Synthesis and structure of an infinite-chain form of ZrI 2 (α)

Abstract

The synthesis of a second polymorph of ZrI 2 has been achieved by a transport reaction between ZrI 4 and zirconium metal under a 750 850 ° C gradient in a sealed tantalum tube. The black lath-like crystals produced in the 775°C region occur in space group P2 1 m with a = 6.821(2) Å, b = 3.741(1) Å, c = 14.937(3) Å, β = 95.66(3)°, Z = 4. A total of 669 independent reflections with 2 θ ≤ 50° and I > 3 σ( I) were measured at room temperature on a four-circle automated diffractometer with monochromatized Mo Kα radiation and were corrected for absorption (μ = 190 cm −1). The structure was solved by direct methods and full-matrix least-squares refinement of all atoms with anisotropic thermal parameters to give final residuals R = 0.064 and R w = 0.079. This phase is isoelectronic and isostructural with β-MoTe 2, a distorted CdI 2-type structure in which the zirconium atoms are displaced 0.440 Å from the octahedral centers along a to form infinite zigzag metal chains ( d ZrZr = 3.182(3) Å) parallel to b. The phase is a diamagnetic semiconductor at room temperature ( E g ∼ 0.1 eV).