NEW ZR(6)MTE(2) (M=MN,FE,CO,NI,RU,PT), ZR6FE0.6SE2.4, AND ZR6FE0.57S2.43 INTERMETALLICS - STRUCTURAL LINKS BETWEEN BINARY (ZR,HF)(3)M ALLOYS AND POROUS METAL-RICH TELLURIDES

The synthesis of the group IV ternary chalcogenides Zr(6)MTe(2) (M = M n, Fe, Co, Ni, Ru, Pt) and Zr(6)Fe(1-x)Q(2+x) (Q = S, Se) is reported, as are the single-crystal structures of Zr6FeTe2, Zr6Fe0.6Se2.4, and Zr6Fe0.57S2.43. The structure of Zr6FeTe2 was refined in the hexagonal space group P (6) over bar 2m (No. 189, Z = 1) with lattice parameter s a = 7.7515(5) Angstrom and c = 3.6262(6) Angstrom, and the structure s of Zr6Fe0.6Se2.4 and Zr6Fe0.57S2.43 were refined in the orthorhombic space group Pnnm (No. 58, Z = 4) with lattice parameters a = 12.737(2 ) Angstrom, b = 15.780(2) Angstrom, and c = 3.5809(6) Angstrom and a = 12.519(4) Angstrom, b = 15.436(2) Angstrom, and c = 3.4966(6) Angstro m, respectively. The cell parameters of Mn-, Co-, Ni-, Ru-, and Pt-con taining tellurides were also determined. The Zr6Te2 compounds are isos tructural with Zr6CoAl2, while Zr(6)Fe(1-x)Q(2+x) (Q = S, Se) were fou nd to adopt a variant of the Ta2P-type structure. Chains of condensed M-centered, tetrakaidecahedra of zirconium constitute the basic struct ural unit in all these compounds. The modes of cross-linking that give rise to the Zr6FeTe2 and Zr(6)Fe(1-x)Q(2+x) structures, differences a mong the title compounds, and the influence of chalcogen size differen ces are discussed. The stoichiometric nature of Zr6FeTe2 and its contr ast with sulfur and selenium congeners apparently result from a Te-Fe size mismatch. The importance of stabilization of both Zr6FeSe2 and Zr 6FeTe2 compounds by polar intermetallic Zr-Fe bonding is underscored b y a bonding analysis derived from electronic band structure calculatio ns.