A new quasi-one-dimensional niobium oxychloride cluster compound Cs2Ti4Nb6Cl18O6: structural effects of ligand combination.

The new niobium oxychloride cluster compound, Cs2Ti4Nb6Cl18O6, was obtained by solid-state synthesis techniques in the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional cluster compounds. Cs2Ti4Nb6Cl18O6 crystallizes in the trigonal system, with unit cell parameters a= 11.1903(7), c = 15.600(2) A, space group P3bar1c, Z = 2. Its crystal structure was determined by single-crystal X-ray diffraction techniques. The full-matrix least-squares refinement against F(2) converged to R(1) = 0.048 (F(o) > 4sigma(F(o))), wR(2) = 0.069 (all data). The structure is based on an octahedral cluster unit (Nb6Cl(i)6O(i)6)Cl(a)6 in which the six edge-bridging oxide ligands are arranged in two sets of three on opposite sides of the Nb6 octahedron. Ti(3+) ions link the clusters through O(i) and Cl(a) ligands to form linear chains running along the c axis. The location of titanium ions correlates with the arrangement of oxide ligands around the Nb6 metal core. The chains interact with each other through additional Ti(3+) and Cs(+) ions. Interchain interactions are significantly weaker than intrachain interactions, resulting in a quasi-one-dimensional character of the overall structure.