = Rb). The crystal structure of A2Ti2Nb6Cl14O5 has one-dimensional character. It is based on chains formed by (Nb6 ) octahedral niobium clusters connected to each other through apical chloride ligands and titanium counterions. The chains are held together by alkali ...