Sb-Sb interactions in the hafnium-rich antimonide Hf6TiSb4

(Hf,Ti)(7)Sb-4 is accessible via arc-melting of suitable mixtures of Hf, Ti , and HfSb2. Its crystal structure is the first representative of a new str ucture type, as was determined by single-crystal analysis for Hf7-xTixSb4 w ith x = 1.05(7) approximate to 1. Hf6TiSb4 crystallizes in the monoclinic s pace group P2(1)/c, with the lattice dimensions a = 841.0(1), b = 1102.9(1) , c = 1099.3(1) pm, and beta = 111.13(1)degrees (Z = 4). All seven independ ent metal sites are statistically occupied by different mixtures of hafnium and titanium, forming a three-dimensional network of metal atoms M which i ncludes the Sb atoms in its (capped) square antiprismatic voids. The metal substructure can be described on the basis of semiregular 488 nets. Besides numerous M-Sb and M-M bonds, a nonlinear Sb-3 unit is present with bonding Sb-Sb interactions. Extended Huckel calculations, performed on the hypothe tical model structure Hf7Sb4, point to metallic properties.