The new compound Ta4SI11 has been prepared by direct reaction of the elements at 430 °C for 2 weeks in evacuated Pyrex ampules and characterized by single-crystal X-ray diffraction, X-ray photoelectron spectroscopy, magnetic susceptibility measurements, and semiempirical electronic structure calculations. Ta4SI11 crystallizes with orthorhombic symmetry in space group Pmmn; a = 16.135(3) Å, b = 3.813(1) Å, c = 8.131(2) Å, and Z = 1. The disordered structure involves two crystallographically distinct sites for Ta atoms, both of which are 50% occupied as well as a bridging anion site that is 50% S and 50% I. Magnetic susceptibility above 100 K gives μeff = 1.53 μB to suggest one unpaired electron per formula unit. X-ray photoelectron spectroscopy and extended Hückel calculations suggest that the structure consists of Ta3 triangles and “isolated” Ta atoms, leading to the formulation (Ta3)9+(Ta4+)(S2-)(I-)11 and we hypothesize that each Ta3 is capped by a sulfur atom.
Available at: http://works.bepress.com/gordon-miller/94/