A New Rare-Earth Indium Antimonide, (RE)In(1)(-)(x)()Sb(2) (RE = La-Nd), Featuring In Zigzag Chains and Sb Square Nets

A new series of ternary rare-earth indium antimonides, (RE)In(1)(-)(x)()Sb(2) (RE = La-Nd), has been synthesized through reaction of the elements at 950 degrees C. The structure of LaIn(0.81(1))Sb(2) has been determined by single-crystal X-ray diffraction (monoclinic space group -P2(1)/m, Z = 2, a = 4.521(3) Å, b = 4.331(3) Å, c = 11.913(7) Å, beta = 99.6680(11) degrees ). The structure is built up of alternating layers of compositions and separated by the La atoms. The layer is described as a nearly square net of Sb atoms held by weak one-electron bonds, while the layer is derived from edge-sharing InSb(4) tetrahedra distorted in such a way as to produce In-In zigzag chains. Extended Hückel band structure calculations are used to explain the bonding and predict that anisotropic metallic behavior should be observed.