Abstract
The title compounds are produced through reactions of Sc, ScI[sub 3], and LiI or NaI at 750-850C in sealed niobium tubing. The slightly paramagnetic lithium phase has a fixed composition near LiScI[sub 3] judging from Guinier powder data and direct analyses. The structure refined from single-crystal X-ray data (P[bar 6]c2, Z = 2, a = 7.2861 (9) [angstrom], c = 6.768 (2) [angstrom], R/R[sub w] = 0.96/3.2%) contains equally spaced scandium atoms (d(Sc-Sc) = 3.384 (1) [angstrom]) in chains of confacial ScI[sub 6/3] octahedra that lie normal to hcp iodine layers. Lithium in iodine octahedra is ordered so as to define confacial trigonal prisms about each chain. The sodium phase has a fixed composition close to Na[sub 0.5]ScI[sub 3] according to the same criteria as well as the structural refinement (Na[sub 0.53(2)]ScI[sub 3]: P31c, Z = 4, a = 7.492 (2), c = 13.699 (3) [angstrom], R/R[sub W] = 2.2/3.2% for data to 2[theta] = 60[degree]). The scandium atoms are paired within slightly distorted chains of confacial octahedra normal to hcp iodine layers (d(Sc-Sc) = 3.278 (5), 3.572 (5) [angstrom]). Sodium at [approximately]50% occupancy within iodine octahedra presents a novel arrangement, trigonal prisms centered around each dimer that are alternatelymore » rotated by [approximately]60[degree] along the chain. The phase exhibits a small, temperature-independent paramagnetism. The results are compared with those for other nominal d[sup 1] trihalides.« less
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