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Sn(24)P(19.3)I(8) (I) and Sn(24)As(19.3)I(8) (II) have been prepared by a standard ampule synthesis. I crystallizes in a cubic space group Pm&thremacr;n, a = 10.9540(10) Å, z = 1. The crystal structure of I is built of the 3D net composed of tin and phosphorus atoms, while iodine atoms occupy large polyhedral holes of two different types, pentagonal dodecahedral and tetrakaidodecahedral. An arrangement of such polyhedra follows that of the clathrate-I type. The 3D net has vacancies at one of the phosphorus atoms positions. The vacancies cause the split of the tin atomic position into two, having different coordination, which is reflected in the (119)Sn Mössbauer spectrum. The vacancy concentration correlates well with the occupancy factors of the split tin atomic positions, and in accordance with the Zintl-Klemm formalism for valence compounds, I is a narrow-gap semiconductor. Powder diffraction data shows that II belongs to the same clathrate family, but has an 8 times larger face-centered cubic unit cell.

Two new subvalent bismuth telluroiodides, Bi 2 TeI and Bi 4 TeI 1.25 , were prepared by the gas phase synthesis. The compositions of these phases were determined by energy dispersive X ray spectroscopy. X ray diffraction study of melt grown Bi 2 TeI single crystals demonstrated that the compound crystallizes in the monoclinic system (space group C/2m) with the unit cell parameters a = 7.586(1) Å, b = 4.380(1) Å, c = 17.741(3) Å, β = 98.20°. The layered crystal structure of Bi 2 TeI consists of weakly bonded two dimensional blocks with a stoichiometry of the title compound. The blocks are stacked along the c axis. Each block consists of eight atomic layers alternating in the Te-Bi-I-Bi-Bi-I-Bi-Te order and includes a double layer of bismuth atoms. Based on the results of ab initio quantum chemical calculations, the title compound is expected to possess a pronounced anisotropy of conductivity.Key words: low dimensional phases, layered compounds, main group metal-metal bond ing, bismuth telluroiodides.Bismuth is one of a few p metals, which can form crystalline compounds containing extended metal-metal bond systems. For example, the crystal structures of subvalent iodides and mixed subvalent iodide bromides Bi 4 I 4-n Br n 6 consist of one dimensional fragments, which can be de scribed as corrugated bismuth strips of width 4, 14, or 18 atoms, respectively, which are bounded on both sides by halogen atoms. The geometry of these strips is very similar to the atomic arrangement in the crystal structure of bismuth metal. In addition, two dimensional electro neutral Bi 2 layers, which also retain the structure of bis muth metal, were found in the crystals of subvalent bis muth selenides 7-9 and tellurides. 7,10,11The structures of subvalent bismuth chalcogenides, for example, with compositions BiQ and Bi 4 Q 3 (Q = Se, Te), can be considered as a result of intercalation of Bi 2 layers into the crystal structures of layered se lenides and tellurides with composition Bi 2 Q 3 formed by weakly bonded two dimensional electroneutral Bi 2 Q 3 blocks.The aim of the present study was to intercalate bis muth double layers into the crystal structure of bismuth telluroiodide BiTeI. This compound crystallizes in the hexagonal system 12 (space group P3m1, a = 4.3302(1) Å, c = 6.854(1) Å) and can be described as a distorted 2H CdI 2 type crystal structure, in which the tellurium and iodine atoms in the anion sublattice are completely ordered so that the tellurium atoms replace one layer of iodine atoms in the starting CdI 2 structure (Fig. 1).The shortest Bi-Te and Bi-I bonding distances (3.039 and 3.272 Å, respectively) and the Te-I non bonded distance (3.93 Å) suggest a layered character of the structure. Since the geometry of the Bi-Te and Bi-I bond systems in BiTeI (Te-Bi-Te and I-Te-I angles are 83° and 91°, respectively) is similar to that of the Bi-Bi bond system in the Bi 2 layer of subvalent bismuth tellurides (in BiTe 11 and Bi 4 Te 3 , 11 the Bi-Bi distances are 3.267 and 3.098 Å, and the Bi-Bi-Bi angles are 85°a nd 91°, re...

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