Layered niobium titanium oxychloride cluster compounds with six-member ring opening channels

New niobium oxychloride cluster compounds corresponding to the general formula, A₅Ti₈Nb₁₈Cl₅₃O₁₂ (A=K, In), have been prepared in sealed quartz tubes from a mixture containing NbCl₅, Nb₂O₅, Nb, Ti, and KCl or In by solid-state reactions at 750°C. Their structure was determined using single-crystal X-ray diffraction; Crystal data: trigonal, (No. 164) (for K: a=16.8303(11) Å, c=9.0510(8) Å, V=2220.3(3) Å³ and Z=1; for In: a=16.889(2) Å, c=9.0684(2) Å, V=2240.0(6) Å³ and Z=1). The full-matrix least-squares refinement of all data against F² converged to R₁=0.044, wR₂=0.088 for K, and R₁=0.050, wR₂=0.140 for In. The structure consists of octahedral (Nb₆C1₈ⁱO₄ⁱ)C1₆^a cluster units that share four outer chloride ligands with four adjacent clusters to form a two-dimensional framework that generates six- and three-member rings similar to those found in hexagonal tungsten bronze. Additional linkages within the same layer are provided by Ti₃Cl₇O₆ trimers. Adjacent layers are stacked in registry with each other leading to the formation of six-member ring openings channels parallel to the 001] direction in which a disordered A₅(Ti₂Cl₉)]²⁺ species are located. Magnetic susceptibility studies show paramagnetic behavior with a magnetic moment of 3.74 μ_B per formula unit.