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Syntheses and Structures of the Infinite Chain Compounds Cs4Ti3Se13, Rb4Ti3S14, Cs4Ti3S14, Rb4Hf3S14, Rb4Zr3Se14, Cs4Zr3Se14, and Cs4Hf3Se14

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posted on 2001-04-13, 00:00 authored by Fu Qiang Huang, James A. Ibers
The alkali metal/group 4 metal/polychalcogenides Cs4Ti3Se13, Rb4Ti3S14, Cs4Ti3S14, Rb4Hf3S14, Rb4Zr3Se14, Cs4Zr3Se14, and Cs4Hf3Se14 have been synthesized by means of the reactive flux method at 823 or 873 K. Cs4Ti3Se13 crystallizes in a new structure type in space group C22-P21 with eight formula units in a monoclinic cell at T = 153 K of dimensions a = 10.2524(6) Å, b = 32.468(2) Å, c = 14.6747(8) Å, β = 100.008(1)°. Cs4Ti3Se13 is composed of four independent one-dimensional [Ti3Se134-] chains separated by Cs+ cations. These chains adopt hexagonal closest packing along the [100] direction. The [Ti3Se134-] chains are built from the face- and edge-sharing of pentagonal pyramids and pentagonal bipyramids. Formal oxidation states cannot be assigned in Cs4Ti3Se13. The compounds Rb4Ti3S14, Cs4Ti3S14, Rb4Hf3S14, Rb4Zr3Se14, Cs4Zr3Se14, and Cs4Hf3Se14 crystallize in the K4Ti3S14 structure type with four formula units in space group C2h6-C2/c of the monoclinic system at T = 153 K in cells of dimensions a = 21.085(1) Å, b = 8.1169(5) Å, c = 13.1992(8) Å, β = 112.835(1)° for Rb4Ti3S14; a = 21.329(3) Å, b = 8.415(1) Å, c = 13.678(2) Å, β = 113.801(2)° for Cs4Ti3S14; a = 21.643(2) Å, b = 8.1848(8) Å, c = 13.331(1) Å, β = 111.762(2)° for Rb4Hf3S14; a = 22.605(7) Å, b = 8.552(3) Å, c = 13.880(4) Å, β = 110.919(9)° for Rb4Zr3Se14; a = 22.826(5) Å, b = 8.841(2) Å, c = 14.278(3) Å, β = 111.456(4)° for Cs4Zr3Se14; and a = 22.758(5) Å, b = 8.844(2) Å, c = 14.276(3) Å, β = 111.88(3)° for Cs4Hf3Se14. These A4M3Q14 compounds (A = alkali metal; M = group 4 metal; Q = chalcogen) contain hexagonally closest-packed [M3Q144-] chains that run in the [101] direction and are separated by A+ cations. Each [M3Q144-] chain is built from a [M3Q14] unit that consists of two MQ7 pentagonal bipyramids or one distorted MQ8 bicapped octahedron bonded together by edge- or face-sharing. Each [M3Q14] unit contains six Q22- dimers, with Q−Q distances in the normal single-bond range 2.0616(9)−2.095(2) Å for S−S and 2.367(1)−2.391(2) Å for Se−Se. The A4M3Q14 compounds can be formulated as (A+)4(M4+)3(Q22-)6(Q2-)2.