The new compounds Y7I12C2N and Ho7I12C2N have been prepared by reaction of stoichiometric amounts of the metals (RE), REI3, REN and C in closed Ta capsules at 1150 and 1120K, respectively. Pure samples of the compounds were obtained after 5 days annealing time. The crystals with xenomorphic shape are olive-green (Y7I12C2N) or red-brown (Ho7I12C2N) in colour and sensitive to air and moisture. Y7I12C2N crystallizes in the space group P 1̄ (No. 2) with lattice constants a = 971.24(7), b = 1030.38(7), c = 1673.58(11) pm and α = 101.366(5), β = 92.758(5), γ = 112.799(5)°. According to Guinier photographs Ho7I12C2N is isotypic with the lattice consiants u - 968.8(3), b = 1028.7(3), r. = 1667.8(5) pm and α = 101.31(2), β = 92.78(2), γ = 112.80(1)°.
In the structure the C atoms are present as C2 units with a C -C distance of 144 pm. These C2 units are octahedrally coordinated by Y atoms (o1). The N atoms are in the center of Y4 tetrahedra, which are linked via a common edge to form double tetrahedra (t2). By condensation of N-centered double tetrahedra (t2) with a C2-centered Y octahedron (o1) the characteristic units o1t2o1 are formed. The I atoms coordinate all free edges and corners of these units and connect them via Ii - Ia contacts parallel [100] and [001].
The compounds are semiconducting. Ho7I12C2N exhibits Curie-Weiss behaviour with θ = 15(1) K and μeff = 10.5(1) μB.
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