Structure Structure D 2000Ternary Aluminides with the Ideal Composition A 2 Pt 6 Al 15 (A: Y, Gd-Tm, Zr).-The title compounds are prepared by arc melting of the elements followed by annealing in a high-frequency furnace. The structures of the compounds are determined by powder XRD. Single crystal data are reported for Y1.357Pt4Al9.99 and Zr1.00Pt4Al10.22 (hexagonal, space group P63/mmc, Z = 1). -(NIERMANN,

The new cubic compound Fe0.5Ni0.5P3 (a = 775.29(5) pm) as well as the known compounds CoP3 and NiP3 were synthesized from the elemental components using tin as a flux. Their skutterudite (CoAs3) type structures were refined from single‐crystal X‐ray data. The new compound GdFe4P12 was prepared by reaction of an alloy Gd1/3Fe2/3 with phosphorus in a tin flux. Its cubic “filled” skutterudite (LaFe4P12 type) structure was refined from single‐crystal X‐ray data: a = 779.49(4) pm, R = 0.019 for 304 structure factors and 11 variable parameters. SmFe4P12 shows Van Vleck paramagnetism while GdFe4P12 is a soft ferromagnet with a Curie temperature of TC = 22(5) K. Both are metallic conductors. The new isotypic polyarsenide NdFe4As12 (a = 830.9(1) pm) was obtained by reacting NdAs2 with iron and arsenic in the presence of a NaCl/KCl flux. The new isotypic polyantimonide Eu0.54(1)Co4Sb12 (a = 909.41(8) pm) was prepared by reaction of EuSb2 with cobalt and antimony. Its structure was refined from single‐crystal X‐ray data to a residual of 0.024 (137 F values, 12 variables). A comparison of the Fe–P and P–P bond lengths in the compounds AFe4P12, where the A atoms (A = Ce, Eu, Gd, Th) have differing valencies, suggests that the Fermi level cuts through Fe–P bonding and P–P antibonding bands.

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The title compounds were prepared by reacting powders of the binary transition metal alloys with phosphorus in a tin melt. They crystallize with a monoclinic structure of space group C 2/c, which was determined from single-crystal X-ray data; VNi4P16: a = 1956.0(3), b = 565.9(1), c = 1106.6(2) pm, ß = 100.99(1)°, R -0.020 for 1904 structure factors and 97 variable parameters; NbNi4P16: a = 1973.0(3), b = 571.2(3), c = 1117.2(2) pm, ß = 100.74(1)°, R = 0.023 for 2431 F-values and 97 variables; WNi4P16: a = 1964.2(3), b = 568.3(2), c = 1109.3(2) pm,/? = 101.04(2)°, R = 0.031 for 371 F-values and 43 variables. The T atoms (T = V, Nb, W) have eight P neighbors, which form a slightly distorted square antiprism, and the Ni atoms have appro ximately octahedral P coordination. The P atoms form novel P8 units, which consist of 6 -membered rings with a P2 side chain. Chemical bonding is discussed on the basis of classical twoelectron bonds. A comparison of the interatomic distances suggests that the Fermi level cuts through a band formed by antibonding nickel-phosphorus states. A band structure is propos ed, which also rationalizes the metallic conductivity and the Pauli paramagnetism of the com pounds.The transition metals (T) form numerous poly phosphides with the composition TP4 [1]. Ternary compounds with a T : P ratio of 1:4 are also known, e.g. M oFe2P 12 and W Fe2P 12 [2], TiMn2P 12 [3], NbMn2P12, MoMn2P12, and WMn2P12 [4], VFe2P 12 [5], NbFe2P12 [6 ,7], MoNiP8 and WNiP8 [8 ]. In these polyphosphides the early transition metals have mostly square-antiprismatic or cubic (MoNiP8 and WNiP8) phosphorus coordination, while the late transition metals are surrounded octahedrally by phosphorus atoms. In VP4 • 4 NiP3 = VNi4P 16 and the isotypic compounds NbNi4P 16 and WNi4P16 report ed here the T : P ratio is 1:3.2 and thus these com pounds form an entirely new structure type. How ever, the near-neighbor coordinations of the tran sition metals are very similar to those of the struc tures with the composition T T '2P12. Again the chemical bonding in the TNi4P 16 polyphosphides can be rationalized on the basis of classical twoelectron bonds. A preliminary account of the struc ture of VNi4P 16 has been given earlier [5].* Reprint requests to W. Jeitschko. PreparationThe title compounds can be prepared in wellcrystallized form by reacting a T-nickel alloy (T = V, Nb, W) with red phosphorus in a tin melt. This preparation m ethod has been used with good results in the past for the preparation of Ti2NiP5 [9], Mo(W )NiP8 [8 ] and VFe2P 12 [5]. Starting materials were powders of vanadium, niobium, tungsten and nickel (all 99,9%), red phosphorus (Hoechst, "ultrapur"), and tin (Merck, "rein"). The T-nickel alloys were prepared by arc melting of cold-pressed pellets with the atomic ratio T : Ni = 1:1 or 1:2. The alloys were then ground to fine powders and react ed with red phosphorus and tin in the ratio (T /N i): P : Sn = 1:25:20 in evacuated sealed silica tubes (tube volume 5 cm3, P content 0.5 g). The tubes were annealed at 450 °C f...