CsTi2Cl7-II:: Synthesis, crystal structure, and magnetic properties

Single crystals of a second modification of CsTi2Cl7 (II) were obtained from the reaction of CsCl with TiCl2 and C6Cl6 (monoclinic, P2(1)/m (No.11), Z = 2, a = 635.4(3), b = 1163,0(2), c = 728,0(2) pm, beta = 91,49(4)degrees). X-ray pure powder samples are obtained from the binary components in 1:2 molar mixtures of CsCl and TiCl3 (melting at 900 degrees C and annealing at 550 degrees C below the melting point). The crystal structure of CsTi2Cl7-II contains layers of densest packings of spheres of the compositions CsCl3 and Cl-4, respectively, that are stacked alternatively in the [010] direction according to the sequence ...ABAC... Ti3+ resides in one quarter of the octahedral holes between these layers in a way that confacial bioctahedra are connected via two common edges forming a zigzag chain running parallel to [010]. This structure with Ti3+-Ti3+ distances of 323 and 347pm, respectively, is reflected in the antiferromagnetic behavior with interactions about sixteen times stronger within the dimers than between them (J = -490 cm(-1) bzw. J = -30 cm(-1)).