Synthesis and structure of an infinite-chain form of ZrI2 (α)

Article abstract of DOI:10.1016/0022-4596(81)90092-X

The synthesis of a second polymorph of ZrI₂ has been achieved by a transport reaction between ZrI₄ 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 P2₁ m with a = 6.821(2) A, b = 3.741(1) A, c = 14.937(3) A, β = 95.66(3)°, Z = 4. A total of 669 independent reflections with 2θ ≤ 50° and I > 3σ(I) were measured at room temperature on a four-circle automated diffractometer with monochromatized MoKα 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-MoTe₂, a distorted CdI₂-type structure in which the zirconium atoms are displaced 0.440 A from the octahedral centers along a to form infinite zigzag metal chains (d_ZrZr = 3.182(3) A) parallel to b. The phase is a diamagnetic semiconductor at room temperature (E_g ～ 0.1 eV).